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Updated: Aug 5, 2026
07:56
A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Relativity and decoherence of spacetime superpositions
Joshua Foo1,2,3,4,5,6, Cendikiawan Suryaatmadja3, Robert B Mann3,7
1Centre for Quantum Computation & Communication Technology, School of Mathematics & Physics, The University of Queensland, St. Lucia, QLD Australia.
NPJ Quantum Information
|July 25, 2026
Summary
Quantum gravity theories may involve spacetime geometry superpositions. This study introduces a framework showing these superpositions are relative, not fundamentally quantum-gravitational, impacting entanglement and decoherence studies.
Area of Science:
- Theoretical Physics
- Quantum Gravity
- Quantum Information
Background:
- Quantum gravity theories predict quantum superpositions of spacetime geometry.
- Such states could arise from mass distributions in spatial superpositions.
- Existing literature often labels these as genuinely quantum-gravitational.
Purpose of the Study:
- To introduce a framework for describing quantum superpositions of spacetime states.
- To analyze the nature of spacetime superpositions and their relation to quantum gravity.
- To clarify assumptions in studies of gravitationally-induced entanglement and decoherence.
Main Methods:
- Developed a framework for 'quantum superpositions of spacetime states'.
- Introduced the concept of relativity of spacetime superpositions.
- Demonstrated re-expression of superpositions on a fixed background via coordinate transformations.
Main Results:
- Identified an inherent ambiguity in labeling spacetime superpositions as quantum-gravitational.
- Showed that superpositions differing by a coordinate transformation can be described on a fixed background.
- Implications for gravitationally-induced entanglement and decoherence of gravitational sources.
Conclusions:
- Spacetime superpositions are relative and not necessarily fundamentally quantum-gravitational.
- Decoherence of gravitational sources is not fundamental but depends on external reference frames.
- The framework clarifies assumptions in quantum gravity research, particularly concerning entanglement and decoherence.
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