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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
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Unquestionable Bell Theorem for Interwoven Frustrated Downconversion Processes
Paweł Cieśliński1,2, Jan-Åke Larsson3, Marcin Markiewicz1,4
1University of Gdansk, International Centre for Theory of Quantum Technologies, 80-309 Gdańsk, Poland.
Physical Review Letters
|March 20, 2026
Summary
Interwoven frustrated parametric down-conversion (PDC) processes demonstrate Bell nonclassicality. On-off switching reveals violations of the Clauser-Horne inequality, confirming quantum phenomena in this new interferometry.
Area of Science:
- Quantum Optics
- Quantum Information
- Foundations of Quantum Mechanics
Background:
- Parametric down-conversion (PDC) processes exhibit interference based on path identity.
- Previous experiments using local phase shifts did not violate Bell inequalities due to local realistic models.
Purpose of the Study:
- To demonstrate Bell nonclassicality in interwoven frustrated PDC processes.
- To establish a new platform for exploring quantum phenomena using path-identity-based interference.
Main Methods:
- Utilizing on-off switching of local PDC processes for measurement control.
- Analyzing interference effects to test the Clauser-Horne inequality.
Main Results:
- A proper violation of the Clauser-Horne inequality was observed using on-off switching.
- The destructive interference was significant enough to violate the inequality.
Conclusions:
- The study confirms the nonclassicality of path-identity-based interferometry.
- The on-off switching approach provides a robust method for Bell analysis and discovering quantum phenomena.
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