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Related Experiment Video

Updated: May 10, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Entanglement swapping between photons that have never coexisted.

E Megidish¹, A Halevy, T Shacham

¹Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel.

Physical Review Letters

|June 11, 2013

Summary

Quantum entanglement can occur between particles that never coexist in time. This study demonstrates entanglement between timelike separated photons, challenging conventional understanding of quantum nonlocality.

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Generation and Coherent Control of Pulsed Quantum Frequency Combs

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

Related Experiment Videos

Last Updated: May 10, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

Area of Science:

Quantum Mechanics
Quantum Information Science
Quantum Optics

Background:

The timing and order of quantum measurements are fundamental questions in quantum mechanics.
Quantum nonlocality, typically associated with spacelike separated particles, has not been fully explored in timelike separated systems.

Purpose of the Study:

To investigate the role of timing and order in quantum measurements.
To demonstrate that quantum entanglement can exist between particles with timelike separation.

Main Methods:

Generation and characterization of entangled photon pairs.
Utilizing entanglement swapping between two temporally separated photon pairs.
Detection of a photon before the creation of its entangled partner.

Main Results:

Successfully created and characterized entangled photons that never coexisted.
Demonstrated entanglement between one photon from an early pair and one from a later pair.
Observed a two-photon quantum state confirming entanglement across timelike separation.

Conclusions:

Entanglement can be shared between quantum systems that are timelike separated.
The nonlocality of quantum mechanics extends to temporal as well as spatial separation.
Quantum measurement order does not affect final results, even with temporal separation.