An anonymous reader quotes a report from PCWorld: Quantum computers are based on atomic-scale quantum bits, or qubits, that can represent both 0 and 1 simultaneously. Realizing that potential, however, depends on the ability to build working quantum circuits. The quantum version of the classic Fredkin gate exchanges two qubits depending on the value of the third. It could be a key component of quantum circuitry, but because of the complexity involved, no one has ever managed to build one in the real world -- until now. Whereas the Fredkin gate typically requires a circuit of five logic operations, researchers from Griffith University and the University of Queensland used the quantum entanglement of particles of light to implement the controlled-SWAP operation directly. Essentially, the scientists demonstrated how to build large quantum circuits directly, without having to use numerous small logic gates. That, in turn, puts real quantum computers within closer reach.