Related Experiment Video
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, clarifying entanglement and decoherence.
Area of Science:
- Theoretical Physics
- Quantum Gravity
- Spacetime Geometry
Background:
- Quantum gravity theories predict quantum superpositions of spacetime geometry.
- Such states can arise from mass distributions in spatial superpositions.
- Existing literature often labels these as genuinely quantum-gravitational.
Purpose of the Study:
- Introduce a framework for describing quantum superpositions of spacetime states.
- Analyze the relativity of spacetime superpositions.
- Clarify the nature of quantum-gravitational superpositions and their implications.
Main Methods:
- Developed a framework for "quantum superpositions of spacetime states."
- Introduced the concept of relativity of spacetime superpositions.
- Applied the framework to scenarios like gravitationally-induced entanglement and decoherence.
Main Results:
- Demonstrated that superpositions differing by coordinate transformations can be described on a fixed background.
- Unveiled ambiguity in labeling superpositions as genuinely quantum-gravitational.
- Showed decoherence of gravitational sources is not fundamental but depends on external reference frames.
Conclusions:
- The relativity of spacetime superpositions challenges their interpretation as inherently quantum-gravitational.
- Decoherence in gravitational systems is observer-dependent, not a fundamental property.
- The framework provides clarity on assumptions in quantum gravity research, particularly concerning entanglement and decoherence.
Related Concept Videos
01:17Space-Time Curvature and the General Theory of Relativity
In 1905, Albert Einstein published his special theory of relativity. According to this theory, no matter in the universe can attain a speed greater than the speed of light in a vacuum, which thus serves as the speed limit of the universe.
This has been verified in many experiments. However, space and time are no longer absolute. Two observers moving relative to one another do not agree on the length of objects or the passage of time. The mechanics of objects based on Newton's laws of motion,...
This has been verified in many experiments. However, space and time are no longer absolute. Two observers moving relative to one another do not agree on the length of objects or the passage of time. The mechanics of objects based on Newton's laws of motion,...
01:17The Principle of Superposition and the Gravitational Field
The principle of superposition applies to gravitational forces of objects that are sufficiently far apart. It states that the net gravitational force on a point object is the vector sum of the gravitational forces on it due to various objects. The principle helps calculate the force by listing the individual forces and then vectorially summing them up. However, it should be noted that the principle of superposition is not always apparent. In the presence of a second force, the first force could...
01:07Interference and Superposition of Waves
When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect of the waves is the sum of the individual waves' effects. However, it does not imply that the individual waves affect the propagation of other waves.
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
01:18Principle of Equivalence
According to Albert Einstein (1897-1955), free-falling and feeling weightless are intrinsically linked. If a person were in free-fall under gravity, for example, diving towards the Earth from an airplane, they would feel completely weightless. Similarly, a person descending in a lift may feel partially weightless. Broadly speaking, it is assumed that an object in a uniform gravitational field and an object undergoing constant acceleration in the absence of gravity are under the same...
01:18Superposition Theorem
The superposition principle is a fundamental concept stating that in a linear circuit, the voltage across (or current through) an element can be determined by summing the individual contributions of each independent source acting in isolation. When dealing with linear circuits containing multiple independent sources, this principle serves as a valuable tool for analysis. To apply the superposition principle effectively, one should focus on a single independent source at a time while...
04:08The Uncertainty Principle
Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that there is a fundamental limit to how accurately one can measure both a particle’s position and its momentum simultaneously. The more accurate the measurement of the momentum of a particle is known, the less accurate the position at that time is known and vice versa. This is what is now called the Heisenberg uncertainty principle. He mathematically...