Princeton Researchers Develop Rice Sized Laser Princeton University researchers have built a rice sized laser powered by single electrons tunneling through artificial atoms known as quantum dots.Quantum dots are nanocrystals, which are made of semiconductor materials that are small enough to exhibit quantum mechanical properties.

Jacob Taylor, an adjunct assistant professor at the Joint Quantum Institute, University of Maryland-National Institute of Standards and Technology and one of the researchers, said, �The device uses about one-billionth of the power needed to run a hair dryer and represents a major step in efforts to build quantum-computing systems. I consider this to be a really important result for our long-term goal, which is entanglement between quantum bits in semiconductor-based devices.�

However, the researchers weren�t trying to build a mini-maser. A maser is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The word maser is derived from the acronym MASER: �microwave amplification by stimulated emission of radiation�. The researchers wanted to explore the use of double quantum dots, joining two dots together to form qubits. Qubits are the basic units of information in quantum computers.

Researchers stated that the goal was to get to double quantum dots to communicate with each other. They used extremely thin nanowires that were made of indium arsenide to fabricate the quantum dots. The placed the qubits 6 mm apart in a cavity that was made from niobium at a temperature near absolute zero (-459 degrees Fahrenheit).

They found that the electrons flowed in a single-file through each dot, which emitted photons in the microwave region of the light spectrum. The photons bounced off mirrors on either side of the cavity, creating a beam of microwave light.

�We designed dots to emit photons when single electrons jump from a higher to a lower energy level across the double dot. It is like a line of people crossing a wide stream by leaping onto a rock so small that it can only hold one person. They are forced to cross the stream one at a time. These double quantum dots are zero-dimensional as far as the electrons are concerned � they are trapped in all three spatial dimensions,� explained Jason Petta, an associate professor of physics at Princeton University and leader of the study.

The findings were published in the Science journal.