Robust Quantum Computation with Quantum Dots

TL;DR

This paper proposes a robust quantum computing scheme using composite qubits encoded in quantum dots, which are immune to decoherence and do not require local magnetic field control, simplifying universal quantum gate implementation.

Contribution

It introduces a new composite qubit design in quantum dots that resists decoherence and enables universal gates without local magnetic fields.

Findings

Decoherence-free subspace in quantum dots enhances qubit stability.

Universal gates achieved by simple tunneling barrier modifications.

Single-pulse controlled-phase gate implementation.

Abstract

Quantum computation in solid state quantum dots faces two significant challenges: Decoherence from interactions with the environment and the difficulty of generating local magnetic fields for the single qubit rotations. This paper presents a design of composite qubits to overcome both challenges. Each qubit is encoded in the degenerate ground-state of four (or six) electrons in a system of five quantum dots arranged in a two-dimensional pattern. This decoherence-free subspace is immune to both collective and local decoherence, and resists other forms of decoherence, which must raise the energy. The gate operations for universal computation are simple and physically intuitive, and are controlled by modifying the tunneling barriers between the dots--Control of local magnetic fields is not required. A controlled-phase gate can be implemented in a single pulse.