5/29/2009 PERMALINK
Breakthrough in the quantum control of light
Researchers at UC Santa Barbara have demonstrated a breakthrough in the quantum control of photons, the energy quanta of light, that represents a significant advance in quantum computing and other applications. UCSB physics researchers Max Hofheinz, John Martinis, and Andrew Cleland used a superconducting electronic circuit known as a Josephson phase qubit to prepare highly unusual quantum states using microwave-frequency photons. The image shows a "quantum state with zero, three
and six photons simultaneously (theory on left, experiment on right)." A quantum computer based on this breakthrough might be able to quickly break any normal encryption scheme, like those used to protect bank transactions.

In the experiments, photons were stored in a microwave cavity, a "light trap" in which the light bounces back and forth as if between two mirrors. The research shows that states can be created in which a light trap simultaneously has different numbers of photons stored in it. Measuring the quantum state by counting how many photons are stored forces the trap to "decide" how many there are; but prior to counting, the light trap exists in a quantum superposition, with all three outcomes possible.