Year: 2025
Type: article
Abstract: The development of large-scale quantum networks requires reliable quantum channels, the quality of which can be quantified by the framework of quantum process tomography. In this work, we leverage ancilla-assisted process tomography (AAPT) and Bayesian inference to probe a 1.6 km deployed fiber-optic link. We send one of the two polarization-entangled photons at Alice in one building to Bob in another, exploiting the local qubit as an ancilla system to characterize the corresponding quantum channel. Monitoring over a 24 h period returns a steady process fidelity of 97.6(1)%, while controllable spectral filtering with passbands from 0.025 to 4.38 THz finds fidelities that first increase, and then level off with bandwidth, suggesting both stable operation with time and minimal polarization mode dispersion. To our knowledge, these results represent the first AAPT of a deployed quantum link, revealing a valuable tool for in situ analysis of entanglement-based quantum networks.
Source: Optics Letters
DOI: 10.1364/ol.545625
Authors: Arefur Rahman, Noah I. Wasserbeck, Zachary Goisman, Rhea P. Fernandes, Brian T. Kirby, Muneer Alshowkan, Chris Kurtz, Joseph M. Lukens
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
Funders: U.S. Department of Energy, Cisco Systems
Awards: G105175708, G5008466161
OpenAlex ID: W4408221070