Auxiliary-level-assisted operations with charge qubits in semiconductors

TL;DR

This paper proposes a new method for manipulating charge qubits in semiconductors using auxiliary levels and microwave pulses, enabling fast one-qubit operations with manageable decoherence.

Contribution

It introduces a novel scheme for qubit rotations utilizing auxiliary molecular levels and resonant microwave pulses in semiconductor charge qubits.

Findings

Single microwave pulse can transfer electron between donor sites.

Various one-qubit gates can be implemented with this scheme.

Decoherence due to phonons is weak enough for coherent control.

Abstract

We present a new scheme for rotations of a charge qubit associated with a singly ionized pair of donor atoms in a semiconductor host. The logical states of such a qubit proposed recently by Hollenberg et al. are defined by the lowest two energy states of the remaining valence electron localized around one or another donor. We show that an electron located initially at one donor site can be transferred to another donor site via an auxiliary molecular level formed upon the hybridization of the excited states of two donors. The electron transfer is driven by a single resonant microwave pulse in the case that the energies of the lowest donor states coincide or two resonant pulses in the case that they differ from each other. Depending on the pulse parameters, various one-qubit operations, including the phase gate, the NOT gate, and the Hadamard gate, can be realized in short times. Decoherence of an electron due to the interaction with acoustic phonons is analyzed and shown to be weak enough for coherent qubit manipulation being possible, at least in the proof-of-principle experiments on one-qubit devices.