‘Quantum negativity’ can power ultra-precise measurements

  Artist's impression of a quantum metrology device  Credit: Hugo Lepage

Scientists have found that a physical property called ‘quantum negativity’ can be used to take more precise measurements of everything from molecular distances to gravitational waves.

The researchers, from the University of Cambridge, Harvard and MIT, have shown that quantum particles can carry an unlimited amount of information about things they have interacted with. The results, reported in the journal Nature Communications, could enable far more precise measurements and power new technologies, such as super-precise microscopes and quantum computers.

Metrology is the science of estimations and measurements. If you weighed yourself this morning, you’ve done metrology. In the same way as quantum computing is expected to revolutionise the way complicated calculations are done, quantum metrology, using the strange behaviour of subatomic particles, may revolutionise the way we measure things.

We are used to dealing with probabilities that range from 0% (never happens) to 100% (always happens). To explain results from the quantum world however, the concept of probability needs to be expanded to include a so-called quasi-probability, which can be negative. This quasi-probability allows 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 probability of an atom being at a certain position and travelling with a specific speed might be a negative number, such as –5%.   

An experiment whose explanation requires negative probabilities is said to possess ‘quantum negativity.’ The scientists have now shown that this quantum negativity can help take more precise measurements.

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Image:  Artist's impression of a quantum metrology device

Credit: Hugo Lepage

Reproduced courtesy of the University of Cambridge


The University of Cambridge is acknowledged as one of the world's leading higher education and research institutions. The University was instrumental in the formation of the Cambridge Network and its Vice- Chancellor, Professor Stephen Toope, is also the President of the Cambridge Network.

University of Cambridge (cam.ac.uk)