A team of scientists has discovered a physical property, termed "quantum negativity," that allows for more precise measurements and can power new technologies.
Researchers from Harvard, Massachusetts Institute of Technology (MIT), and the University of Cambridge have found the novel property. Quantum particles have the capacity to carry an unlimited amount of information about materials they interacted with.
Quantum Negativity
The study proposed that there is a way to improve the rate of Fisher information, the average information that an unknown parameter carried by a variable from a trial, to cost through post-selection. Researchers illustrate that the improvement comes from "the negativity of a particular quasi-probability distribution," in itself a quantum extension of the conventional probability distribution.
In introducing the study, the team differentiated classical and quantum probabilities. In classical phenomena, which is used in conventional applications, the values are real and non-negative. Probabilities of an event happening best illustrate it - ranging from 0% (impossible, or will never happen) to 100% (definite, or will surely happen).
For non-classical distributions, such as used in explaining quantum states, values can take negative and non-real positions. Technically, quasi-probabilities do not strictly follow some of Kolmogorov's axioms of probability theory. It especially contradicts the first one - "The probability of any event is a non-negative real number."
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Quasi-probability allows negative probabilities, like a -100%, to explain concepts such as quantum entanglement. Experiments that are explained through the use of negative quasi-probabilities create the so-called "quantum negativity."
Quantum Advantage in Metrology
Metrology is one of the fields benefiting from advancements in quantum technology. The science of measurements and estimations might find existing paradigms in taking quantifiable observations. Most conventional measurements require a probe of some sort, taking measurements from weight to temperature to electrical flow.
High-end measurement instruments, however, use quantum particles instead of physical probes. The particles then interact with the item being measured, with a device detecting and analyzing the response of the quantum particles.
Current technologies are limited in terms of the rate at which detection can interact with external input. Theoretically, more particles interacting with the target means more information can be gathered.
In a statement in the University of Cambridge press release, lead author Dr. David Arvidsson-Shukur of Cambridge's Cavendish Laboratory said that they have adapted tools from standard information theory and applied them to quasi-probabilities. "Filtering quantum particles can condense the information of a million particles into one." Dr Arvidsson-Shukur explains that while this should have been "forbidden" under the rules of normal probability theory, quantum negativity makes it possible.
To test these theoretical results, an experimental group from the University of Toronto, in Canada, has started the creation of a quantum device that uses a single-photon laser. Should precise measurements be achievable with the experimental setup, it will allow the creation of new technologies like photonic quantum computers.
Moreover, this newfound advantage in metrology from quantum negativity can improve precision in measuring distances, angles, temperatures, and magnetic fields. These ultra-precise measurements are also important in advancing physics experiments, like measuring electric and magnetic field fluctuations.
"Our discovery opens up exciting new ways to use fundamental quantum phenomena in real-world applications," Arvidsson-Shukur commented.
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