Stabilization and operation of a Kerr-cat qubit
Stabilization and operation of a Kerr-cat qubit
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DOI：
10.1038/s41586-020-2587-z
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发表时间：
2020-08-13
期刊：
影响因子：
64.8
通讯作者：
Devoret, M. H.
中科院分区：
文献类型：
--
作者：
Grimm, A.;Frattini, N. E.;Devoret, M. H.
宏观上不同的经典态-所谓的薛定谔猫态-的量子叠加是量子计量学、量子通信和量子计算的资源。具体地说，振荡器中两个相反相位相干态的叠加编码了防止相位反转误差(1，2)的量子比特。然而，要使这一概念成为编码和操作错误保护量子信息的实用方法，还需要克服几个挑战。这种保护必须通过稳定这些高激发态来维持，同时，系统必须与编码量子比特上的快速门和编码信息的量子非破坏读出兼容。在这里，我们实验证明了一种基于克尔非线性和单模压缩(1，3)在超导微波谐振腔(4)中相互作用产生和稳定薛定谔猫态的方法。与单光子Fock态编码相比，稳定的、错误保护的量子比特的横向弛豫时间增加了一个数量级以上。我们在比最短相干时间快60多倍的时间尺度上执行所有单量子比特门操作，并在稳定的情况下演示了受保护量子比特的单次读出。我们的结果展示了快速量子控制和对错误的稳健性的结合，这是稳定的宏观态所固有的，以及这些态作为量子信息处理资源的潜力(5-8)。在超导微波谐振腔中产生和稳定的量子比特通过将其编码为克尔非线性和单模压缩产生的薛定谔猫态，显示出对倒相误差的内在稳健性。
Quantum superpositions of macroscopically distinct classical states-so-called Schrodinger cat states-are a resource for quantum metrology, quantum communication and quantum computation. In particular, the superpositions of two opposite-phase coherent states in an oscillator encode a qubit protected against phase-flip errors(1,2). However, several challenges have to be overcome for this concept to become a practical way to encode and manipulate error-protected quantum information. The protection must be maintained by stabilizing these highly excited states and, at the same time, the system has to be compatible with fast gates on the encoded qubit and a quantum non-demolition readout of the encoded information. Here we experimentally demonstrate a method for the generation and stabilization of Schrodinger cat states based on the interplay between Kerr nonlinearity and single-mode squeezing(1,3)in a superconducting microwave resonator(4). We show an increase in the transverse relaxation time of the stabilized, error-protected qubit of more than one order of magnitude compared with the single-photon Fock-state encoding. We perform all single-qubit gate operations on timescales more than sixty times faster than the shortest coherence time and demonstrate single-shot readout of the protected qubit under stabilization. Our results showcase the combination of fast quantum control and robustness against errors, which is intrinsic to stabilized macroscopic states, as well as the potential of of these states as resources in quantum information processing(5-8).A qubit generated and stabilized in a superconducting microwave resonator by encoding it into Schrodinger cat states produced by Kerr nonlinearity and single-mode squeezing shows intrinsic robustness to phase-flip errors.