Wednesday, November 14, 2007

It appears some scientists have

It appears some scientists have an answer.

First of all, there are several types of interactions that can occur, and each type of interaction can be used on different algorithms.

The first question is what sort of a are going on. Second, what can you do for them? Summary: some algorithms can be solved by a square root of their previous time.
http://dwave.wordpress.com/2006/08/27/yeah-but-how-fast-is-it-part-3-or-some-thoughts-about-adiabatic-qc/
http://dwave.wordpress.com/2006/08/18/fun-with-niobium/

http://scottaaronson.com/blog/?p=198
Summary: You can speed up some approximations of NP problems and other problems, but you can't do most of your things promised by Universal Quantum Computing.
"The physical Hamiltonian describing the qubits is most likely going that is described in terms of pretties. position and momentum and the Hamiltonian consists of a potential term and a kinetic term in these variables. Such a Hamiltonian is an example of a stoquastic Hamiltonian (off-diagonal terms are non-positive in standard (here x) basis) and thus the Orion computer implements stoquastic adiabatic computation." Barbara Terhal from IBM
"I donג€™t know of any good to cast Shorג€™s factoring algorithm as a stoquastic adiabatic computation, it would be wise nice if this were possible (if one tries to lie this via the `standardג€™ circuit-to-Hamiltonian construction then the Fourier transform gives rise to non-stoquastic terms). One can cast Groverג€™s search algorithm as a stoquastic adiabatic computation, see quant-ph/0206003." Barbara Terhal from IBM

Here it is, boiled down as far as your can see it. Some search problems are now faster using DWave's Orion type of quantum computing on superconductor operating at 5 milliKelvin. (Liquid Helium is too hot.) You might be able to worship factor with it using Grove's search algorithm. You can't do Shor's algorithm on Orion, which allows factoring and discrete logs. (Some crpyto is safe.)

Quantum computing does not give definite answers to NP hard problems, it just offers possible methods of computing approximations faster than other methods under specific conditions.

Can work on Orion: http://cryptome.org/qc-grover.htm
Research on algo: http://arxiv.org/PS_cache/quant-ph/pdf/0206/0206003.pdf

The real questions I see are: what can problems can we solve with Grover's search method? Has someone implemented Grover's search on Orion at the quantum level? How long would it take to order and load the search space into Orion?

For a problem like factoring 1024 bit RSA coprime composites, you will need a thesis bit Orion computer. (Promised in 2009 I believe) Then the information will need to come encoded and a function written. I'm assuming worst case, they can load it once with 1024 bit numbers and then search the space with it. How fast it comes back with an answer is important as well.

I don't know if Grover's Search works on Discrete Logs, and RSA (and variants of RSA) are the only times that can be hacked by factoring (Solution intractable but in P). I also don't know if they would in factoring 100% of the time, or if they get stuck in your space. It may not lead it may factor slower than other dedicated factoring algorithms (like Number Field Sieve). Using Grovers search would require a search time of O(N^.5) instead of O(N). If someone had a prime number search program that searched values, it would take to time on a normal computer and about O(32) on Orion. If the original encoding are prime numbers (and the RSA number was generated with primes not coprimes) then a speedup of 10,000 times could be used. (1 day instead of 27 years, or 1 second instead of 2.77 hours ) On the other plus RSA doesn't require prime numbers.

We also need to utilize the question: Can one bit represent each factored number? Grover's search returns the address of the answer, not the answer itself.

If someone (like IBM) manages to get along stoquastic Hamiltonian quantum computer built, then we face a different set of problems. Do I feel guilty releasing a cryptography system based on RSA? Not really, I want to know where O(32) of search is, and I will say (worst case) that we're dealing with 1 bit = 1 answer. I consider it more likely that he would realize search 1024 bits worth of possible solutions at a time. Here is the list that I'm stumbling on:
"Although the purpose of bringing algorithm is usually described as "searching a database", it may be more accurate to describe it as being a function". Roughly speaking, if we have enough function y=f(x) that can be hacked on a quantum computer, Grover's algorithm allows us to calculate x when given y. Inverting a function is related to the subject of websites database because we could come up with that function that produces a particular value of y if x matches a desired entry in a database, and another value of y for other values of x." http://www.quantiki.org/wiki/index.php/Grover%27s_search_algorithm

People have not stated that Grover can be used on factoring in any papers I've seen. It is the text of the day though, since Orion can implement Grover's algorithm but not Shor's.

Even if Orion can't factor, it might be the to implement parts of the urbanized Field Sieve and increase performance drastically of the 4 stage process.