Quantum internet gives new insights into Einstein’s relativity

Physicists have used quantum networking technology to probe the relationship between Einstein’s General Theory of Relativity and quantum mechanics.

Quantum internet research is an offshoot of quantum computing engineering. Quantum networks would use quantum mechanics to transmit information rather than electrons running through copper wire or individual photons through fibre optical cables.

Theoretically, a quantum internet could use entangled particles to enable more data to be transmitted more efficiently, quickly and securely.

Such technology is a while away from being rolled out. But new research published in the journal PRX Quantum shows how the embryonic technology of quantum networks could be used to probe how curved space-time affects quantum mechanics.

It would be the first time such a test is done.

Quantum mechanics is a powerful tool for understanding the very small world of atoms and particles but breaks down on the large scale of the universe. Meanwhile, the curved spacetime of general relativity explains gravitational interactions of the biggest structures in the universe but doesn’t gel with quantum mechanics.

Finding a theory to unify quantum mechanics and relativity has been a holy grail of modern physics for decades.

“The interplay between quantum theory and gravity is one of the most challenging problems in physics today, but also fascinating,” says author Igor Pikovski, a professor at the Stevens Institute of Technology in the US. “Quantum networks will help us test this interplay for the first time in actual experiments.” 

Pikovski and colleagues have proposed a test using entangled W-states (a quantum state involving 3 quantum bits, or qubits) in atomic clocks and how the quantum effects in these systems are influenced by the curvature of spacetime in the vicinity of Earth.

Atomic clocks have already been used to prove a consequence of Einstein’s theories – “time dilation”, where time is slower in Earth’s orbit (where the gravitational field is weaker) than on the planet’s surface.

The researchers say that qubits should also experience the curvature of spacetime and its effect on the flow of time.

“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.” 

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