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As they search through decades-old test, researchers support the case of quantum mechanics


The experiment closes the loophole to gain new evidence for quantum interactions

WASHINGTON – In a new study, researchers are demonstrating creative tactics to get rid of loopholes that have long confused quantum mechanics tests. With their innovative method, the researchers were able to show quantum interactions between two particles more than 180 meters (590 feet) apart, while eliminating the possibility that their interactions over the past 11 years have affected their interactions.

A paper explaining these results will be presented at the Frontiers in Optics + Laser Science conference (FIO + LS), September 15-19, in Washington, D.C., USA.

Quantum phenomena are being studied for applications in computing, encryption, perception and beyond, but researchers are not yet fully aware of the physics behind them. New work could help improve the application of quantum by improving methods of probing quantum mechanics.

Signature: Researchers created entangled pairs of photons and split two photons of each pair in opposite directions to two measuring stations. At each measuring station, the telescope received photons from a selected source of cosmic radiation at least 11 light-years from Earth. Cosmic photon detection signals generate random bits to select measurement settings for the Bell non-gap test. In this experiment, the researchers closed the detection and locality loopholes and imposed a time limit of 11 years before the experiment to exclude local hidden variable models.

Credit: Ming-Han Li, USTC, Shanghai

Test of quantum theories

Physicists have long struggled with various ideas about the forces that govern our world. Although theories of quantum mechanics have gradually outperformed classical mechanics, many aspects of quantum mechanics are still mysterious. In the sixties, physicist John Bell proposed a way to test quantum mechanics known as Bell's inequality.

The idea is that two batches, called Alice and Bob, make measurements on particles that are far apart but connected to each other through quantum bonding.

If the world were really governed only by quantum mechanics, these remote particles with quantum interactions would be governed by a non-local correlation such that measuring the position of one particle affects the position of the other. However, some alternative theories suggest that particles only interact with one another, but are actually connected to other hidden variables by following not classical but quantum physics.

Researchers have done many experiments to test Bella's inequality. However, experiments may not always be perfect and there are some pitfalls that can lead to misleading results. Although most experiments have strongly supported the conclusion that quantum interactions exist, these shortcomings still leave little room for researchers to inadvertently influence hidden variables, thus leaving room for doubt.

Closing errors

In a new study, Li and his colleagues demonstrate ways to bridge these gaps, and add evidence that quantum mechanics regulates the interaction between the two particles.

“We implemented a gapless Bello test with measurement settings set by remote cosmic photons. So we tested the completeness of quantum mechanics with high probability, ”said Ming-Han Li of China University of Science and Technology, the lead author of this paper.

Their experimental setup includes three main components: a device that periodically emits entangled pairs of photons, and two stations that measure photons. These stations are Alice and Bob, talking about Bell's inequality. The first measuring station is 93 meters (305 feet) from the source of the pair of photons, and the second is 90 meters (295 feet) in the opposite direction.

The entangled photons travel through single-mode optical fibers to measuring stations, where their polarization state is measured by a Pockels cell and photons are detected by superconducting nanowire single-photon detectors.

In designing their experiment, the researchers sought to overcome three main problems: the idea that loss and noise make detection unreliable (detection failure); , and the idea that choosing a measurement setting that is not "truly free and random" allows the result to be controlled for a hidden reason in the common past (lack of choice of choice).

To address the first problem, Li and his colleagues showed that their settings achieved a sufficiently low level of loss and noise by comparing measurements taken at the beginning and end of the photon trip. To solve the second problem, they created an experimental setting with a similar spacing between the events of the measurement setup option. To look at the third, they based their choice of measurement setups on the behavior of cosmic photons from 11 years, which offers great confidence that nothing in the common past of the particles – for at least the last 11 years – has created a hidden variable affecting the result.

By combining theoretically calculated predictions with experimental results, the researchers were able to demonstrate quantum interactions between the interwoven photon pairs with a high degree of reliability and reliability. Their experiment thus provides convincing evidence that particle behavior has quantum effects rather than hidden variables.

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