Limits on the heralding efficiencies and spectral purities of spectrally filtered single photons from photon-pair sources
Limits on the heralding efficiencies and spectral purities of spectrally filtered single photons from photon-pair sources
复制标题
光子对源经光谱滤波后的单光子在预示效率和光谱纯度方面的限制
DOI：
10.1103/physreva.95.061803
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发表时间：
2017-02
影响因子：
2.9
通讯作者：
E. Meyer-Scott;N. Montaut;J. Tiedau;L. Sansoni;H. Herrmann;T. Bartley;C. Silberhorn
中科院分区：
文献类型：
--
作者：
E. Meyer-Scott;N. Montaut;J. Tiedau;L. Sansoni;H. Herrmann;T. Bartley;C. Silberhorn
由参量下转换或四波混频产生的光子对可以在多端口干涉仪中相互干扰，或者在遥远的节点之间携带纠缠以用于纠缠交换。这要求光子是光谱纯的，以确保良好的干涉，并具有高的预示效率，以准确地知道所涉及的光子数，并随着光子数的增长保持高速率。光谱滤波通常用于去除噪声和定义光谱特性。对于预告单光子高纯度和预告效率是可能的过滤的预告臂，但当两个光子在典型的对源被过滤，我们表明，预告效率的一个或两个光子强烈降低，甚至通过理想的光谱滤波器与100%的传输在通带：任何改善减少状态的光谱纯度从过滤是在降低预告效率的成本。我们认为一个纯粹的，无损的单光子的保真度，对称化它包括两个光子对，并显示这个数量是本质上有限的光谱相关性的来源。然后，我们提供了一个框架，这种效果的基准常见的光子对源，并提出了一个实验，我们不同的光子过滤器的带宽和测量的纯度和相应的减少预示效率的增加。
Photon pairs produced by parametric down-conversion or four-wave mixing can interfere with each other in multiport interferometers or carry entanglement between distant nodes for use in entanglement swapping. This requires the photons to be spectrally pure to ensure good interference and have high heralding efficiency to know accurately the number of photons involved and to maintain high rates as the number of photons grows. Spectral filtering is often used to remove noise and define spectral properties. For heralded single photons high purity and heralding efficiency are possible by filtering the heralding arm, but when both photons in typical pair sources are filtered, we show that the heralding efficiency of one or both of the photons is strongly reduced even by ideal spectral filters with 100% transmission in the passband: any improvement in reduced-state spectral purity from filtering comes at the cost of lowered heralding efficiency. We consider the fidelity to a pure, lossless single photon, symmetrize it to include both photons of the pair, and show this quantity is intrinsically limited for sources with spectral correlation. We then provide a framework for this effect for benchmarking common photon-pair sources and present an experiment where we vary the photon filter bandwidths and measure the increase in purity and corresponding reduction in heralding efficiency.