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.