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2015-11-10, 21:15   #34
xilman
Bamboozled!

"𒉺𒌌𒇷𒆷𒀭"
May 2003
Down not across

2×3×52×73 Posts

Quote:
 Originally Posted by chalsall Why not? Seems reasonable to me based on the available empirical evidence. Please (PLEASE) tell me why I might be incorrect.

https://www.lightbluetouchpaper.org/...tum-mechanics/
https://www.lightbluetouchpaper.org/2015/02/23/maxwell/

Ross and I have been discussing this in some depth. I'm not yet convinced that one of my objections has yet been met. It concerns neutrinos and angular momentum ...

2015-11-10, 21:19   #35
CRGreathouse

Aug 2006

135338 Posts

Quote:
 Originally Posted by chalsall End of the day, perhaps all must assume that they cannot communicate securely unless they have access to quantum communications?
No. There's a whole field (called post-quantum cryptography) which studies classical algorithms which can resist attacks from quantum computers.

 2015-11-11, 02:15 #36 jwaltos     Apr 2012 Gracie on alert. 24·52 Posts Here is a link: http://www.nature.com/nature/journal...ture10120.html The above paper and a related one dated 2012 (I believe both exist in arXiv) can provide further perspectives on this topic. A short and relatively easy read is: Broadband Quantum Cryptography by D.J. Rogers.
 2015-11-11, 02:33 #37 LaurV Romulan Interpreter     Jun 2011 Thailand 24·13·47 Posts Thanks for the last posts, fascinating materials to read! (in this corner of the world/building, we didn't keep pace with the subject for some time...)
2015-11-11, 17:12   #38
Nick

Dec 2012
The Netherlands

24×109 Posts

Quote:
 Originally Posted by xilman Ross and I have been discussing this in some depth. I'm not yet convinced that one of my objections has yet been met. It concerns neutrinos and angular momentum ...
If you and Ross decide to debate the issues in public, that would certainly be worth visiting Britain for!

2015-11-11, 23:31   #39
chalsall
If I May

"Chris Halsall"
Sep 2002

26E116 Posts

Quote:
 Originally Posted by CRGreathouse For one thing, the D-Wave system isn't a general-purpose quantum computer and in particular is incapable of running Shor's algorithm.
Yes, I am aware of that. But, Google and NASA et al did run several tests (including based on how close to Absolute Zero the qbits got) which suggests strongly (empirically) that quantum effects were involved.

2015-11-11, 23:33   #40
chalsall
If I May

"Chris Halsall"
Sep 2002

37×269 Posts

Quote:
 Originally Posted by xilman Ross and I have been discussing this in some depth. I'm not yet convinced that one of my objections has yet been met. It concerns neutrinos and angular momentum ...
OK. I'm the first to admit that I am (and few are) nowhere near in your league.

My "out of my butt" statement is based solely on two premises. First, that over time we puny humans will harness more and more qbits.

Second, that no one should assume they're communications are secure.

I could, of course, be wrong. (P.S. Thanks for the reading material; my weekend is booked.)

2015-11-12, 02:58   #41
science_man_88

"Forget I exist"
Jul 2009
Dumbassville

26×131 Posts

Quote:
 Originally Posted by chalsall Understood. But let's run a thought experiment... (This is actually true; if you have a few million dollars available you can buy one from D-Wave Systems today; Google and NASA have.)
just came across http://nextbigfuture.com/2015/11/los...ry-orders.html

Quote:
 Los Alamos National Laboratory will acquire and install the latest D-Wave quantum computer, the 1000+ qubit D-Wave 2X™ system.

Last fiddled with by wblipp on 2015-11-14 at 01:42 Reason: fix quotes

2015-11-12, 15:03   #42
CRGreathouse

Aug 2006

3×1,993 Posts

Quote:
 Originally Posted by chalsall Yes, I am aware of that. But, Google and NASA et al did run several tests (including based on how close to Absolute Zero the qbits got) which suggests strongly (empirically) that quantum effects were involved.
That's a generous interpretation. So far there's no indication that useful work is being done quantum mechanically. It's true, there seem to be some minor quantum effects, but with their rapid decoherence and long annealing time it doesn't seem likely that anything useful can be done here. I'm more interested in the Martinis Group approach which seems far more likely to succeed.

2015-11-12, 19:25   #43
chalsall
If I May

"Chris Halsall"
Sep 2002

37·269 Posts

Quote:
 Originally Posted by CRGreathouse I'm more interested in the Martinis Group approach which seems far more likely to succeed.
I also find that interesting.

But, as we all know, a smart investor supports many different paths along the "edge" to see what works best; and tangentially, to see if they can complement each other.

2015-11-12, 19:38   #44
only_human

"Gang aft agley"
Sep 2002

2×1,877 Posts

Quote:
 Originally Posted by chalsall I also find that interesting. But, as we all know, a smart investor supports many different paths along the "edge" to see what works best; and tangentially, to see if they can complement each other.
There is this progress too. It will be nice to not depend on superconductors.
Basic quantum computation achieved with silicon for first time (newscientist.com)
Quote:
 “This is a seminal breakthrough in the world of quantum computer development – with some caveats,” says Thomas Schenckel of the Lawrence Berkley National Laboratory in California. Although easier to scale up, “silicon-based qubits are still way behind superconducting qubits”, he says. But that doesn’t diminish the potential of the work. “Nothing beats what we can do in silicon in terms of economical scaling and large-scale integration,” Schenkel says. Journal reference: Nature, DOI: 10.1038/nature15263
When I looked at the abstract at the Nature paywalled article, I don't recall seeing any mention of temperatures. This involves CNOT gates involving electron spin, I think. There are four slides that are available sitting just outside the paywall door but I didn't to look at them.

edit: well, I just peeked at the slides:
Quote:
 All measurements were performed in a dilution refrigerator with base temperature T ≈ 50 mK and a dc magnetic field of strength B0 = 1.4 T.

Last fiddled with by only_human on 2015-11-12 at 19:50

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