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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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Entanglement and Superposition Are Equivalent Concepts in Any Physical Theory
Guillaume Aubrun1, Ludovico Lami2, Carlos Palazuelos3,4
1Institut Camille Jordan, Université Claude Bernard Lyon 1, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne CEDEX, France.
Physical Review Letters
|May 6, 2022
Summary
We prove that nonclassical general probabilistic theories (GPTs) are equivalent to those with "superpositions" and can be entangled. This allows for secure key distribution, similar to quantum theory.
Area of Science:
- Foundations of Physics
- Quantum Information Theory
- General Probabilistic Theories
Background:
- General Probabilistic Theories (GPTs) extend quantum mechanics, exploring the fundamental nature of physical theories.
- Nonclassicality in GPTs is defined by state spaces that are not simplices.
- Entanglement and superpositions are key features of quantum theory with significant implications.
Purpose of the Study:
- To establish equivalences between nonclassicality, superpositions, and entangleability in GPTs.
- To explore the role of superpositions in enabling cryptographic protocols within GPTs.
- To demonstrate the broader applicability of quantum concepts beyond standard quantum theory.
Main Methods:
- Formal mathematical proofs establishing logical equivalences between three distinct properties of GPTs.
- Analysis of the structure of state spaces to define and identify nonclassical theories.
- Investigation of composite systems and measurements to define and detect entangleability.
Main Results:
- Demonstrated the equivalence of nonclassicality, the existence of superpositions, and entangleability for any two GPTs.
- Defined superpositions in GPTs as distinguishable ensembles only before measurement.
- Showed that superpositions (strong incompatibility) are sufficient for secret key distribution protocols like BB84.
Conclusions:
- Nonclassicality, superpositions, and entangleability are fundamentally linked concepts in the broader framework of GPTs.
- The presence of superpositions in GPTs is a sufficient condition for secure key distribution, mirroring quantum capabilities.
- This work deepens our understanding of the essential features that enable quantum information processing.
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