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Submission + - Laser that is powered by one electron at a time (princeton.edu) 1

Taco Cowboy writes: Princeton University researchers have built a rice grain-sized laser powered by single electrons tunneling through artificial atoms known as quantum dots. The tiny microwave laser, or "maser," is a demonstration of the fundamental interactions between light and moving electrons

The researchers built the device — which uses about one-billionth the electric current needed to power a hair dryer — while exploring how to use quantum dots, which are bits of semiconductor material that act like single atoms, as components for quantum computers

The device demonstrates a major step forward for efforts to build quantum-computing systems out of semiconductor materials, according to co-author and collaborator Jacob Taylor, an adjunct assistant professor at the Joint Quantum Institute, University of Maryland-National Institute of Standards and Technology. "I consider this to be a really important result for our long-term goal, which is entanglement between quantum bits in semiconductor-based devices" Taylor said

The researchers fabricated the double quantum dots from extremely thin nanowires (about 50 nanometers, or a billionth of a meter, in diameter) made of a semiconductor material called indium arsenide. They patterned the indium arsenide wires over other even smaller metal wires that act as gate electrodes, which control the energy levels in the dots

To construct the maser, they placed the two double dots about 6 millimeters apart in a cavity made of a superconducting material, niobium "This is the first time that the team at Princeton has demonstrated that there is a connection between two double quantum dots separated by nearly a centimeter, a substantial distance" Taylor said

When the device was switched on, electrons flowed single-file through each double quantum dot, causing them to emit photons in the microwave region of the spectrum. These photons then bounced off mirrors at each end of the cavity to build into a coherent beam of microwave light

One advantage of the new maser is that the energy levels inside the dots can be fine-tuned to produce light at other frequencies, which cannot be done with other semiconductor lasers in which the frequency is fixed during manufacturing, Petta said. The larger the energy difference between the two levels, the higher the frequency of light emitted

"In this paper the researchers dig down deep into the fundamental interaction between light and the moving electron" Gmachl said. "The double quantum dot allows them full control over the motion of even a single electron, and in return they show how the coherent microwave field is created and amplified. Learning to control these fundamental light-matter interaction processes will help in the future development of light sources"

Earth

Breaking the Squid Barrier 126

An anonymous reader writes "Dr. Steve O'Shea of Auckland, New Zealand is attempting to break the record for keeping deep sea squid alive in captivity, with the goal of being able to raise a giant squid one day. Right now, he's raising the broad squid, sepioteuthis australis, from egg masses found in seaweed. This is a lot harder than it sounds, because the squid he's studying grow rapidly and eat only live prey, making it hard for them to keep the squid from becoming prey themselves. If his research works out, you might one day be able to visit an aquarium and see giant squid."

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