Recent research shows that gravity and quantum information are deeply connected and that the shape of spacetime can be traced back to the way information is stored in quantum fields.

Einstein's theory of general relativity describes gravity as the curvature of space and time caused by matter and energy. Quantum theory, on the other hand, describes the microscopic world. Uniting the two is one of the biggest open problems in physics.

In 1995, the physicist Ted Jacobson showed that Einstein's equations can be derived from thermodynamics, the physics of heat and entropy, much like the laws governing a gas emerge from the motion of its molecules. This suggested that gravity might not be fundamental but could emerge from something deeper.

In their research, published in the journal Physical Review Letters, the authors reconstruct the thermodynamic derivation of general relativity through sophisticated mathematical methods that connect quantum information to spacetime geometry.

However, it emerges from the paper and extensive conversations with the authors that their research could provide new clues about the origin of gravity, a tentative conclusion they reach through their use of quantum relative entropy.

The authors build on the idea that space and gravity may not be fundamental features of nature but may instead emerge from the quantum world. Rather than relying on the classical notion of entropy, they employ quantum relative entropy, a precise mathematical measure from quantum information theory that quantifies how distinguishable two quantum states are.

“We show that this quantity, evaluated at a horizon—a boundary in spacetime beyond which no information can be received—equals the energy flowing across that horizon,” explained Dr. Albert Much, Assistant Professor of Quantum Field Theory and ‪General Relativity and co-author of the study.
“Combined with the well-established relation between entropy and the area of horizons, as illustrated by Bekenstein and Hawking, this leads directly to the equations that describe how quantum matter curves spacetime.”

Relative entropy measures how well two quantum states can be told apart. Imagine the surface of the sea, which is never perfectly still. Its constant rippling is like the quantum vacuum, the state we call empty space. Now imagine a wave passing across this surface. Relative entropy tells us how well one can distinguish that wave from the rippling background.

When information becomes gravity

The authors argue that the significance of their findings rests on the genuine novelty of their proof. At the same time, they acknowledge that the fundamental ingredients of the deep connection between information and gravity were already known.

However, the researchers emphasize that this relationship was often presented in terms of physical intuition and suggestive arguments rather than through a fully rigorous mathematical framework supported by precise derivations and proofs.

For decades, the connection between entropy and gravity relied on analogies with classical thermodynamics. The work indicates that the precise quantum notion of information can take its place, a development the authors regard as a meaningful step toward understanding quantum gravity.

“Our derivation uses mathematically rigorous and well-defined quantities, replacing earlier heuristic arguments,” Dr. Much emphasized. “This supports the view that spacetime and gravity may emerge from more fundamental quantum information, a key clue in the search for a theory of quantum gravity.”

The research suggests that gravity is, at its core, rooted in quantum information. The way space and time curve may be governed by how quantum states can be distinguished from one another.

“The equations of gravity, in their quantum-corrected form, can be obtained from quantum information,” noted Dr. Much. “It is a little like plucking a guitar string: matter is the pluck, spacetime is the string, and the note it produces is Einstein's equations."

Quantum field theory in curved spacetime, which describes quantum matter in a gravitational background, is often seen as a first step toward quantum gravity. The research’s findings, according to co-author Philipp Dorau, a theoretical physicist at the Institute for Theoretical Physics, Leipzig University, Germany, suggest that this first step hints at a more fundamental relation: local spacetime curvature is tied to quantum information.

“Most of the ingredients for our work have been known for decades. Physicists have long studied how quantum matter behaves near horizons, such as those of black holes, as well as the thermal properties of empty space,” Dorau maintained. “It was recent progress in understanding relative entropy that gave us the missing link between quantum information, thermodynamics, and gravity.”

Bridging the quantum-gravity divide

While the research does not have immediate applications, its value lies in deepening our understanding of the foundations of nature. Historically, such foundational work has often had an enormous long-term impact. General relativity, once considered a purely theoretical framework, is now essential to technologies such as GPS, said Dr. Much.

“Moreover, quantum information, the language of our work, is the same framework that underlies quantum computing and quantum technologies,” he added.

The findings, if confirmed and further developed, could help bridge one of the deepest divides in modern physics: the still-unresolved gap between the quantum laws governing the microscopic world and Einstein’s theory of gravity.

Aware of this profound divide, the authors do not treat gravity as a fundamental force in its own right. Rather, their work lends support to the idea that spacetime itself may emerge from the informational structure of the quantum universe.

They now aim to extend their findings to more general scenarios, including different forms of quantum matter, more general quantum states, and light-like surfaces, which play a central role in black-hole physics.

“We are currently trying to generalize this to full quantum gravity, and it seems to me that this connection that we have identified will serve as a testbed for the various theories of quantum gravity,” Dr. Much said.

He added that their future research would focus on formulating the quantum component that can be inserted on one side of these equations “and see if the right thing (namely Einstein equations + corrections) comes out on the other side.”

“Our long-term goal is to know and clarify how far gravity can be derived from quantum information alone, which may offer guidance toward a full theory of quantum gravity.”

Recent research shows that gravity and quantum information are deeply connected and that the shape of spacetime can be traced back to the way information is stored in quantum fields.

Einstein's theory of general relativity describes gravity as the curvature of space and time caused by matter and energy. Quantum theory, on the other hand, describes the microscopic world. Uniting the two is one of the biggest open problems in physics.

In 1995, the physicist Ted Jacobson showed that Einstein's equations can be derived from thermodynamics, the physics of heat and entropy, much like the laws governing a gas emerge from the motion of its molecules. This suggested that gravity might not be fundamental but could emerge from something deeper.

In their research, published in the journal Physical Review Letters, the authors reconstruct the thermodynamic derivation of general relativity through sophisticated mathematical methods that connect quantum information to spacetime geometry.

However, it emerges from the paper and extensive conversations with the authors that their research could provide new clues about the origin of gravity, a tentative conclusion they reach through their use of quantum relative entropy.

The authors build on the idea that space and gravity may not be fundamental features of nature but may instead emerge from the quantum world. Rather than relying on the classical notion of entropy, they employ quantum relative entropy, a precise mathematical measure from quantum information theory that quantifies how distinguishable two quantum states are.

“We show that this quantity, evaluated at a horizon—a boundary in spacetime beyond which no information can be received—equals the energy flowing across that horizon,” explained Dr. Albert Much, Assistant Professor of Quantum Field Theory and ‪General Relativity and co-author of the study.
“Combined with the well-established relation between entropy and the area of horizons, as illustrated by Bekenstein and Hawking, this leads directly to the equations that describe how quantum matter curves spacetime.”

Relative entropy measures how well two quantum states can be told apart. Imagine the surface of the sea, which is never perfectly still. Its constant rippling is like the quantum vacuum, the state we call empty space. Now imagine a wave passing across this surface. Relative entropy tells us how well one can distinguish that wave from the rippling background.

When information becomes gravity

The authors argue that the significance of their findings rests on the genuine novelty of their proof. At the same time, they acknowledge that the fundamental ingredients of the deep connection between information and gravity were already known.

However, the researchers emphasize that this relationship was often presented in terms of physical intuition and suggestive arguments rather than through a fully rigorous mathematical framework supported by precise derivations and proofs.

For decades, the connection between entropy and gravity relied on analogies with classical thermodynamics. The work indicates that the precise quantum notion of information can take its place, a development the authors regard as a meaningful step toward understanding quantum gravity.

“Our derivation uses mathematically rigorous and well-defined quantities, replacing earlier heuristic arguments,” Dr. Much emphasized. “This supports the view that spacetime and gravity may emerge from more fundamental quantum information, a key clue in the search for a theory of quantum gravity.”

The research suggests that gravity is, at its core, rooted in quantum information. The way space and time curve may be governed by how quantum states can be distinguished from one another.

“The equations of gravity, in their quantum-corrected form, can be obtained from quantum information,” noted Dr. Much. “It is a little like plucking a guitar string: matter is the pluck, spacetime is the string, and the note it produces is Einstein's equations."

Quantum field theory in curved spacetime, which describes quantum matter in a gravitational background, is often seen as a first step toward quantum gravity. The research’s findings, according to co-author Philipp Dorau, a theoretical physicist at the Institute for Theoretical Physics, Leipzig University, Germany, suggest that this first step hints at a more fundamental relation: local spacetime curvature is tied to quantum information.

“Most of the ingredients for our work have been known for decades. Physicists have long studied how quantum matter behaves near horizons, such as those of black holes, as well as the thermal properties of empty space,” Dorau maintained. “It was recent progress in understanding relative entropy that gave us the missing link between quantum information, thermodynamics, and gravity.”

Bridging the quantum-gravity divide

While the research does not have immediate applications, its value lies in deepening our understanding of the foundations of nature. Historically, such foundational work has often had an enormous long-term impact. General relativity, once considered a purely theoretical framework, is now essential to technologies such as GPS, said Dr. Much.

“Moreover, quantum information, the language of our work, is the same framework that underlies quantum computing and quantum technologies,” he added.

The findings, if confirmed and further developed, could help bridge one of the deepest divides in modern physics: the still-unresolved gap between the quantum laws governing the microscopic world and Einstein’s theory of gravity.

Aware of this profound divide, the authors do not treat gravity as a fundamental force in its own right. Rather, their work lends support to the idea that spacetime itself may emerge from the informational structure of the quantum universe.

They now aim to extend their findings to more general scenarios, including different forms of quantum matter, more general quantum states, and light-like surfaces, which play a central role in black-hole physics.

“We are currently trying to generalize this to full quantum gravity, and it seems to me that this connection that we have identified will serve as a testbed for the various theories of quantum gravity,” Dr. Much said.

He added that their future research would focus on formulating the quantum component that can be inserted on one side of these equations “and see if the right thing (namely Einstein equations + corrections) comes out on the other side.”

“Our long-term goal is to know and clarify how far gravity can be derived from quantum information alone, which may offer guidance toward a full theory of quantum gravity.”