Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Quantum Computing, Communication, and Simulation

Experimental distribution of genuine time-bin entanglement at telecom wavelength

Kannan Vijayadharan, Francesco B. L. Santagiustina, Costantino Agnesi, Vojtěch Švarc, Paolo Villoresi, Giuseppe Vallone

Published Mar 12, 2024• 0 citations
Publisher

Abstract

Entanglement is a unique resource for quantum information processing, which allows for device-independent (DI) quantum communication protocols, such as Quantum Key Distribution and Quantum Random Number Generation. Loophole-free violation of Bell inequalities is a necessary condition for DI protocols. While timebin entanglement is promising for long-distance distribution over fiber optics, its most common implementation suffers from a post-selection loophole (PSL) which invalidates Bell non-locality tests. We present an implementation of a postselection-free “genuine” time-bin entanglement scheme working with 1550 nm biphotons with an estimated Bell violation of S = 2.56.

DOI
10.1117/12.3001070

Related papers

Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement

Francesco Vedovato, Costantino Agnesi, Marco Tomasin +4 more

Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bell's inequality with "genuine" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed us to obtain a postselection-loophole-free Bell violation of more than 9 standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modern integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.

arXiv:1804.10150•Physical Review Letters•Nov 9, 2018•67 citations

Postselection-loophole-free Bell test under strict spacetime constraints

Kannan Vijayadharan, Matías Rubén Bolaños, Andrea Pompermaier +5 more

Entanglement gives rise to correlations between distant quantum systems that cannot be explained by local realistic theories. Bell inequality violations provide a direct way to reveal these correlations and certify nonlocality, especially when the relevant experimental loopholes are closed. Time-bin encoding, in which quantum information is encoded into well-defined temporal modes, is a commonly used platform for distributing photonic entanglement in optical fibers. Yet loophole-free Bell tests with time-bin entanglement have received comparatively little attention, owing in part to the postselection loophole introduced by conventional interferometric measurements. Here, we demonstrate a fiber-based platform for Bell tests with time-bin entanglement that simultaneously closes the locality, freedom-of-choice, and postselection loopholes. We observe a CHSH violation of $S=2.583 \pm 0.002$, exceeding the local-realistic bound by over 265 standard deviations. Notably, this rigorous certification of nonlocality is achieved at a separation distance of $49.0 \pm 0.7$ m, substantially shorter than previous photonic Bell tests addressing comparable space-time constraints. Beyond its foundational significance, our results demonstrate time-bin entanglement as a viable route towards practical device-independent quantum communication and a future quantum internet.

quant-pharXiv:2608.28190•Aug 31, 2026•0 citations

First experimental realization of genuine time-bin entanglement

Francesco Vedovato, Costantino Agnesi, Marco Tomasin +4 more

The postselection loophole rendered to date time-bin entanglement unsuitable for quantum cryptography and conclusive Bell's test. We implemented a time-bin entanglement scheme free of the postselection, opening up to its exploitation in quantum information protocols.

Quantum Information and Measurement (QIM)•Jan 1, 2019•0 citations

UltrafaSt Post-Selection Free Time-Bin Entanglement on a Thin Film Lithium Niobate Photonic Chip

Matteo Bacchi, A. C. de C. Bernardi, Marco Clementi +8 more

The distribution of entangled photons between remote parties is fundamental for quantum communication protocols such as quantum teleportation and quantum key distribution (QKD). Among the various encoding schemes, time-bin entanglement is particularly promising as it ensures reliable long-distance communication for both optical fibre and free-space channels. However, the practical utility of time bin entanglement is constrained by the post-selection loophole (PSL), which allows for the possibility of local hidden variable models [1]. Temporal post-selection also opens the door to attack schemes and demands high temporal resolution. Initial efforts to close the PSL employed hyperentangled states combining polarization and time-bin degrees of freedom [2]. Later, Vedovato et al. used active switching to remove the need for post-selection [3], and an integrated “hug” scheme was used to demonstrate PSL-free certification through a phase-stabilized optical link [4].

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 23, 2025•0 citations

Postselection-Loophole-Free Time-Bin Entanglement Bell Test

Francesco Vedovato, Costantino Agnesi, Marco Tomasin +4 more

Time-bin entanglement is an important resource for quantum information protocols, rendered unusable by the postselection-loophole. We present the first time-bin entanglement Bell test free of this loophole, enabling its use in future implementations.

Frontiers in Optics•Jan 1, 2019•0 citations

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

Marcello Bacchi, Andrea Bernardi, Marco Clementi +8 more

Time-bin entanglement is a 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 and to birefringence in optical fibers. Projective measurements on some bases in the time-bin encoding need, however, postselection in the time domain 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 the temporal postselection loophole. The receivers are realized using thin-film lithium niobate and operate at a switching frequency of 5 GHz. We demonstrate a Bell inequality violation by more than 24 standard deviations without the need for time resolution at the time-bin separation level.

arXiv:2505.04598•Physical Review Applied•May 12, 2026•1 citation
Entanglement is a unique resource for quantum information processing, which allows for device-independent (DI) quantum communication protocols, such as Quantum Key Distribution and Quantum Random Number Generation. Loophole-free violation of Bell inequalities is a necessary condition for DI protocols. While timebin entanglement is promising for long-distance distribution over fiber optics, its most common implementation suffers from a post-selection loophole (PSL) which invalidates Bell non-locality tests. We present an implementation of a postselection-free “genuine” time-bin entanglement scheme working with 1550 nm biphotons with an estimated Bell violation of S = 2.56.
Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bell's inequality with "genuine" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed us to obtain a postselection-loophole-free Bell violation of more than 9 standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modern integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.
Entanglement gives rise to correlations between distant quantum systems that cannot be explained by local realistic theories. Bell inequality violations provide a direct way to reveal these correlations and certify nonlocality, especially when the relevant experimental loopholes are closed. Time-bin encoding, in which quantum information is encoded into well-defined temporal modes, is a commonly used platform for distributing photonic entanglement in optical fibers. Yet loophole-free Bell tests with time-bin entanglement have received comparatively little attention, owing in part to the postselection loophole introduced by conventional interferometric measurements. Here, we demonstrate a fiber-based platform for Bell tests with time-bin entanglement that simultaneously closes the locality, freedom-of-choice, and postselection loopholes. We observe a CHSH violation of S=2.583±0.002S=2.583 \pm 0.002S=2.583±0.002, exceeding the local-realistic bound by over 265 standard deviations. Notably, this rigorous certification of nonlocality is achieved at a separation distance of 49.0±0.749.0 \pm 0.749.0±0.7 m, substantially shorter than previous photonic Bell tests addressing comparable space-time constraints. Beyond its foundational significance, our results demonstrate time-bin entanglement as a viable route towards practical device-independent quantum communication and a future quantum internet.
The distribution of entangled photons between remote parties is fundamental for quantum communication protocols such as quantum teleportation and quantum key distribution (QKD). Among the various encoding schemes, time-bin entanglement is particularly promising as it ensures reliable long-distance communication for both optical fibre and free-space channels. However, the practical utility of time bin entanglement is constrained by the post-selection loophole (PSL), which allows for the possibility of local hidden variable models [1]. Temporal post-selection also opens the door to attack schemes and demands high temporal resolution. Initial efforts to close the PSL employed hyperentangled states combining polarization and time-bin degrees of freedom [2]. Later, Vedovato et al. used active switching to remove the need for post-selection [3], and an integrated “hug” scheme was used to demonstrate PSL-free certification through a phase-stabilized optical link [4].
Time-bin entanglement is a 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 and to birefringence in optical fibers. Projective measurements on some bases in the time-bin encoding need, however, postselection in the time domain 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 the temporal postselection loophole. The receivers are realized using thin-film lithium niobate and operate at a switching frequency of 5 GHz. We demonstrate a Bell inequality violation by more than 24 standard deviations without the need for time resolution at the time-bin separation level.