New Research Suggests Way to Distinguish Between Classical and Quantum gravity
LONDON – A new theoretical study published Oct. 22 in Nature proposes a potential experimental pathway to determine whether gravity operates at a quantum level, deepening the long-standing mystery surrounding quantum gravity. Researchers Rabia Aziz and Leonard Howl demonstrate that even if gravity is fundamentally classical, it could still induce entanglement between particles, but the resulting correlations would be significantly weaker than those predicted by a quantum theory of gravity.
The work builds upon a thought experiment originally proposed by physicist Richard Feynman, exploring the potential for gravitational interactions to entangle quantum particles. Entanglement, a core principle of quantum mechanics, links the fates of two or more particles, regardless of the distance separating them.
“If you see the effects at a strong scale then you know it’s quantum gravity,” Howl stated.
The key difference lies in the strength of the correlations observed. In a scenario with quantum gravity, knowing the quantum spin of one entangled particle instantly reveals the spin of its partner. However, under classical gravity, the correlation is probabilistic – repeated measurements would reveal the partner particle’s spin to be aligned less frequently.
While the research doesn’t rule out option models, such as the one published in 2023 by Jonathan Oppenheim at university College London combining classical general relativity with quantum field theory, it offers insights into the behavior of classical gravity itself.
Currently, performing the experiment remains a significant challenge. “It’s still an open question as to whether you could do it,” Howl explained, citing the need to eliminate “decoherence” – factors that disrupt quantum superposition. Research groups in the U.K., Austria, and elsewhere are actively working to overcome these hurdles.
Howl anticipates debate surrounding the team’s findings but remains optimistic that Feynman’s experiment could be realized in the coming decades, providing a definitive test for the existence of quantum gravity.
