Slashdot links to a Gizmag article discussing some new research out of the University of Bristol.
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.
Single photon quantum walks have been achieved before. What this group did was to overcome the difficulties of managing two photons in identical states and account for their inevitable interference. The big hurdle was increasing from one to two, the researchers are optimistic that scaling from two to any number of particles should be much easier to accomplish.
There has been a lot of questions around what quantum computing will practically do better than classical computers. This still doesn’t directly answer those questions but it is a key bit of progress towards non-trivially complex quantum computers. Once we have one that approaches the register size of even the early vacuum tube goliaths, then we should be able to start mapping out practical applications and benefits.
Two-photon walk a giant stride for quantum computing, Gizmag (via Slashdot)