故障量子器件的识别
Identification of malfunctioning quantum devices
AI总结：
该研究针对量子网络中的故障器件识别问题，分析了不同故障类型下的最优检测方案，证明局域测量在大网络极限下可达最优，纠缠探针可提升幺正操作故障的识别效果，并明确了不同量子信道故障的纠缠需求。
摘要：
我们研究了由N个量子器件组成的网络中故障器件的准确识别问题，该问题可视为经典异常检测的量子对应版本。当待检测器件为制备相同纯量子态的源、故障源产生不同的异常纯态时，我们证明最优的成功识别概率需要采用全局量子测量。我们还提出了若干自适应与非自适应的局域测量策略，在待检测器件数量趋于无穷大的极限下，这些策略可达到相同的最优成功概率。当故障器件执行已知的幺正操作时，我们证明使用纠缠探针可带来性能提升，当幺正参数超过特定阈值时甚至能实现完美识别。最后，若故障器件实现已知的量子比特信道，我们发现对于秩一和秩二Pauli信道，任意规模的网络都可通过乘积态输入和可分测量达到检测位置的最优概率；而对于秩三和一般振幅阻尼信道，最优识别需要与N个量子比特附属系统产生纠缠。
英文摘要：
We consider the problem of correctly identifying a malfunctioning quantum device that forms part of a network of $N$ such devices, which can be considered as the quantum analogue of classical anomaly detection. In the case where the devices in question are sources assumed to prepare identical quantum pure states, with the faulty source producing a different anomalous pure state, we show that the optimal probability of successful identification requires a global quantum measurement. We also put forth several local measurement strategies -- both adaptive and non-adaptive, that achieve the same optimal probability of success in the limit where the number of devices to be checked are large. In the case where the faulty device performs a known unitary operation we show that the use of entangled probes provides an improvement that even allows perfect identification for values of the unitary parameter that surpass a certain threshold. Finally, if the faulty device implements a known qubit channel we find that the optimal probability for detecting the position of rank-one and rank-two Pauli channels can be achieved by product state inputs and separable measurements for any size of network, whereas for rank-three and general amplitude damping channels optimal identification requires entanglement with N qubit ancillas.
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