Minimal Message Machine for Quantum Computing

One solitary quantum pulse of electromagnetic radiation, no more, no less, produced by one single electron, will be the product of a new device under construction by nanotechnologists at the USC Viterbi School of Engineering.

Colleagues at the University of Texas/Austin will build the USC device’s counterpart, a detector for that single pulse, as their part of a joint $1.3 million study just funded by the National Science Foundation. The interdisciplinary team includes three members of the National Academy of Engineering.  

According to the researchers, the ultimate goal is to use such singleton photons in cryptographic devices and, ultimately, general-purpose computers, as part of the continuing search for smaller, faster, and more efficient information processing devices.

The quantum dots that the USC team will use to generate single photons, one at a time, are nanoscale devices that perform the photoelectric process Einstein explained in reverse. The dots are minute particles of a highly engineered semiconductor material. Classic photoelectric materials produce electric current — electrons — when struck by sufficiently energetic photons, in a mechanism Einstein explained. The same mechanism, working in reverse, sends out a single photon when energized by an electron.

While single photon emitters have been built before, the USC model is designed as a model of Einsteinian economy. The excitation will come from one single electron.

To turn a mesa containing an array of such dots into a single photon signal device, an array of microscopic photonic crystal resonant cavities is built in the mesa. Each resonance cavity will contain a single quantum dot.

Creating the crystal is only the first step. To activate it in a useful way, an elaborate electronic control system is needed, which will feed a single electron of precisely the correct electric potential into the system at precisely the right time. This potential is so minute that, to avoid introduction of potentially stray electrons into the system, the electronics will function at extremely low temperature -- 10 Kelvin, (-441° Fahrenheit, -263° Celsius).

Using resonance effects, the group hopes to speed up the rate of production of single photons, so that the process happens in 100 picoseconds -- ten times faster than existing devices. (100 picoseconds are to one second what one second is to 317 years).

Visit http://viterbi.usc.edu.