Researchers develop practical method for measuring quantum entanglement

Researchers develop practical method for measuring quantum entanglement
Michael Fanto (left), an RIT microsystems engineering Ph.D. student and the experimental lead for the Air Force Research Laboratory Quantum Information Science group; James Schneeloch (center), a postdoctoral researcher with the Air Force Research Laboratory U.S. Air Force; and Gregory Howland (right), RIT assistant professor, were among the researchers to develop a new technique to measure quantum entanglement. Credit: A. Sue Weisler/RIT

Rochester Institute of Technology researchers have helped develop a new technique for quantifying entanglement that has major implications for developing the next generation of technology in computing, simulation, secure communication and other fields. The researchers outlined their new method for measuring entanglement in a recent Nature Communications article.

When two quantum particles—such as photons, electrons or atoms—become entangled, they have special correlations that show up in their measurements even when the particles are separated by an enormous distance. This unique property, which can only be explained through , is at the heart of many of the technologies as part of the National Quantum Initiative.

"Quantum entanglement is a resource that can be used to do important tasks such as quantum computing or ," said Assistant Professor Gregory Howland, a member of RIT's Future Photon Initiative. "Two people that have entangled can generate an unbreakable key for sending messages back and forth to one another in such a way that if some third party intercepts the message, by the laws of physics it's impossible for them to decode the message."

As quantum technologies become more complex, users will need a way to calculate how much exists within a given system. For the system in this study—involving spatially entangled photon pairs—the new technique needed a million-times fewer measurements than previous methods. And because the technique is based on , the measurement technique has the added benefit of never overestimating how much entanglement is in a system.

"This turns out to be critical because it means we never accidentally tell you that you have more of the resource than you really have," Howland said. "It's especially important for something like secure communication, where you're trying to avoid an adversary intercepting a message."

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More information: James Schneeloch et al. Quantifying entanglement in a 68-billion-dimensional quantum state space, Nature Communications (2019). DOI: 10.1038/s41467-019-10810-z James
Journal information: Nature Communications

Citation: Researchers develop practical method for measuring quantum entanglement (2019, August 26) retrieved 22 October 2019 from
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Aug 26, 2019
While quantum entanglement [spooky action at a distance] was first describe via quantum mechanics, it is ironic that it can not be understood within the field of space-time of ordinary matter. Perhaps it is more akin to understanding how dark energy, as the medium in which matter interacts, manages the concept of time. If we consider that this pre-existing medium is like a single space-time fabric without distinction, unlike matter, then we might want to consider the concept of inter-dimensional travel among the locality of points in space-time; i.e., the difference of time as it is measure from one dimension to another: e.g., one dimensional space-time, two dimensional space-time, three dimensional space-time, and so on.

Aug 27, 2019
A useful "universal method for quantifying entanglement in any large quantum system shared by two parties." If the entanglement is good the two systems are highly correlated and they can chose nearly separable joint distributions, so can capture the measure with sampling densely in regions of the observables where the correlations are found to be located.

it is ironic that it can not be understood within the field of space-time of ordinary matter.

We all note that the article claims it can be understood - measured - with little effort, even though entanglement as such is (as the paper notes) "enigmatic". Not surprisingly since we know GR and QFT plays nice [say, ].

dark energy, as the medium in which matter interacts, manages the concept of time.

And this makes little sense. Dark energy likely is vacuum energy, so *is* part of the particle fields. And it is GR that "manages" time (ensures causality).

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