A new study reveals that quantum networks can do more than secure communication, they can also test how quantum mechanics behaves in the warped spacetime described by Einstein’s theory of gravity. Credit: SciTechDaily.com
Scientists demonstrate that quantum networks of clocks offer a new way to explore the interplay between quantum mechanics and curved space-time.
Quantum networking is advancing rapidly across the globe. As a foundational technology in the emerging field of quantum science, it holds the promise of building a worldwide quantum internet. Such a system would allow for secure communication on a massive scale and make it possible to link quantum computers over vast distances. Efforts to turn this vision into reality are already well underway, both on the ground and in orbit.
In a recent breakthrough, researchers have discovered that quantum networks may have capabilities beyond secure communication. A collaborative study led by Igor Pikovski from Stevens Institute of Technology, along with Jacob Covey at the University of Illinois at Urbana-Champaign and Johannes Borregaard at Harvard University, has opened up a new scientific possibility. Their findings, published in PRX Quantum, reveal that quantum networks can be used to investigate how space-time curvature influences quantum mechanics. This marks the first experimental approach of its kind.
While quantum theory has consistently stood up to experimental testing, its behavior in the presence of gravity remains uncertain. Einstein’s theory of general relativity redefined gravity not as a force, but as a result of the bending of space and time—a concept known as curved space-time. This curvature gives rise to unusual effects, such as the slowing of time near massive objects like planets. These effects have been confirmed with high precision and have also made their way into mainstream culture through science fiction stories, including the film Interstellar.
But how does this changing flow of time affect quantum mechanics? Could quantum theory or general relativity, or both, require modification where they intertwine? While a full theory of quantum gravity remains lacking, there are suggestions that quantum principles might change in the presence of curved spacetime. However, probing this frontier was so far impossible in experiments.
A New Approach Using Quantum Networks
In a previous study published in Physical Review Research, Pikovski and Borregaard have shown that the time is ripe for experiments to explore these questions, using quantum networks. They showed how two unique, but distinct features of quantum theory and gravity come into play simultaneously.
In quantum theory, there exist superpositions: matter can exist not only in specific, definite states, but also in mixtures of them at the same time. Quantum computing exploits this fact to build qubits —superpositions of bits of 0 and 1. Then, quantum networks can spread such qubits across large distances. But in the vicinity of Earth, these qubits would also be affected by curved space-time because the flow of time itself changes. The researchers showed that superpositions of atomic clocks in quantum networks would pick up different time-flows in superposition, and that this opens the door to probe how quantum theory and curved space-time intertwine.
“The interplay between quantum theory and gravity is one of the most challenging problems in physics today, but also fascinating,” says Igor Pikovski, Geoffrey S. Inman Junior Professor at Stevens Institute of Technology, and one of the authors. “Quantum networks will help us test this interplay for the first time in actual experiments.”
Teaming up with Covey’s lab, Pikovski and Borregaard then developed a concrete protocol. The team showed how quantum effects can be distributed across network nodes using so-called entangled W-states, and how interference between these entangled systems is recorded. By exploiting modern quantum capabilities, such as quantum teleportation (transferring the quantum state of a particle to another particle) and entangled Bell-pairs (maximally entangled states of two qubits) in atom arrays, a test of quantum theory on curved space-time can be achieved.
Rethinking the Role of Quantum Networks
“We assume that quantum theory holds everywhere — but we really don’t know if this is true,” says Pikovski. “It might be that gravity changes how quantum mechanics works. In fact, some theories suggest such modifications, and quantum technology will be able to test that.”
The results of Pikovski, Covey, and Borregaard demonstrate that quantum networks are not only a useful practical tool for a future quantum internet, but that they also provide unique opportunities for the study of fundamental physics that cannot be achieved with classical sensing. At the very least, a test of how quantum mechanics behaves on curved space-time is now possible.
References: “Probing curved spacetime with a distributed atomic processor clock” by Jacob P. Covey, Igor Pikovski and Johannes Borregaard, 2025, PRX Quantum.
DOI: 10.48550/arXiv.2502.12954
“Testing quantum theory on curved spacetime with quantum networks” by Johannes Borregaard and Igor Pikovski, 27 May 2025, Physical Review Research.
DOI: 10.1103/PhysRevResearch.7.023192
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