Ultra-precise measurement powered by quantum negativity – “Highly counterintuitive and truly amazing!”


Quantum laser light shines on a chemical molecule that we want to measure. Then light passes our “magic” quantum filter. This filter weakens a lot of light, while condensing all the useful information in weak light to finally reach the camera detector. Sincerely: Hugo Lepage

Scientists have found that a physical property called ‘quantum negativity’ can be used to more accurately measure everything from molecular distances Gravitational waves.

Researchers from Cambridge University, Harvard and MIT, Has shown that quantum particles can carry unlimited amounts of information about the things with which they interact. Magazine reported results Nature communication, Can enable more precise measurements and power new techniques such as super precision microscopes and quantum computers.

Metrology is the science of estimation and measurement. If you weigh yourself this morning, you have metrology done. in the same way as quantum computing Revolution is expected from the way complex calculations are done, quantum metrology, using the strange behavior of sub-atomic particles, can revolutionize the way we measure things.

We are used to dealing with probabilities that range from 0% (never happens) to 100% (always happens). However to interpret the results from the quantum world, the concept of probability needs to be expanded to include a so-called quasi-probability, which can be negative. This allows quasi-probability quantum concepts such as Einstein’s ‘spooky action at a distance’ and wave-particle duality to be explained in an intuitive mathematical language. For example, the possibility of a Atom Being at a fixed position and traveling with a specific speed can be a negative number, such as -5%.

An experiment whose explanation requires negative probabilities is called ‘quantum negativity’. Scientists have now shown that this quantum negativity can help take more precise measurements.

All metrology requires investigation, which can be simple scales or thermometers. However, in state-of-the-art metrology, probes are quantum particles, which can be controlled at the sub-atomic level. These quantum particles are made to interact with the object to be measured. The particles are then analyzed by a detection device.

In theory, the greater the number of particles to be examined, the more information will be available for the detection device. But in practice, there is a cap on the rate at which detection equipment can analyze particles. The same is true in everyday life: applying sunglasses can remove excess light and improve vision. But there is a limit to how much filtering can improve our eyesight – sunglasses that are too dark are harmful.

The lead author of Cambridge’s Cavendish Laboratory and Sarah Woodhead Fellow, Dr. David Arvidson-Shukur said, “We have adapted the tool from standard information theory to quasi-probabilities and shown that filtering quantum particles can give information of one million particles.” Girton College. “This means that detection devices can operate at their ideal flow rates while receiving information at very high rates. This is prohibited according to general probability theory, but quantum negativity makes it possible. “

An experimental group at the University of Toronto has already started building technology to use these new theoretical results. Their goal is to create a quantum device that uses single-photon laser light to provide incredibly accurate measurements of optical components. Such measurements are important for creating advanced new technologies, such as photonic quantum computers.

“Our discovery opens up exciting new ways to use fundamental quantum phenomena in real-world applications,” Arvidsson-Shukur said.

Quantum metrology can improve the measurement of things including distance, angle, temperature and magnetic field. These more precise measurements can lead to better and faster technologies, but also better resources to investigate basic physics and improve our understanding of the universe. For example, many technologies rely on accurate alignment of components or the ability to realize small changes in electric or magnetic fields. High precision in alignment mirrors may allow for more accurate microscopes or binoculars, and better methods of measuring the Earth’s magnetic field may lead to better navigation tools.

Quantum metrology is currently used to increase the accuracy of gravitational wave detection in Nobel laureates LIGO Hanford Observatory. But for most applications, quantum metrology has been highly expensive and unacceptable with current technology. The newly-published results present an inexpensive way of performing quantum metrology.

Co-author Alexander Lasek, PhD candidate at Cavender Laboratory, said, “Scientists often say that ‘there’s no such thing as a free meal, which means you can’t get anything.” However, in quantum metrology, This price can be reduced arbitrarily. It’s very clear, and really amazing! “

Co-author and ITAMP Postdoctoral Fellow at Harvard University, Drs. Nicole Yunger Helper said: “Multiplying multiplication every day: six times seven is equal to six times seven. Quantum theory includes multiplication that does not commute. Lack of commutation allows us to improve metrology using quantum physics. Huh.

“Quantum physics enhances metrology, computations, cryptography, and more; but rigorously proving that it is difficult. We showed that quantum physics enables us to extract more information from experiments with classical physics only. The key to proof of the possibilities. There is a quantum version – mathematical objects that resemble probabilities but can assume negative and non-real values. “

Reference: 28 July 2020, Nature communication.
DOI: 10.1038 / s41467-020-17559-w

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