A new spin on quantum computing

20 November 2006

A University of Utah physicist took a step toward developing a quantum computer by showing it is feasible to read data stored in the form of the magnetic spins of phosphorus atoms.

‘Our work represents a breakthrough in the search for a nanoscopic mechanism that could be used for a data readout device,’ said Christoph Boehme, assistant professor of physics at the University of Utah. ‘We have demonstrated experimentally that the nuclear spin orientation of phosphorus atoms embedded in silicon can be measured by very subtle electric currents passing through the phosphorus atoms.’

‘We have resolved a major obstacle for building a particular kind of quantum computer, the phosphorus-and-silicon quantum computer. For this concept, data readout is the biggest issue, and we have shown a new way to read data.’

In the new study, Boehme and colleagues used silicon doped with phosphorus atoms. By applying an external electrical current, they were able to read the net spin of 10,000 of the electrons and nuclei of phosphorus atoms near the surface of the silicon.

The study demonstrates it is possible to use electrical methods to detect or read data stored as not only electron spins but as the more stable spins of atomic nuclei.

‘We discovered a mechanism that will allow us to measure the spins of the nuclei of individual phosphorus atoms in a piece of silicon when the phosphorus is close to the surface, within about 50 atoms,’ Boehme said. ‘With improved design, it should be possible to build a much smaller device that lets us read a single phosphorus nucleus.’