Storing a Qubit in a Single Atom

One of the building blocks for the next generation of quantum computing and communications systems is a way of storing and regenerating photonic qubits. These are generally encoded in the polarisation of photons.

To date, physicists have done this by transferring the qubit from a photon to an ensemble of quantum particles such as a crystal lattice or a small cloud of atoms.

Today, Holger Specht and pals at the Max Planck Institute for Quantum Optics in Garching, Germany, have gone one better. They've found a way to store the qubit from a polarised photon in a single atom of rubidium and then release it again later.…