Annameng Ma | Searcharxiv

arXiv2025

Unraveling quantum phase estimation: exploring the impact of multi-photon interference on the quantum Fisher information

Quantum interference is known to become extinct with distinguishing information, as illustrated by the ubiquitous double-slit experiment or the two-photon HOM effect. In the former case single particle interference is destroyed with which-path information while in the latter bunching interference tails-off as photons become distinguishable. It has been observed that when more than two particles are involved, these interference patterns are in general a non monotonic function of the distinguishability. Here we perform a comprehensive characterization, both theoretically and experimentally, of four-photon interference by analyzing the corresponding correlation functions, contemplating several degrees of distinguishability across different parameters. This study provides all the necessary tools to quantify the impact of multi-photon interference on precision measurements of parameters such as phase, frequency, and time difference. We apply these insights to quantify the precision in the estimation of an interferometric phase in a two-port interferometer using a four-photon state. Our results reveal that, for certain phase values, partially distinguishable multi-photon states can achieve higher Fisher information values compared to the two-photon experiment. These findings highlight the potential of distinguishable multi-photon states for enhanced precision in quantum metrology and related applications.

quant-ph↗

arXiv2025

A Large-Scale Reconfigurable Multiplexed Quantum Photonic Network

Entanglement distribution in quantum networks will enable next-generation technologies for quantum-secured communications, distributed quantum computing and sensing. Future quantum networks will require dense connectivity, allowing multiple users to share entanglement in a reconfigurable and multiplexed manner, while long-distance connections are established through the teleportation of entanglement, or entanglement swapping. While several recent works have demonstrated fully connected, local multi-user networks based on multiplexing, extending this to a global network architecture of interconnected local networks remains an outstanding challenge. Here we demonstrate the next stage in the evolution of multiplexed quantum networks: a prototype global reconfigurable network where entanglement is routed and teleported in a flexible and multiplexed manner between two local multi-user networks composed of four users each. At the heart of our network is a programmable 8x8-dimensional multi-port circuit that harnesses the natural mode-mixing process inside a multi-mode fibre to implement on-demand high-dimensional operations on two independent photons carrying eight transverse-spatial modes. Our circuit design allows us to break away from the limited planar geometry and bypass the control and fabrication challenges of conventional integrated photonic platforms. Our demonstration showcases the potential of this architecture for enabling large-scale, global quantum networks that offer versatile connectivity while being fully compatible with an existing communications infrastructure.

quant-ph↗