Title: Mitigating photon loss in linear optical quantum circuits: classical postprocessing methods outperforming postselection Show Chinese title

Title: 减轻线性光学量子电路中的光子损耗：经典后处理方法优于后选择

Abstract: Photon loss rates set an effective upper limit on the size of computations that can be run on current linear optical quantum devices. We present a family of techniques to mitigate the effects of photon loss on both output probabilities and expectation values derived from noisy linear optical circuits composed of an input of $n$ photons, an $m$-mode interferometer, and $m$ single photon detectors. Central to these techniques is the construction of objects called recycled probabilities. Recycled probabilities are constructed from output statistics affected by loss, and are designed to amplify the signal of the ideal (lossless) probabilities. Classical postprocessing techniques then take recycled probabilities as input and output a set of loss-mitigated probabilities, or expectation values. We provide analytical and numerical evidence that these methods can be applied, up to large sample sizes, to produce more accurate outputs than those obtained from postselection - which is currently the standard method of coping with photon loss when sampling from discrete variable linear optical quantum circuits. In contrast, we provide strong evidence that the popular zero noise extrapolation technique cannot improve on on the performance of postselection for any photon loss rate. Show Chinese abstract

Abstract: 光子损耗率对当前线性光学量子设备上可以运行的计算规模设定了有效的上限。 我们提出了一类技术，以减轻由包含输入$n$光子、$m$模式干涉仪和$m$单光子探测器组成的噪声线性光学电路对输出概率和期望值的影响。 这些技术的核心是构建称为回收概率的对象。 回收概率是从受损耗影响的输出统计中构建的，并旨在增强理想（无损耗）概率的信号。 然后，经典后处理技术将回收概率作为输入，并输出一组减轻损耗的概率或期望值。 我们提供了分析和数值证据，表明这些方法可以应用于大样本量，以产生比从后选择（目前在从离散变量线性光学量子电路采样时的标准方法）获得的结果更准确的输出。 相反，我们提供了强有力的证据，表明流行的零噪声外推技术无法在任何光子损耗率下优于后选择的性能。