Post-selection free time-bin entanglement on a thin-film lithium niobate photonic chip

TL;DR

This paper demonstrates a chip-integrated receiver using thin-film lithium niobate that can certify time-bin entanglement without post-selection, enabling loophole-free Bell tests and high secure key rates in quantum communication.

Contribution

The work introduces a high-speed optical switch on a lithium niobate chip for loophole-free Bell tests in time-bin entanglement, eliminating the need for post-selection.

Findings

Bell inequality violation by over 24 standard deviations

Operation at a 5 GHz switching frequency

Loophole-free certification of time-bin entanglement

Abstract

Time-bin entanglement is the most commonly used form of entanglement for quantum communication protocols over fiber networks, due to the natural resilience of this encoding scheme to thermal phase fluctuations in optical fibers. Projective measurements on some bases in the time-bin encoding need, however, post-selection of the measured events, introducing a loophole in Bell tests and requiring high temporal resolution. In this work, we demonstrate chip-integrated receivers for time-bin entanglement certification including a high-speed optical switch to remove such post-selection loophole. The receivers are realized using thin-film lithium niobate and operate at a switching frequency of 5 GHz, enabling high secure key rates. We demonstrate a Bell inequality violation by more than 24 standard deviations without the need for time resolution at the time-bin separation level.