Richard Howl and Joseph Aziz at the Department of Physics, Royal Holloway, University of London, demonstrated quantum entanglement mediated by gravity in research published in October 2025. Their findings, appearing in Nature, suggest a fundamental link between gravity and quantum mechanics, challenging existing theoretical frameworks. The team showed that classical theories of gravity can, in fact, produce entanglement between two masses, a previously unconfirmed prediction. This breakthrough, detailed in their paper titled “Classical theories of gravity produce entanglement” (DOI: 10.1038/s41586-025-09595-7), opens new avenues for exploring the interplay between these two foundational pillars of physics, and builds on earlier work by Richard Feynman regarding quantum gravity.
Classical Gravity Can Generate Quantum Entanglement
Recent work by Joseph Aziz and Richard Howl demonstrates that classical theories of gravity can, in fact, generate quantum entanglement. This finding challenges the long-held assumption that detecting entanglement necessitates a quantum theory of gravity, opening new avenues for experimental verification. Their research extends existing descriptions of matter within theorems relating classical gravity to local interactions, revealing the potential for transmitting quantum information through purely classical gravitational means. This unexpected result suggests a pathway to probe the quantum nature of gravity using currently available experimental techniques.
Specifically, Aziz and Howl found that placing a massive object in a quantum superposition of two locations, and allowing it to interact gravitationally with another mass, can induce entanglement. The scale of this effect differs from predictions made by theories of quantum gravity, providing a crucial parameter for designing robust experiments. This builds on a thought experiment originally proposed by Richard Feynman in 1957, which envisioned using an object with a Planck mass (approximately 0.02 mg) in superposition to test for gravitational entanglement. The researchers emphasize that this classical mechanism offers a distinct signature, allowing for differentiation from entanglement arising from fully quantum gravity theories.
This discovery is particularly significant because it suggests that evidence for the quantum nature of gravity might be attainable without requiring a complete quantum theory. While previous attempts to unify gravity with quantum mechanics, including string theory and loop quantum gravity, remain incomplete, this work offers a practical experimental route. The ability to generate entanglement through classical gravity provides a clear target for experiments, potentially resolving the decades-long quest to reconcile Einstein’s theory of general relativity with the principles of quantum mechanics. This offers a potentially simpler path for experimental validation than awaiting a fully realized theory of quantum gravity.
Entanglement & Gravity: A Path to Quantum Theory
Building on this foundation, Richard Howl and Joseph Aziz extended the theoretical description of matter to encompass the full framework of quantum field theory. This allowed for a more nuanced analysis of how gravity might interact with quantum systems and generate entanglement, even within classically described gravitational fields. Their work demonstrates that classical gravity isn’t necessarily incompatible with entanglement generation; rather, the scale and characteristics of that entanglement differ significantly from predictions made by theories of full quantum gravity. This distinction provides a crucial pathway for experimental verification, allowing scientists to differentiate between classical and quantum gravitational effects.
The researchers found that the resulting entanglement scales differently than anticipated in many quantum gravity models, offering a unique signature for experimental detection. Specifically, the effect’s magnitude allows for calculations determining the parameters and form of the experiment needed to definitively demonstrate the quantum nature of gravity. Richard Feynman’s original thought experiment, proposing a superposition of a Planck mass object, remains central to this endeavor, although the precise measurement prescription for confirming quantum effects remained unclear in his initial formulation. The current work clarifies that even a successful demonstration of entanglement via gravity using classical theories doesn’t disprove quantum gravity, but instead defines the boundaries within which a true quantum theory must operate.
This investigation addresses a long-standing challenge in physics: the difficulty of reconciling general relativity with quantum mechanics. While other fundamental forces have successfully integrated with quantum theory, gravity has stubbornly resisted quantization using standard methods. The findings by Joseph Aziz and Richard Howl do not offer a complete unification, but they provide a crucial experimental target. A successful demonstration of entanglement generated by classical gravity, followed by the observation of deviations from these predicted characteristics, would strongly suggest the necessity of a fully quantum theory of gravity. This approach shifts the focus from searching for a complete theory to designing targeted experiments capable of revealing the subtle quantum signatures hidden within gravitational interactions.
The findings from Joseph Aziz and Richard Howl demonstrate that even theories with classical gravity can generate quantum entanglement via local processes. This is a crucial distinction, offering a pathway to experimentally test the quantum nature of gravity itself, a long-sought goal in physics. This development could enable researchers to design experiments that robustly differentiate between classical and quantum gravity theories, refining our understanding of fundamental interactions.
The implications extend beyond quantum computing to broader areas of physics, potentially reshaping how we view the relationship between gravity and quantum mechanics. For scientists, this research provides a concrete framework for exploring entanglement’s role in gravitational systems and, ultimately, unifying these core principles of the universe.
