Speaker: 杨宇翔助理教授，香港大学

Inviter: 骆顺龙研究员

Title: Quantum metrology with network states

Language: Chinese

Time & Venue: 2024.07.01 11:00-12:00 南楼 733

Abstract: Armed with quantum correlations, quantum sensors in a network have shown the potential to outclass their classical counterparts in distributed sensing tasks such as clock synchronization and reference frame alignment. On the other hand, this analysis was done for simple and idealized networks, whereas the correlation shared within a practical quantum network, captured by the notion of network states, is much more complex. In this talk, I will introduce a general framework of network state metrology. We prove a general bound that limits the performance of using quantum network states to estimate a global parameter, establishing the necessity of genuine multipartite entanglement for achieving a quantum advantage. The bound can also serve as an entanglement witness in networks and can be generalized to states generated by shallow circuits. Moreover, while our bound prohibits local network states from achieving the Heisenberg limit, we design a probabilistic protocol that, once successful, attains this ultimate limit of quantum metrology. Our work establishes both the limitation and the possibility of quantum metrology within quantum networks.