Quantum Pairs Walking (2)

Harnessing quantum information could allow powerful computations that are inaccessible to classical systems. But many quantum features of a single particle simply reflect its wavelike aspects. Experiments in Physical Review Letters simultaneously manipulate pairs of particles, whose interlinked behavior cannot be emulated by classical waves. Linda Sansoni of Sapienza University of Rome, Italy, and her colleagues implemented the quantum version of a discrete random walk using photons in a centimeter-sized glass chip. They first focused intense laser pulses along chosen paths, which tweak the glass’s refractive index to create stable waveguides for later photons. Running two parallel waveguides alongside each other for about two millimeters gives a photon a 50/50 chance of jumping between them.