Document:

EX-10.3

 Exhibit 10.3 

SPONSOR SUPPORT AGREEMENT 

This Sponsor Support Agreement (this “Sponsor Agreement”) is dated as of October 6, 2021, by and among
Supernova Partners II LLC, a Cayman Islands limited liability company (the “Sponsor Holdco”), the Persons set forth on Schedule I hereto (together with the Sponsor Holdco, each, a “Sponsor” and,
together, the “Sponsors”), Supernova Partners Acquisition Company II, Ltd., a Cayman Islands exempted company which shall domesticate as a Delaware corporation prior to the Closing in accordance with the Merger Agreement
(such entity, including the continuing corporation, “Acquiror”), and Rigetti Holdings, Inc., a Delaware corporation (the “Company” and collectively with the Sponsors and Acquiror, the
“Parties”). Capitalized terms used but not defined herein shall have the respective meanings ascribed to such terms in the Merger Agreement (as defined below). 

RECITALS 
 WHEREAS, as of
the date hereof, the Sponsors collectively are the holders of record and the “beneficial owners” (within the meaning of Rule 13d-3 under the Exchange Act) of 8,418,000 Acquiror
Class B Ordinary Shares and 4,450,000 Acquiror Warrants in the aggregate as set forth on Schedule I attached hereto (all such securities or other equity securities, together with any shares of Acquiror’s capital stock or other
equity securities of which ownership of record or the power to vote (including, without limitation, by proxy or power of attorney) is hereafter acquired by any such Sponsor during the period from the date hereof through the conclusion of the Interim
Period, including any and all Founder Shares, Founder Warrants and New Securities, are referred to herein as the “Subject Securities”); 

WHEREAS, contemporaneously with the execution and delivery of this Sponsor Agreement, Acquiror, Supernova Merger Sub, Inc., a Delaware
corporation (“First Merger Sub”), Supernova Romeo Merger Sub, LLC, a Delaware limited liability company (“Second Merger Sub” and, together with First Merger Sub, “Merger Subs”
and each, a “Merger Sub”) and the Company have entered into an Agreement and Plan of Merger (as amended, supplemented, restated or otherwise modified from time to time, the “Merger Agreement”), dated
as of the date hereof, pursuant to which, among other transactions, (i) Acquiror will domesticate as a Delaware corporation, (ii) First Merger Sub will merge with and into the Company (the “First Merger”), with the
Company surviving such First Merger as a wholly owned subsidiary of Acquiror, and (iii) immediately following the First Merger and as part of the same overall transaction as the First Merger, the Company will merge with and into Second Merger
Sub (the “Second Merger” and, together with the First Merger, the “Mergers”), with the Second Merger Sub surviving such Second Merger as a wholly owned subsidiary of Acquiror, on the terms and
conditions set forth therein; and 
 WHEREAS, as an inducement to Acquiror and the Company to enter into the Merger Agreement and to
consummate the transactions contemplated therein, the parties hereto desire to agree to certain matters as set forth herein. 

 AGREEMENT 

NOW, THEREFORE, in consideration of the foregoing and the mutual agreements contained herein, and intending to be legally bound hereby, the
parties hereto hereby agree as follows: 
 ARTICLE I 

SPONSOR SUPPORT AGREEMENT; COVENANTS 

Section 1.1 Binding Effect of Merger Agreement. Each Sponsor hereby acknowledges that it has read the Merger Agreement and this
Sponsor Agreement and has had the opportunity to consult with its tax and legal advisors. Each Sponsor shall be bound by and comply with Sections 9.04(b) (Exclusivity) and 9.06 (Confidentiality; Publicity) of the Merger
Agreement (and any relevant definitions contained in any such sections) as if such Sponsor was an original signatory to the Merger Agreement with respect to such provisions and each reference to Acquiror in such provision referred to such Sponsor.

 Section 1.2 No Transfer. 

(a) Each Sponsor shall not, during the Interim Period (except, in each case, pursuant to the Merger Agreement), (i) directly or indirectly
sell, transfer, hypothecate, pledge, encumber, assign, hedge, swap, convert or otherwise dispose of (including by merger (including by conversion into securities or other consideration), by tendering into any tender or exchange offer, by
testamentary disposition, by operation of Law or otherwise), either voluntarily or involuntarily, any of its Subject Securities, (ii) enter into any Contract or option with respect to any transaction specified in clause (i) or any swap or
other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any of its Subject Securities, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or
(iii) publicly announce any intention to effect any transaction specified in clauses (i) or (ii) (any transaction specified in clauses (i), (ii) or (iii), a “Transfer”); provided, however, that the
foregoing shall not restrict Transfers (I) to (x) Acquiror’s officers or directors, (y) any affiliates or family members of Acquiror’s officers or directors, or (z) any members or partners of Sponsor Holdco or their
affiliates, any affiliates of Sponsor Holdco, or any employees of such affiliates; (II) in the case of an individual, by gift to a member of such individual’s immediate family or to a trust, the beneficiary of which is a member of such
individual’s immediate family, an affiliate of such individual or to a charitable organization; (III) in the case of an individual, by virtue of laws of descent and distribution upon death of such individual; or (IV) in the case of an
individual, pursuant to a qualified domestic relations order; provided, further, that any such Transfer shall be permitted only if, as a precondition to such Transfer, the transferee agrees in a writing, reasonably satisfactory in form
and substance to the Company, to assume all of the obligations of the transferor under, and be bound by all of the terms of, this Sponsor Agreement; provided, further, that any Transfer permitted under this
Section 1.2 shall not relieve the transferor of its obligations under this Sponsor Agreement. Any Transfer in violation of this Section 1.2 shall be null and void. 

(b) As used in this Sponsor Agreement, Subject Securities shall include any and all Acquiror Class B Ordinary Shares that a Sponsor
currently or hereafter beneficially owns prior to the Domestication, including the Acquiror Class B Ordinary Shares set forth on Schedule I attached hereto, and for all periods after completion of the Domestication, any and all shares of
Domesticated Acquiror Common Stock that a Sponsor currently or hereafter 

  
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beneficially owns, including the shares of Domesticated Acquiror Common Stock issued upon conversion of the Acquiror Class B Ordinary Shares set forth on Schedule I attached hereto
(collectively, the “Founder Shares”), and any and all Acquiror Warrants that a Sponsor currently or hereafter beneficially owns prior to the Domestication, including the Acquiror Warrants set forth on Schedule I
attached hereto, and (y) for all periods after completion of the Domestication, any and all Domesticated Acquiror Warrants, including the Domesticated Acquiror Warrants issued upon conversion of the Acquiror Warrants set forth on Schedule
I attached hereto (collectively, the “Founder Warrants”). 
 Section 1.3 New Shares. In the event
that (a) any Acquiror Shares, Acquiror Warrants or other equity securities of Acquiror are issued to a Sponsor during the Interim Period pursuant to any stock dividend, stock split, recapitalization, reclassification, combination or exchange of
Acquiror Shares, Acquiror Warrants of, on or affecting any Acquiror Shares or Acquiror Warrants owned by such Sponsor or otherwise, (b) a Sponsor purchases or otherwise acquires beneficial ownership of any Acquiror Shares , Acquiror
Warrants or other equity securities of Acquiror after the date of this Sponsor Agreement, or (c) a Sponsor acquires the right to vote or share in the voting of any Acquiror Shares or other equity securities of Acquiror during the Interim Period
(such Acquiror Shares, Acquiror Warrants or other equity securities of Acquiror, collectively the “New Securities”), then such New Securities acquired or purchased by such Sponsor shall be subject to the terms of this Sponsor
Agreement to the same extent as if they constituted the Subject Securities owned by such Sponsor as of the date hereof. 
 Section 1.4
Closing Date Deliverables. On the Closing Date, the Sponsor Holdco shall deliver to Acquiror and the Company a duly executed copy of that certain Amended and Restated Registration Rights Agreement, by and among Acquiror, the Company, the
Sponsor Holdco and certain of the Company’s stockholders or their respective affiliates, as applicable, in substantially the form attached as Exhibit C to the Merger Agreement. 

Section 1.5 Sponsor Agreements. 

(a) During the Interim Period, at any duly called meeting of the shareholders of Acquiror or at any adjournment thereof, or in any other
circumstance in which the vote, consent or other approval of the shareholders of Acquiror is sought, in each case, as contemplated by the Merger Agreement, each Sponsor shall (i) appear at each such meeting or otherwise cause all of its Subject
Securities that are entitled to vote on such matter at such meeting to be counted as present thereat for purposes of calculating a quorum and (ii) vote (or cause to be voted), or execute and deliver a written consent (or cause a written consent
to be executed and delivered) covering, all of its Subject Securities that are entitled to vote on such matter: 
 (i) in
favor of the Transactions; 
 (ii) against any Business Combination Proposal or any proposal relating to a Business
Combination Proposal (in each case, other than the Transactions); 

  
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 (iii) against any merger agreement or merger (other than the Merger
Agreement and the Merger), consolidation, combination, sale of substantial assets, reorganization, recapitalization, dissolution, liquidation or winding up of or by Acquiror; 

(iv) against any change in the business, management or Board of Directors of Acquiror (other than in connection with the
Acquiror Shareholder Matters); and 
 (v) against any proposal, action or agreement that would (A) impede, frustrate,
prevent or nullify any provision of this Sponsor Agreement, the Merger Agreement or any Merger, (B) result in a breach in any respect of any covenant, representation, warranty or any other obligation or agreement of Acquiror or Merger Sub under
the Merger Agreement, (C) result in any of the conditions set forth in Section 10.03 of the Merger Agreement not being fulfilled or (D) change in any manner the dividend policy or capitalization of, including the voting rights of any
class of capital stock of, Acquiror. 
 Each Sponsor hereby agrees that it shall not commit or agree to take any action inconsistent with
the foregoing. The obligations of each Sponsor specified in this Section 1.5 shall apply whether or not any Acquiror Change in Recommendation occurs. 

(b) Each Sponsor shall comply with, and fully perform all of its obligations, covenants and agreements set forth in, the Insider Letter,
including the obligations of the Sponsors pursuant to Section 3 therein to not redeem any Founder Shares owned by such Sponsor in connection with the transactions contemplated by the Merger Agreement, and each Sponsor hereby further agrees that
such Sponsor shall not redeem any Subject Securities owned by such Sponsor in connection with any shareholder approval of the Transactions and hereby waives any and all rights to elect or effect any Acquiror Shareholder Redemption arising in
connection with the Transactions. 
 (c) During the Interim Period, each Sponsor shall not modify or amend any Contract between or among
such Sponsor, anyone related by blood, marriage or adoption to such Sponsor or any Affiliate of such Sponsor (other than Acquiror or any of its Subsidiaries), on the one hand, and Acquiror or any of Acquiror’s Subsidiaries, on the other hand,
including, for the avoidance of doubt, the Insider Letter. 
 (d) Each Sponsor hereby agrees that such Sponsor shall waive, and hereby does
waive, any and all anti-dilution or similar rights (if any) that may otherwise be available under applicable Law or pursuant to any Contract between or among such Sponsor or any Affiliate of such Sponsor (other than Acquiror or any of its
Subsidiaries), on the one hand, and Acquiror or any of Acquiror’s Subsidiaries, on the other hand, with respect to the transactions contemplated by the Merger Agreement, including the PIPE Investment, and that it shall not take any action in
furtherance of exercising any such rights. 

  
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 (e) Each Sponsor hereby waives any and all rights to convert any loans, borrowings, notes
or other funds advanced by such Sponsor or any of its Affiliates to Acquiror or any of its Subsidiaries prior to the Closing (a “Working Capital Loan”) into warrants or other securities (derivative or otherwise) of any
Acquiror Party or the Company, including any and all rights to convert any such Working Capital Loans in accordance with the Insider Letter, any applicable warrant agreement, the Governing Documents of the Acquiror Parties or any other Contract, and
Acquiror take such necessary or appropriate actions within its power so as to ensure, that each and any Working Capital Loan shall be repaid solely in cash subject to, and upon the consummation of the Closing. 

(f) No Actions to Breach Agreement. No Sponsor shall take any action that would make any representation or warranty of such Sponsor contained
herein untrue or incorrect or have the effect of preventing or disabling such Sponsor from performing its obligations under this Sponsor Agreement. 

(g) Maintenance of Records. Each Sponsor hereby authorizes Acquiror and the Company to maintain a copy of this Agreement at either its
executive office or registered office. 
 (h) Update of Schedule I. If any Sponsor acquires record or beneficial ownership of any New
Securities during the Interim Period (or becomes aware, during the Interim Period, of its record or beneficial ownership of any Subject Securities, which securities are not already set forth on Schedule I), such Sponsor shall promptly notify the
Company and Acquiror in writing, and Schedule I shall be updated to reflect such Sponsor’s ownership of such New Securities or Subject Securities, as applicable. 

Section 1.6 No Inconsistent Agreement. Each Sponsor hereby represents and covenants that such Sponsor has not entered into, and
shall not enter into, any agreement that would restrict, limit or interfere with the performance of such Sponsor’s obligations hereunder. 

ARTICLE II 
 LOCK-UP AND VESTING 
 Section 2.1 Lock-Up.

 (a) Subject to Section 2.1(b), each Sponsor hereby agrees that such Sponsor shall not Transfer any Lock-up Shares until the end of the Lock-up Period (the “Lock-up”). 

(b) Notwithstanding the provisions set forth in Section 2.1(a), each Sponsor or its Permitted Transferees may Transfer the Lock-up Shares during the Lock-up Period (i) to (A) Acquiror’s officers or directors, (B) any Affiliates or family members of Acquiror’s officers or
directors, or (C) any members or partners of Sponsor Holdco or their Affiliates, any Affiliates of Sponsor Holdco, or any employees of such Affiliates; (ii) in the case of an individual, by gift to a member of such individual’s
immediate family or to a trust, the beneficiary of which is a member of such individual’s immediate family, an Affiliate of such individual or to a charitable organization; (iii) in the case of an individual, by virtue of laws of descent
and distribution upon death of such individual; (iv) in the case of an individual, pursuant to a qualified domestic relations order; (v) by virtue of the laws of the State of Delaware or the Sponsor Holdco’s limited liability company
agreement upon dissolution of the Sponsor; or (vi) 

  
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in the event of Acquiror’s liquidation, merger, capital stock exchange or other similar transaction which results in all of Acquiror’s stockholders having the right to exchange their
shares of Domesticated Acquiror Common Stock for cash, securities or other property subsequent to the Closing Date; provided, that each transferee contemplated by clauses (i) through (vii) (each, a “Permitted
Transferee”) must agree in writing to be bound by the Lock-up. 
 (c) The Lock-up in this Section 2.1 shall supersede the lock-up provisions contained in Section 5 of the Insider Letter, which provisions in
Section 5 of the Insider Letter shall be of no further force or effect. 
 (d) For purposes of this Section 2.1: 

(i) the term “Lock-up Period” means the period beginning on
the Closing Date (as defined in the Merger Agreement) and ending on the earlier to occur of (A) six months after the Closing Date, (B) such date that the closing price of Domesticated Acquiror Common Stock equals or exceeds $12.00 per
share (as adjusted for stock splits, stock dividends, reorganizations, recapitalizations and the like) for any 20 trading days within any period of 30 consecutive trading days commencing at least 90 calendar days following the Closing Date and
(C) the date on which Acquiror consummates a sale, merger, liquidation, exchange offer or other similar transaction after the Closing Date that results in the stockholders of Acquiror immediately prior to such transaction having beneficial
ownership of less than 50% of the outstanding voting securities of Acquiror, directly or indirectly, immediately following such transaction which results in its stockholders having the right to exchange their shares of Domesticated Acquiror Common
Stock for cash, securities or other property having a value that equals or exceeds $12.00 per share; 
 (ii) the term
“Lock-up Shares” means the Founder Shares and Founder Warrants (including the Founder Shares issuable upon exercise thereof) held by each Sponsor immediately following the Closing
(other than Domesticated Acquiror Common Stock acquired in the public market or pursuant to a transaction exempt from registration under the Securities Act of 1933, as amended, pursuant to a subscription agreement where the issuance of Domesticated
Acquiror Common Stock occurs on or after the Closing); provided, that, for clarity, Domesticated Acquiror Common Stock issued in connection with the PIPE Investment shall not constitute Lock-up Shares;

 (iii) the term “Permitted Transferees” means, prior to the expiration of the Lock-up Period, any person or entity to whom such Sponsor is permitted to transfer such Lock-up Shares prior to the expiration of the
Lock-up Period pursuant to Section 1.8(b); and 
 (iv) the
term “Insider Letter” means that certain Letter Agreement, dated March 1, 2021, by and among Acquiror, its current executive officers and directors, and Sponsor Holdco, as may be amended. 

Section 2.2 Vesting.  

  
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 (a) Each of the Sponsors agrees that, as of immediately prior to (but subject to) the
Closing, the Sponsor Vesting Shares shall be unvested and shall be subject to the vesting and forfeiture provisions set forth in this Section 2.2. 

(b) The Sponsor Vesting Shares shall vest (and shall not be subject to forfeiture) upon the occurrence of the Triggering Event. If the
Triggering Event does not occur on or prior to the expiration of the Vesting Period, the Sponsor Vesting Shares shall not vest, and shall be forfeited and deemed transferred by the forfeiting holder to Acquiror and shall be cancelled by Acquiror and
cease to exist. 
 (c) In the event that there is a Company Sale during the Vesting Period that will result in all of the holders of
Domesticated Acquiror Common Stock receiving a Company Sale Price, in the form of cash or marketable securities (or any combination thereof), that is at least equal to or in excess of the applicable Trading Threshold per share (a
“Triggering Company Sale”), then immediately prior to the consummation of such Triggering Company Sale, if the Triggering Event has not previously occurred, the Triggering Event shall be, and the related vesting conditions
with respect to the Sponsor Vesting Shares shall also be, deemed to have occurred upon the consummation of such Triggering Company Sale and the holders of such Sponsor Vesting Shares shall be eligible to participate in such Triggering Company Sale,
in each case, if and to the extent that the consideration paid per share of Domesticated Acquiror Common Stock in such Triggering Company Sale is at least equal to the applicable Trading Threshold per share. For avoidance of doubt, in the event
there is a Company Sale during the Vesting Period and the Triggering Event has not occurred prior to such Company Sale: (i) if the applicable Company Sale Price for acquisition of the Domesticated Acquiror Common Stock is greater than or equal
to $12.50 per share of Domesticated Acquiror Common Stock but less than $15.00 per share of Domesticated Acquiror Common Stock, the Sponsor Vesting Shares that are not Sponsor Redemption-Based Vesting Shares shall be deemed to have fully vested; and
(ii) if the applicable Company Sale Price for acquisition of the Domesticated Acquiror Common Stock is greater than or equal to $15.00 per share of Domesticated Acquiror Common Stock, all Sponsor Vesting Shares shall be deemed to have fully
vested. 
 (d) Subject to the limitations contemplated herein, the Sponsors shall have all of the rights of a stockholder of Acquiror with
respect to the Founder Shares, including the right to receive dividends and/or distributions made to the holders of Domesticated Acquiror Common Stock and to voting rights generally granted to holders of Domesticated Acquiror Common Stock;
provided, however, that, subject to Section 2.2(c), the unvested Sponsor Vesting Shares shall not entitle the holder thereof to consideration in connection with any sale or other transaction and may not be offered, sold,
transferred, redeemed, assigned, pledged, hypothecated, encumbered or otherwise disposed of (whether by operation of law or otherwise) by the Sponsors, as the case may be, or be subject to execution, attachment or similar process, and shall bear a
customary legend with respect to such transfer restrictions. Any attempt to so sell, transfer, assign, pledge, hypothecate, encumber or otherwise dispose of such unvested Sponsor Vesting Shares shall be null and void. 

  
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 (e) If, and as often as, there are any changes in Acquiror or the Founder Shares by way of
stock split, stock dividend, combination or reclassification, or through a Company Sale or other merger, consolidation, reorganization, recapitalization or business combination, or by any other means, equitable adjustment shall be made to the
provisions of this Sponsor Agreement (including, if applicable, the dollar amounts set forth in the definition of “Trading Threshold”) as may be required so that the rights, privileges, duties and obligations hereunder
(including the vesting rights with respect to the Sponsor Vesting Shares in this Section 2.2) shall continue with respect to Acquiror, Acquiror’s successor or the surviving entity of such transaction and the Founder Shares, each as so
changed. Each of the Sponsors will promptly inform the Company of any elections made by such Sponsor under Section 83(b) of the Internal Revenue Code in connection with the Closing with respect to Founder Shares held by such Sponsor. 

(f) Each Sponsor hereby agrees that, with respect to all of its unvested Founder Shares, such Founder Shares shall be present at all
stockholder meetings for purposes of a quorum and voted at all such meetings, or voted, consented or approved in any other circumstances, upon which such vote, consent or other approval (including providing any written consent as of any specified
date) is sought or obtained by or from the stockholders of Acquiror, in the same manner (including by voting “for” or “against,” abstaining or withholding votes) as, and in the same proportion to, the votes cast “for”
or “against,” and abstentions or vote withholdings made, in respect of all shares of Domesticated Acquiror Common Stock, held by the holders thereof (other than the unvested Founder Shares). 

(g) Any economic rights (including rights to dividends) of unvested Founder Shares shall be set aside for so long as such unvested Founder
Shares remain unvested. Should unvested Founder Shares become vested in accordance with subsection (c) above, such Founder Shares shall become entitled to all such economic rights that were set aside during the unvested period, including in the
form of a lump sum payment of all dividends that were set aside, together with interest on such set-aside dividends, at the prime rate published in The Wall Street Journal for the relevant date each such
dividend was set aside through the date of the lump sum payment. 
 (h) For purposes of this Section 2.2: 

(i) “Company Sale” means (which, for the avoidance of doubt, shall not include the Transactions): (x)
any transaction or series of related transactions following the Closing that results in any Person or “group” (within the meaning of Section 13(d)(3) of the Exchange Act) acquiring Equity Securities that represent more
than 50% of the total voting power of the then outstanding voting securities of Acquiror (or the equity interests of the surviving Person outstanding immediately after such transaction or transactions) or (y) a sale or disposition following the
Closing of all or substantially all of the assets of Acquiror and its Subsidiaries on a consolidated basis, in each case other than a transaction or series of related transactions which results in at least 50% of the combined voting power of the
then outstanding voting securities of Acquiror (or any successor to Acquiror) immediately following the closing of such transaction (or 

  
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series of related transactions) being beneficially owned, directly or indirectly, by individuals and entities (or Affiliates of such individuals and entities) who were the beneficial owners,
respectively, of Equity Securities representing more than 50% of the total voting power of the then outstanding voting securities of Acquiror immediately prior to such transaction (or series of related transactions). 

(ii) “Company Sale Price” means the price per share for Domesticated Acquiror Common Stock in a
Company Sale. In the event of a Company Sale of a type described in clause (y) of the definition thereof, or if and to the extent the price paid per share in a Company Sale includes any escrows, holdbacks, deferred purchase price, earnouts or
other contingent consideration, Acquiror’s Board of Directors shall determine the price paid per share of Domesticated Acquiror Common Stock in such Company Sale in good faith. If and to the extent the price is payable in whole or in part with
consideration other than cash, the price for such non-cash consideration shall be determined as follows: (x) with respect to any securities: (A) the average of the closing prices of the sales of the
securities on all securities exchanges on which the securities may at the time be listed averaged over a period of twenty-one (21) days consisting of the day as of which such value is being determined and
the twenty (20) consecutive business days prior to such day or (B) if the information in (A) is not practically available, the value of each such security shall be equal to the fair value thereof as of the date of valuation as
determined by an independent, nationally recognized investment banking firm to be appointed with the mutual approval of Acquiror and the Company on the basis of an orderly sale to a willing, unaffiliated buyer in an
arm’s-length transaction, taking into account all factors determinative of value as the investment banking firm determines relevant (and, in the case of clause (A) or (B), reduced by the amount of
any transfer Taxes payable in connection with such sale) and (y) with respect to any other non-cash assets, the fair value thereof as of the date of valuation as determined by an independent, nationally
recognized investment banking firm to be appointed with the mutual approval of Acquiror and the Company on the basis of an orderly sale to a willing, unaffiliated buyer in an arm’s-length transaction,
taking into account all factors determinative of value as the investment banking firm determines relevant (and reduced by the amount of any transfer Taxes payable in connection with such sale). 

(iii) “Promote Sponsor Vesting Shares” means 2,479,000 Founder Shares. 

(iv) “Redeemable Shares” means the issued and outstanding Acquiror Class A Ordinary Shares that
are entitled to exercise their right to cause Acquiror to redeem all of such Acquiror Class A Ordinary Shares pursuant to the Governing Documents of Acquiror, excluding, for the avoidance of doubt, any Class A Ordinary Shares that are
Subject Securities. 
 (v) “Sponsor Redemption-Based Vesting Shares” means a number of Founder
Shares (A) equal to 1,000,000 Founder Shares, if and only if holders of one hundred percent (100%) of the Redeemable Shares exercise their right to cause Acquiror to redeem such Redeemable Shares pursuant to the Governing Documents of Acquiror,
and the Transactions are consummated notwithstanding such Acquiror 

  
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Shareholder Redemption, (B) determined by straight-line interpolation between 1,000,000 Founder Shares with respect to one hundred percent (100%) redemption of the Redeemable Shares (at
which the number of Founder Shares subject to this clause (B) would be 1,000,000) and 0 Founder Shares with respect to redemptions of less than twenty percent (20%) of the Redeemable Shares, if and only if the holders of more twenty percent
(20%) of the Redeemable Shares exercise their right to cause Acquiror to redeem such Redeemable Shares pursuant to the Governing Documents of Acquiror but less than one hundred percent (100%) of the holders of Redeemable Shares exercise their right
to cause Acquiror to redeem all of such Redeemable Shares pursuant to the Governing Documents of Acquiror, and (C) 0 Founder Shares, if and only if the holders of twenty percent (20%) or less of the Redeemable Shares exercise their right to cause
Acquiror to redeem such Redeemable Shares pursuant to the Governing Documents of Acquiror. 
 (vi) “Sponsor
Vesting Shares” means the Promote Sponsor Vesting Shares and the Sponsor Redemption-Based Vesting Shares, if any. 

(vii) “Trading Day” means any day on which shares of Domesticated Acquiror Common Stock are actually
traded on the principal securities exchange or securities market on which shares of Domesticated Acquiror Common Stock are then traded. 

(viii) “Trading Threshold” means (A) in the case of the Promote Sponsor Vesting Shares, $12.50,
and (B) in the case of Sponsor Vesting Shares that are Sponsor Redemption-Based Vesting Shares, $15.00. 
 (ix)
“Triggering Event” means the date following the Closing but prior to the expiration of the Vesting Period on which the daily volume-weighted average sale price of one share of Domesticated Acquiror Common Stock quoted on NYSE
(or the exchange on which the shares of Domesticated Acquiror Common Stock are then listed) is, for the first time, greater than or equal to the applicable Trading Threshold for any twenty (20) Trading Days (which may or may not be consecutive)
within any thirty (30) consecutive Trading Day period within the Vesting Period; provided, that, for the avoidance of doubt, (i) any Trading Days that meet the applicable Trading Threshold for both Sponsor Redemption-Based Vesting
Shares and other Sponsor Vesting Shares will count towards the twenty (20) day threshold for each of the Sponsor Redemption-Based Shares and the other Sponsor Vesting Shares and (ii) a Triggering Event may occur with respect to both the
Sponsor Redemption-Based Vesting Shares and other Sponsor Vesting Shares at the same, or over some or all of the same period of, time. 

(x) “Vesting Period” means the period beginning at the Closing and ending on the fifth (5th)
anniversary of the Closing Date. 

  
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 ARTICLE III 

REPRESENTATIONS AND WARRANTIES 

Section 3.1 Representations and Warranties of the Sponsors. Each Sponsor represents and warrants as of the date hereof to Acquiror
and the Company (solely with respect to itself, himself or herself and not with respect to any other Sponsor) as follows: 
 (a)
Organization; Due Authorization. If such Sponsor is not an individual, it is duly organized, validly existing and in good standing under the Laws of the jurisdiction in which it is incorporated, formed, organized or constituted, and the
execution, delivery and performance of this Sponsor Agreement and the consummation of the transactions contemplated hereby are within such Sponsor’s corporate, limited liability company or organizational powers and have been duly authorized by
all necessary corporate, limited liability company or organizational actions on the part of such Sponsor. If such Sponsor is an individual, such Sponsor has full legal capacity, right and authority to execute and deliver this Sponsor Agreement and
to perform his or her obligations hereunder. This Sponsor Agreement has been duly executed and delivered by such Sponsor and, assuming due authorization, execution and delivery by the other parties to this Sponsor Agreement, this Sponsor Agreement
constitutes a legally valid and binding obligation of such Sponsor, enforceable against such Sponsor in accordance with the terms hereof subject to the Enforceability Exceptions. If this Sponsor Agreement is being executed in a representative or
fiduciary capacity, the Person signing this Sponsor Agreement has full power and authority to enter into this Sponsor Agreement on behalf of the applicable Sponsor. 

(b) Ownership. Such Sponsor is the record and beneficial owner (as defined in the Securities Act) of, and has good title to, all of
such Sponsor’s Subject Securities, and there exist no Liens or any other limitation or restriction (including any restriction on the right to vote, sell or otherwise dispose of such Subject Securities (other than transfer restrictions under the
Securities Act)) affecting any such Subject Securities, other than Liens pursuant to (i) this Sponsor Agreement, (ii) the Acquiror Governing Documents, (iii) the Merger Agreement or (iv) any applicable securities Laws. Such
Sponsor’s Subject Securities are the only equity securities in Acquiror owned of record or beneficially by such Sponsor on the date of this Sponsor Agreement. Other than the Founder Warrants, such Sponsor does not hold or own any rights to
acquire (directly or indirectly) any equity securities of Acquiror or any equity securities convertible into, or which can be exchanged for, equity securities of Acquiror. 

(c) Voting Rights. Such Sponsor (i) has the right to vote, dispose of and to issue instructions with respect to the matters set forth
herein, whether by ownership or by proxy, in each case, with respect to such Sponsor’s Subject Securities, (ii) has not entered into any voting agreement or voting trust that is inconsistent with such Sponsor’s obligations pursuant to
this Sponsor Agreement, (iii) has not granted a proxy or power of attorney with respect to any of such Sponsor’s Subject Securities that is inconsistent with such Sponsor’s obligations pursuant to this Agreement, and (iv) has not
entered into any agreement or undertaking that is otherwise inconsistent with, or would interfere with, or prohibit or prevent it from satisfying, its obligations pursuant to this Sponsor Agreement. None of such Sponsor’s Subject Securities are
subject to any proxy, voting trust or other agreement or arrangement with respect to the voting of such Subject Securities, except as provided hereunder and under the Insider Letter. 

  
 11 

 (d) Filings. Other than the filings, notices and reports pursuant to, in compliance with or
required to be made under the Exchange Act, no filings, notices, reports, consents, registrations, approvals, permits, waivers, expirations of waiting periods or authorizations are required to be obtained by such Stockholder from, or to be given by
such Sponsor to, or to be made by such Sponsor with, any Governmental Authority in connection with the execution, delivery and performance by such Sponsor of this Sponsor Agreement, the consummation of the transactions contemplated hereby or the
Transactions. 
 (e) No Conflicts. The execution and delivery of this Sponsor Agreement by such Sponsor does not, and the
performance by such Sponsor of his, her or its obligations hereunder will not, constitute or result in (i) a breach or violation of, or a default under, the Governing Documents of such Sponsor (if such Sponsor is not a natural person) or the
rights of such Sponsor’s spouse or domestic partner (if such Sponsor is a natural person and has a spouse or domestic partner, as applicable), (ii) with or without notice, lapse of time or both, a breach or violation of, a termination (or right
of termination) of or a default under, the loss of any benefit under, the creation, modification or acceleration of any obligations under or the creation of a Lien on any of the properties, rights or assets of such Sponsor pursuant to any Contract
binding upon such Sponsor or, assuming (solely with respect to performance of this Sponsor Agreement and the transactions contemplated hereby), compliance with the matters referred to in Section 3.1(d), under any applicable Law to which such
Stockholder is subject, (iii) any change in the rights or obligations of any party under any Contract legally binding upon such Sponsor or such Sponsor’s Subject Securities) or (iv) any violation of applicable Law, except, in the case
of clauses (ii), (iii) or (iv) directly above, for any such breach, violation, termination, default, creation, acceleration or change that would not, individually or in the aggregate, reasonably be expected to prevent or materially delay or
impair such Sponsor’s ability to perform its obligations under this Sponsor Agreement or to consummate the transactions contemplated hereby or the Transactions. 

(f) Litigation. There are no Actions pending against such Sponsor, or to the knowledge of such Sponsor threatened against such
Sponsor, before (or, in the case of threatened Actions, that would be before) any arbitrator or any Governmental Authority, which in any manner challenges or seeks to prevent, enjoin or materially delay the performance by such Sponsor of its, his or
her obligations under this Sponsor Agreement. 
 (g) Brokerage Fees. Except as described on Section 6.07 of the Acquiror
Disclosure Letter, no broker, finder, investment banker or other Person is entitled to any brokerage fee, finders’ fee or other commission in connection with the transactions contemplated by the Merger Agreement based upon arrangements made by
such Sponsor, for which Acquiror or any of its Affiliates may become liable. 
 (h) Affiliate Arrangements. Except as set forth on
Schedule II attached hereto, neither such Sponsor nor any anyone related by blood, marriage or adoption to such Sponsor or, to the knowledge of such Sponsor, any Person in which such Sponsor has a direct or indirect legal, contractual or
beneficial ownership of five percent (5%) or greater is party to, or has any rights with respect to or arising from, any Contract with Acquiror or its Subsidiaries. 

  
 12 

 (i) Loans and Advances. Such Sponsor represents and warrants that, as of the date
hereof, there are no outstanding Working Capital Loans. 
 (j) Acknowledgment. Such Sponsor understands and acknowledges that each
of Acquiror and the Company is entering into the Merger Agreement in reliance upon such Sponsor’s execution and delivery of this Sponsor Agreement. 

ARTICLE IV 

MISCELLANEOUS 

Section 4.1 Termination. This Sponsor Agreement and all of its provisions shall terminate and be of no further force or effect
upon the earliest of (a) the termination of the Merger Agreement in accordance with its terms in circumstances where the Closing does not occur, (b) if the Closing occurs, then the provisions set forth in ARTICLE I and ARTICLE III shall
terminate upon such Closing and the provisions set forth in ARTICLE II and this ARTICLE IV shall survive the Closing, and shall terminate upon the latter of (A) the expiration of the Lock-up Period and
(B) the earlier to occur of (I) the occurrence (or deemed occurrence) of a Triggering Event or Triggering Company Sale on or before the conclusion of the Vesting Period and (II) the conclusion of the Vesting Period, and upon such
termination, this Sponsor Agreement shall forthwith become void and have no further force or effect, without any liability on the part of any Party and (c) the written agreement of the Sponsor, Acquiror and the Company. Upon such termination of
this Sponsor Agreement, all obligations of the parties under this Sponsor Agreement will terminate, without any liability or other obligation on the part of any party hereto to any Person in respect hereof or the transactions contemplated hereby,
and no party hereto shall have any claim against another (and no person shall have any rights against such party), whether under contract, tort or otherwise, with respect to the subject matter hereof; provided, however, that the
termination of this Sponsor Agreement shall not relieve any party hereto from liability arising in respect of any breach of this Sponsor Agreement prior to such termination. Notwithstanding the foregoing, ARTICLE IV shall survive the termination of
this Sponsor Agreement. 
 Section 4.2 Governing Law. This Sponsor Agreement, and all claims or causes of action (whether in
contract or tort) that may be based upon, arise out of or relate to this Sponsor Agreement or the negotiation, execution or performance of this Sponsor Agreement (including any claim or cause of action based upon, arising out of or related to any
representation or warranty made in or in connection with this Sponsor Agreement) will be governed by and construed in accordance with the internal Laws of the State of Delaware applicable to agreements executed and performed entirely within such
State, including its statute of limitations, without giving effect to principles or rules of conflict of laws to the extent such principles or rules would require or permit the application of the Laws or statute of limitations of another
jurisdiction. 
 Section 4.3 CONSENT TO JURISDICTION AND SERVICE OF PROCESS; WAIVER OF JURY TRIAL. 

  
 13 

 (a) THE PARTIES TO THIS SPONSOR AGREEMENT SUBMIT TO THE EXCLUSIVE JURISDICTION OF THE STATE
COURTS LOCATED IN WILMINGTON, DELAWARE OR THE COURTS OF THE UNITED STATES LOCATED IN WILMINGTON, DELAWARE IN RESPECT OF THE INTERPRETATION AND ENFORCEMENT OF THE PROVISIONS OF THIS SPONSOR AGREEMENT AND ANY RELATED AGREEMENT, CERTIFICATE OR OTHER
DOCUMENT DELIVERED IN CONNECTION HEREWITH AND BY THIS SPONSOR AGREEMENT WAIVE, AND AGREE NOT TO ASSERT, ANY DEFENSE IN ANY ACTION FOR THE INTERPRETATION OR ENFORCEMENT OF THIS SPONSOR AGREEMENT AND ANY RELATED AGREEMENT, CERTIFICATE OR OTHER
DOCUMENT DELIVERED IN CONNECTION HEREWITH, THAT THEY ARE NOT SUBJECT THERETO OR THAT SUCH ACTION MAY NOT BE BROUGHT OR IS NOT MAINTAINABLE IN SUCH COURTS OR THAT THIS SPONSOR AGREEMENT MAY NOT BE ENFORCED IN OR BY SUCH COURTS OR THAT THEIR PROPERTY
IS EXEMPT OR IMMUNE FROM EXECUTION, THAT THE ACTION IS BROUGHT IN AN INCONVENIENT FORUM, OR THAT THE VENUE OF THE ACTION IS IMPROPER. SERVICE OF PROCESS WITH RESPECT THERETO MAY BE MADE UPON ANY PARTY TO THIS SPONSOR AGREEMENT BY MAILING A COPY
THEREOF BY REGISTERED OR CERTIFIED MAIL, POSTAGE PREPAID, TO SUCH PARTY AT ITS ADDRESS AS PROVIDED IN SECTION 3.8. 

(b) WAIVER OF TRIAL BY JURY. EACH PARTY HERETO HEREBY ACKNOWLEDGES AND AGREES THAT ANY CONTROVERSY WHICH MAY ARISE UNDER THIS SPONSOR
AGREEMENT IS LIKELY TO INVOLVE COMPLICATED AND DIFFICULT ISSUES, AND THEREFORE EACH SUCH PARTY HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT SUCH PARTY MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING
OUT OF OR RELATING TO THIS SPONSOR AGREEMENT OR THE TRANSACTIONS CONTEMPLATED BY THIS SPONSOR AGREEMENT. EACH PARTY CERTIFIES AND ACKNOWLEDGES THAT (I) NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED, EXPRESSLY OR
OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER, (II) EACH SUCH PARTY UNDERSTANDS AND HAS CONSIDERED THE IMPLICATIONS OF THIS WAIVER, (III) EACH SUCH PARTY MAKES THIS WAIVER
VOLUNTARILY AND (IV) EACH SUCH PARTY HAS BEEN INDUCED TO ENTER INTO THIS SPONSOR AGREEMENT BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION 3.3. 

Section 4.4 Assignment. This Sponsor Agreement and all of the provisions hereof will be binding upon and inure to the benefit of
the parties hereto and their respective heirs, successors and permitted assigns. Neither this Sponsor Agreement nor any of the rights, interests or obligations hereunder will be assigned (including by operation of law) without the prior written
consent of the parties hereto. 
 Section 4.5 Specific Performance. The Parties agree that irreparable damage (for which
monetary damages, even if available, would not be an adequate remedy) would occur, and that the Parties would not have any adequate remedy at law, in the event that any of the provisions of this Sponsor Agreement were not performed in accordance
with their specific 

  
 14 

 
terms or were otherwise breached. It is accordingly agreed that the Parties shall be entitled to specific performance, an injunction or injunctions, or other equitable relief to prevent breaches
or threatened breaches of this Sponsor Agreement and to enforce specifically the terms and provisions of this Sponsor Agreement, including each Sponsor’s obligations under Section 1.5(a), without proof of actual
damages or otherwise (and each Party hereby waives any requirement for the securing or posting of any bond in connection with such remedy), this being in addition to any other remedy to which they are entitled at Law or in equity. Each Party
acknowledges and agrees that the right of specific enforcement is an integral part of the transactions contemplated hereby and that, without such right, none of the Parties would have entered into this Sponsor Agreement. Each Party agrees that it
will not oppose the granting of specific performance and other equitable relief on the basis that the other Parties have an adequate remedy at Law. 

Section 4.6 Amendment. This Sponsor Agreement may not be amended, changed, supplemented, waived or otherwise modified or
terminated, except upon the execution and delivery of a written agreement executed by Acquiror, the Company and the Sponsor Holdco. 

Section 4.7 Severability. If any provision of this Sponsor Agreement is held invalid or unenforceable by any court of competent
jurisdiction, the other provisions of this Sponsor Agreement will remain in full force and effect. Any provision of this Sponsor Agreement held invalid or unenforceable only in part or degree will remain in full force and effect to the extent not
held invalid or unenforceable. 
 Section 4.8 Notices. All notices and other communications among the parties hereto shall be in
writing and shall be deemed to have been duly given (a) when delivered in person, (b) when delivered after posting in the United States mail having been sent registered or certified mail return receipt requested, postage prepaid,
(c) when delivered by FedEx or other nationally recognized overnight delivery service or (d) when e-mailed during normal business hours (and otherwise as of the immediately following Business Day),
addressed as follows: 
 If to Acquiror: 

Supernova Partners Acquisition Company II, Ltd. 

4301 50th Street, NW 

Suite 300, PMB 1044 

Washington, DC 20016 

Attn: Robert Reid, CEO; Michael S. Clifton, CFO 

E-mail: robert@supernovaspac.com; michael@supernovaspac.com 

with a copy to (which will not constitute notice): 

Latham & Watkins LLP 

555 Eleventh Street, NW 

Suite 1000 

  
 15 

 Washington, DC 20004-1304 

Attn: Nicholas P. Luongo; Ryan J. Maierson; Patrick H. Shannon 

E-mail: nick.luongo@lw.com; ryan.maierson@lw.com; patrick.shannon@lw.com 

If to the Company: 

RigettiHoldings, Inc. 

775 Heinz Avenue 

Berkeley, CA 94710 

Attention:    Chad Rigetti; Taryn Naidu; Rick Danis 

Email:         chad@rigetti.com; taryn@rigetti.com; rick@rigetti.com 

with a copy to (which shall not constitute notice): 

Cooley LLP 

55 Hudson Yards 

New York, NY 10001-2157 

Attention:    Adam Dinow; David Silverman; Rupa Briggs 

Email:          adinow@cooley.com; david.silverman@cooley.com;

 rbriggs@cooly.com 

If to a Sponsor: 

To such Sponsor’s address set forth in Schedule I 

with a copy to (which will not constitute notice): 

Latham & Watkins LLP 

555 Eleventh Street, NW 

Suite 1000 

Washington, DC 20004-1304 

Attn: Nicholas P. Luongo; Ryan J. Maierson; Patrick H. Shannon 

E-mail: nick.luongo@lw.com; ryan.maierson@lw.com; patrick.shannon@lw.com 

Section 4.9 Counterparts. This Sponsor Agreement may be executed in two or more counterparts (any of which may be delivered by
electronic transmission), each of which shall constitute an original, and all of which taken together shall constitute one and the same instrument. 

Section 4.10 Entire Agreement. This Sponsor Agreement and the agreements referenced herein constitute the entire agreement and
understanding of the parties hereto in respect of the subject matter hereof and supersede all prior understandings, agreements or representations by or among the parties hereto to the extent they relate in any way to the subject matter hereof. 

Section 4.11 Further Assurances. From time to time, at the Company’s request and without further consideration, each Sponsor
shall execute and deliver such additional documents and take all such further action as may be necessary or reasonably requested to effect the actions and consummate the Transactions and the transactions contemplated hereby. 

  
 16 

 Section 4.12 Mutual Release.  

(a) Effective as of the Closing, Acquiror, on behalf of itself and its Subsidiaries and its and their respective successors and assigns
(each, an “Acquiror Releasing Party”), hereby unconditionally and irrevocably forever releases and discharges each Sponsor and each of its Affiliates, and any past, present or future directors, managers, officers, employees,
Representatives, agents, lenders, investors, partners, principals, members, managers, direct or indirect shareholders or equityholders of any of the foregoing Persons, and the respective successors and assigns of the foregoing Persons (each, an
“Acquiror Released Party”), of and from, and hereby unconditionally and irrevocably waives, releases and discharges any and all proceedings, covenants, claims, liabilities, suits, judgments, accounts, actions and causes of
action of any kind or character whatsoever, known or unknown, suspected or unsuspected, in Contract, direct or indirect, primary or secondary, at Law or in equity, that such Acquiror Releasing Party ever had, now has or ever may have or claim to
have against any Acquiror Released Party, for or by reason of any matter, circumstance, event, action, inaction, omission, cause or thing arising at or prior to the Closing, or otherwise related to the
pre-Closing period; provided, that nothing contained in this Section 4.11(a) shall be construed as a waiver of any rights under (i) this Sponsor Agreement, (ii) any other
Transaction Agreement to which any Acquiror Releasing Party is party or (iii) with respect to any Acquiror Released Party who is a natural person, any indemnification, employment or other similar arrangements (including any such arrangement
providing for exculpation or advancement of expenses). Acquiror, on behalf of itself and the other Acquiror Releasing Parties, expressly waives all rights afforded by any statute which limits the effect of a release with respect to unknown claims,
and understands the significance of this release of unknown claims and waiver of statutory protection against a release, on behalf of itself and the other Acquiror Releasing Parties, of unknown claims, and acknowledges and agrees that this waiver is
an essential and material term of this Sponsor Agreement. Acquiror, on behalf of itself and each other Acquiror Releasing Party, acknowledges that each Sponsor will be relying on the waiver and release provided in this Section 4.11(a) in
connection with entering into this Sponsor Agreement and that this Section 4.11(a) is intended for the benefit of the Acquiror Released Parties and to grant third party beneficiary rights to each Acquiror Released Party to enforce this
Section 4.11(a). 
 (b) Effective as of the Closing, each Sponsor, on behalf of itself and its Subsidiaries and its and their
respective successors and assigns (each, a “Sponsor Releasing Party”), hereby unconditionally and irrevocably forever releases and discharges Acquiror and each of its Affiliates, and any past, present or future directors,
managers, officers, employees, Representatives, agents, lenders, investors, partners, principals, members, managers, direct or indirect shareholders or equityholders of any of the foregoing Persons, and the respective successors and assigns of the
foregoing Persons (each, a “Sponsor Released Party”), of and from, and hereby unconditionally and irrevocably waives, releases and discharges any and all proceedings, covenants, claims, liabilities, suits, judgments,
accounts, actions and causes of action of any kind or character whatsoever, known or unknown, suspected or unsuspected, in Contract, direct or indirect, primary or secondary, at Law or in equity, that such Sponsor Releasing Party ever had, now has
or ever may have or claim to have against any Sponsor 

  
 17 

 
Released Party, for or by reason of any matter, circumstance, event, action, inaction, omission, cause or thing arising at or prior to the Closing, or otherwise related to the pre-Closing period; provided, that nothing contained in this Section 4.11(b) shall be construed as a waiver of any rights under (i) this Sponsor Agreement, (ii) any other Transaction
Agreement to which such Sponsor or any of its associated Sponsor Releasing Parties is party, (iii) any indemnification, employment or other similar arrangements (including any such arrangement providing for exculpation or advancement of
expenses), (iv) any Affiliate Agreement set forth on Schedule II, or (v) any obligation to pay any Acquiror Expenses. Each Sponsor, on behalf of itself and each of its associated Sponsor Releasing Parties, expressly waives all rights afforded
by any statute which limits the effect of a release with respect to unknown claims, and understands the significance of this release of unknown claims and waiver of statutory protection against a release, on behalf of itself and its associated
Sponsor Releasing Parties, of unknown claims, and acknowledges and agrees that this waiver is an essential and material term of this Sponsor Agreement. Each Sponsor, on behalf of itself and each of its associated Sponsor Releasing Parties,
acknowledges that Acquiror will be relying on the waiver and release provided in this Section 4.11(b) in connection with entering into this Sponsor Agreement and that this Section 4.11(b) is intended for the benefit of the
Sponsor Released Parties and to grant third party beneficiary rights to each Sponsor Released Party to enforce this Section 4.11(b). 

Section 4.13 Disclosure. Each Sponsor hereby authorizes the Company and Acquiror to publish and disclose in any announcement or
disclosure relating to the Transactions, including any such announcement or disclosure required or requested by the SEC (or as otherwise required or requested pursuant to any applicable Laws or any other Governmental Authorities), such
Sponsor’s identity and ownership of the Subject Securities, the nature of such Sponsor’s obligations under this Agreement and a copy of this Sponsor Agreement, if reasonably deemed appropriate by Acquiror and the Company. Each Sponsor will
promptly provide any information reasonably requested in writing by Acquiror or the Company for any regulatory application or filing made or approval sought in connection with the transactions contemplated by the Merger Agreement (including filings
with the SEC). 
 [THE REMAINDER OF THIS PAGE IS INTENTIONALLY BLANK] 

  
 18 

 IN WITNESS WHEREOF, the Sponsors, Acquiror, and the Company have each caused this Sponsor
Support Agreement to be duly executed as of the date first written above. 
  

			
	SPONSORS:
	
	SUPERNOVA PARTNERS II LLC
		
	By:	 	/s/ Michael Clifton
		 	Name: Michael Clifton
		 	Title: Chief Financial Officer

 
	
	
	/s/ Spencer M. Rascoff
	Name: Spencer M. Rascoff

 
	
	
	/s/ Alexander M. Klabin
	Name: Alexander M. Klabin

 
	
	
	/s/ Robert D. Reid
	Name: Robert D. Reid

 
	
	
	/s/ Michael S. Clifton
	Name: Michael S. Clifton

  
 [Signature Page to
Sponsor Support Agreement] 

 
			
	ACQUIROR:
	
	SUPERNOVA PARTNERS ACQUISITION COMPANY II, LTD.
		
	By:	 	/s/ Michael Clifton
		 	Name: Michael Clifton
		 	Title: Chief Financial Officer

  
 [Signature Page to
Sponsor Support Agreement] 

 
			
	COMPANY:
	
	RIGETTI HOLDINGS, INC.
		
	By:	 	/s/ Rick Danis
		 	Name: Rick Danis
		 	Title: Secretary

  
 [Signature Page to
Sponsor Support Agreement] 

 Schedule I 

Sponsor Founder Shares and Founder Warrants 
  

									
	 Sponsor
	  	Acquiror Class B Ordinary
Shares	 	 	Acquiror Warrants	 
	 Supernova Partners II LLC
  

4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016
	  	 	8,418,000	 	 	 	4,450,000	 
	 Spencer M. Rascoff
  

c/o Supernova Partners II LLC

4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016
	  	 	—   	(1) 	 	 	—   	(1) 
	 Alexander M. Klabin
  

c/o Supernova Partners II LLC

4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016
	  	 	—   	(1) 	 	 	—   	(1) 
	 Robert D. Reid
  

c/o Supernova Partners II LLC

4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016
	  	 	—   	(1) 	 	 	—   	(1) 
	 Michael S. Clifton
  

c/o Supernova Partners II LLC

4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016
	  	 	—   	(1) 	 	 	—   	(1) 

  

	(1)	 Messrs. Rascoff, Klabin, Reid and Clifton are among the members of Supernova Partners II LLC and share voting
and investment discretion with respect to the ordinary shares held of record by Supernova Partners II LLC. Each of Messrs. Rascoff, Klabin, Reid and Clifton disclaims any beneficial ownership of the securities held by Supernova Partners II LLC other
than to the extent of any pecuniary interest he may have therein, directly or indirectly. 

  
 [Schedule I to Sponsor
Support Agreement] 

 Schedule II 

Affiliate Agreements 
  

	 	1.	 Registration Rights Agreement, dated March 1, 2021, by and among Acquiror, Sponsor Holdco and certain
other security holders named therein 

  

	 	2.	 Letter Agreement, dated March 1, 2021, by and among Acquiror, its current executive officers and directors
and Sponsor Holdco, as may be amended 

  

	 	3.	 Private Placement Warrants Purchase Agreement, dated March 1, 2021, by and between Acquiror and Sponsor
Holdco 

  

	 	4.	 Promissory Note, dated December 22, 2020, by and between Acquiror and Sponsor Holdco

  

	 	5.	 Indemnity Agreements, dated March 1, 2021, by and between Acquiror and each of the following:

  

	 	a.	 Jim Lanzone 

  

	 	b.	 Rajeev Singh 

  

	 	c.	 Spencer Rascoff 

  

	 	d.	 Robert Reid 

  

	 	e.	 Katie Curnutte 

  

	 	f.	 Gregg Renfrew 

  

	 	g.	 Ken Fox 

  

	 	h.	 Damien Hooper-Campbell 

 

	 	i.	 Michael Clifton 

  

	 	j.	 Alexander Klabin 

  
 [Schedule II to Sponsor
Support Agreement]EX-10.4

 Exhibit 10.4 

COMPANY HOLDERS SUPPORT AGREEMENT 

This Company Holders Support Agreement (this “Agreement”), dated as of October 6, 2021, is entered into by and among
Supernova Partners Acquisition Company II, Ltd., a Cayman Islands exempted company which shall domesticate as a Delaware corporation prior to the Closing in accordance with the Merger Agreement (such entity, including the continuing corporation,
“Acquiror”), Rigetti Holdings, Inc., a Delaware corporation (the “Company”), and certain of the stockholders of the Company, whose names appear on the signature pages of this Agreement (such
stockholders, the “Stockholders”, and Acquiror, the Company and the Stockholders, each a “Party”, and collectively, the “Parties”). 

RECITALS 
 WHEREAS,
concurrently herewith, Acquiror, Supernova Merger Sub, Inc., a Delaware corporation (“First Merger Sub”), Supernova Romeo Merger Sub, LLC, a Delaware limited liability company (“Second Merger Sub” and,
together with First Merger Sub, “Merger Subs” and each, a “Merger Sub”), and the Company, are entering into an Agreement and Plan of Merger (as amended, supplemented, restated or otherwise modified
from time to time, the “Merger Agreement”; capitalized terms used but not otherwise defined in this Agreement shall have the meanings ascribed to them in the Merger Agreement), pursuant to which, among other transactions,
(i) Acquiror will domesticate as a Delaware corporation, (ii) First Merger Sub will merge with and into the Company (the “First Merger”), with the Company surviving such First Merger as a wholly owned subsidiary of
Acquiror, and (iii) immediately following the First Merger and as part of the same overall transaction as the First Merger, the Company will merge with and into Second Merger Sub (the “Second Merger” and, together with
the First Merger, the “Mergers”), with the Second Merger Sub surviving such Second Merger as a wholly owned subsidiary of Acquiror, subject to the terms and conditions set forth therein; 

WHEREAS, as of the date hereof, each Stockholder is the sole record owner and “beneficial owner” (as such term is used
herein, within the meaning of Rule 13d-3 under the Securities Exchange Act of 1934, as amended (together with the rules and regulations promulgated thereunder, the “Exchange Act”)) of,
and has the sole power to dispose of and vote (or direct the voting of), the number, class and series of shares of Company Stock set forth opposite such Stockholder’s name on Schedule 1 attached hereto (such shares, together with
(1) any shares of Company Stock (or any securities convertible into or exercisable or exchangeable for Company Stock) of which such Stockholder has record or beneficial ownership as of the date hereof and that are not reflected on Schedule
1, (2) any additional shares of Company Stock (or any securities convertible into or exercisable or exchangeable for shares of Company Stock) of which such Stockholder acquires record or beneficial ownership after the date hereof, including by
Transfer (as defined below), purchase, as a result of a stock dividend, stock split, recapitalization, combination, reclassification, exchange or change of such shares, or upon exercise or conversion of any securities, and (3) any additional
shares of Company Stock with respect to which such Stockholder has the right to vote through a proxy or otherwise, such Stockholder’s “Covered Shares”); 

 WHEREAS, the Stockholders agree to take all action necessary to terminate, subject to
and effective immediately prior to the Closing, each of the following agreements (to the extent the Stockholder is party thereto): (i) that certain Amended and Restated Investors’ Rights Agreement, dated as of February 18, 2020, by and
among the Company as assignee of Rigetti & Co, Inc., a Delaware corporation (“Rigetti”), the Investors and the Key Holders (each as defined therein); (ii) that certain Amended and Restated Voting Agreement, dated as
of February 18, 2020, by and among the Company as assignee of Rigetti, the Investors and the Common Holders (each as defined therein); (iii) that certain Amended and Restated Right of First Refusal and
Co-Sale Agreement, dated as of February 18, 2020, by and among the Company as assignee of Rigetti, the Investors, the Legacy Converted Investors and the Common Holders (each as defined therein); and
(iv) each of the other investment agreements identified on Section 5.25 of the Company Disclosure Letter (such agreements described in clauses (i)-(iv), collectively, the “Investment Agreements”); and 

WHEREAS, as a condition and inducement to the willingness of Acquiror to enter into the Merger Agreement, the Company and the
Stockholders are entering into this Agreement. 
 AGREEMENT 

NOW, THEREFORE, in consideration of the foregoing and the mutual covenants and agreements herein contained, and intending to be legally
bound hereby, Acquiror, the Company and each Stockholder hereby agree as follows: 
 1. Agreement to Vote. Prior to the Termination
Date (as defined below), each Stockholder, solely in his, her or its capacity as a stockholder or proxy holder of the Company, irrevocably and unconditionally agrees to validly execute and deliver to the Company in respect of all of the
Stockholder’s Covered Shares entitled to vote or consent on matters put to a vote or consent, as applicable, of the Company’s stockholders (such Covered Shares, each Stockholder’s “Voting Covered Shares”), as
soon as reasonably practicable after the Registration Statement is declared effective under the Securities Act, and in any event within forty-eight (48) hours thereafter, a written consent in respect of all of the Stockholder’s Voting
Covered Shares approving the Merger Agreement and the Transactions. In addition, prior to the Termination Date, each Stockholder, in his, her or its capacity as a stockholder or proxy holder of the Company, irrevocably and unconditionally agrees
that (i) it shall, and shall cause each other holder of record of any of such Stockholder’s Voting Covered Shares to, take any and all actions necessary or reasonably requested by Acquiror or the Company in order to effect the conversion,
effective as of immediately prior to and conditioned upon the Closing, of all of the outstanding shares of Company Preferred Stock into Company Common Stock pursuant to the terms of the Governing Documents of the Company, including, without
limitation, approval, execution and delivery of a written request for such conversion pursuant to Section 4(b) of Article V thereof, and (ii) at any meeting of the stockholders of the Company (whether annual or special and whether or not
an adjourned or postponed meeting, however called and including any adjournment or postponement thereof) and in connection with any written consent of stockholders of the Company, such Stockholder shall, and shall cause each other holder of record
of any of such Stockholder’s Voting Covered Shares to: 
 (a) when such meeting is held, appear at such meeting or otherwise cause the
Stockholder’s Voting Covered Shares to be counted as present thereat for the purpose of establishing a quorum; 

  
 2 

 (b) vote (or execute and return an action by written consent), or cause to be voted at such
meeting (or validly execute and return and cause such consent to be granted with respect to), all of such Stockholder’s Voting Covered Shares owned as of the record date for such meeting (or the date that any written consent is executed by such
Stockholder) in favor of the Transactions and the adoption of the Merger Agreement and any other matters necessary or reasonably requested by the Company or Acquiror for consummation of the Transactions; 

(c) in any other circumstances upon which a consent or other approval is required under the Company’s Governing Documents or the
Investment Agreements or otherwise sought with respect to the Merger Agreement or the Transactions, including the Merger, vote, consent or approve (or cause to be voted, consented or approved) all of such Stockholder’s Voting Covered Shares in
favor thereof; and 
 (d) vote (or execute and return an action by written consent), or cause to be voted at such meeting (or validly
execute and return and cause such consent to be granted with respect to), all of such Stockholder’s Voting Covered Shares against (i) any Acquisition Transaction or any proposal relating to an Acquisition Transaction (in each case, other
than the Transactions); (ii) any merger agreement or merger (other than the Merger Agreement and the Merger), consolidation, combination, sale of substantially all assets, reorganization, recapitalization, dissolution, liquidation or winding up of
or by the Company; and (iii) any proposal, action or agreement that would (A) impede, frustrate, prevent or nullify any provision of this Agreement, the Merger Agreement or the Merger, (B) result in a breach in any respect of any
covenant, representation, warranty or any other obligation or agreement of the Company under the Merger Agreement or (C) result in any of the conditions set forth in Article X of the Merger Agreement not being fulfilled. 

The obligations of each Stockholder specified in this Section 1 shall apply whether or not the Transactions are
recommended by the Board of Directors of the Company or the Board of Directors of the Company has previously recommended the Transactions but changed such recommendation. 

2. No Inconsistent Agreements. Each Stockholder hereby covenants and agrees that such Stockholder shall not (i) enter into any
voting agreement, voting trust or other agreement with respect to any of such Stockholder’s Covered Shares that is inconsistent with such Stockholder’s obligations pursuant to this Agreement, (ii) grant a proxy, power of attorney or
similar right with respect to any of such Stockholder’s Covered Shares that is inconsistent with such Stockholder’s obligations pursuant to this Agreement, or (iii) enter into any other agreement or undertaking that is otherwise
inconsistent with, or would reasonably be expected to interfere with, or would reasonably be expected to prohibit or prevent it from satisfying, its obligations pursuant to this Agreement. 

  
 3 

 3. Termination; Non-Survival of Representations
and Warranties. 
 (a) This Agreement shall terminate upon the earlier to occur of (i) the Closing and (ii) the termination of
the Merger Agreement in accordance with its terms in circumstances where the Closing does not occur (the earlier such date under clause (i) or (ii) being referred to herein as the “Termination Date”), and upon such
termination, this Agreement shall forthwith become void and have no further force or effect, without any liability on the part of any Party; provided, that (A) no such termination shall relieve any Party of any liability for its pre-termination fraud or material breach of this Agreement, (B) this Section 3(a), Section 5(d), Section 5(e), Section 5(f), Section 5(h),
Section 7, and Sections 9 through 21 shall survive any such termination and (C) Section 5(c) shall survive any such termination under clause (i) above until the expiration of the Lock-Up Period (as defined in the Domestication Bylaws). 
 (b) None of the representations or warranties
contained in this Agreement or in any certificate or other writing delivered pursuant hereto shall survive the Closing. 
 4.
Representations and Warranties of the Stockholders. Each Stockholder hereby represents and warrants (severally and not jointly and as to itself only) to Acquiror and the Company as follows: 

(a) Such Stockholder is the sole record owner and beneficial owner (within the meaning of Rule 13d-3
under the Exchange Act) of, and has good, valid and marketable title to, or has a valid proxy to vote, such Stockholder’s Covered Shares, free and clear of any Liens (other than as created by this Agreement or the Governing Documents of the
Company (including, for the purposes hereof, any agreements between or among stockholders of the Company and the Investment Agreements)). As of the date hereof, other than the Covered Shares set forth opposite such Stockholder’s name on
Schedule 1, such Stockholder does not own beneficially or of record any shares of Company Stock (or any securities convertible into shares of Company Stock) or any interest therein. 

(b) Such Stockholder, in each case except as provided in this Agreement or, before giving effect to Section 5(i), the Investment
Agreements or the Governing Documents of the Company, (i) has the right to vote, dispose of and to issue instructions with respect to the matters set forth herein, whether by ownership or by proxy, in each case, with respect to such
Stockholder’s Covered Shares, (ii) has not entered into any voting agreement or voting trust that is inconsistent with such Stockholder’s obligations pursuant to this Agreement, (iii) has not granted a proxy or power of attorney
with respect to any of such Stockholder’s Covered Shares that is inconsistent with such Stockholder’s obligations pursuant to this Agreement, and (iv) has not entered into any agreement or undertaking that is otherwise inconsistent
with, or would interfere with, or prohibit or prevent it from satisfying, its obligations pursuant to this Agreement. 
 (c) Such
Stockholder affirms that (i) if the Stockholder is a natural person, he or she has all the requisite power and authority and has taken all action necessary in order to execute and deliver this Agreement, to perform his or her obligations
hereunder and to consummate the transactions contemplated hereby, and (ii) if the Stockholder is not a natural person, it (A) is a legal entity duly organized, validly existing and, to the extent such concept is applicable, in good
standing under the Laws of the jurisdiction of its organization, and (B) has all 

  
 4 

 
requisite corporate or other power and authority to, and has taken all corporate or other action necessary in order to, execute, deliver and perform its obligations under this Agreement and to
consummate the transactions contemplated hereby. This Agreement has been duly executed and delivered by such Stockholder and, subject to the due execution and delivery of this Agreement by each of the Company and Acquiror, constitutes a legally
valid and binding agreement of such Stockholder enforceable against such Stockholder in accordance with the terms hereof subject to the Enforceability Exceptions. 

(d) Other than the filings, notices and reports pursuant to, in compliance with or required to be made under the Exchange Act, no filings,
notices, reports, consents, registrations, approvals, permits, waivers, expirations of waiting periods or authorizations are required to be obtained by such Stockholder from, or to be given by such Stockholder to, or to be made by such Stockholder
with, any Governmental Authority in connection with the execution, delivery and performance by such Stockholder of this Agreement, the consummation of the transactions contemplated hereby or the Transactions. 

(e) The execution, delivery and performance of this Agreement by such Stockholder does not, and the consummation of the transactions
contemplated hereby and the Transactions will not, constitute or result in (i) a breach or violation of, or a default under, the Governing Documents of such Stockholder (if such Stockholder is not a natural person) or the rights of such
Stockholder’s spouse or domestic partner (if such Stockholder is a natural person and has a spouse or domestic partner, as applicable), (ii) with or without notice, lapse of time or both, a breach or violation of, a termination (or right of
termination) of or a default under, the loss of any benefit under, the creation, modification or acceleration of any obligations under or the creation of a Lien on any of the properties, rights or assets of such Stockholder pursuant to any Contract
binding upon such Stockholder or, assuming (solely with respect to performance of this Agreement and the transactions contemplated hereby), compliance with the matters referred to in Section 4(d), under any applicable Law to which such
Stockholder is subject, (iii) any change in the rights or obligations of any party under any Contract legally binding upon such Stockholder or (iv) any violation of applicable Law, except, in the case of clauses (ii), (iii) or
(iv) directly above, for any such breach, violation, termination, default, creation, acceleration or change that would not, individually or in the aggregate, reasonably be expected to prevent or materially delay or impair such
Stockholder’s ability to perform its obligations hereunder or to consummate the transactions contemplated hereby or the Transactions. 

(f) As of the date of this Agreement, there is no Action pending against such Stockholder or, to the knowledge of such Stockholder, threatened
against such Stockholder that, in any manner, questions the beneficial or record ownership of the Stockholder’s Covered Shares or the validity of this Agreement, or challenges or seeks to prevent, enjoin or materially delay the performance by
such Stockholder of its obligations under this Agreement. 
 (g) Such Stockholder is a sophisticated investor and has adequate information
concerning the business and financial condition of Acquiror and the Company to make an informed decision regarding this Agreement and the Transactions and has independently and based on such information as the Stockholder has deemed appropriate made
its own analysis and decision to enter into this Agreement. Such Stockholder acknowledges that Acquiror and the Company have not made and do not make any representation or warranty, whether express or implied, of any kind or character. Such
Stockholder acknowledges that the agreements contained herein are irrevocable. 

  
 5 

 (h) Such Stockholder understands and acknowledges that Acquiror is entering into the Merger
Agreement in reliance upon such Stockholder’s execution and delivery of this Agreement and the representations, warranties, covenants and other agreements of such Stockholder contained herein. 

(i) No investment banker, broker, finder or other intermediary is entitled to any broker’s, finder’s, financial advisor’s or
other similar fee or commission for which Acquiror or the Company is or could be liable in connection with the Merger Agreement or this Agreement or any of the respective transactions contemplated hereby or thereby, in each case based upon
arrangements made by or on behalf of such Stockholder in his, her or its capacity as a stockholder of the Company. 
 5. Certain
Covenants of the Stockholders. Except in accordance with the terms of this Agreement, each Stockholder hereby covenants and agrees as follows: 

(a) No Transfers Prior to Termination Date. Each Stockholder shall not, prior to the Termination Date (except, in each case, pursuant to
the Merger Agreement), (i) directly or indirectly sell, transfer, hypothecate, pledge, encumber, assign, hedge, swap, convert or otherwise dispose of (including by merger (including by conversion into securities or other consideration), by tendering
into any tender or exchange offer, by testamentary disposition, by operation of Law or otherwise), either voluntarily or involuntarily, any of its Covered Shares, (ii) enter into any Contract or option with respect to any transaction specified
in clause (i) or any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any of its Covered Shares, whether any such transaction is to be settled by delivery of such
securities, in cash or otherwise, or (iii) publicly announce any intention to effect any transaction specified in clauses (i) or (ii) (any transaction specified in clauses (i), (ii) or (iii), a “Transfer”);
provided, however, that the foregoing shall not restrict Transfers (I) to (w) such Stockholder’s officers or directors, (x) any affiliates or family members of such Stockholder’s officers or directors, (y) any
members or partners of such Stockholder or their affiliates, any affiliates of such Stockholder, or any employees of such affiliates; (z) to another Stockholder of the Company that is a party to this Agreement and bound by the terms and
obligations hereof, (II) in the case of an individual, by gift to a member of such individual’s immediate family or to a trust, the beneficiary of which is a member of such individual’s immediate family, an affiliate of such
individual or to a charitable organization; (III) in the case of an individual, by virtue of laws of descent and distribution upon death of such individual; or (IV) in the case of an individual, pursuant to a qualified domestic relations
order (a “Permitted Transfer”); provided, further, that any Permitted Transfer shall be permitted only if, as a precondition to such Transfer, the transferee agrees in a writing, reasonably satisfactory in form
and substance to Acquiror, to assume all of the obligations of the transferring Stockholder under, and be bound by all of the terms of, this Agreement; provided, further, that any Transfer permitted under this Section 5(b) shall not
relieve the transferring Stockholder of its obligations under this Agreement. Any Transfer in violation of this Section 5(b) shall be null and void. 

  
 6 

 (b) Post-Closing Lock-Up. Each Stockholder
hereby acknowledges that it has read the Domestication Bylaws, including Section 42 thereof, and understands that such section provides that certain of such Stockholder’s Covered Shares will be subject to Transfer restrictions (i.e., a “lock-up”) following the Closing, as and to the extent set forth therein. Accordingly, each Stockholder hereby agrees to be bound by and comply with Section 42 of the Domestication Bylaws as if such
section was set forth herein and made a part hereof. Notwithstanding anything to the contrary herein, to the extent the Board of Directors of Acquiror waives or repeals, or otherwise relaxes, any of the
lock-up restrictions set forth in Section 42 of the Domestication Bylaws (whether acting pursuant to Section 42 of the Domestication Bylaws or otherwise), such lock-up
restrictions shall be identically waived, repealed or relaxed, as applicable, with respect to the Stockholders. 
 (c) No Actions to
Breach Agreement. Each Stockholder shall not take any action that would make any representation or warranty of such Stockholder contained herein untrue or incorrect or have the effect of preventing or disabling such Stockholder from performing
its obligations under this Agreement. 
 (d) Maintenance of Records. Each Stockholder hereby authorizes Acquiror and the Company to
maintain a copy of this Agreement at either its executive office or registered office. 
 (e) Binding Effect of Merger Agreement.
Each Stockholder hereby acknowledges that it has read the Merger Agreement and this Agreement and has had the opportunity to consult with its tax, legal and other advisors with respect thereto and hereto. Each Stockholder shall be bound by and
comply with Section 9.04(a) (Exclusivity) and Section 9.06 (Confidentiality; Publicity) of the Merger Agreement (and any relevant definitions contained in any such sections) as if such Stockholder was an original signatory to
the Merger Agreement with respect to such provisions and each reference to the Company in such provision referred to such Stockholder. 

(f) Closing Date Deliverables. On the Closing Date, each Stockholder that is requested by the Company to execute the Registration
Rights Agreement shall deliver to Acquiror and the Company a duly executed copy of the Registration Rights Agreement, in substantially the form attached as Exhibit C to the Merger Agreement. 

(g) No Challenges; Waiver of Appraisal Rights. Each Stockholder shall not commence, join in, facilitate, assist or encourage, and shall
take all actions necessary to opt out of any class in any class action with respect to, any claim, derivative or otherwise, against any of the Acquiror Parties, the Company, the Sponsor, any of their respective Affiliates or any of the respective
Representatives (including directors, officers and employees) of the foregoing Persons, or any of the respective successors or assigns of any of the foregoing Persons, challenging the validity of, or seeking to enjoin the operation of, any provision
of this Agreement or alleging a breach of any fiduciary duty of any Person in connection with the evaluation, negotiation or entry into the Merger Agreement or any other Transaction Agreement or the consummation of the Transactions. Each Stockholder
hereby irrevocably and unconditionally waives, and agrees not to assert, exercise or perfect (or attempt to exercise, assert or perfect), any rights of appraisal or rights to dissent from the Merger or appraisal or dissenters’ rights that it
may at any time have under applicable Laws, including Section 262 of the DGCL. 

  
 7 

 (h) Termination of Affiliate Agreements and Certain Other Agreements. Each
Stockholder, by this Agreement with respect to its Covered Shares, severally and not jointly, hereby agrees to take all action necessary to terminate, subject to and effective immediately prior to the Closing, (a) all Affiliate Agreements to
which such Stockholder is party (including the Investment Agreements) other than those that are set forth on Section 7.07 of the Company Disclosure Letter (a redacted version of which, showing only the surviving Affiliate Agreements applicable
to such Stockholder, has previously been reviewed by such Stockholder); (b) all Investment Agreements to which such Stockholder or its Affiliates is a party; and (c) any rights under any letter or agreement providing for redemption rights, put
rights, purchase rights or other similar rights not generally available to stockholders of the Company. The Company and each Stockholder hereby waives any right to notice, right to consent to transfer, right of first offer, right of first refusal or
similar rights with respect to the disposition of any shares of Company Stock in the Transaction, in each case that such Stockholder may have under any Investment Agreements or under the Company’s Organizational Documents. 

(i) Acknowledgment of Treatment of Company Warrants. Each Stockholder, to the extent such Stockholder is a holder of Company Warrants,
acknowledges and agrees to the treatment of Company Warrants as described in Section 3.05 of the Merger Agreement. 
 (j) Release of
Claims. Effective as of, and conditioned upon occurrence of, the Closing, each Stockholder, for itself and on behalf of each of its Affiliates and each of their respective successors (each, a “Releasing Party”), hereby unequivocally,
voluntarily, knowingly, willingly, unconditionally, completely and, irrevocably releases, acquits, exculpates and forever waives and relinquishes all claims, suits, debts, demands, liabilities, setoffs, counterclaims, actions, manners of action and
causes of action of whatever kind or nature, whether known or unknown (collectively, “Claims”), which any Releasing Party has, may have or might have or may assert now or in the future, against the Company and its Subsidiaries and their
respective Representatives (in each case, solely in their capacity as such), successors and permitted assigns, and, after the Closing, the Acquiror and its Subsidiaries, and each of their respective officers, directors, owners, partners, managers or
employees (in each case, solely in their capacity as such) (collectively, the “Released Parties”) to the extent arising out of, based upon or resulting from any Contract, transaction, event, circumstance, action, failure to act or
occurrence of any sort or type, whether known or unknown, and which, in each and every case, occurred, existed, was taken, permitted, incurred or begun at or prior to the Closing, in each case solely with regard to the Company, the business or
operations of the Company prior to the Closing or the Transactions; provided, that nothing contained in this Section 5(j) shall be construed as a waiver of any rights under (i) this Agreement, (ii) any other Transaction
Agreement to which any Releasing Party is party, (iii) if such Stockholder is an employee of the Company, rights to accrued but unpaid salary, bonuses, expense reimbursements (in accordance with Company’s employee expense reimbursement
policy), accrued vacation and other benefits under the Company’s employee benefit plans, or (iv) any indemnification, employment or other similar arrangements (including any such arrangement providing for exculpation or advancement of
expenses), including any rights to indemnification, exculpation, advancement of expense or similar rights set forth in the Governing Documents of the Company, any indemnification agreement between the Company and such Stockholder, or as provided by
law or any directors’ and officers’ liability insurance. 

  
 8 

 (k) Update of Schedule 1. If any Stockholder acquires record or beneficial ownership
of any Covered Shares following the date hereof (or becomes aware, following the date hereof, of its record or beneficial ownership of any Covered Shares as of the date hereof, which shares are not already set forth on Schedule 1), such
Stockholder shall promptly notify the Company and Acquiror in writing (email being sufficient), and Schedule 1 shall be updated to reflect such Stockholder’s ownership of such additional Covered Shares. 

6. Further Assurances. From time to time, at Acquiror’s request and without further consideration, each Stockholder shall execute
and deliver such additional documents and take all such further action as may be necessary or reasonably requested to effect the actions and consummate the Transactions and the transactions contemplated hereby. 

7. Disclosure. Such Stockholder hereby authorizes the Company and Acquiror to publish and disclose in any announcement or disclosure
relating to the Transactions, including any such announcement or disclosure required or requested by the SEC (or as otherwise required or requested pursuant to any applicable Laws or any other Governmental Authorities), such Stockholder’s
identity and ownership of the Covered Shares and the nature of such Stockholder’s obligations under this Agreement and, a copy of this Agreement, if deemed appropriate by Acquiror and the Company. Each Stockholder will promptly provide any
information reasonably requested in writing by Acquiror or the Company for any regulatory application or filing made or approval sought in connection with the transactions contemplated by the Merger Agreement (including filings with the SEC). 

8. Changes in Company Stock. In the event (i) of a stock split, stock dividend or distribution, or any change in Company Stock by
reason of any split-up, reverse stock split, recapitalization, combination, reclassification, exchange of shares or the like, (ii) the Stockholder purchases or otherwise acquires beneficial ownership of
any Company Stock or (iii) the Stockholder acquires the right to vote or share in the voting of any Company Stock, the term “Covered Shares” shall be deemed to refer to and include such shares as well as all such stock
dividends and distributions and any securities into which or for which any or all of such shares may be changed or exchanged or which are received in such transaction. 

9. Amendment and Modification. This Agreement may not be amended, modified or supplemented in any manner, whether by course of conduct
or otherwise, except by an instrument in writing signed by Acquiror, the Company and each Stockholder charged with such amendment, modification or supplement. 

10. Waiver. No failure or delay by any Party exercising any right, power or privilege hereunder shall operate as a waiver thereof nor
shall any single or partial exercise thereof preclude any other or further exercise thereof or the exercise of any other right, power or privilege. The rights and remedies of the Parties hereunder are cumulative and are not exclusive of any rights
or remedies which they would otherwise have hereunder. Any agreement on the part of a Party to any such waiver shall be valid only if set forth in a written instrument executed and delivered by such Party. 

  
 9 

 11. Notices. All notices and other communications hereunder shall be in writing and shall be
deemed given if delivered personally, by email (with confirmation of receipt) or sent by a nationally recognized overnight courier service, such as Federal Express, to the Parties at the following addresses (or at such other address for a Party as
shall be specified by like notice made pursuant to this Section 11): 
 if to the Stockholder, to the address or email address set
forth opposite such Stockholder’s name on Schedule 1, or in the absence of such address or email address being set forth on Schedule 1, the address (including email) set forth in the Company’s books and records, 

with a copy (which shall not constitute notice) to: 

Cooley LLP 
 55 Hudson Yards

 New York, NY 10001-2157 

Attention:    Adam Dinow, David Silverman, Rupa Briggs 

Email:          adinow@cooley.com; david.silverman@cooley.com; 

rbriggs@cooley.com 
 if to the
Company, to it at: 
 Rigetti Holdings, Inc. 

775 Heinz Avenue 
 Berkeley, CA
94710 
 Attention:    Chad Rigetti; Taryn Naidu; Rick Danis 

Email:          chad@rigetti.com; taryn@rigetti.com; rick@rigetti.com 

with a copy (which shall not constitute notice) to: 

Cooley LLP 
 55 Hudson Yards

 New York, NY 10001-2157 

Attention:    Adam Dinow; David Silverman; Rupa Briggs 

Email:          adinow@cooley.com; david.silverman@cooley.com;
rbriggs@cooley.com 

  
 10 

 if to Acquiror prior to the Closing, to it at: 

Supernova Partners Acquisition Company II, Ltd. 

4301 50th Street, NW 
 Suite
300, PMB 1044 
 Washington, DC 20016 

Attention:     Robert Reid, CEO; Michael Clifton, CFO 

Email:          robert@supernovaspac.com; michael@supernovaspac.com 

with a copy (which shall not constitute notice) to: 

Latham & Watkins LLP 

555 Eleventh Street, 
 NW Suite
1000 
 Washington, DC 20004-1304 

Attention:     Nicholas P. Luongo; Ryan J. Maierson; Patrick H. Shannon 

Email:          nick.luongo@lw.com; ryan.maierson@lw.com; 

patrick.shannon@lw.com 
 if to
Acquiror after the Closing, to it at: 
 Rigetti Computing Inc. 

775 Heinz Avenue 
 Berkeley, CA
94710 
 Attention:    Chad Rigetti; Taryn Naidu; Rick Danis 

Email: chad@rigetti.com; taryn@rigetti.com; rick@rigetti.com 

In addition to the foregoing, in the case of any pre-Closing notices sent by any Stockholder to any
other Stockholder or the Company, or sent by the Company to any Stockholder, copies shall also be sent to Acquiror (to the person specified to receive pre-Closing notices on behalf of Acquiror) and to
Latham & Watkins LLP (to the persons referenced above). 
 12. No Ownership Interest. Nothing contained in this Agreement
shall be deemed to vest in Acquiror any direct or indirect ownership or incidence of ownership of or with respect to the Covered Shares of any Stockholder. All rights, ownership and economic benefits of and relating to the Covered Shares of each
Stockholder shall remain vested in and belong to such Stockholder, and Acquiror shall have no authority to direct any Stockholder in the voting or disposition of any of such Stockholder’s Covered Shares, except as otherwise provided herein.

 13. Entire Agreement; Time of Effectiveness. This Agreement and the Merger Agreement constitute the entire agreement and
understanding, and supersede all prior agreements and understandings, both written and oral, between the Parties with respect to the subject matter hereof. 

14. No Third-Party Beneficiaries. Each Stockholder hereby agrees that its representations, warranties and covenants set forth herein
are solely for the benefit of Acquiror and the Company in accordance with and subject to the terms of this Agreement, and this Agreement is not intended to, and does not, confer upon any Person other than the Parties, any

  
 11 

 
rights or remedies hereunder, including the right to rely upon the representations, warranties and covenants set forth herein, and the Parties hereby further agree that this Agreement may only be
enforced against, and any Action that may be based upon, arise out of or relate to this Agreement, or the negotiation, execution or performance of this Agreement, may only be made against, the Persons expressly named as parties to this Agreement.

 15. Governing Law and Venue; Service of Process; Waiver of Jury Trial. 

(a) This Agreement, and all claims or causes of action based upon, arising out of, or related to this Agreement or the transactions
contemplated hereby, shall be governed by, and construed in accordance with, the internal Laws of the State of Delaware, including its statute of limitations, without giving effect to principles or rules of conflict of laws to the extent such
principles or rules would require or permit the application of the Laws or statute of limitations of another jurisdiction. 
 (b) Any Action
based upon, arising out of or related to this Agreement or the transactions contemplated hereby may only be brought in the Court of Chancery of the State of Delaware or, if such court lacks jurisdiction, the state and federal courts in the State of
Delaware, and each of the Parties irrevocably submits to the exclusive jurisdiction of each such court in any such Action, waives any objection it may now or hereafter have to personal jurisdiction, venue or to convenience of forum, agrees that all
claims in respect of the Action shall be heard and determined only in any such court, and agrees not to bring any Action arising out of or relating to this Agreement or the transactions contemplated hereby in any other court. Nothing herein
contained shall be deemed to affect the right of any Party to serve process in any manner permitted by Law or to commence legal proceedings or otherwise proceed against any other Party in any other jurisdiction, in each case, to enforce judgments
obtained in any Action brought pursuant to this Section 15(b). 
 (c) EACH OF THE PARTIES HEREBY KNOWINGLY, INTENTIONALLY,
VOLUNTARILY AND IRREVOCABLY WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY ACTION BASED UPON, ARISING OUT OF OR RELATED TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY. 

16. Assignment; Successors. Neither this Agreement nor any of the rights, interests or obligations hereunder shall (a) be assigned
by any of the Stockholders, in whole or in part (whether by operation of Law or otherwise), without the prior written consent of Acquiror and the Company or (b) be assigned by Acquiror or the Company, in whole or in part (whether by operation
of law or otherwise), without the prior written consent of the Company (in the case of an attempted assignment by Acquiror) or Acquiror (in the case of an attempted assignment by the Company). Any such assignment without such consent shall be null
and void. This Agreement shall be binding upon, inure to the benefit of and be enforceable by the Parties and their respective successors and permitted assigns. 

  
 12 

 17. Enforcement. The Parties agree that irreparable damage (for which monetary
damages, even if available, would not be an adequate remedy) would occur, and that the Parties would not have any adequate remedy at law, in the event that any of the provisions of this Agreement were not performed in accordance with their specific
terms or were otherwise breached. It is accordingly agreed that the Parties shall be entitled to specific performance, an injunction or injunctions, or other equitable relief to prevent breaches or threatened breaches of this Agreement and to
enforce specifically the terms and provisions of this Agreement, including each Stockholder’s obligations under Section 1, without proof of actual damages or otherwise (and each Party hereby waives any requirement for the securing or
posting of any bond in connection with such remedy), this being in addition to any other remedy to which they are entitled at Law or in equity. Each Party acknowledges and agrees that the right of specific enforcement is an integral part of the
transactions contemplated hereby and that, without such right, none of the Parties would have entered into this Agreement. Each Party agrees that it will not oppose the granting of specific performance and other equitable relief on the basis that
the other Parties have an adequate remedy at Law. 
 18. Severability. If any term or other provision of this Agreement is held by a
court of competent jurisdiction or other authority to be invalid, void, unenforceable or against its regulatory policy, the remainder of the terms and provisions of this Agreement shall remain in full force and effect and shall in no way be
affected, impaired or invalidated. Upon such a determination, the Parties shall negotiate in good faith to modify this Agreement so as to effect the original intent of the Parties as closely as possible in an acceptable manner in order that the
transactions contemplated hereby be consummated as originally contemplated to the fullest extent possible. 
 19. Counterparts. This
Agreement may be executed in one or more counterparts, all of which shall be considered one and the same agreement, it being understood that each Party need not sign the same counterpart. Signatures delivered electronically or by facsimile shall be
deemed to be original signatures. 
 20. Interpretation and Construction. The words “hereof,” “herein” and
“hereunder” and words of like import used in this Agreement shall refer to this Agreement as a whole and not to any particular provision of this Agreement. The descriptive headings used herein are inserted for convenience of reference only
and are not intended to be part of or to affect the meaning or interpretation of this Agreement. References to Sections and Schedules are to Sections and Schedules of this Agreement, respectively, unless otherwise specified. Any singular term in
this Agreement shall be deemed to include the plural, and any plural term the singular. The definitions contained in this Agreement are applicable to the masculine as well as to the feminine and neuter genders of such term. Whenever the words
“include,” “includes” or “including” are used in this Agreement, they shall be deemed to be followed by the words “without limitation,” whether or not they are in fact followed by those words or words of like
import. “Writing,” “written” and comparable terms refer to printing, typing and other means of reproducing words (including electronic media) in a visible form. References to any statute shall be deemed to refer to
such statute as amended from time to time and to any rules or regulations promulgated thereunder. References to any person include the successors and permitted assigns of that person. References from or through any date mean, unless otherwise
specified, from and including such date or through and including such date, respectively. In the event an ambiguity or question of intent or interpretation arises, this Agreement will be construed as if drafted jointly by the Parties, and no
presumption or burden of proof will arise favoring or disfavoring any Party by virtue of the authorship of any of the provisions of this Agreement. The term “or” is not exclusive. 

  
 13 

 21. Capacity as a Stockholder or Proxy Holder. Notwithstanding anything herein to the
contrary, each Stockholder is signing this Agreement solely in such Stockholder’s capacity as a stockholder or proxy holder of the Company, and not in any other capacity, and this Agreement shall not limit, prevent or otherwise affect the
actions of such Stockholder or any Affiliate or Representative thereof, or any of their respective Affiliates, in his or her capacity, if applicable, as an officer or director of the Company (or any Subsidiary of the Company) or any other Person,
including in the exercise of his or her fiduciary duties as a director or officer of the Company or any Subsidiary of the Company. No Stockholder shall be liable or responsible for any breach, default, or violation of any representation, warranty,
covenant or agreement hereunder by any other Stockholder that is also a Party and each Stockholder shall solely be required to perform its obligations hereunder in its individual capacity. 

[The remainder of this page is intentionally left blank.] 

  
 14 

 IN WITNESS WHEREOF, the Parties have caused this Agreement to be executed (where applicable,
by their respective officers or other authorized Persons thereunto duly authorized) as of the date first written above. 
  

			
	SUPERNOVA PARTNERS ACQUISITION COMPANY II, LTD.
		
	By:	 	 
	Name:	 	
	Title:	 	

  

			
	RIGETTI HOLDINGS, INC.
		
	By:	 	 
	Name:	 	
	Title:	 	

  
 [Signature Page to
Company Holders Support Agreement] 

 
			
	[STOCKHOLDER]
		
	By:	 	 
	Name:	 	[•]
	Title:	 	[•]

  
 [Signature Page to
Company Holders Support Agreement] 

 Schedule 1 

Covered Shares 
  

																	
	 Stockholder Name
	  	Number of Shares of
Company Class A
Common Stock	 	 	Number of Shares of
Company Class B
Common Stock	 	 	Number of Shares of
Company Series C
Preferred Stock	 	 	Number of Shares of
Company Series C-1
Preferred Stock	 
	 [_____]
	  	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 
	 [_____]
	  	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 
	 [_____]
	  	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 	 	 	[_____	] 

  
 Schedule 1-1

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