Yale University scientists have made an important step toward the development of a quantum computer, a machine of unprecedented power and speed, by finding a new way to manipulate microwave signals.
Both regular and quantum computers receive, store and manipulate information to make calculations. However, the process is complicated within quantum computers by the fragility of quantum information.
In come photons. Photons are the smallest units of microwave signals and it turns out that they can serve as the memory for a quantum computer, just like RAM on a regular one. Because photons act weakly with the substance they travel through, such as coaxial cables, air or wires, they have the capacity to hold quantum information for long periods of time.
In coming to their discovery that photons can be used for quantum computer memory, the researchers made an artificial medium in which photons repel photons, a setting that allows for efficient encoding of quantum information.
"Our experiment has shown that we can create a medium that on the one hand enables us to manipulate the photon state, and on the other hand does not absorb the photons, which would destroy the quantum information stored in them," says postdoctoral researcher at Yale and lead author of the paper Gerhard Kirchmair. "This creates a source for novel quantum states without the need for complicated control techniques and could simplify certain quantum computation algorithms. In the long run it could be used as one of the many resources required to build a quantum computer."
Further developments could be built upon the study, allowing for additional progress toward a quantum computer.
"The tricky bit for future experiments will be to switch on and off this effect at will, so that it only happens if we want it to happen," Kirchmair says. "We already have experiments on the way that show that we can do that."
The research team was led by Yale applied physics professor Robert J. Schoelkopf and was supported by the National Science Foundation, the French Angence Nationale de la Recherche, the U.S. Army, the Swiss NSF and the British Engineering and Physical Sciences Research Council.
The study is pubilshed in the journal Nature.
