Ultrafast optical control of entanglement between two quantum dot spins

TL;DR

This paper demonstrates ultrafast optical control of entanglement between two electron spins in quantum dots, significantly advancing the speed and scalability of quantum information processing.

Contribution

It introduces a method to achieve rapid optical entanglement of two quantum dot spins using ultrafast laser techniques and vertically-stacked quantum dots.

Findings

Two-qubit gate speeds are over ten times faster than previous systems.

Optical control of entanglement is viable in semiconductor quantum dots.

The approach enhances prospects for scalable quantum information platforms.

Abstract

The interaction between two quantum bits enables entanglement, the two-particle correlations that are at the heart of quantum information science. In semiconductor quantum dots much work has focused on demonstrating single spin qubit control using optical techniques. However, optical control of entanglement of two spin qubits remains a major challenge for scaling from a single qubit to a full-fledged quantum information platform. Here, we combine advances in vertically-stacked quantum dots with ultrafast laser techniques to achieve optical control of the entangled state of two electron spins. Each electron is in a separate InAs quantum dot, and the spins interact through tunneling, where the tunneling rate determines how rapidly entangling operations can be performed. The two-qubit gate speeds achieved here are over an order of magnitude faster than in other systems. These results demonstrate the viability and advantages of optically controlled quantum dot spins for multi-qubit systems.