Scientists achieve breakthrough in quantum control of light

May 31st, 2009 - 12:37 pm ICT by ANI  

Washington, May 31 (ANI): Researchers at UC Santa Barbara have demonstrated a breakthrough in the quantum control of photons, the energy quanta of light, which is a significant result in quantum computation, and could eventually have implications in banking, drug design, 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 breakthrough is the result of four years of work in the laboratories of Cleland and Martinis.

Using large numbers, with hundreds of digits, encryption codes are changed daily and would take years of traditional computing to break.

Quantum computing could potentially break those codes quickly, destroying current encryption schemes.

In the experiments, the photons were stored in a microwave cavity, a “light trap” in which the light bounces back and forth as if between two mirrors.

In earlier work, these researchers showed they could create and store photons, one at a time, with up to 15 photons stored at one time in the light trap.

The research shows that they can create states in which the light trap simultaneously has different numbers of photons stored in it.

For example, it can simultaneously have zero, three, and six photons at the same time.

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.

Explaining the paradoxical simultaneity of quantum states, Cleland said, “These superposition states are a fundamental concept in quantum mechanics, but this is the first time they have been controllably created with light.”

“This experiment can be thought of as a quantum digital-to-analog converter,” Martinis added.

As digital-to-analog converters are key components in classical communication devices, this experiment might enable more advanced communication protocols for the transmission of quantum information.

The scientists said their research is leading to the construction of a quantum computer, which will have applications in information encryption and in solving or simulating problems that are not amenable to solution using standard computers. (ANI)

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