Pulses of light dramatically accelerate quantum computers

University of Michigan researchers used pulses of light dramatically to accelerate quantum computers, in the process also making important strides in technology which could be used effectively to foil national and personal security threats. The researchers say it is a leap that could lead to tougher protections of information and quicker deciphering of hackers’ encryption codes. A new paper on the results of this research appears in the 17 August 2007 issue of Science (see below). Duncan Steel, the Robert J. Hiller Professor at Michigan Engineering’s Department of Electrical Engineering and Computer Science and the Department of Physics, is one of the lead authors of the paper. Faculty from the University of California-San Diego and the Naval Research Laboratory in Washington, D.C., also contributed. The researchers used short, coherent pulses of light to create light-matter interactions in quantum dots — particles so small that the addition or deletion of electrons changes their properties. They found they could control the frequency and phase shifts in the optical network, which is crucial in powering an optically driven quantum computer, Steel said. Optically driven quantum computers can crack highly encrypted codes in seconds. The fastest of today’s desktop computers would require twenty years. Part of what makes quantum computers so fast is that they are masters of multitasking. “Quantum computers are capable of massive parallel computations,” Steel said. “That’s why these machines are so fast.”

Note that the technology the researchers used to power them in this study is relatively cheap. “We’re particularly excited about our findings because they show that we can achieve these results by using quantum dots and readily available, relatively inexpensive optical telecommunications technology to drive quantum computers,” Steel said. “Quantum dots replace transistors in these computers, and our results show that it only takes a few billionths of a watt to drive it.” The Wolverine researchers are using quantum dot systems to pave the way for numerous quantum level applications, such as quantum dot dressed state lasers, optical modulators, and quantum logic devices.

This discovery in quantum dot spectroscopy is an important stepping stone to building a quantum computer for the future. Spectroscopy is the study of the interaction between light and matter.

-read more in Xiaodong Xu et al., “Coherent Optical Spectroscopy of a Strongly Driven Quantum Dot,” Science 317. no. 584017 (August 2007): 929-32 (sub. req.)