Tunable Hybrid Qubit in a GaAs Double Quantum Dot

TL;DR

This paper demonstrates a tunable hybrid qubit in a GaAs double quantum dot, showing improved coherence times and new control methods for semiconductor qubits through electrical manipulation and exploiting dot anharmonicity.

Contribution

Introduces a new electrically controllable hybrid qubit in GaAs quantum dots with enhanced coherence by leveraging dot anharmonicity and a novel working point.

Findings

Qubit decoherence time is significantly improved.

New anticrossing helps preserve quantum coherence.

Electrical manipulation enables full control of the qubit.

Abstract

We experimentally demonstrate a tunable hybrid qubit in a five-electron GaAs double quantum dot. The qubit is encoded in the (1,4) charge regime of the double dot and can be manipulated completely electrically. More importantly, dot anharmonicity leads to quasiparallel energy levels and a new anticrossing, which help preserve quantum coherence of the qubit and yield a useful working point. We have performed Larmor precession and Ramsey fringe experiments near the new working point and find that the qubit decoherence time is significantly improved over a charge qubit. This work shows a new way to encode a semiconductor qubit that is controllable and coherent.