Lingenfelter Andrew, Clerk Aashish A
Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637 USA.
Department of Physics, University of Chicago, Chicago, IL 60637 USA.
npj Quantum Inf. 2023;9(1):81. doi: 10.1038/s41534-023-00748-y. Epub 2023 Aug 11.
Noise is an ever-present challenge to the creation and preservation of fragile quantum states. Recent work suggests that spatial noise correlations can be harnessed as a resource for noise mitigation via the use of spectator qubits to measure environmental noise. In this work we generalize this concept from spectator qubits to a spectator mode: a photonic mode which continuously measures spatially correlated classical dephasing noise and applies a continuous correction drive to frequency-tunable data qubits. Our analysis shows that by using many photon states, spectator modes can surpass many of the quantum measurement constraints that limit spectator qubit approaches. We also find that long-time data qubit dephasing can be arbitrarily suppressed, even for white noise dephasing. Further, using a squeezing (parametric) drive, the error in the spectator mode approach can exhibit Heisenberg-limited scaling in the number of photons used. We also show that spectator mode noise mitigation can be implemented completely autonomously using engineered dissipation. In this case no explicit measurement or processing of a classical measurement record is needed. Our work establishes spectator modes as a potentially powerful alternative to spectator qubits for noise mitigation.
噪声对于脆弱量子态的创建和保存而言是一个始终存在的挑战。近期的研究表明，通过使用旁观者量子比特来测量环境噪声，空间噪声关联可以被用作减轻噪声的一种资源。在这项工作中，我们将这一概念从旁观者量子比特推广到了旁观者模式：一种光子模式，它持续测量空间相关的经典退相噪声，并对频率可调的数据量子比特施加连续的校正驱动。我们的分析表明，通过使用多个光子态，旁观者模式可以超越许多限制旁观者量子比特方法的量子测量约束。我们还发现，即使对于白噪声退相，长时间的数据量子比特退相也可以被任意抑制。此外，使用压缩（参量）驱动，旁观者模式方法中的误差在所用光子数上可以呈现海森堡极限缩放。我们还表明，旁观者模式噪声减轻可以使用工程耗散完全自主地实现。在这种情况下，无需对经典测量记录进行明确的测量或处理。我们的工作确立了旁观者模式作为一种在减轻噪声方面可能比旁观者量子比特更强大的替代方案。
