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; 

  
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 (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. 

  
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 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 

  
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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. 

  
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 (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. 

  
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 (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. 

  
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 (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. 

  
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 (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. 

  
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 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 

  
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 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


  
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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. 

  
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 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. 

  
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 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.] 

  
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 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