Wednesday, January 21, 2015

Maser from artificial molecules emitted microwaves bundled

Maser are the little-known sisters of lasers. They emit no concentration of light, but coherent microwave radiation. Still lags behind the development of the measles of lasers for decades. But now succeeded American physicists to develop a new type of grain from tiny quantum dots. As they report in the journal "Science", based on the amplification of microwave tunneling processes of individual electrons. Such masers could be used in the future for the control of quantum bits, the basic units of quantum computers.
"Our Maser is pumped through the tunneling of single electrons," says Jason Petta, of Princeton University, the basic principle of their small prototype. To use this quantum mechanical phenomenon, Petta sat with his colleagues two tiny quantum dots from the semiconductor indium arsenide on a substrate and contacted them via a plurality of electrodes made of gold and titanium. This module coupled to a resonator in which the microwaves at a fixed frequency could be increased.
Researchers now stored a voltage at their Maser, tunnelten single electrons through the quantum dots, which are also referred to as artificial molecules. In this case, the quantum dots were generated photons, which contributed to an enhancement of microwaves in the resonator. Test runs showed that a 1000-fold enhancement was achieved at the frequency of 7880.6 MHz with this structure. A big advantage over previous measles that were pumped with light pulses from a laser, is the purely electric mode.
According Petta the emitted wavelength such semiconductor maser can be adjusted over a wide frequency range between giga- and terahertz. This only would the composition and structure of the quantum dots used to be adjusted. Many applications for Maser does not yet exist. Yet Petta can imagine that coherent microwave radiation for the control of quantum computers are suitable. "Our findings are an important advance in order to generate an entanglement between two qubits about an inch apart," said Petta. The quantum mechanical entanglement of these basic units of quantum computers is the basis to solve complex computational tasks in parallel and thus more efficient than traditional processors.

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