Postselected quantum metrological scheme is especially advantageous when the final measurements are either very noisy or expensive in practical experiments. In this work, we put forward a general theory on the compression channels in postselected quantum metrology. We define the basic notions characterizing the compression quality and illuminate the underlying structure of lossless compression channels. Previous experiments on Postselected optical phase estimation and weak-value amplification are shown to be particular cases of this general theory. Furthermore, for two categories of bipartite systems, we show that the compression loss can be made arbitrarily small even when the compression channel acts only on one subsystem. These findings can be employed to distribute quantum measurements so that the measurement noise and cost are dramatically reduced.

翻译：后选择量子计量方案在实际实验中，当最终测量过程噪声较大或成本高昂时，具有显著优势。本文提出了关于后选择量子计量中压缩通道的通用理论。我们定义了表征压缩质量的基本概念，并阐明了无损压缩通道的内在结构。先前关于后选择光学相位估计与弱值放大的实验被证明是该通用理论的特例。此外，对于两类双组分系统，我们证明即使压缩通道仅作用于一个子系统，其压缩损耗亦可被控制到任意小。这些发现可用于分布式量子测量，从而显著降低测量噪声与成本。