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Updated: Nov 27, 2025
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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
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When Photons Are Lying about Where They Have Been
1Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel.
Entropy (Basel, Switzerland)
|December 3, 2020
Summary
A Dove prism does not alter a photon's past in nested interferometers. Experiments claiming to show a changed past are flawed, not due to altered photon history but incorrect demonstrations.
Area of Science:
- Quantum mechanics
- Optics
- Photonics
Background:
- The concept of a photon's 'past' in quantum experiments is debated.
- Nested Mach-Zehnder interferometers are used to probe quantum phenomena.
- Dove prisms alter light path but their effect on quantum history is unclear.
Purpose of the Study:
- To analyze the effect of a Dove prism on photon history in a nested Mach-Zehnder interferometer.
- To address the interpretation of experiments claiming to demonstrate a photon's past.
- To explain discrepancies in experimental results with and without a Dove prism.
Main Methods:
- Theoretical analysis of photon behavior in nested Mach-Zehnder interferometers.
- Examination of the role of the Dove prism in altering experimental outcomes.
- Application of Bohmian mechanics to describe photon trajectories.
Main Results:
- The Dove prism does not change the historical path of a photon.
- Experimental demonstrations of a photon's past are shown to be incorrect when a Dove prism is inserted.
- An explanation is provided for signals observed when the photon was minimally present.
Conclusions:
- The past of a photon in a nested interferometer is invariant to Dove prism insertion.
- Experimental interpretations regarding quantum history require re-evaluation.
- Bohmian trajectories offer a framework for understanding these quantum phenomena.
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