EMT/QIS: GaAs hole spins as qubits: Eliminating hyperfine interaction-induced decoherence

Princeton University, Princeton NJ

Investigators

Abstract

EMT/QIS: GaAs hole spins as qubits: Eliminating hyperfine interaction-induced decoherence Quantum Computing is an emerging area of science and engineering. Its broad goal is to harness the superposition of quantum states for computing purposes. The elementary building block of a quantum computer is the quantum bit (qubit). Quantum bits have been demonstrated in a wide variety of systems ranging from trapped ions, to electron spins in semiconductors, to superconductors. In order to be useful, a qubit must be properly initialized, measured, and coupled to other qubits. The quality of a qubit is characterized by a lifetime (T1) and a coherence time (T2). These time scales vary by several orders of magnitude from one system to another (e.g. trapped ion versus superconducting qubits). It is therefore customary to quote a quality factor, Q, which is the ratio of the coherence time to the typical gate operation time. We will build qubits based on hole spins in GaAs nanometer-size quantum dots. Hole spins are promising candidates since the hole wavefunctions have p-like orbitals. As a result, hyperfine interactions with the host crystal nuclei are expected to be negligible, leading to spin coherence times approaching the hole spin lifetime of 300 microseconds. Taking into account the typical gate operation time of ~150 ps, a hole spin qubit, if realized, could have a quality factor of nearly 2 million, well beyond the threshold for fault tolerance. The primary goal of this project is to accurately measure, and determine what limits, the quantum coherence times of hole spins in GaAs quantum dots.