Ultrafast optical rotations of electron spins in quantum dots

TL;DR

This paper demonstrates ultrafast optical rotations of electron spins in quantum dots on a picosecond scale, enabling rapid spin control crucial for quantum computing, using laser pulses as control fields.

Contribution

It introduces a method for performing high-fidelity, ultrafast spin rotations in quantum dots using periodic optical pumping and laser pulses.

Findings

Achieved spin rotations on a picosecond timescale

Controlled spins about arbitrary axes

Demonstrated potential for rapid quantum information processing

Abstract

Coherent manipulation of quantum bits (qubits) on time scales much shorter than the coherence time is a key prerequisite for quantum information processing. Electron spins in quantum dots (QDs) are particularly attractive for implementations of qubits. Efficient optical methods for initialization and readout of spins have been developed in recent years. Spin coherence times in the microsecond range have been demonstrated, so that spin control by picosecond optical pulses would be highly desirable. Then a large number of spin rotations could be performed while coherence is maintained. A major remaining challenge is demonstration of such rotations with high fidelity. Here we use an ensemble of QD electron spins focused into a small number of precession modes about a magnetic field by periodic optical pumping. We demonstrate ultrafast optical rotations of spins about arbitrary axes on a picosecond time scale using laser pulses as control fields.