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Researchers Create a 'Universal Entangler' for New Quantum Tech

posted by Fnord666 on Thursday February 28 2019, @11:51AM   Printer-friendly
from the weaving-a-tangled-skein dept.

Phoenix666 writes:

Phys.org:

One of the key concepts in quantum physics is entanglement, in which two or more quantum systems become so inextricably linked that their collective state can't be determined by observing each element individually. Now Yale researchers have developed a "universal entangler" that can link a variety of encoded particles on demand.

The discovery represents a powerful new mechanism with potential uses in quantum computing, cryptography, and quantum communications. The research is led by the Yale laboratory of Robert Schoelkopf and appears in the journal Nature.
...
"We've shown a new way of creating gates between logically-encoded qubits that can eventually be error-corrected," said Schoelkopf, the Sterling Professor of Applied Physics and Physics at Yale and director of the Yale Quantum Institute. "It's a much more sophisticated operation than what has been performed previously."

The entangling mechanism is called an exponential-SWAP gate. In the study, researchers demonstrated the new technology by deterministically entangling encoded states in any chosen configurations or codes, each housed in two otherwise isolated, 3-D superconducting microwave cavities.

It's a tangled web we weave, when we're practicing to receive...

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  • (Score: 0) by Anonymous Coward on Thursday February 28 2019, @01:35PM

    by Anonymous Coward on Thursday February 28 2019, @01:35PM (#808093)

    "so inextricably linked that their collective state can't be determined by observing each element individually". Wasn't the entire point of entanglement that aparently separate subsystems are in fact intricately connected such that by observing just one you know the state of the other subsystem?

    The first sentence is correct. What you learn after measuring one subsystem is about the state of the other subsystem after the measurement, which is not the same as the statebefore the measurement; in particular, after the measurement the subsystems are no longer entangled. And from measurement of one side you only learn about the state on the other side if you already know the complete pre-measurement state. In which case of course you won't learn about it anyway because you already know it.

    So in short, for fully entangled two-party states:

    • Either you know the pre-measurement state, then from measuring one part you learn about the post-measurement state of the other part.
    • Or you don't know the pre-measurement state (other than that it is fully entangled), then from measuring one part you learn nothing about either the pre-measurement state, nor the post-measurement state of the other side.

    Having said that, as soon as more than two subsystems get involved, things get much more complicated.