Using nanoscale transistors to measure single donor spins in semiconductors

Abstract

Abstract. We propose a technique for measuring the state of a single donor electron spin using a field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is facilitated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outline experimental requirements. Our measurement provides a single-shot, projective, and quantum non-demolition measurement of an electron-encoded qubit state.Keywords: Quantum computation, Quantum measurement PACS: 03.67.Lx, 84.37.+q The spin of electrons bound to donors in silicon is considered a promising candidate qubit for quantum information processing [1]. An integral part of any quantum computation architecture is the capacity for high-fidelity qubit readout; however, the detection of spin states of single donor electrons and nuclei in silicon has remained elusive. In this paper we analyze spin dependent scattering between conduction electrons and neutral donors as a spin-to-charge-transport conversion technique, and show that quantum non-demolition (QND) measurements of single electron spin-encoded qubit states are realistically achievable when mediated via nuclear spin states. Such a measurement will also be of value to the developing field of spintronics where the electrical detection of spin states is valuable. Our readout takes advantage of two features: i) the ability to perform electron spin resonance spectroscopy using a two-dimensional electron gas (2DEG), and ii) the hyperfine shift induced on dopant electron Zeeman energies by the dopant nuclear spin state. In the following, we first describe the experimental apparatus and the techniques of 2DEG mediated spin resonance spectroscopy, and then we present our proposal for spin state measurement, analyze the sensitivity of the measurement scheme and establish the key factors that determine signal-to-noise.The physical setting. Figure 1(a) shows a cross section of a 2DEG spin readout device with a single implanted donor. Prior studies have used similar devices with bulk-doping [2,3] or a large number of implanted donors (10 6 ) [4] in the 2DEG channel. The 2DEG is operated in accumulation mode and thus scattering occurs between conduction electrons and electron(s) bound to the shallow donor(s). The basic principle exploited in these studies is the role of the exchange interaction in electron-electron scattering. At a scattering event between a conduction electron and a loosely bound donor impurity electron, the Pauli principle demands that the combined wave function of the two electrons be antisymmetric with respect to coordinate exchange. This constraint, together with the