Ancilla-Free Quantum Error Correction Codes for Quantum Metrology
Ancilla-Free Quantum Error Correction Codes for Quantum Metrology
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DOI：
10.1103/physrevlett.122.040502
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发表时间：
2019-01-30
影响因子：
8.6
通讯作者：
Jiang, Liang
中科院分区：
文献类型：
--
作者：
Layden, David;Zhou, Sisi;Jiang, Liang
量子纠错最近已成为增强马尔可夫噪声下量子传感的工具。它的工作原理是纠正传感器中的错误，同时让信号印在逻辑状态上。这种方法通常需要专门的纠错码，因为大多数现有代码都会纠正主要错误和信号。然而，迄今为止，很少有人知道这样的专用代码，其中大多数都需要无噪声、可控的辅助装置。我们在这里表明，当信号哈密顿量和误差算子交换时，不需要这样的辅助，这是量子传感器中退相干的常见限制类型。我们给出了一个半定程序，用于寻找一般情况下最佳的无辅助传感代码，以及两种常见传感场景的封闭式代码：经历相移的量子位和有损玻色子模式。最后，我们分析了量子位代码在任意空间噪声相关性下提供的灵敏度增强，超出了正交信号和噪声算子的理想极限。
Quantum error correction has recently emerged as a tool to enhance quantum sensing under Markovian noise. It works by correcting errors in a sensor while letting a signal imprint on the logical state. This approach typically requires a specialized error-correcting code, as most existing codes correct away both the dominant errors and the signal. To date, however, few such specialized codes are known, among which most require noiseless, controllable ancillas. We show here that such ancillas are not needed when the signal Hamiltonian and the error operators commute, a common limiting type of decoherence in quantum sensors. We give a semidefinite program for finding optimal ancilla-free sensing codes in general, as well as closed-form codes for two common sensing scenarios: qubits undergoing dephasing, and a lossy bosonic mode. Finally, we analyze the sensitivity enhancement offered by the qubit code under arbitrary spatial noise correlations, beyond the ideal limit of orthogonal signal and noise operators.