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Researchers at the University of Vienna led by Philip Walther just pioneered the field of quantum mechanics and general relativity by measuring the effect of the rotation of Earth on quantum entangled photons, as stated in a press release.

In the Vienna experiment, they used an interferometer, which is the most sensitive to rotations. Its unparalleled precision makes it the ultimate tool for measuring rotational speeds, limited only by the boundaries of classical physics.

Interferometers employing quantum entanglement have the potential to break those bounds. If two or more particles are entangled, only the overall state is known, while the state of the individual particle remains undetermined until measurement.

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 which is prone to decoherence, lead author Raffaele Silvestri explained to Interesting Engineering. Until now.

Here is where the Vienna experiment made the difference. They built a giant optical fibre 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.

It is extremely challenging to make precision measurements in large-scale devices by employing these probe states, Silvestri extrapolated to Interesting Engineering.

We have overcome those hurdles by increasing, with innovative techniques, the long-term stability in time of our huge interferometer.'

A significant hurdle the researchers faced was isolating and extracting Earths steady rotation signal.

The core of the matter lays in establishing a reference point for our measurement, where light remains unaffected by Earths rotational effect, Silvestri said in a press release.

Given our inability to halt Earths from spinning, we devised a workaround: splitting the optical fibre into two equal-length coils and connecting them via an optical switch.

By toggling the switch on and off, the researchers could effectively cancel the rotation signal at will, which also allowed them to extend the stability of their large apparatus.

We have basically tricked the light into thinking its in a non-rotating universe, added Silvestri.

To clarify, Silvestri told Interesting Engineering humorously to not take it too literally.

They swapped the propagation direction of the two counter-propagating photons for half of the propagation length in the optical fiber. This means that when the photons come back to the starting point the delay that they have accumulated, which quantifies Earth rotational speed, is null.

So being that the interferometer is attached to the Earths surface and its rotating with it, the Earths rotation-induced effect is cancelled. Its almost as if the photons dont feel or see any rotation in the end, tricked into thinking they are in a non-rotating reference frame AKA universe.

This enables them to compare the behavior of the entangled state from a rotating to an effectively non-rotating reference frame and brings also several technical advantages as noise suppression and higher stability in the long term.

This technique has never been employed in a quantum Sagnac interferometer and is an innovative invention for this reason, he concluded.

The experiment, which was conducted as part of the research network TURIS hosted by the University of Vienna and the Austrian Academy of Sciences, has successfully observed the effect of the rotation of Earth on a maximally entangled two-photon state.

This confirms the interaction between rotating reference systems and quantum entanglement, as described in Einsteins special theory of relativity and quantum mechanics, with a thousand-fold precision improvement compared to previous experiments.

That represents a significant milestone since, a century after the first observation of Earths rotation with light, the entanglement of individual quanta of light has finally entered the same sensitivity regimes, said Haocun Yu, who worked on this experiment as a Marie-Curie Postdoctoral Fellow.

I believe our result and methodology will set the ground to further improvements in the rotation sensitivity of entanglement-based sensors. This could open the way for future experiments testing the behavior of quantum entanglement through the curves of spacetime, added Philip Walther.

In other words, the next step, Silvestri said, would be increasing the sensitivity by a significant amount to be able to detect general relativistic effects as Frame-Dragging (or Lense-Thirring) on an entangled photon pair. This is a gravitational effect that is predicted by Einsteins general theory of relativity in presence of a rotating massive body, as a rotating Earth drags its spacetime curvature and it simply manifests itself as a small correction to the Earth rotational speed.

This measurement would represent the first experimental test of the behavior of quantum mechanics in curved spacetimes, shining light into this unexplored regime.

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Maria Mocerino Originally from LA, Maria Mocerino has been published in Business Insider, The Irish Examiner, The Rogue Mag, Chacruna Institute for Psychedelic Plant Medicines, and now Interesting Engineering.

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Earth's rotation measured 1000x better with quantum entanglement - Interesting Engineering