Flux qubits with long coherence times for hybrid quantum circuits

Area of Science:

• Quantum computing
• Superconducting circuits
• Cavity quantum electrodynamics

Background:

• Superconducting flux qubits are essential for quantum computing.
• Previous flux qubit designs faced limitations in coherence times.
• Embedding qubits in cavities can enhance their performance.

Purpose of the Study:

• To measure the performance of superconducting flux qubits within a 3D copper cavity.
• To investigate the impact of cavity embedding on qubit coherence.
• To assess the potential for coherent coupling with individual spins.

Main Methods:

• Fabrication of superconducting flux qubits on a sapphire substrate.
• Inductive coupling of qubits to an on-chip superconducting resonator.
• Measurement of qubit energy relaxation time and pure dephasing time.

Main Results:

• Qubits achieved an intrinsic energy relaxation time between 6-20 microseconds.
• Pure dephasing times ranged from 3-10 microseconds.
• Significant improvement in coherence times compared to previous studies.

Conclusions:

• The enhanced coherence of flux qubits in a cavity is demonstrated.
• This improvement paves the way for coherent coupling of flux qubits to individual spins.
• The results contribute to advancing superconducting quantum computing technologies.