Operational characterization of multi-photon entanglement in linear optics networks

2020年，我们将继续对多光子线性光学网络中量子态的表征进行研究。我们以实验可行的方式建立了多光子线性光学网络（LONs）互补特性表征的理论，该理论已发表在“新物理杂志22,103054（2020）”上。该理论可用于多光子LON系统的纠缠检测，而不会陷入玻色子采样的计算复杂性。它使我们能够将多部量子系统中已建立的纠缠检测方法扩展到多部量子系统。因此，在测量中可以物理地检测到多光子LON系统中的“模间纠缠”。我们已经在“AQIS 2020”和“QIP 2021”会议上介绍了这一结果。比纠缠检测更进一步，我们想要评估LONs中量子态和目标态之间的相似性。为此，我们需要首先建立一个使用状态验证器的量子态保真度估计理论。因此，我们提出了一种利用一组局部测量来估计二部qudit系统中纠缠态的量子态保真度的协议，该协议已发表在“Entropy 22,889（2020）”上。基于这一理论，人们可以在实验中构建和评估LONs中多光子态的状态验证器，以估计量子态保真度的下界和上界。这一结果已经在“2020量子信息科学研讨会”上发表。

In 2020, we have continued our research on the characterization of quantum states in multiphoton linear optics networks.We have established a theory for the characterization of complementary properties in multiphoton linear optics networks (LONs) in an experimentally feasible way, which has been published in “New Journal of Physics 22, 103054 (2020)”. This theory can be then employed for entanglement detection in multiphoton LON systems without falling into the computational complexity of boson sampling. It allows us to extend well-established methods for entanglement detection in multipartite qudit systems to multipartite LONs. As a result, “entanglement between modes” in multiphoton LON systems can be physically detected in measurements. We have presented this result at the conferences “AQIS 2020” and “QIP 2021”.A step further than the entanglement detection, we would like to evaluate the similarity between a quantum state and a target state in LONs. To this end, we need to first establish a theory for quantum state fidelity estimation employing state verifiers. We have therefore proposed a protocol for quantum state fidelity estimation for entangled states in bipartite qudit systems employing a set of local measurements, which has been published in “Entropy 22, 889 (2020)”. Based on this theory, one can construct and evaluate state verifiers for multiphoton states in LONs in experiments to estimate lower and upper bounds on quantum state fidelity. This result has been presented at the conference “Workshop on quantum information science 2020”.