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Coexistent quantum channel characterization using quantum process tomography with spectrally resolved detection

Publication Type
Conference Paper
Book Title
Proceedings of SPIE Volume 12446: Quantum Computing, Communication, and Simulation III
Publication Date
Publisher Location
Bellingham, Washington, United States of America
Conference Name
Quantum West 2023
Conference Location
San Francisco, California, United States of America
Conference Sponsor
The International Society for Optics and Photonics (SPIE)
Conference Date

The coexistence of classical and quantum signals over the same optical fiber is critical for quantum networks operating within the existing communications infrastructure. Here, we characterize the quantum channel that results from distributing approximate single-photon polarization-encoded qubits simultaneously with classical light of varying intensities through a 25 km fiber-optic channel. We use spectrally resolved quantum process tomography with a newly developed Bayesian reconstruction method to estimate the quantum channel from experimental data, both with and without classical noise. Furthermore, we show that the coexistent fiber-based quantum channel has high process fidelity with an ideal depolarizing channel if the noise is dominated by Raman scattering. These results aid future development of quantum repeater designs and quantum error-correcting codes which benefit from realistic channel error models.