Physicists at the University of Vienna have experimentally measured the rotation rate of our planet using maximally path-entangled quantum states of light in a large-scale interferometer.
For more than a century, interferometers have been important instruments to experimentally test fundamental physical questions.
They disproved the luminiferous ether, helped establish special relativity and enabled the measurement of tiny ripples in space-time itself known as gravitational waves.
With recent advances in technology, interferometers can nowadays also operate using various different quantum systems including electrons, neutrons, atoms, superfluids, and Bose-Einstein condensates.
“If two or more particles are entangled, only the overall state is known, while the state of the individual particle remains undetermined until measurement,” said co-lead author Dr. Philip Walther and his colleagues.
“This can be used to obtain more information per measurement than would be possible without it.”
“However, the promised quantum leap in sensitivity has been hindered by the extremely delicate nature of entanglement.”
For their research, the authors built a giant optical fiber Sagnac interferometer and kept the noise low and stable for several hours.
This enabled the detection of enough high-quality entangled photon pairs such to outperform the rotation precision of previous quantum optical Sagnac interferometers by a thousand times.
“In a Sagnac interferometer, two particles traveling in opposite directions of a rotating closed path reach the starting point at different times,” the researchers explained.
“With two entangled particles, it becomes spooky: they behave like a single particle testing both directions simultaneously while accumulating twice the time delay compared to the scenario where no entanglement is present.”
“This unique property is known as super-resolution.”
In the experiment, two entangled photons were propagating inside a…
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