Optically controlled phase gate for two spin qubits in coupled quantum dots

TL;DR

This paper proposes a fast, optically controlled phase gate for two spin qubits in coupled quantum dots, utilizing hole tunneling and Pauli blocking to achieve high-fidelity quantum logic operations within 10 ps.

Contribution

It introduces a novel scheme for ultrafast quantum gates in quantum dots using optical control and tunneling effects, with potential for high-speed quantum computing.

Findings

Gate operation time estimated at 10 ps

Fidelity of over 90% achievable

Applicable to vertically stacked InAs quantum dots

Abstract

We present a feasible scheme for performing an optically controlled phase gate between two conduction electron spin qubits in adjacent self assembled quantum dots. Interaction between the dots is mediated by the tunneling of the valence hole state which is activated only by applying a laser pulse of the right polarization and frequency. Combining the hole tunneling with the Pauli blocking effect, we obtain conditional dynamics for the two quantum dots, which is the essence of our gating operations. Our results are of explicit relevance to the recent generation of vertically stacked self-assembled InAs quantum dots, and show that by a design which avoids unintended dynamics the gate could be implemented in theory in the 10 ps range and with a fidelity over 90%. Our proposal therefore offers an accessible path to the demonstration of ultrafast quantum logic in quantum dots.