Silicon transistors continue to shrink to the size where quantum effects become important. Spin-based quantum computers could make use of these quantum effects if the spin state on an electron can be read accurately.

Andrea Morello and co-workers, University of New South Wales, Australia, have used spin-dependant tunneling to displace an electron to a location which was dependant on its spin state. A charge detector that was both electrostatically and tunnel-coupled to the electron site allowed accurate (> 90 %) and fast single-shot spin readouts.

The detector is compatible with current microelectronic technology as it is silicon-based. It consists of a silicon single-electron transistor with small regions of phosphorus donors implanted next to it.

• Single-shot readout of an electron spin in silicon
  A. Morello, J. Pla, F. Zwanenburg, K. Chan, K. Tan et al.,
  Nature 2010, 467, 687–691.
  DOI: 10.1038/nature09392