Can I just try to clarify the significance of this thread to us, and say why I think we should all sit up and take notice of Quantum Computing (QC) and the D-J algorithm in particular.
http://en.wikipedia.org/wiki/Deutsch%E2%80%93Jozsa_algorithm The second sentence begins "Although of little practical use…" You'd think it some airy-fairy topic in which only a QC specialist could possibly be interested. You'd be wrong. Let me bring it down to earth for the rest of us. To keep it brief I'll omit if's and but's. Remember from your schooldays Young's Fringes, aka the double-slit interferometer? It appears you can turn down the intensity of the beam until it's only one photon per second, yet the fringes still appear. But block one of the slits and the fringes disappear. Q: how does an individual photon going through one slit know if the other slit is blocked or not? A: because it's a quantum particle, not a classical one. Now before you say it's iffy to talk of a given photon going through one or the other slit, I'm told the experiment has been repeated with electrons. It's harder to credit an electron following two paths at once. The D-J algorithm is the photon's problem of navigating 2 slits, expressed as an algorithm recognizable to a computer programmer. You could say (sticking your neck out) that the photon plus slits implements a quantum computer which runs the D-J algorithm. The black-box function f under discussion returns either 0 or 1 – but might possibly never be able to return 0. This corresponds to the trajectory of a stream of photons thru slits 0 and 1 – but slit 0 might possibly be blocked. Hugely simplified, the principle of operation is: feed f a qubit and look for fringes. A pretty simple quantum computer. But according to complexity theory it outperforms any conceivable classical computer at its task. Before I came across the D-J algorithm, I was convinced QC was nothing but alchemy. A modern Philosopher's Stone – a quantum-mechanical backwater fluffed-up by people who viewed acquiring expertise in a "difficult" topic as their meal ticket. No incentive to make the topic accessible, nor to moderate their claims. Now I've seen the light. A photon at a time. Far from being "of little practical use", Deutsch's apparatus has been adapted by Shor to factorizing a large number into primes. What price the RSA cryptosystem when quantum computers arrive? https://en.wikipedia.org/wiki/RSA_%28cryptosystem%29 And will it stop there? On Sat, Jul 25, 2015 at 11:20 PM, 'Pascal Jasmin' via Programming <[email protected]> wrote: > I second request for Shor algorithm if possible. > > > ----- Original Message ----- > From: Ian Clark <[email protected]> > To: [email protected] > Cc: > Sent: Saturday, July 25, 2015 6:18 PM > Subject: Re: [Jprogramming] Quantum algebra with J > > @Fausto > The last time I dipped into the QC literature (in connection with a > paper offered to the BAA for review) I found it short on helpful > material for the non-specialist, and long on smoke-and-mirrors. So can > I reiterate Raul's request for simple worked examples? Not a "detailed > doc with all the gates and other verbs explained". > > For starters, could you implement the Deutsch-Josza algorithm with > your package? That would impress me. > http://en.wikipedia.org/wiki/Deutsch%E2%80%93Jozsa_algorithm > > Seeing Shor's and Grover's algorithms done in your package would > impress me even more. > http://en.wikipedia.org/wiki/Quantum_algorithm > > On Fri, Jul 24, 2015 at 9:54 PM, Fausto Saporito > <[email protected]> wrote: >> Hello Raul, >> >> yes. I'm preparing a detailed doc with all the gate and other verbs >> explained. >> >> regards, >> Fausto >> >> 2015-07-22 1:47 GMT+02:00 Raul Miller <[email protected]>: >>> This looks like it could be fun, though I don't really have the >>> background to intuit a lot of what's going on here. >>> >>> I did notice that you've a lot of code which you are not exercising >>> (the gates, for example). It might be worth working through some >>> examples? >>> >>> Thanks, >>> >>> -- >>> Raul >>> >>> >>> On Tue, Jul 21, 2015 at 4:58 AM, Fausto Saporito >>> <[email protected]> wrote: >>>> Hello all, >>>> >>>> I wrote, just for fun, a basic quantum algebra package to handle >>>> qubits and some operations. >>>> >>>> Here's the code: https://github.com/TheFausap/qcalgebra >>>> >>>> this is very basic j code... unfortunately with some for loops. I >>>> tried to limit them, but I'm still Learning. >>>> >>>> regards, >>>> fausto >>>> ---------------------------------------------------------------------- >>>> For information about J forums see http://www.jsoftware.com/forums.htm > >>> ---------------------------------------------------------------------- >>> For information about J forums see http://www.jsoftware.com/forums.htm >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
