Patent ID: 12191051

DETAILED DESCRIPTION

The following detailed description is merely illustrative and is not intended to limit embodiments and/or application or uses of embodiments. Furthermore, there is no intention to be bound by any expressed or implied information presented in the preceding Background or Summary sections, or in the Detailed Description section.

One or more embodiments are now described with reference to the drawings, where like referenced numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of the one or more embodiments. It is evident, however, in various cases, that the one or more embodiments can be practiced without these specific details.

As used herein, a quantum circuit can be a set of operations, such as gates, performed on a set of real-world physical qubits with the purpose of obtaining one or more qubit measurements. A quantum processor can comprise the one or more real-world physical qubits.

Qubit states only can exist (or can only be coherent) for a limited amount of time. Thus, an objective of operation of a quantum logic circuit (e.g., including one or more qubits) can be to maximize the coherence time of the employed qubits. Time spent to operate the quantum logic circuit can undesirably reduce the available time of operation on one or more qubits. This can be due to the available coherence time of the one or more qubits prior to decoherence of the one or more qubits. For example, a qubit state can be lost in less than 100 to 200 microseconds in one or more cases.

Operation of the quantum circuit can be facilitated, such as by a waveform generator, to produce one or more physical pulses and/or other waveforms, signals and/or frequencies to alter one or more states of one or more of the physical qubits. The altered states can be measured, thus allowing for one or more computations to be performed regarding the qubits and/or the respective altered states.

Operations on qubits generally can introduce some error, such as some level of decoherence and/or some level of quantum noise, further affecting qubit availability. Quantum noise can refer to noise attributable to the discrete and/or probabilistic natures of quantum interactions.

A two-level system (TLS), among other noise causes, can comprise a source of noise that can cause deterioration of coherence parameters (e.g., shorter T1) of one or more qubits of a quantum logic circuit. TLSs are believed to be able to coherently or incoherently couple to the qubit leading to either faster energy relaxation times or rate of energy decay (e.g., shorter T1s corresponding to an exponential 1/e decay time) as well as faster phase decoherence (e.g., T2). That is, the noise can couple to a low-energy thermal fluctuator, for example, which can randomly change the TLS energy resonance (or the equivalent frequency of the TLS resonance). A TLS can spectrally diffuse into and out of resonance with the qubit frequency when the TLS is in the vicinity of a qubit frequency. This is a source of T1 fluctuation.

The qubit frequency is the resonance frequency of a qubit energy transition between two states such as, but not limited to, the ground and first excited states of the qubit. The vicinity of a qubit frequency is a frequency range which in some embodiments can range from about 10 megahertz (MHz) below the qubit frequency to about 10 MHz above the qubit frequency. In other embodiments, the vicinity of a qubit frequency can range from about 100 MHZ below the qubit frequency to about 100 MHz above the qubit frequency. In still other embodiments, the vicinity of a qubit frequency can range from about 1 gigahertz (GHz) below the qubit frequency to about 1 GHz above the qubit frequency. Without being limited to theory, it is believed that such two-level systems can be caused by atomic scale defects in surface oxides on the metals and/or on the substrate material of a physical real-world qubit and can be electromagnetically active. Indeed, a qubit, such as a transmon itself is a resonator with an electromagnetic excitation, and thus a qubit excitation can couple with a two-level system (TLS) and can cause performance issues for a quantum logic circuit, such as, but not limited to, deterioration of qubit parameters, such as qubit gate error rate.

Due to presence of two-level systems in/at the quantum system and/or due to maintenance and/or diagnostics to be performed relative to coherence times of a particular qubit, one or more qubits, such as superconducting qubits, can be unavailable and/or not recommended for use with the quantum logic circuit, even if desired for use. Furthermore, absent understanding of such two-level systems and their associated fluctuations relative to the frequency domain of one or more qubits of a quantum system, coherence of the qubit can be affected. Loss of coherence can cause failure of execution of a quantum circuit.

One or more embodiments are now described with reference to the drawings, wherein like referenced numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of the one or more embodiments. It is evident, however, in various cases, that the one or more embodiments can be practiced without these specific details.

Further, the embodiments depicted in one or more figures described herein are for illustration only, and as such, the architecture of embodiments is not limited to the systems, devices and/or components depicted therein, nor to any particular order, connection and/or coupling of systems, devices and/or components depicted therein. In one or more described embodiments, computer and/or computing-based elements can be used in connection with implementing one or more of the systems, devices, components and/or computer-implemented operations shown and/or described in connection with the figures described herein.

Turning first generally toFIG.1, one or more embodiments described herein can include one or more devices, systems and/or apparatuses that can facilitate performing a swap or state transfer operation between a superconducting qubit device and a linear resonator that can be part of the transduction device. For example,FIG.1illustrates a diagram of an example, non-limiting, quantum coherent interconnect system100that comprises a quantum device102, a microwave optical transducer104, and a coherent interconnect106between the quantum device102and the microwave optical transducer104. With embodiments, and without limitation, the microwave optical transducer104can include a lumped element resonator or a distributed element resonator. The system100can include a first qubit package120that can include the quantum device102; and the system100can include a first transducer package122that can include the microwave optical transducer104. The first qubit package120can be coupled with a first transducer package122via the coherent interconnect106. The first qubit package120, the coherent interconnect106, and the transducer package can be disposed within a first dilution refrigerator140(e.g., Dilution Refrigerator A), and similarly, the second qubit package130, the second coherent interconnect134, and the second transducer package132can be disposed within a second dilution refrigerator142(e.g., Dilution Refrigerator B).

With examples, the system100can include a second qubit package130coupled with a second transducer package132. The second qubit package130can be substantially similar and/or include similar components and configurations as the first qubit package120. Alternatively, the second qubit package130can include different quantum components than the first qubit package120. The second transducer package132can be substantially similar and/or include similar components and configurations as the first transducer package122. Alternatively, the second qubit package130can include different transducer components than the first transducer package122. A second coherent interconnect134can couple the second qubit package130with the second transducer package132. The second qubit package130can include a second quantum device136, and the second transducer package132can include a second microwave optical transducer138.

The coherent interconnect106and/or the second coherent interconnect134can include a first cable and a second cable that can couple the first qubit package120with the first transducer package122and can couple the second qubit package130with the second transducer package132. Further, the first cable and the second cable can include one or more of a variety of lengths coupling the first qubit package120with the first transducer package122and coupling the second qubit package130with the second transducer package132over a variety of distances. For example and without limitation, the first cable and the second cable can be superconducting coaxial cables include a length of about 5 centimeters (e.g., which can be up to about 10 centimeters or more or less).

Further, one or more optical signals, which can be generated from a first pulsed optical pump150and a second pulsed optical pump152, can be converted with a microwave signal154,156to entangle the state of the quantum device102coupled to the first transducer package122with the second transducer package132. Bell measurements can be taken at room temperature exterior to the first dilution refrigerator140and the second dilution refrigerator142. In this manner, the first transducer package122(e.g., the quantum device102) can interact with the second transducer package132(e.g., a second quantum device136) to transfer or swap qubit states of the quantum devices102,136. The one or more optical signals can be brought into one or more microwave optical transducers104,138of the transducer packages122,132, which can be converted with a microwave signal154,156to result in a quantum optical signal where protocols can be engaged to facilitate the entanglement of the state of the quantum device102in the first dilution refrigerator140with the second quantum device136in the second dilution refrigerator142, promoting modular connectivity and scalability between quantum devices.

With examples, such as generally illustrated inFIG.2, a non-limiting quantum coherent interconnect system200can include a quantum device202, a microwave optical transducer204including a microwave resonator206, and a coherent interconnect208connected between the quantum device202and the microwave resonator206. The non-limiting quantum coherent interconnect system200can transfer a state of a qubit of the quantum device202to the microwave resonator206of the microwave optical transducer204. Further, the quantum device202of the non-limiting quantum coherent interconnect system200can include a quantum state (e.g., the quantum state can be a superposition of the 0 and 1 state) to transfer to another quantum device elsewhere (e.g., outside the qubit package from the first dilution refrigerator140to the second dilution refrigerator142as shown inFIG.1). The quantum device202can be one or more of a variety of qubit integrated devices, such as a transmon qubit202A.

In embodiments, the coherent interconnect208can be responsible for transferring the quantum state of the quantum device202to the optical microwave transducer204. Further, the microwave optical transducer204can be separately packaged from the quantum device202(e.g., such as illustrated inFIG.1). The coherent interconnect208can include a flux-tunable element212and/or a superconducting coaxial cable210including one or more of a variety of lengths. For example and without limitation, a length of the superconducting coaxial cable210can include a range of up to about 10 centimeters, or more or less. In examples, the length can be about 5 centimeters. With embodiments, the superconducting coaxial cable210can be in the ground state, and the microwave optical transducer204can be in the ground state.

With embodiments, as illustrated inFIG.2, the superconducting coaxial cable210can include a DC-SQUID216. The superconducting coaxial cable210can include a flux-tunable DC-SQUID216to facilitate frequency tuning of modes of the superconducting coaxial cable210. Additionally, the coherent interconnect208can include a flux-tunable element212(e.g., a coupler) that can modulate the coupling between the quantum device202and the coherent interconnect208.

Further,FIG.2illustrates a circuit200′ representative of non-limiting quantum coherent interconnect system200, further representative of non-limiting quantum coherent interconnect system100. For example and without limitation, the circuit200′ can include a quantum device202(e.g., a transmon qubit202A) coupled to a microwave optical transducer204including a microwave resonator206via a coherent interconnect208. The quantum device202can be grounded, as shown inFIG.2. The coherent interconnect208can include a flux-tunable element212that can modulate the coupling between the quantum device202and the coherent interconnect208. The flux-tunable element212can include an Gmon coupler or a Radio Frequency Superconducting Quantum Interference Device (RF SQUID)220.

Additionally, the superconducting coaxial cable210of the non-limiting quantum coherent interconnect system200can include a cable portion216and a DC-SQUID218. The DC-SQUID218of the superconducting coaxial cable210can be inductively coupled to the flux-tunable element212(e.g., the grounded transmon/RF SQUID). The cable portion216of the superconducting coaxial cable210can be coupled (e.g., capacitively or inductively) with the microwave optical transducer204and the microwave resonator206. The superconducting coaxial cable210can include a length of about 5 centimeters and a spacing of modes at about 2 GHZ Free Spectral Range (FSR).

In embodiments, the quantum device202, the microwave optical transducer204(e.g., the microwave resonator206), and the coherent interconnect208(e.g., the flux-tunable element212and the superconducting coaxial cable210) of the non-limiting quantum coherent interconnect system200can be flux-tunable components. The quantum state (e.g., |qubit, cable, resonator)) of the quantum device202can be transferred to the microwave resonator206via the coherent interconnect208. The quantum state of the quantum device202can be tuned to be in resonance with a mode of the superconducting coaxial cable210(e.g., α|0)+|1)|0)|0)). In response to the quantum device202tuned to be resonant with the superconducting coaxal cable210, the quantum state of the quantum device202can be transmitted to the superconducting coaxial cable210by activating the flux-tunable element212(e.g., the coupler). Thereafter, the quantum state of the quantum device202can be transmitted to the flux-tunable element212. In response to transmitting the quantum state of the quantum device202to the flux-tunable element212(e.g., the coupler), the mode of the superconducting coaxial cable210can be tuned to be in resonance with the flux-tunable element212. Thereafter, the quantum state can be transferred to the mode of the superconducting coaxial cable210.

In response to transmitting the quantum state of the quantum device202to the flux-tunable element212(e.g., the coupler) and to the mode of the superconducting coaxial cable210, the superconducting coaxial cable210can be tuned to be in resonance with the microwave optical transducer204. Additionally or alternatively, in embodiments where the microwave resonator206can be flux-tunable, the microwave resonator206can be tuned to be resonant with the mode of the superconducting coaxial cable210(e.g., with or without tuning the superconducting coaxial cable210). Such tuning can enable the system100to transfer a quantum state form the quantum device202to the microwave optical transducer204(e.g., |0)(α|0)+β|1)|0)). Flux tuning the quantum device202, the microwave optical transducer204, the flux-tunable element212(e.g., coupler), and the superconducting coaxial cable210can provide the largest range of frequencies for the non-limiting quantum coherent interconnect system200by using flux-tunable elements. With embodiments, increasing the number of flux-tunable elements can increase the tunable frequency range.

With embodiments, the transfer of quantum states can occur bi-directionally using a time reversed pulsed sequence to facilitate the transfer from the microwave resonator206to the quantum device202(e.g., |0)|0)(α|0)+β|1)). In examples, the time reversed pulsed sequence can include the above process performed in a reserved direction, such that the quantum state can be transmitted from the microwave optical transducer204to the quantum device202. Further, the microwave optical transducer204can be tuned to be resonant with the superconducting coaxial cable210; the superconducting coaxial cable210can be tuned to be resonant with the flux-tunable element212(e.g., the coupler); and the flux-tunable element212can be tuned to be resonant with the quantum device202such that a quantum state can be transferred between resonant states. Quantum state transfer between a quantum device202and a microwave resonator206of a coherent interconnect208can occur bi-directionally in accordance with one or more embodiments described herein.

With examples, such as generally illustrated inFIG.3, a non-limiting quantum coherent interconnect system300can include a quantum device302, a microwave optical transducer304(e.g., which can include a lumped element or a distributed element resonator) and a coherent interconnect308. The non-limiting quantum coherent interconnect system300can transfer a state of a qubit of the quantum device302to the microwave optical transducer304. The quantum device302can be one or more of a variety of qubit integrated devices, such as a transmon qubit302A.

In embodiments, the coherent interconnect308can be responsible for transferring the quantum state of the quantum device302to the microwave optical transducer304. Further, the microwave optical transducer304can be separately packaged from the quantum device302. The coherent interconnect308can be a superconducting coaxial cable310including one or more of a variety of lengths. With embodiments, the superconducting coaxial cable310can be in the ground state, and the microwave optical transducer304can be in the ground state.

With embodiments, as illustrated inFIG.3, the superconducting coaxial cable310can include a DC-SQUID318. The superconducting coaxial cable310can include a flux-tunable DC-SQUID318to facilitate frequency tuning of mode frequencies of the superconducting coaxial cable310. Additionally, the coherent interconnect308can include a flux-tunable element (e.g., a coupler)312that can modulate the coupling between the quantum device302and the coherent interconnect308.

Further,FIG.3illustrates a circuit300′ representative of non-limiting quantum coherent interconnect system300, further representative of embodiments of non-limiting quantum coherent interconnect system100,200. For example and without limitation, the circuit300′ can include a quantum device302(e.g., a transmon qubit302A) coupled to a microwave optical transducer304via a coherent interconnect308. The quantum device302can be grounded, as shown inFIG.3. The coherent interconnect308can include a flux-tunable element312that can modulate the coupling between the quantum device302and the coherent interconnect308. The flux-tunable element312can include a grounded transmon/RF SQUID320.

Additionally, the superconducting coaxial cable310of the non-limiting quantum coherent interconnect system300can include a cable portion316and a DC-SQUID318. The DC-SQUID318of the superconducting coaxial cable310can be inductively coupled to the flux-tunable element312(e.g., the grounded transmon/RF SQUID320). The cable portion316of the superconducting coaxial cable310can be coupled (e.g., capacitively or inductively) with the microwave optical transducer304and the microwave resonator306. The superconducting coaxial cable310can include a length of about 5 centimeters and a spacing of modes at about 2 GHZ Free Spectral Range (FSR).

In embodiments, the quantum device302, the microwave optical transducer304, and the coherent interconnect308(e.g., the flux-tunable element312and the superconducting coaxial cable310) of the non-limiting quantum coherent interconnect system300can be flux-tunable. The quantum state of the quantum device302can be transferred to the microwave optical transducer304via the coherent interconnect308. The transmon qubit302A of the quantum device302can include a quantum state. The transmon qubit302A of the quantum device302can be tuned to be in resonance with a mode of the superconducting coaxial cable310. In response to tuning the quantum device302to be in resonance with the superconducting coaxial cable310, the flux-tunable element312can be activated to transfer the quantum state from the quantum device302to the mode of the superconducting coaxial cable310. The mode of the superconducting coaxial cable310can be tuned to be in resonance with the microwave optical transducer304. The microwave optical transducer304can include a fixed frequency whereby the superconducting coaxial cable310can be tuned to be resonant with the microwave optical transducer304. Such tuning can enable the system100to transfer a quantum state form the quantum device302to the microwave optical transducer304. Further, the transfer of quantum states can occur bi-directionally using a time reversed pulsed sequence to effectuate the transfer from the microwave optical transducer304to the quantum device302.

In examples, the time reversed pulsed sequence can include the above process performed in a reserved direction, such that the quantum state can be transmitted from the microwave optical transducer304to the quantum device302. Further, the superconducting coaxial cable210can be tuned to be resonant with the microwave optical transducer304; the flux-tunable element312can be tuned to be resonant with the superconducting coaxial cable310; and the quantum device302can be tuned to be in resonant with the flux-tunable element312such that a quantum state can be transferred between resonant states. Quantum state transfer between a quantum device302and a microwave optical transducer304of a coherent interconnect308can occur bi-directionally in accordance with one or more embodiments described herein.

With embodiments, the non-limiting quantum coherent interconnect system300can be represented by the following Hamiltonian equation:

H^s(t)≈∑q=a,b[ωq(t)⁢qˆ†⁢qˆ+12⁢αq⁢qˆ†⁢qˆ†⁢qˆ⁢qˆ]︸A+ωr⁢r^†⁢rˆ︸B+∑n=-NNωc⁢n(t)⁢c^†⁢c^n︸C+∑q=a,b∑n=-NNgq⁢n(t)⁢(qˆ⁢cˆn†+qˆ†⁢cˆn)︸D+∑n=-NNgrn(rˆ†⁢cˆn+rˆ⁢cˆn†)︸E

As illustrated in the Hamiltonian equation above, a first portion of the Hamiltonian equation (e.g., portion A) can represent/describe the behavior of the quantum device302; and a second portion of the Hamiltonian equation (e.g., portion B) can represent/describe the behavior of the microwave optical transducer304. Further, the superconducting coaxial cable310and the various tunable modes can be represented/described by a third portion of the Hamiltonian equation (e.g., portion C). A fourth portion of the Hamiltonian equation (e.g., portion D) can represent/describe the interaction between the quantum device302and the superconducting coaxial cable310. Additionally, a fifth portion of the Hamiltonian equation (e.g., portion E) can represent/describe the interaction between the superconducting coaxial cable310and the microwave optical transducer304.

As shown inFIG.4, the circuit400′ can include the quantum device302having a transmon qubit402A (e.g., that is not grounded) and the flux-tunable element312can be a qubit-like coupler. Additionally or alternatively, the superconducting coaxial cable310can include a SQUID318that can be placed away from end points of the superconducting coaxial cable310such that the superconducting coaxial cable310can be capacitively bonded to the flux-tunable element312. Further, the SQUID318can be disposed between a first end point402and a second end point404of the superconducting coaxial cable310(e.g., such that the SQUID318can be disposed on-chip or on-substrate). The first end point402can be capacitively coupled to the flux-tunable element312(e.g., the tunable coupler) via capacitor406and the second end point404can be capacitively coupled to the microwave optical transducer304via capacitor408.

With examples, such as illustrated inFIG.5, the non-limiting quantum coherent interconnect system300can be simulated to generate simulation results diagrams500and502. The first simulation results diagram500can represent time domain simulations. Further, the Hamiltonian equation from above can be integrated over time to observe the dynamics of the system300. Such as can be seen from first simulation results diagram500, the quantum device302can start by having a frequency of about 4.0 GHZ. Additionally, the microwave optical transducer304can include a fixed frequency of about 5.0 GHz; and the superconducting coaxial cable310can include a frequency of about 4.5 GHZ. The quantum device302can be brought into resonance with the superconducting coaxial cable310such that quantum state can be exchanged. The frequency of the quantum device302can be increased to about 4.5 GHz to substantially match the frequency of the superconducting coaxial cable310(e.g., such as illustrated at plot504on first and second simulation results diagrams500,502).

In embodiments, the superconducting coaxial cable310can be brought into resonance with the microwave optical transducer304such that quantum information can be transferred from the superconducting coaxial cable310to the microwave optical transducer304. For example, the frequency of the superconducting coaxial cable310can be increased to about 5.0 GHz to substantially match the frequency of the microwave optical transducer304, where quantum state can be transferred (e.g., such as illustrated at plot506on first and second simulation results diagrams500,502). The simulation can include using 5 levels for the quantum device302and using 4 levels for the superconducting coaxial cable310. Further, −240 MHz anharmonicity for the quantum device302can be achieved; and the quantum device302can be modeled as a duffing oscillator yielding a 99.5% state transfer fidelity rate.

With examples, one or more equations can model the tuning range for the superconducting coaxial cable310(e.g., the cable portion316and the DC-SQUID318) used in the one or more embodiments of the non-limiting quantum coherent interconnect system100,200,300.FIG.6generally illustrates a superconducting coaxial cable602terminated at a DC-SQUID604. The presence of the DC-SQUID604can modify the effective inductance of the microwave optical transducer304at one end and can be treated as a boundary condition. The Helmholtz equation can be solved for the flux field inside the microwave optical transducer304with boundary conditions as modified by the presence of the DC-SQUID604By tuning the external flux, we can change the boundary condition for the Helmholtz equation and solve for the cable in terms of flux via Fourier transform:

∂x2Φ~(x,ω)+(ωvp)2⁢Φ~(x,ω)=0

The boundary conditions for the above equation are as follows. As expressed in the following equation, the left part of the cable602is not coupled to anything external, so the current can be zero:

-1l⁢∂xΦ~(x,ω)❘"\[LeftBracketingBar]"x=0=0

In the above equation, x can be a variable to represent any arbitrary position along the cable602, and d can be a variable to represent a specific point towards the right part of the cable602(e.g., an end point). Secondly, the current that leaves the cable602is equal to the current that goes into the capacitor CJ (which can be the sum of the currents of the capacitor and DC-SQUID604, collectively). The tunablity of the DC-SQUID604(e.g., as shown inFIG.3) is represented by the cosine shown in the equation below (where the cosine term represents the tunability of the cable602due to the DC-SQUID604):

-1l⁢∂xΦ~(x,ω)❘"\[LeftBracketingBar]"x=d=-CJ⁢ω⁢Φ~(d,ω)+Φ~(d,ω)LJ❘"\[LeftBracketingBar]"cos⁡(π⁢ΦexternalΦ0)❘"\[RightBracketingBar]"

Using the Helmholtz equation, a discrete set of modes can be determined of the cable602by the following equation:
Φ(x,kn)=Ancos(knx)

A characteristic equation representative for the mode frequency (kn=ωn/vp) as a function of externally applied flux Φexternalcan be expressed as:

kn⁢d⁢tan⁢(kn⁢d)=-CJc⁢d⁢(kn⁢d)2+l⁢dLJ⁢❘"\[LeftBracketingBar]"cos⁡(π⁢ΦexternalΦ0)❘"\[RightBracketingBar]"

With embodiments,FIG.7includes simulation results diagram700demonstrating a non-limiting example of parameters for the superconducting coaxial cable310. For example and without limitation, the superconducting coaxial cable310can include a length of about 5 centimeters, can be coupled with a 5 fF capacitor, and can be coupled with a DC-SQUID318including an inductance of 1 nH. The superconducting coaxial cable310can achieve a tuning range of about 710 MHz. One or more DC-SQUIDS318coupled with the cable portion316can include junctions; and, larger junctions can yield a greater tuning range for the superconducting coaxial cable310.

In examples,FIG.7illustrates three modes (e.g., mode1, mode2, and mode3) of the superconducting coaxial cable310as a function of the external flux applied to the DC-SQUID318. The second mode (mode2) of the superconducting coaxial cable310can be used to execute the transfer of quantum information between the quantum device302(e.g., at a first frequency702) and the microwave optical transducer304(e.g., at a second frequency704).

With examples, such as generally illustrated inFIG.8, a non-limiting quantum coherent interconnect system800can include a quantum device802, a microwave optical transducer804and a coherent interconnect808. The non-limiting quantum coherent interconnect system800can transfer a state of a qubit of the quantum device802to the microwave optical transducer804. The quantum device802can be one or more of a variety of qubit integrated devices, such as a transmon qubit802A.

In embodiments, the coherent interconnect808can be responsible for transferring the quantum state of the quantum device802to the microwave optical transducer804. Further, the microwave optical transducer804can be separately packaged from the quantum device802. The coherent interconnect808can be a superconducting coaxial cable810including one or more of a variety of lengths. The superconducting coaxial cable810can include a DC-SQUID814. The superconducting coaxial cable10can include a flux-tunable DC-SQUID814to facilitate frequency tuning of mode frequencies of the superconducting coaxial cable810.

Further,FIG.8illustrates a circuit800′ representative of non-limiting quantum coherent interconnect system800. For example and without limitation, the non-limiting quantum coherent interconnect system800and circuit800′ can include a quantum device802(e.g., a transmon qubit802A) coupled to a microwave optical transducer804via a coherent interconnect808(e.g., which can include the superconducting coaxial cable810comprised of a cable portion812and a DC-SQUID814). The quantum device802can be grounded and can be connected with an inductive coupling816in series. The DC-SQUID814of the superconducting coaxial cable810can be inductively coupled to the quantum device802at inductive coupling816. The cable portion812of the superconducting coaxial cable810can be capacitively coupled with the microwave optical transducer804at coupling818. The superconducting coaxial cable810can control the transfer of information between the quantum device802by tuning the DC-SQUID814of the superconducting coaxial cable810(e.g., the coherent interconnect808).

In embodiments, the quantum device802and the coherent interconnect808(e.g., the superconducting coaxial cable810) of the non-limiting quantum coherent interconnect system800can be flux-tunable. The quantum state of the quantum device802can be transferred to the microwave optical transducer804via the coherent interconnect808. The transmon qubit802A of the quantum device802can include a quantum state. The transmon qubit802A of the quantum device802can be tuned to be in resonance with a mode of the superconducting coaxial cable810. In response to tuning the quantum device802to be in resonance with the superconducting coaxial cable810, mode of the superconducting coaxial cable810can be tuned to be in resonance with the microwave optical transducer804. The microwave optical transducer804can include a fixed frequency (e.g., which is not flux-tunable) such that the superconducting coaxial cable810can be tuned to be resonant with the microwave optical transducer804. Such tuning can enable the system800to transfer a quantum state form the quantum device802to the microwave optical transducer804(e.g., without a coupler or flux-tunable element). Further, the transfer of quantum states can occur bi-directionally using a time reversed pulsed sequence to effectuate the transfer from the microwave optical transducer804to the quantum device802.

In examples, the time reversed pulsed sequence can include the above process performed in a reserved direction, such that the quantum state can be transmitted from the microwave optical transducer804(e.g., the lumped element or distributed element resonator) to the quantum device802. Further, the superconducting cable810can be tuned to be resonant with the microwave optical transducer804to pass the quantum state from the microwave optical transducer804to the superconducting coaxial cable810; and the quantum device802can be tuned to be in resonant with the superconducting coaxial cable810such that a quantum state can be transferred between resonant states. Quantum state transfer between a quantum device802and a microwave optical transducer804of a coherent interconnect808can occur bi-directionally in accordance with one or more embodiments described herein.

Further,FIG.9illustrates a circuit900′ representative of non-limiting quantum coherent interconnect system800. For example and without limitation, the circuit900′ can include a quantum device802(e.g., a transmon qubit802A that is not grounded) coupled to a microwave optical transducer804via a coherent interconnect808. The superconducting coaxial cable810of the non-limiting quantum coherent interconnect system800can include a first end point902and a second end point904by which the DC-SQUID814can be disposed between (e.g., such that the DC-SQUID814can be disposed on a substrate). The first end point902can be capacitively coupled with the quantum device802; and the second end point904can be capacitively coupled with the microwave optical transducer804. The superconducting coaxial cable810can include a length of about 5 centimeters and a spacing of modes at about 2 GHZ Free Spectral Range (FSR).

With embodiments,FIG.10illustrates a non-limiting quantum coherent interconnect system1000that can include a quantum device1002, a microwave optical transducer1004and a coherent interconnect1008. The non-limiting quantum coherent interconnect system1000can transfer a state of a qubit of the quantum device1002to the microwave optical transducer1004. The quantum device1002can be one or more of a variety of qubit integrated devices, such as a transmon qubit1002A.

In embodiments, the coherent interconnect1008can be responsible for transferring the quantum state of the quantum device1002to the microwave optical transducer1004. Further, the microwave optical transducer1004can be separately packaged from the quantum device1002, and the coherent interconnect1008can be a superconducting coaxial cable1010.

In example embodiments, the microwave optical transducer1004can be flux tunable. Further, the non-limiting quantum coherent interconnect system1000including a tunable frequency microwave optical transducer1004can be represented by the below Hamiltonian equation:

H^s(t)≈{ωq(t)⁢qˆ†⁢qˆ+12∝qqˆ†⁢qˆ†⁢qˆ⁢qˆ}︸A+{ωr⁢rˆ†⁢rˆ}︸B+∑j=q,rgj⁢c(J^+J^†)⁢(cˆ+cˆ†)︸C+{∑n=-NNωc⁢n⁢cˆ†⁢cˆn}︸D

The first portion of the above equation (e.g., portion A) can represent the quantum device1002; the second portion of the above equation (e.g., portion B) can represent the tunable microwave optical transducer1004; the third portion of the above equation (e.g., portion C) can represent the interaction between either the a qubit of the quantum device1004(q) or the (r) microwave resonator206(e.g., of the microwave optical transducer1004) with the superconducting coaxial cable1010; and the fourth portion of the above equation (e.g., portion D) can represent the superconducting coaxial cable1010. With the tunable microwave optical transducer1004, quantum information (e.g., a quantum state) can be transferred from the quantum device1002to the variable frequency microwave optical transducer1004via the fixed frequency superconducting coaxial cable1010(e.g., the coherent interconnect1008). The quantum device1002and the microwave optical transducer1004can be tuned to be substantially resonant with the fixed frequency of the superconducting coaxial cable1010to effectuate the transfer of quantum information in a scalable manner.

With additional examples, the microwave optical transducer1004can include a fixed frequency. The non-limiting quantum coherent interconnect system1000including a fixed frequency microwave optical transducer1004can be represented by the below Hamiltonian equation:

H^s(t)≈{ωq(t)⁢qˆ†⁢qˆ+12∝qqˆ†⁢qˆ†⁢qˆ⁢qˆ}︸A+{ωr⁢rˆ†⁢rˆ}︸B+{∑n=-NNωc⁢n⁢cˆ†⁢cˆn}︸C+{∑n=-Nj=q,rgjn(J^⁢c^n†+J^†⁢c^n)}︸D

The first portion of the above equation (e.g., portion A) can represent the quantum device1002; the second portion of the above equation (e.g., portion B) can represent the fixed frequency microwave optical transducer1004; the third portion of the above equation (e.g., portion C) can represent the modes of the superconducting coaxial cable1010(e.g., the coherent interconnect1008); and the fourth portion of the above equation (e.g., portion D) can represent the interaction between either a qubit of the quantum device1004(q) or the (r) microwave resonator206(e.g., of the microwave optical transducer1004) with the superconducting coaxial cable1010. With the fixed frequency microwave optical transducer1004, quantum information can be transferred from the quantum device1002to the fixed frequency microwave optical transducer1004via the fixed frequency superconducting coaxial cable1010by bringing the quantum device1002into resonance with the microwave optical transducer1004(e.g., a state of the microwave optical transducer1004).

In examples, the time reversed pulsed sequence can include the above process performed in a reserved direction, such that the quantum state can be transmitted from the microwave optical transducer1004to the quantum device1002. Further, the superconducting coaxial cable1010can be tuned to be resonant with the microwave optical transducer1004to pass the quantum state from the microwave optical transducer1004to the superconducting coaxial cable1010; and the quantum device1002can be tuned to be in resonant with the superconducting coaxial cable1000such that a quantum state can be transferred between resonant states. Quantum state transfer between a quantum device1002and a microwave optical transducer1004of a coherent interconnect1008can occur bi-directionally in accordance with one or more embodiments described herein.

FIG.11illustrates a flow diagram of an example, non-limiting method1100to facilitate quantum state transfer between a quantum device and a microwave resonator of a coherent interconnect in accordance with one or more embodiments described herein. Repetitive description of like elements and/or processes employed in respective embodiments is omitted for sake of brevity.

At1102, the non-limiting method1100to facilitate quantum state transfer can comprise enabling bi-directional transfer of a quantum state between a quantum device and a microwave resonator of a microwave optical transducer via a coherent interconnect connected between the quantum device and the microwave optical transducer. In embodiments of the non-limiting method1100, the quantum device can be separately packaged from the microwave optical transducer.

At1104, the non-limiting method1100to facilitate quantum state transfer can comprise determining a desired frequency (e.g., of the cable) to tune the quantum device to be in resonance with. With embodiments, the desired frequency can be a frequency of the cable, a frequency of the flux-tunable element (e.g., the coupler), and/or a frequency of the microwave optical transducer.

At1106, the non-limiting method1100to facilitate quantum state transfer can comprise tuning the quantum device to be in resonance with a mode of a cable of the coherent interconnect.

At1108, the non-limiting method1100to facilitate quantum state transfer can comprise activating coupling to transfer the quantum state to the mode of the cable.

At1110, the non-limiting method1100to facilitate quantum state transfer can comprise tuning the mode of the cable to be in resonance with the microwave optical transducer.

At1112, the non-limiting method1100to facilitate quantum state transfer can comprise tuning a lumped element of the microwave resonator to be in resonance with the mode of the cable.

Aspects of the one or more embodiments described herein are described herein with reference to flowchart illustrations or block diagrams of methods, apparatus (systems), and devices according to one or more embodiments described herein. It will be understood that each block of the flowchart illustrations or block diagrams, and combinations of blocks in the flowchart illustrations or block diagrams, can be implemented by computer readable program instructions. These computer readable program instructions can be provided to a processor of a general purpose computer, special purpose computer or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart or block diagram block or blocks. The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus or other device to cause a series of operational acts to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus or other device implement the functions/acts specified in the flowchart or block diagram block or blocks.

The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, computer-implementable methods or computer program products according to one or more embodiments described herein. In this regard, each block in the flowchart or block diagrams can represent a module, segment or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In one or more alternative implementations, the functions noted in the blocks can occur out of the order noted in the Figures. For example, two blocks shown in succession can, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

While the subject matter has been described above in the general context of computer-executable instructions of a computer program product that runs on a computer or computers, those skilled in the art will recognize that the one or more embodiments herein also can be implemented in combination with other program modules. Generally, program modules include routines, programs, components, data structures or the like that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the inventive computer-implemented methods can be practiced with other computer system configurations, including single-processor or multiprocessor computer systems, mini-computing devices, mainframe computers, as well as computers, hand-held computing devices (e.g., PDA, phone), microprocessor-based or programmable consumer or industrial electronics or the like. The illustrated aspects can also be practiced in distributed computing environments in which tasks are performed by remote processing devices that are linked through a communications network. However, some, if not all aspects of the one or more embodiments can be practiced on stand-alone computers. In a distributed computing environment, program modules can be located in both local and remote memory storage devices.

As used in this application, the terms “component,” “system,” “platform,” “interface,” or the like, can refer to or can include a computer-related entity or an entity related to an operational machine with one or more specific functionalities. The entities disclosed herein can be either hardware, a combination of hardware and software, software, or software in execution. For example, a component can be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program or a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components can reside within a process or thread of execution and a component can be localized on one computer or distributed between two or more computers. In another example, respective components can execute from various computer readable media having various data structures stored thereon. The components can communicate via local or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system or across a network such as the Internet with other systems via the signal). As another example, a component can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, which is operated by a software or firmware application executed by a processor. In such a case, the processor can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, a component can be an apparatus that provides specific functionality through electronic components without mechanical parts, where the electronic components can include a processor or other means to execute software or firmware that confers at least in part the functionality of the electronic components. In an aspect, a component can emulate an electronic component via a virtual machine, e.g., within a cloud computing system.

In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. Moreover, articles “a” and “an” as used in the subject specification and annexed drawings should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. As used herein, the terms “example” and/or “exemplary” are utilized to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as an “example” and/or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art.

As it is employed in the subject specification, the term “processor” can refer to substantially any computing processing unit or device comprising, but not limited to, single-core processors; single-processors with software multithread execution capability; multi-core processors; multi-core processors with software multithread execution capability; multi-core processors with hardware multithread technology; parallel platforms; and parallel platforms with distributed shared memory. Additionally, a processor can refer to an integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic controller (PLC), a complex programmable logic device (CPLD), a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Further, processors can exploit nano-scale architectures such as, but not limited to, molecular and quantum-dot based transistors, switches and gates, in order to optimize space usage or enhance performance of user equipment. A processor can also be implemented as a combination of computing processing units.

Herein, terms such as “store,” “storage,” “data store,” data storage,” “database,” and substantially any other information storage component relevant to operation and functionality of a component are utilized to refer to “memory components,” entities embodied in a “memory,” or components comprising a memory. It is to be appreciated that memory or memory components described herein can be either volatile memory or nonvolatile memory or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), flash memory or nonvolatile random access memory (RAM) (e.g., ferroelectric RAM (FeRAM). Volatile memory can include RAM, which can act as external cache memory, for example. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), direct Rambus RAM (DRRAM), direct Rambus dynamic RAM (DRDRAM) or Rambus dynamic RAM (RDRAM). Additionally, the disclosed memory components of systems or computer-implemented methods herein are intended to include, without being limited to including, these and any other suitable types of memory.

What has been described above include mere examples of systems and computer-implemented methods. It is, of course, not possible to describe every conceivable combination of components or computer-implemented methods for purposes of describing the one or more embodiments, but one of ordinary skill in the art can recognize that many further combinations and permutations of the one or more embodiments are possible. Furthermore, to the extent that the terms “includes,” “has,” “possesses,” and the like are used in the detailed description, claims, appendices and drawings such terms are intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.

The descriptions of the one or more embodiments provided herein have been presented for purposes of illustration but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.