New logic gate uses quantum states

Ars Technica : Quantum computing uses properties of subatomic particles to store a range of possible values other than the 0 and 1 of traditional binary data storage. However, the logic gates used to manipulate and perform calculations on quantum bits have not made use of quantum states themselves. Now, researchers from the Max Planck Institute of Quantum Optics in Garching, Germany, have created what they call a quantum gate, which uses the entanglement of a photon and an atom to perform logic operations. In the gate, an atom is trapped in a cavity between two mirrors, and laser pulses deliver photons with a range of polarizations into the cavity. If the atom becomes entangled with a photon that has the same vibrational frequency, the photon undergoes a phase shift that can be detected after it leaves the cavity. If they don’t have the same frequency, the photon doesn’t undergo a phase shift. That conditional phase shift uses quantum mechanical properties to duplicate a basic logic gate.