Measuring the Charge and Spin States of Electrons on Individual Dopant Atoms in Silicon

We review an ongoing effort to demonstrate technologies required for quantum computing with phosphorus donors in silicon. The main aspect of our research is to achieve control over charge and spin states of individual dopant atoms. This work has required the development of new techniques for engineering silicon nanodevices at the atomic level. We follow an approach for implanting single phosphorus ions into silicon substrates with integrated p–i–n detectors. Configuring our devices with radio-frequency single-electron transistors (RF-SETs) allows for charge sensing at low temperatures. In this context, we perform measurements of single-electron charge transfer between individual phosphorus donors. In a parallel effort, we employ nanoscale Schottky contacts for populating and depopulating individual dopant atoms. Of particular interest is coherent manipulation of single-electron charge and spin states on individual dopant atoms. Charge manipulation between coupled donor states may be achieved by either external microwave pumping or intrinsic tunnel coupling. Spin manipulation, on the other hand, involves magnetic resonance. In this context, we pursue electrically detected spin resonance in phosphorus-doped devices with a decreasing number of dopant atoms.