Quantum computers rely on the tiniest objects and smallest interactions in the universe. Scientists measure the atomic spin of molecules and manipulate atoms to make these experimental computers, which one day may perform exceptionally complex calculations.
But even though quantum theory tries to describe the tiniest particles that make up matter and how they interact with each other and with energy, experimental quantum computers are anything but small.
“You need a room full of equipment,” said Dr. Pierre M. Petroff, a professor of electrical and computer engineering and material science at the University of California at Santa Barbara.
But the world’s dimmest light source, a device created by a team that included Petroff, may change that.
In a paper published in the journal Science on Dec. 22, Petroff and two colleagues, Atac Imamoglu and Evelyn L. Hu, described a tiny, mushroom-shaped semiconductor that would spit out a single photon, or basic particle of light, on command.
The device may someday allow the development of quantum computers that are based on light particles rather than the movement of atoms. And, perhaps more important, such computers may be the first quantum machines that, at least theoretically, can talk to each other.
“It appears to be the first step to a reliable, single photon source,” said Dr. Emanuel H. Knill of the Los Alamos National Laboratory, an author of a paper that appears Thursday in the journal Nature that proposed using photons rather than molecules for quantum computers.
The single photon spitter, which is more formally known as a quantum dot single-photon turnstile device, is based on a structure that Petroff created seven years ago. The quantum dot, as he put it, is an “electron jail.”
The secret to keeping electrons in captivity is mixing semiconductor materials with different electrical properties on the same surface. Semiconductors, like the silicon in computer chips, become conductors when exposed to different levels of energy.
