Noise Suppression Using Symmetric Exchange Gates in Spin Qubits.

Area of Science:

• Quantum computing
• Solid-state physics
• Spintronics

Background:

• Spin qubits in Gallium Arsenide (GaAs) are promising for quantum computation.
• Improving the fidelity of quantum gates is crucial for scalable quantum computing.
• Conventional methods for controlling spin qubits, like detuning, face limitations.

Purpose of the Study:

• To demonstrate a substantial improvement in the spin-exchange gate quality factor for GaAs spin qubits.
• To compare the effectiveness of symmetric control versus conventional detuning.
• To investigate the sources of decoherence in both control schemes.

Main Methods:

• Implementing symmetric control using nanosecond voltage pulses on the interdot barrier.
• Modulating the exchange interaction while maintaining symmetry between quantum dots.
• Developing and applying a model that accounts for electrical and nuclear noise sources.

Main Results:

• Achieved up to a six-fold increase in the spin-exchange gate quality factor using symmetric control.
• Observed excellent agreement between experimental results and the noise model for both methods.
• Identified that symmetric exchange rotations are primarily limited by nuclear field noise-induced rotation-axis fluctuations, not direct exchange noise.

Conclusions:

• Symmetric control offers a significant advancement over detuning for GaAs spin qubits.
• Understanding noise sources is critical for further improving qubit performance.
• The findings pave the way for more robust and scalable solid-state quantum computing.