A maser has been developed that is roughly the size of a grain of rice, possibly signifying a major advance in the development of quantum computers.
Masers are similar to lasers, except they use microwaves instead of light to create a beam.
Princeton University researchers linked together pairs of artificial molecules, made of semiconducting material, known as quantum dots. Extremely thin nanowires, constructed from indium arsenide, were used to connect the tiny units to each other. The pairs were then placed inside a tiny well of niobium, a superconductor, about one-quarter inch apart from each other. That cavity was lined with mirrors on two sides. When a stream of individual electrons was fed to the system, the quantum dots produced microwave radiation, which bounced between the mirrors, creating a focused beam, similar to a laser.
"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," Claire Gmachl, an electrical engineering professor at Princeton University, said.
Masers (short for microwave amplification by stimulated emission of radiation) have been discussed and theorized by physicists for decades. The first primitive maser was constructed in 1953 at Columbia University. However, these early devices had to be cooled to a temperature just above absolute zero, preventing widespread adoption of the technology. In 2012, physicists from Imperial College London and the National Physical Laboratory developed the world's first practical room-temperature maser.
Quantum dots are capable of absorbing electromagnetic energy at one wavelength, and emit light at a different frequency. The devices are already being used in some electronic devices, and could significantly improve the performance of televisions, smartphones and other electronic displays.
Princeton researchers created the new device in order to study how these pairs could be used to manage quantum bits, the basic unit of computation in quantum computers.
"I consider this to be a really important result for our long-term goal, which is entanglement between quantum bits in semiconductor-based devices," Jacob Taylor from the Joint Quantum Institute at the University of Maryland-National Institute of Standards and Technology, said.
Quantum computers could herald a new age in information technology, processing data far faster than is currently possible utilizing silicon-based systems. While a modern-day processor works on one calculation at a time, a quantum microchip would handle millions of calculations at once. A future 30-qubit computer might operate 1,000 times faster than a contemporary desktop system.
Semiconductor double quantum dot micromaser, an article detailing the development of the new maser, was published in the journal Science.