A decoherence-free subspace in a charge quadrupole qubit

TL;DR

This paper introduces a quadrupole charge qubit in a triple quantum dot that is designed to be immune to uniform electric field fluctuations, significantly improving gate fidelity in solid-state quantum computing.

Contribution

The authors propose a novel quadrupole charge qubit design that generalizes decoherence-free subspaces to charge qubits, enabling enhanced noise suppression during quantum gate operations.

Findings

Simulations show gate fidelities are 10-1,000 times higher than traditional charge qubits.

The quadrupole design simplifies noise suppression pulse sequences.

Any Coulomb-interaction-based qubit scheme could benefit from this design.

Abstract

Quantum computing promises significant speed-up for certain types of computational problems. However, robust implementations of semiconducting qubits must overcome the effects of charge noise that currently limit coherence during gate operations. Here we describe a scheme for protecting solid-state qubits from uniform electric field fluctuations by generalizing the concept of a decoherence-free subspace for spins, and we propose a specific physical implementation: a quadrupole charge qubit formed in a triple quantum dot. The unique design of the quadrupole qubit enables a particularly simple pulse sequence for suppressing the effects of noise during gate operations. Simulations yield gate fidelities 10-1,000 times better than traditional charge qubits, depending on the magnitude of the environmental noise. Our results suggest that any qubit scheme employing Coulomb interactions (for example, encoded spin qubits or two-qubit gates) could benefit from such a quadrupolar design.