Thread: magical photons
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Old 12-02-2020, 07:57 PM
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Shiraz (Ray)
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Barry

yes, maybe we are wasting our time

the links to the two blogs were included as a courtesy, because they give some useful background when reading the main paper linked to in post#10. This is a peer reviewed paper published in the journal Nature and dealing with the attainment of quantum supremacy by the Google computer. The leader of the team is a distinguished 62 yo scientist "Dr. Martinis was a NIST Fellow, and is a Fellow of the American Physical Society. At the University of California, Santa Barbara he currently holds the Wooster Chair in experimental physics". This is serious work by serious people and it is perhaps excessively dismissive to characterize it as "crap" and "a lot of acneyed gamers, ...getting their rocks off" https://www.nature.com/articles/s41586-019-1666-5

there have been numerous recent papers dealing with Bell's inequality testing including photons, electron spin, superconducting devices etc. A lot of work has gone into closing off any loopholes that might pollute the tests and still allow a chance for local realism - QM always wins. A very quick search this side of the paywalls yielded the following and there are lots more:

https://arxiv.org/pdf/1508.05949.pdf Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km 2015

https://physics.aps.org/featured-art...ett.115.250401 Significant-Loophole-Free Test of Bell’s Theorem with Entangled Photons 2015

https://journals.aps.org/prl/abstrac...ett.117.210502 Experimental Ten-Photon Entanglement 2016

https://www.nature.com/articles/srep30289 Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis 2016

https://www.osapublishing.org/optica...optica-4-4-388 Xianxin Guo et al, Testing the Bell inequality on frequency-bin entangled photon pairs using time-resolved detection, Optica (2017).

https://physics.aps.org/synopsis-for...ett.121.220404 Synopsis: Quantum Entanglement With 10 Billion Atoms, November 29, 2018

https://arxiv.org/pdf/1805.04431.pdf Challenging local realism with human choices The BIG Bell Test Collaboration† Nov2018

and for some pictures of entangled photons,
https://advances.sciencemag.org/content/5/7/eaaw2563 Imaging Bell-type nonlocal behavior 2019

Sure quantum computers are just analog computers if there is no entanglement. (https://www.ornl.gov/event/quantum-s...-supercomputer) The linked abstract may indicate that the Google computer (or a closely related one) is fully entangled across the whole array.

The Google computer is clearly not able to factorise large primes. but that is not what it was built to do. It has however established that functional moderate-scale quantum computers can be built, that even at this early stage one of them works much faster than any conventional processor on a specific quantum test problem, and that there is no fundamental physics yet discovered that will stand in the way of future advances (such as error management). And of course it will not crack the various quantum encrypted comms systems - nothing ever will - that is the point. https://www.researchgate.net/publica...m_cryptography

Re your comment bemoaning the lack of "realists", philosophical arguments about the interpretation of QM/pilotwave/manyworlds etc will continue, but could possibly be of limited interest to many people working on applications of QM - which seems to be a very successful engineering tool that can be applied without worrying in the slightest about concepts of what the universe is really like. The philosophical arguments will continue and will probably lead to new ways of describing the universe, but it seems likely to me that the engineering-level maths has already been so successful in so many fields that it will not change radically.

Cheers ray

Last edited by Shiraz; 13-02-2020 at 05:28 PM.
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