Universal controlled-phase gate with cat-state qubits in circuit QED

Xiong, Zhi‐Gang; Zheng, Zhen-Fei; Yu, Li; Su, Qi-Ping; Yang, Chui‐Ping

doi:10.1103/physreva.96.052317

Cited by 25 publications

(12 citation statements)

References 58 publications

(78 reference statements)

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“…Along similar lines as the above self-Kerr rotation, Ref. [59] has proposed a two-qubit control-phase gate for a simpler version of the cat code. (Recall that such a gate should produce |1 α1,Π1 , 1 α2,Π2 → −|1 α1,Π1 , 1 α2,Π2 while leaving the remaining two-qubit components unchanged.)…”

Section: Cross-kerr Control-phase Gatementioning

confidence: 99%

Pair-cat codes: autonomous error-correction with low-order nonlinearity

Albert

Mundhada

Grimm

et al. 2019

Quantum Sci. Technol.

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We introduce a driven-dissipative two-mode bosonic system whose reservoir causes simultaneous loss of two photons in each mode and whose steady states are superpositions of pair-coherent/Barut-Girardello coherent states. We show how quantum information encoded in a steady-state subspace of this system is exponentially immune to phase drifts (cavity dephasing) in both modes. Additionally, it is possible to protect information from arbitrary photon loss in either (but not simultaneously both) of the modes by continuously monitoring the difference between the expected photon numbers of the logical states. Despite employing more resources, the two-mode scheme enjoys two advantages over its one-mode cat-qubit counterpart with regards to implementation using current circuit QED technology. First, monitoring the photon number difference can be done without turning off the currently implementable dissipative stabilizing process. Second, a lower average photon number per mode is required to enjoy a level of protection at least as good as that of the cat-codes. We discuss circuit QED proposals to stabilize the code states, perform gates, and protect against photon loss via either active syndrome measurement or an autonomous procedure. We introduce quasiprobability distributions allowing us to represent two-mode states of fixed photon number difference in a twodimensional complex plane, instead of the full four-dimensional two-mode phase space. The twomode codes are generalized to multiple modes in an extension of the stabilizer formalism to nondiagonalizable stabilizers. The M -mode codes can protect against either arbitrary photon losses in up to M − 1 modes or arbitrary losses and gains in any one mode.

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Section: Cross-kerr Control-phase Gatementioning

confidence: 99%

Pair-cat codes: autonomous error-correction with low-order nonlinearity

Albert

Mundhada

Grimm

et al. 2019

Quantum Sci. Technol.

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“…We set g kl = 0.01g max , where g max = max{g 1 , g 2 , g 3 } ∼ 2π × 151. 49 MHz, which can be achieved in experiments [56,69]. In addition, assume κ 1 = κ 2 = κ 3 = κ for simplicity.…”

Section: Possible Experimental Implementationmentioning

confidence: 99%

“…Note that the coupling constants chosen here are readily available because a coupling constant ∼ 2π × 636 MHz has been reported for a flux device coupled to a one-dimensional transmission line resonator [40]. We set g kl = 0.01g max , where g max = max{g 1 , g 2 , g 3 } ∼ 2π × 151.49 MHz, which can be achieved in experiments [56,69]. In addition, assume κ 1 = κ 2 = κ 3 = κ for simplicity.…”

Section: Possible Experimental Implementationmentioning

confidence: 99%

Circuit QED: single-step realization of a multiqubit controlled phase gate with one microwave photonic qubit simultaneously controlling n − 1 microwave photonic qubits

Ye¹,

Zheng²,

Yu³

et al. 2018

Opt. Express

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We present a novel method to realize a multi-target-qubit controlled phase gate with one microwave photonic qubit simultaneously controlling n − 1 target microwave photonic qubits. This gate is implemented with n microwave cavities coupled to a superconducting flux qutrit. Each cavity hosts a microwave photonic qubit, whose two logic states are represented by the vacuum state and the single photon state of a single cavity mode, respectively. During the gate operation, the qutrit remains in the ground state and thus decoherence from the qutrit is greatly suppressed.This proposal requires only a single-step operation and thus the gate implementation is quite simple. The gate operation time is independent of the number of the qubits. In addition, this proposal does not need applying classical pulse or any measurement. Numerical simulations demonstrate that high-fidelity realization of a controlled phase gate with one microwave photonic qubit simultaneously controlling two target microwave photonic qubits is feasible with current circuit QED technology. The proposal is quite general and can be applied to implement the proposed gate in a wide range of physical systems, such as multiple microwave or optical cavities coupled to a natural or artificial Λ-type three-level atom.

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“…In recent years, besides progress achieved with SPS qubits, considerable theoretical and experimental activity have also been shifted to QIP with coherent-state (CS) or cat-state (C-S) qubits. There exists a number of works for QIP using qubits encoded with coherent states [6,[8][9][10] or encoded with cat-state qubits [7,[11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Transferring quantum entangled states between multiple single-photon-state qubits and coherent-state qubits in circuit QED

Zhang

Yang

2021

Preprint

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We present a way to transfer maximally-or partially-entangled states of n single-photon-state (SPS) qubits onto n coherent-state (CS) qubits, by employing 2n microwave cavities coupled to a superconducting flux qutrit. The two logic states of a SPS qubit here are represented by the vacuum state and the single-photon state of a cavity, while the two logic states of a CS qubit are encoded with two coherent states of a cavity. Because of using only one superconducting qutrit as the coupler, the circuit architecture is significantly simplified. The operation time for the state transfer does not increase with the increasing of the number of qubits. When the dissipation of the system is negligible, the quantum state can be transferred in a deterministic way since no measurement is required. Furthermore, the higher-energy intermediate level of the coupler qutrit is not excited during the entire operation and thus decoherence from the qutrit is greatly suppressed.As a specific example, we numerically demonstrate that the high-fidelity transfer of a Bell state of two SPS qubits onto two CS qubits is achievable within the present-day circuit QED technology.Finally, it is worthy to note that when the dissipation is negligible, entangled states of n CS qubits can be transferred back onto n SPS qubits by performing reverse operations. This proposal is quite general and can be extended to accomplish the same task, by employing a natural or artificial atom to couple 2n microwave or optical cavities.

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Universal controlled-phase gate with cat-state qubits in circuit QED

Cited by 25 publications

References 58 publications

Pair-cat codes: autonomous error-correction with low-order nonlinearity

Pair-cat codes: autonomous error-correction with low-order nonlinearity

Circuit QED: single-step realization of a multiqubit controlled phase gate with one microwave photonic qubit simultaneously controlling n − 1 microwave photonic qubits

Transferring quantum entangled states between multiple single-photon-state qubits and coherent-state qubits in circuit QED

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