CPM Seminar

Silicon metal oxide semiconductor nanostructures for solid-state quantum computing

Malcolm Carroll

Sandia National Labs

Development of metal oxide semiconductor (MOS) nanostructures for solid-state quantum computing will be described. A primary motivation of this research is the recent unprecedented manipulation of single electron spins in GaAs quantum dots, which has been used to demonstrate a quantum bit [1]. Quantum bits (qubits) are a fundamental element for quantum computing. A critical challenge for quantum computing is development of qubits that maintain long spin decoherence times, which will allow the necessary number of spin operations to be done before the information is lost due to spin decoherence. Development of silicon nanostructures for qubits are being pursued around the world because electron spins in silicon are predicted to have long decoherence times.

This talk will focus on enhancement mode silicon quantum dots fabricated with a double top gated MOS structure that emulates the GaAs lateral quantum dot qubit. One critical concern for silicon MOS quantum dots is that there are defects at the interface and in the insulator which can produce both detrimental electrostatic and paramagnetic effects on the qubit operation. We present stable, lithographically defined, single-period Coulomb-blockade and single-electron charge sensing in a lateral Si MOS quantum dot nanostructure. These are critical steps forward towards demonstrating the same control of electron spins in Si MOS quantum dots as is needed in GaAs quantum dot qubits. Details about the process flow, defect characterization and their impact on the device performance will also be presented. If time permits, the implications of the observed quantum dot behavior, defect characterization and modeling for future qubits and quantum circuit micro-architecture will also be discussed.

We wish to acknowledge the research funding support provided by the laboratory directed research and development (LDRD) program at Sandia National Laboratories and the Laboratory of Physical Sciences. Sandia National Labs is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

[1] J. Petta et al., Science 309, 2180 (2005)