Two-Photon Walk a Giant Leap For Quantum Computing

ElectricSteve writes "Research conducted at the University of Bristol means a number of quantum computing algorithms may soon be able to execute calculations of a complexity far beyond what today's computers allow us to do. The breakthrough involves the use of a specially designed optical chip to perform what's known as a 'quantum walk' with two particles ... and it suggests the era of quantum computing may be approaching faster than the scientific establishment had predicted. A random walk – a mathematical concept with useful applications in computer science – is the trajectory of an object taking successive steps in a random direction, be it over a line (with only two possible directions) or over a multi-dimensional space. A quantum walk is the same concept, but translated to the world of quantum computing, a field in which randomness plays a central role. Quantum walks form an essential part of many of the algorithms that make this new kind of computation so promising, including search algorithms that will perform exponentially faster than the ones we use today."

Comments

Two-Photons Walk

[Anonymous Coward]

into a bar... wait... where am I?

Re: Two-Photons Walk

[marcosdumay]

Just open your eyes, and see where you are. After seeing it you are not going to be anywhere else, but before looking, I can't really tell you.

"Quantum Walk"

[countertrolling]

Here's how it looks under a microscope

Pre-emptive Explanation of Quantum Computing

[mathimus1863]

Because people always get it wrong every time a QC article hits slashdot, here's a link to my previous, highly-modded (upwards) post on QC:

http://slashdot.org/comments.pl?sid=1285849&cid=28520061

Quantum computers can do some cool things, but mostly solve problems no one cares much about (except a few of us mathematicians)

Exponential Speedup??

[mathimus1863]

Summary is wrong. Quantum algorithms cannot provide "exponential" speedup of any problem. If they could, we would be able to [probably] solve NP-complete problems with quantum computers, and that hasn't been proven yet. The best they can do is "super-polynomial" speedup of classical algorithms.

Google "quantum algorithm zoo" to see all the known algorithms and their speedups (and how unexciting most of them are).

Re:Exponential Speedup??

[Catullus]

This comment isn't accurate. There are problems for which quantum computers are indeed exponentially faster than our best known algorithms running on a standard computer. The most important of these is probably simply quantum simulation - i.e. simulating quantum mechanical systems. This has umpteen applications to physics, chemistry and molecular biology (e.g. drug design).

Padding Resume.

[Anonymous Coward]

Seams like it about time to start putting 5 years of real world quantum programming experence on the old resume.

Some background

[Interoperable]

Let me provide some context. This research group specializes in manufacturing arbitrary waveguide structures on chips, then coupling particular quantum states of light into them. The idea is to turn a large optical table worth of mirrors into a tiny chip. What they have done here, is allowed a two photon input state to interfere with itself in the waveguide structure.

While interesting technically, it isn't exactly a huge leap forward because the interaction is linear. What's needed for deterministic quantum computation with light is a very non-linear process. The waveguide structure can replace a large number of mirrors and compact the optics into a tiny space but, at the end of the day, mirrors aren't all that interesting for quantum computation. It is, however, worthwhile because of the impressive miniaturization and the technical challenge of working with quantum light in such tiny structures. A strong non-linear component will be needed for true optical quantum computation, but chips like these show a lot of promise for handling a lot of state preparation and measurement.