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posted by janrinok on Thursday May 24 2018, @02:32AM   Printer-friendly
from the well,-that-cleared-that-up dept.

A team of physicists from ICTP-Trieste and IQOQI-Innsbruck has come up with a surprisingly simple idea to investigate quantum entanglement of many particles. Instead of digging deep into the properties of quantum wave functions - which are notoriously hard to experimentally access - they propose to realize physical systems governed by the corresponding entanglement Hamiltonians. By doing so, entanglement properties of the original problem of interest become accessible via well-established tools. This radically new approach could help to improve understanding of quantum matter and open the way to new quantum technologies.

Quantum entanglement forms the heart of the second quantum revolution: it is a key characteristic used to understand forms of quantum matter, and a key resource for present and future quantum technologies.

Physically, entangled particles cannot be described as individual particles with defined states, but only as a single system. Even when the particles are separated by a large distance, changes in one particle also instantaneously affect the other particle(s). The entanglement of individual particles - whether photons, atoms or molecules - is part of everyday life in the laboratory today.

The physicists turn the concept of quantum simulation upside down by no longer simulating a certain physical system in the quantum simulator, but directly simulating its entanglement Hamiltonian operator, whose spectrum of excitations immediately relates to the entanglement spectrum.

"Instead of simulating a specific quantum problem in the laboratory and then trying to measure the entanglement properties, we propose simply turning the tables and directly realizing the corresponding entanglement Hamiltonian, which gives immediate and simple access to entanglement properties, such as the entanglement spectrum" explains Marcello Dalmonte. "Probing this operator in the lab is conceptually and practically as easy as probing conventional many-body spectra, a well-established lab routine." Furthermore, there are hardly any limits to this method with regard to the size of the quantum system.

This could also allow the investigation of entanglement spectra in many-particle systems, which is notoriously challenging to address with classical computers. Dalmonte, Vermersch and Zoller describe the radically new method in a current paper in Nature Physics and demonstrate its concrete realization on a number of experimental platforms, such as atomic systems, trapped ions and also solid-state systems based on superconducting quantum bits.


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  • (Score: 3, Informative) by maxwell demon on Thursday May 24 2018, @05:03AM (1 child)

    by maxwell demon (1608) on Thursday May 24 2018, @05:03AM (#683428) Journal

    the entanglement happens at any distance, even on galactic scales or larger

    Strictly speaking, we cannot say that, because the largest distance we've covered yet with experiments is still in the vicinity of Earth (I'm not aware of a method to detect entanglement through astronomical observations). Quantum theory says that it should be valid at arbitrary distances, but we cannot completely exclude that there's a limit to its applicability, just as we didn't know that there's a limit of the applicability of Newtonian mechanics before quantum mechanics and relativity were discovered. All we can say for sure is that if there's a limit to quantum mechanics, we haven't yet found it.

    in some sense the wave function breaks down when the entangled particle is 'observed' (or more prosaically when it simply disrupted by macroscopic noise of any kind)

    Exactly: In some sense. What this exactly means, is what all the different interpretations of QM are about.

    the measured result is the same at both ends

    Whether the result is the same or exactly the opposite depends on the exact entangled state (it might even be that the measurement variables are different, so you cannot tell which result is "the same" and which is "the opposite"). But it's a perfect correlation.

    the information doesn't travel from one end to the other, no superluminal speeds are necessary and there's violation of the limits of the speed of light

    Yes.

    --
    The Tao of math: The numbers you can count are not the real numbers.
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  • (Score: 2) by EventH0rizon on Thursday May 24 2018, @06:01AM

    by EventH0rizon (936) on Thursday May 24 2018, @06:01AM (#683439) Journal

    Whether the result is the same or exactly the opposite depends on the exact entangled state (it might even be that the measurement variables are different, so you cannot tell which result is "the same" and which is "the opposite"). But it's a perfect correlation.

    The way I put was a bit sloppy, this is much better