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

Research in Optical Sciences

Entanglement between photons that never co-existed

E. Megidish, A. Halevy, Tomer Shacham, Tom Dvir, Liat Dovrat, H. S. Eisenberg

Published Jan 1, 2012• 1 citation
Publisher

Abstract

We entangle two photons, with the first detected even before the other is created, by using entanglement swapping between temporally-separated polarization-entangled photon pairs. This result shows the nonlocality of quantum mechanics in spacetime.
DOI
10.1364/qim.2012.qt5a.9

Related papers

Entanglement between photons that never co-existed

E. Megidish, A. Halevy, Tomer Shacham +3 more

We entangle two photons, with the first detected even before the other is created, by using entanglement swapping between temporally-separated polarization-entangled photon pairs. This result shows the nonlocality of quantum mechanics in spacetime.

Frontiers in Optics•Jan 1, 2012•4 citations

Entanglement Swapping between Photons that have Never Coexisted

E. Megidish, A. Halevy, Tomer Shacham +3 more

The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the nonlocality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spacelike separation, but also to particles with timelike separation. In order to demonstrate these principles, we generated and fully characterized an entangled pair of photons that have never coexisted. Using entanglement swapping between two temporally separated photon pairs, we entangle one photon from the first pair with another photon from the second pair. The first photon was detected even before the other was created. The observed two-photon state demonstrates that entanglement can be shared between timelike separated quantum systems.

arXiv:1209.4191•Physical Review Letters•May 22, 2013•118 citations

Experimental Entanglement Swapping: Entangling Photons That Never Interacted

Jian-Wei Pan, Dik Bouwmeester, Harald Weinfurter +1 more

We experimentally entangle freely propagating particles that never physically interacted with one another or which have never been dynamically coupled by any other means. This demonstrates that quantum entanglement requires the entangled particles neither to come from a common source nor to have interacted in the past. In our experiment we take two pairs of polarization entangled photons and subject one photon from each pair to a Bell-state measurement. This results in projecting the other two outgoing photons into an entangled state.

Physical Review Letters•May 4, 1998•1,466 citations

Entanglement Swapping Demonstration in the Telecom Band Using Polarization-Entangled Photon Pairs

Yinghong Xue, Akio Yoshizawa, Hidemi Tsuchida +2 more

Entanglement swapping at 1550 nm was experimentally demonstrated based on two polarization‐entangled photon pairs, which were created in two independent PPLN waveguides. Mandel dip was measured by using fourfold coincidences to yield a visibility of 71.8% and verify quantum interference between photons from two separated sources. By making Bell‐state measurement, the two initially independent photons were projected into an entanglement state. An interference visibility of 37.5% was observed for these two photons indicating the entanglement state was successfully swapped by using polarization‐entangled photon pairs in the telecom band.

AIP conference proceedings•Jan 1, 2011•0 citations

Quantum interference and entanglement of photons that do not overlap in time

Ralph Wiegner, C. Thiel, Joachim von Zanthier +1 more

We discuss the possibility of quantum interferences and entanglement of photons that exist at different intervals of time, i.e., one photon being recorded before the other has been created. The corresponding two-photon correlation function is shown to violate Bell's inequalities.

arXiv:1102.1490•Optics Letters•Apr 15, 2011•9 citations

Quantum Entanglement and Non-Local Decoherence

Francesco Forte

Why quantum entanglement and decoherence appear to violate the speed of light.

•Jul 12, 2026•0 citations
The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the nonlocality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spacelike separation, but also to particles with timelike separation. In order to demonstrate these principles, we generated and fully characterized an entangled pair of photons that have never coexisted. Using entanglement swapping between two temporally separated photon pairs, we entangle one photon from the first pair with another photon from the second pair. The first photon was detected even before the other was created. The observed two-photon state demonstrates that entanglement can be shared between timelike separated quantum systems.
We experimentally entangle freely propagating particles that never physically interacted with one another or which have never been dynamically coupled by any other means. This demonstrates that quantum entanglement requires the entangled particles neither to come from a common source nor to have interacted in the past. In our experiment we take two pairs of polarization entangled photons and subject one photon from each pair to a Bell-state measurement. This results in projecting the other two outgoing photons into an entangled state.
Entanglement swapping at 1550 nm was experimentally demonstrated based on two polarization‐entangled photon pairs, which were created in two independent PPLN waveguides. Mandel dip was measured by using fourfold coincidences to yield a visibility of 71.8% and verify quantum interference between photons from two separated sources. By making Bell‐state measurement, the two initially independent photons were projected into an entanglement state. An interference visibility of 37.5% was observed for these two photons indicating the entanglement state was successfully swapped by using polarization‐entangled photon pairs in the telecom band.