What If Gravity Isn't Quantum? New Experiments Examine
Summary
PBS Space Time explores how to test quantum gravity theories without galaxy-sized colliders. The episode contrasts "quantizing gravity" with "gravitizing the quantum," discussing models like Penrose and Oppenheim where classical gravity collapses quantum wave functions. It details potential tabletop experiments, such as measuring stochastic gravitational diffusion or using the QGEM proposal to entangle nanodiamonds via gravity, which would provide evidence for the quantum nature of spacetime.
Topics discussed
Introduction to the quantum gravity problem
The 100-year history of quantum mechanics and relativity
Challenges in quantizing gravity and the graviton
Alternative view: Gravitizing the quantum instead
Testable predictions: Quantum gravity vs classical gravity
Mechanisms of wave function collapse in classical gravity
Testing gravitational diffusion and mass measurement limits
Constraints from large molecule superposition experiments
Quantum entanglement and its role in interactions
The QGEM experiment proposal and Stern-Gerlach basics
Converting spin superposition to spatial superposition
Gravitational interaction between interferometers
Using nanodiamonds to detect gravitational entanglement
Implications: Evidence for gravitons and quantum spacetime
Summary of experimental approaches to quantum gravity
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