Friday, September 10, 2004

"QUANTUM: computer chip circuitry demonstrated"
Yale University researchers have demonstrated how to build a quantum computer operating on quantum bits, or qubits, which hold a superposition of quantum states. The computer uses a superconducting "Cooper box" to store oscillating microwave photons which can be read and written without disturbing their quantum states. Qubits based on the superposition of quantum states can be used to make integrated circuits. "Heisenberg's Uncertainty principle says you can't measure the velocity and position of a particle, and likewise in QED [quantum electrodynamic] circuits you can't measure the voltage and the current at the same time," explained Yale University professor Steven Girvin. Quantum computers derive their power from enabling a superposition of quantum states to simultaneously perform many parallel operations. Those operations allow quantum computers to perform tasks like breaking encryption codes that are impossible for digital computers. Many quantum-state mechanisms have been demonstrated in physics labs, some of which could serve as building blocks for future quantum computers. Likewise, Yale's "qutons," or "qubit on a photon," invention may enable quantum computers to be placed on chips even sooner. The advantages of Yale's method include the relatively small size of its qubit repositories � about a square micron � and the ability to read a qubit's state without disturbing it � the bane of quantum computers to date.