Physicists have made a device small enough to store quantum information in light on a chip. Photons of light can be used to encode quantum ‘bits’ of information, and are particularly useful for communicating securely between quantum computers. But efficient devices that use light to store quantum bits are generally too big to fit on computer chips.
Andrei Faraon at the California Institute of Technology in Pasadena and his colleagues used a crystal of yttrium orthovanadate laced with atoms of the rare-earth metal neodymium as a photonic cavity that can trap particles of light. The researchers encoded quantum information into a photon, and fired it into the crystal. The neodymium atoms absorbed the light and, after a time dictated by the crystal’s structure, released a photon with the same quantum state as the original.
The team’s quantum memory is as efficient as macroscopic devices despite being only 690 nanometres wide and 15 micrometres long.