Quantum networks, the key technology for realizing a global quantum internet, are spearheading a new era of secure communication and quantum computer interconnection. A collaborative research team from Stevens Institute of Technology, the University of Illinois Urbana-Champaign, and Harvard University has published new findings in PRX Quantum, revealing that quantum networks are far more versatile than previously understood.
The study, titled "Detecting Curved Spacetime with Distributed Atomic Clocks in a Quantum Network," is the first to demonstrate the potential of quantum networks for probing the influence of curved spacetime on quantum theory. Quantum physics has excelled in every experimental test to date, yet its behavior becomes far less clear when combined with Einstein's theory of gravity—general relativity. Einstein posited that gravity arises from the curvature of spacetime, a concept confirmed by high-precision measurements and popularized in science fiction. However, how variations in the flow of time affect quantum mechanics—and whether quantum theory and general relativity require modification at their intersection—remains an open question.
The team showed that superpositions of atomic clocks in a quantum network can pick up differing time flows, offering a new avenue to explore the interplay between quantum theory and curved spacetime. "The interaction between quantum theory and gravity is one of the most challenging problems in physics," said Igor Pikovski, professor at Stevens Institute of Technology. "Quantum networks will help us test this interaction in actual experiments for the first time." Working with the Covey lab, the team developed concrete protocols that distribute quantum effects across network nodes using entangled W-states and record interference between entangled systems, laying the groundwork for testing quantum theory in curved spacetime.
The research by Pikovski, Covey, and Borregaard not only underscores the value of quantum networks as practical tools for the future quantum internet but also highlights their unique opportunities for fundamental physics research. At the very least, it is now possible to test the behavior of quantum mechanics in curved spacetime, opening the door to unraveling deeper mysteries in physics.
