Photon pairs take a quantum walk


<p>Hamish Johnston at PhysicsWorld writes: ''A new optical chip that allows pairs of photons to take a quantum walk has been unveiled by an international team of physicists. The tiny device contains an array of 21 coupled optical waveguides and could provide greater insight into quantum interference. Further in the future, the technology could find use in quantum computers.''</p>
<p>''A quantum walk is a variation of the familiar classical random walk – but involving quantum particles such as photons, electrons or atoms. A particle entering a beam splitter, for example, has a 50% chance of either veering right or left. If it is a classical particle it would unambiguously take one of the two paths. A quantum particle however, is placed in a superposition of both paths until a measurement is made. If each of the two paths leads to two more beam splitters, then the particle is in a superposition of four paths and so on.</p>''