Complete All-Optical Quantum Control of Electron Spins in InAs/GaAs Quantum Dot Molecule

TL;DR

This paper proposes a method for complete all-optical quantum control of electron spins in InAs/GaAs quantum dot molecules, enabling universal quantum gates with high fidelity and fast operation for quantum computing.

Contribution

It introduces a feasible scheme for universal quantum control of two electron spin qubits in coupled quantum dots using pulse-shaped laser fields.

Findings

Achieved a two-qubit quantum Fourier transform with fidelity 0.881.

Demonstrated control with gate durations of approximately 414 ps.

Provided pulse shapes for implementing a universal set of quantum gates.

Abstract

The spin states of electrons and holes confined in InAs quantum dot molecules have recently come to fore as a promising system for the storage or manipulation of quantum information. We describe here a feasible scheme for complete quantum optical control of two electron spin qubits in two vertically-stacked singly-charged InAs quantum dots coupled by coherent electron tunneling. With an applied magnetic field transverse to the growth direction, we construct a universal set of gates that corresponds to the possible Raman transitions between the spin states. We detail the procedure to decompose a given two-qubit unitary operation, so as to realize it with a successive application of up to 8 of these gates. We give the pulse shapes for the laser pulses used to implement this universal set of gates and demonstrate the realization of the two-qubit quantum Fourier transform with fidelity of 0.881 and duration of 414 ps. Our proposal therefore offers an accessible path to universal computation in quantum dot molecules and points to the advantages of using pulse shaping incoherent manipulation of optically active quantum dots to mitigate the negative effects of unintended dynamics and spontaneous emission.