论文标题
与量子热噪声的量子计量学的无限因果秩序
Indefinite causal order for quantum metrology with quantum thermal noise
论文作者
论文摘要
研究了具有无限因果秩序的开关量子通道，用于针对受量子热噪声影响的量子统一操作员的相位估计的基本计量任务。在开关通道中以不确定的顺序报告了特定的功能，而使用确定的顺序进行常规估算方法无法访问。相位估计可以通过单独测量对照乘积来执行阶段估计，尽管它没有与统一过程相互作用，但只有探针量子验量。同样，使用完全去极化的输入探针或与单位旋转轴对齐的输入探针变得可能会进行相位估计，而使用常规方法则是不可能的。本研究扩展到热噪声，以前对更对称和各向同性Qubit去极化噪声进行的研究有助于及时探索与量子信号和信息处理相关的量子通道的性质。
A switched quantum channel with indefinite causal order is studied for the fundamental metrological task of phase estimation on a qubit unitary operator affected by quantum thermal noise. Specific capabilities are reported in the switched channel with indefinite order, not accessible with conventional estimation approaches with definite order. Phase estimation can be performed by measuring the control qubit alone, although it does not actively interact with the unitary process -- only the probe qubit doing so. Also, phase estimation becomes possible with a fully depolarized input probe or with an input probe aligned with the rotation axis of the unitary, while this is never possible with conventional approaches. The present study extends to thermal noise, investigations previously carried out with the more symmetric and isotropic qubit depolarizing noise, and it contributes to the timely exploration of properties of quantum channels with indefinite causal order relevant to quantum signal and information processing.
