A quantum physics experiment at the University of Vienna has achieved groundbreaking precision in measuring the Earth’s rotation using entangled photons.
The research utilises an enhanced optical Sagnac interferometer that exploits quantum entanglement to detect rotation effects with unprecedented precision, potentially leading to breakthroughs in both quantum mechanics and general relativity.
Pioneering quantum experiments
A team of researchers has performed a pioneering experiment to measure the effect of the Earth’s rotation on quantum entangled photons. The study, led by Philipp Walter of the University of Vienna, has just been published in the journal Physics Letters. Scientific advancesThis is an important achievement that pushes the limits of rotational sensitivity in entanglement-based sensors and may lay the foundation for further exploration at the intersection of quantum mechanics and general relativity.
Advances in the Sagnac interferometer
The optical Sagnac interferometer is the most sensitive instrument for rotation. It has played a pivotal role in our understanding of fundamental physics since the beginning of the last century, helping to establish Einstein’s theory of special relativity. Today, its unparalleled accuracy makes it the ultimate tool for measuring rotation rates beyond the limits of classical physics.
Quantum entanglement enhances sensitivity
Quantum entanglement-based interferometers have the potential to overcome these limitations: when two or more particles are entangled, only their overall state is known; the states of each particle remain unknown until a measurement is made. This allows much more information to be obtained from each measurement than would be possible without it. However, the extremely delicate nature of quantum entanglement has prevented the expected leap in sensitivity.
This is where the Wien experiment made the difference: they built a huge fibre-optic Sagnac interferometer with low and stable noise over hours, which allowed for a high enough quality detection of entanglement. photon Such a pair exceeds the rotational precision of a conventional quantum-optical Sagnac interferometer by a factor of 1000.
Innovative technology in quantum metrology
In a Sagnac interferometer, two particles moving in opposite directions on a rotating closed path reach a starting point at different times. When the two particles become entangled, a spooky phenomenon occurs: they behave like one particle, testing both directions at the same time while accumulating twice the time delay compared to the case without entanglement. This unique property is known as super-resolution. In the actual experiment, two entangled photons propagate through two kilometers of optical fiber wound in a giant coil, resulting in an interferometer with an active area of more than 700 square meters.
Overcoming challenges in quantum experiments
The biggest hurdle the researchers faced was isolating and extracting the Earth’s stable rotation signal. “The core of the problem lies in establishing a measurement reference point, where the light is not affected by the Earth’s rotation,” explains lead author Raffaele Silvestri. “Since we can’t stop the Earth’s rotation, we devised a workaround by splitting the optical fiber into two equal-length coils and connecting them via an optical switch.”
By toggling the switch on and off, the researchers were able to effectively cancel the rotation signal, which also improved the stability of larger instruments. “We basically tricked light into thinking we were in a non-rotating universe,” Silvestri says.
Confirmation of the Interaction between Quantum Mechanics and the Theory of Relativity
The experiment, which was part of the TURIS research network hosted by the University of Vienna and the Austrian Academy of Sciences, succeeded in observing the effect of the Earth’s rotation on a maximally entangled two-photon state, confirming the interplay between rotating reference frames and quantum entanglement, as described by Einstein’s theory of special relativity and quantum mechanics, with 1000 times more precision than previous experiments.
“This is an important milestone in that, a century after the first observations of the Earth’s rotation with light, the entanglement of individual quanta of light is finally in the same region of sensitivity,” says Haokun Yu, who worked on the experiment as a Marie Curie postdoctoral fellow.
“We believe that our results and methods provide the basis for further improving the rotational sensitivity of entanglement-based sensors. This could pave the way for future experiments testing the behavior of quantum entanglement through space-time curves,” adds Philipp Walter.
Reference: “Experimental Observation of the Earth’s Rotation through Quantum Entanglement” by Raffaele Silvestri, Haokun Yu, Theodor Strömberg, Christopher Hillweg, Robert W. Peterson, and Philip Walter, 14 June 2024; Scientific advances.
DOI: 10.1126/sciadv.ado0215