Princeton University researchers have built an incredibly small "maser" or microwave laser the size of a grain of rice, making it the smallest single electron device ever developed.

The maser is powered by single electrons shooting through "quantum dots" or artificial atoms. It uses only one billionth the amount of electricity used by a hair dryer.

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The maser emits microwave energy, and scientists say it's a perfect way to show how light and moving electrons interact. Scientists say the maser can be fine-tuned even further to emit photons in other wavelengths.

The maser's a great step forward for quantum computing and advances the effort to build a computing system out of a semiconductor material like quantum dots.

The maser is also a major advance for efforts to build quantum-computing systems out of semiconductor materials, said 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 original project aim was to explore how to use double quantum dots (two quantum dots joined together) as quantum bits, or qubits, the basic units of information in quantum computers.

Using nanowires with a diameter of 50 nanometers and constructed from indium arsenide, researchers created the quantum dots with even smaller metal wires that controlled how much energy the dots could contain.

They built it by using two double dots placed about millimeters separately in a niobium cavity and cooled the apparatus to near absolute zero.

Tagslaser, grain of rice, single electrons, quantum physics, microwave laser, quantum-computing system