Tunable Hybrid Qubit in a GaAs Double Quantum Dot.

Area of Science:

• Quantum Computing
• Semiconductor Physics
• Quantum Information Science

Background:

• Quantum dots are promising platforms for qubit development.
• Charge qubits in double quantum dots face challenges with coherence and control.
• Tunable qubit architectures are essential for scalable quantum computers.

Purpose of the Study:

• To demonstrate a tunable hybrid qubit in a GaAs double quantum dot.
• To investigate the role of dot anharmonicity in qubit coherence.
• To improve the coherence time of semiconductor qubits.

Main Methods:

• Experimental demonstration of a hybrid qubit in a five-electron GaAs double quantum dot.
• Encoding the qubit in the (1,4) charge regime.
• Electrical manipulation and characterization using Larmor precession and Ramsey fringe experiments.

Main Results:

• Achieved a tunable hybrid qubit with electrical control.
• Identified quasiparallel energy levels and a new anticrossing due to dot anharmonicity.
• Significantly improved qubit decoherence time compared to a standard charge qubit.

Conclusions:

• The demonstrated hybrid qubit offers a new, controllable, and coherent encoding scheme for semiconductor qubits.
• Dot anharmonicity is crucial for enhancing qubit coherence and identifying optimal working points.
• This work paves the way for more robust quantum information processing in semiconductor systems.