Quantum computers work with qubits instead of the traditional bits of electronic computers. Most experimental implementations of qubits have used ions – but photons may be a better choice.
To date, the most promising approach to building quantum computers has been to use ions trapped in electric fields. Using photons — particles of light — instead would have many advantages, but it’s notoriously difficult to get photons to interact: Two photons that collide in a vacuum simply pass through each other.
In the Sept. 2 issue of the journal Science, researchers at MIT and Harvard University describe an experiment that allows a single photon to control the quantum state of another photon. The result could have wide-ranging consequences for quantum computing and quantum communication, the quantum analog to conventional telecommunications.