Observation of high coherence in Josephson junction qubits measured in a three-dimensional circuit QED architecture

Understand

Superconducting quantum circuits based on Josephson junctions have made rapid progress in demonstrating quantum behavior and scalability.

• However, the future prospects ultimately depend upon the intrinsic coherence of Josephson junctions, and whether superconducting qubits can be adequately isolated from their environment.
• We introduce a new architecture for superconducting quantum circuits employing a three dimensional resonator that suppresses qubit decoherence while maintaining sufficient coupling to the control signal.
• With the new architecture, we demonstrate that Josephson junction qubits are highly coherent, with $T_2 \sim 10 \mu$s to $20 \mu$s without the use of spin echo, and highly stable, showing no evidence for $1/f$ critical current noise.