The experiment of China University of Science and Technology verifies the properties that quantum states can be guided simultaneously in multi-body systems

Source: China University of Science and Technology News

The team of Academician Guo Guangcan of our University has recently made important progress in the basic research of quantum information. Chuanfeng Li, Jinshi Xu, Kai Sun et al. conducted an experimental study of the relationship structure of multi-body quantum guidance, and observed for the first time the non-parthenicity sharing relationship of multi-body quantum guidance, that is, the quantum state of one party can be guided by the other two at the same time. The research results were published in the internationally renowned physics journal Physical Review Letters on March 24.

Quantum guidance describes the ability of one particle to influence the quantum state of another particle through local measurements. As a quantum non-local phenomenon, quantum guidance has a unique asymmetric property, which can further realize one-way quantum guidance, that is, one side can guide the other side, but not the other way around. In the study of many-body quantum guidance, monogamy will limit the sharing ability of quantum guidance among individuals, so that one party cannot be guided by other participants at the same time. However, the theoretical research shows that the multi-body quantum guidance will violate the monogamy phenomenon when the measurement direction is increased, showing the rich guidance sharing relationship structure between the multi-body. To verify this non-monogamous sharing relationship experimentally, we need to be able to make arbitrary measurements of multi-volume subsystems, which requires us to prepare multi-body entangled qubit systems with high fidelity.

Based on the optical platform, Li Chuanfeng, Xu Jinshi, Sun Kai and others have carried out systematic experimental research on quantum guidance in recent years. It includes the verification of all-versus-nothing quantum guidance [PRL 113, 140402 (2014)], the realization of one-way quantum guidance [PRL 116, 160404 (2016); PRL 118, 140404 (2017)], etc. In this work, the research team further used the three degrees of freedom of photon polarization, path and orbital angular momentum to construct a three-qubit system and prepare a series of three-body entangled states with an average fidelity of 96%. By extending the uncertainty criterion of quantum guidance, the research team studied the non-monogamous sharing relation of multi-body quantum guidance. The experimental results show that the quantum state of one party can be guided by the other two parties simultaneously in the three-body subsystem, which violates the traditional monogamous relationship and confirms the shared property of the multi-body quantum guidance. The research team has demonstrated different quantum guidance architectures by fully analyzing three-body systems in the W state (a class of multi-body entangled states). Using the confirmed shared relationship of multi-body quantum-guided non-monogamy, the research team further realized the experimental verification of three-body true entanglement. Compared with conventional methods, this detection method requires fewer measurement resources, demonstrating its efficiency.

Figure 1. Quantum guidance structure in a three-body system. The arrow without a fork indicates that one party can guide the other party, and the arrow with a fork indicates that one party cannot guide the other party. a. Single coordination structure of quantum guidance. Neither party can be directed by the other two simultaneously; b. Shared relationship structure that violates monogamy. A party can be directed by two other parties simultaneously.

（中科院量子信息重点实验室、中科院量子信息和量子科技创新研究院、科研部）