Researchers have found that a physical property called a “quantum negative” can be used to more accurately measure everything from molecular distances to gravitational waves.

Researchers from the University of Cambridge, Harvard and MIT have shown that quantum particles can carry an unlimited amount of information about the things they have interacted with. Results reported in the journal *Natural communications*, could enable much more accurate measurements and use new technologies such as high – precision microscopes and quantum computers.

Metrology is the science of estimates and measurements. If you weighed yourself this morning, you did the metrology. Similarly, how quantum computation is expected to change the way complex computations are performed, quantum metrology, using the strange behavior of subatomic particles, can revolutionize the way we evaluate objects.

We are accustomed to encountering probabilities that range from 0% (never happens) to 100% (always happens). However, in order to explain the results of the quantum world, the concept of probability needs to be extended to include the so-called quasi-probability, which can be negative. This quasi-probability allows quantum concepts such as Einstein’s “terrible action at a distance” and wave-particle duality to be explained in intuitive mathematical language. For example, the probability that an atom is in a certain position and traveling at a certain speed can be a negative number, such as -5%.

An experiment whose explanation requires a negative probability is said to have a “quantum negative.” Researchers have now shown that this quantum negative can help make more accurate measurements.

All metrology requires probes, which can be simple scales or thermometers. However, in modern metrology, probes are quantum particles that can be controlled at the subatomic level. These quantum particles are formed to interact with the object being measured. The particles are then analyzed with a detection device.

Theoretically, the more particles to be probed, the more information the detection device will have. In practice, however, there is a limit to the extent to which detection devices can analyze particles. The same is true in everyday life: by wearing sunglasses, you can filter out excess light and improve vision. However, filtering can improve our vision, that is too much – the damage is too dark sunglasses.

“We adapted tools from standard information theory to quasi-potentiality and showed that quantum particle filtering can aggregate a million particles of information into one,” said lead author Dr. David Arvidsson-Shukur from Cambridge Cavendish Laboratory and Sarah Woodhead Fellow. Girton College. “That means detection devices can operate at ideal flow, receiving information corresponding to much higher speeds. Conventional probability theory prohibits this, but a quantum negative allows it.”

An experimental group at the University of Toronto has already started building technologies to take advantage of these new theoretical results. Their goal is to create a quantum device that uses single-photon laser light to see optical components with incredible accuracy. Such measurements are critical to the development of advanced new technologies such as photonic quantum computers.

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

Quantum metrology can improve the measurement of objects, including distances, angles, temperature, and magnetic fields. These more accurate measurements can help create not only better and faster technology, but also better resources to test basic physics and improve our understanding of the universe. For example, many technologies depend on the precise alignment of components or the ability to sense small changes in the electric or magnetic field. Greater accuracy in aligning mirrors may allow for more accurate microscopes or telescopes, and better methods of measuring the earth’s magnetic field can help create better means of navigation.

Quantum metrology is currently being used to improve the accuracy of gravitational wave detection at the Nobel Prize-winning LIGO Hanford Observatory. However, for many applications, quantum metrology has been too expensive and impossible to achieve using modern technology. The newly published results offer a cheaper way to perform quantum metrology.

“Researchers often say that ‘there is no such thing as a free lunch,’ which means you can get nothing if you don’t want to pay the cost of the calculation,” said doctoral student Alexander Lasek. candidate in the Cavendish laboratory. “But in quantum metrology, that price can be made arbitrarily low. It’s very controversial and really amazing!”

Nicole Yunger Halpern, a co – author at Harvard University and an ITAMP postdoctoral fellow, said: “Daily multiplication goes five times: seven times seven equals seven times six. Quantum theory involves multiplication that does not perceive.

“Quantum physics improves metrology, computation, cryptography, and more; but to prove it strictly is difficult. We have shown that quantum physics allows us to extract more information from experiments than we can with classical physics alone. The key to proof is quantum physics. the version of probabilities is mathematical objects that resemble probabilities, but can see negative and unrealistic values ”.

Maximum accuracy limit for multi-parameter quantum magnetometry

**More information:**

*Natural communications*(2020). DOI: 10.1038 / s41467-020-17559-w

Submitted by the University of Cambridge

**Citation**: “Quantum Negative” can be converted into extremely accurate measurements (July 29, 2020), which can be found in 2020. July 29 From https://phys.org/news/2020-07-quantum-negativity-power-ultra-precise.html

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