Quantum Wrapper Networking for Polarization Entangled Photon Pairs: Noise Investigation and Active Polarization Control

Antı́a Lamas-Linares, John C. Howell, Dirk Bouwmeester

Gamze Gül, James van Howe, Sze Tiong Tan +5 more

We demonstrate automated polarization compensation of quantum datagrams leveraging classical headers as a polarization probe, thereby advancing the functionality of quantum wrapper networking. We furthermore observe minimal performance degradation from Raman scattering noise.

Gamze Gül, James van Howe, Gregory S. Kanter +6 more

Quantum wrapper networking (QWN) is an emerging quantum networking protocol that wraps qubits in classical header bits to enable switching/routing, monitoring, and control without detecting the quantum signal. In this work, we encode header bits with two nonorthogonal polarization references to track and actively compensate for the changing birefringence of a 48 km deployed fiber link. Our method is analytical and deterministic, using motorized waveplates and a variable phase retarder to accurately and stably compensate the channel. We verify successful compensation by measuring the polarization stability of single photon qubits and the visibility of entangled photon pairs under both slow birefringence drift due to environmental fluctuations and large sudden changes designed to emulate those that occur during packet switching and rerouting over different fiber paths. For large, sudden changes, our compensator recovers the Stokes vector of single photons to within 10 degrees of the target state on the Poincaré sphere and restores the two-photon interference visibilities to their original levels on the deployed fiber link. Additionally, experiments monitoring long-term compensation over 44 hours show that active polarization compensation maintains the two-photon interference visibility, whereas disabling the compensator leads to visibility degradation over time, particularly in the diagonal-antidiagonal basis, where the average raw visibility decreases by 7.7%. These results add a polarization-control layer to QWN and illustrate that information-carrying headers can enable deterministic physical-layer compensation in the quantum channel over long-distance deployed fiber links.

M. G. Mingolla, Christian Tomás Schmiegelow, M. A. Larotonda

Yan Xia, Jie Song, Zhen‐Biao Yang +1 more

Mehmet Berkay On, Sunil Kumar Singh, G. Gül +4 more

We experimentally demonstrate optical packet switching for quantum payloads and classical burst headers in a three-node quantum wrapper network. Further, we record coincidence count distributions of polarization-entangled photon pairs between the source node and two distinct destination nodes and measure the coincidence-to-accidental ratio above 6.02.