Coherent Quantum Dynamics of a Superconducting Flux Qubit

TL;DR

This paper demonstrates coherent quantum state manipulation and measurement in a superconducting flux qubit, achieving high-fidelity oscillations and notable coherence times, advancing solid-state quantum computing prospects.

Contribution

First observation of coherent quantum dynamics in a superconducting flux qubit with detailed control and measurement techniques.

Findings

Quantum-state oscillations with high fidelity observed.

Relaxation time of 900 nanoseconds achieved.

Dephasing time of 20 nanoseconds measured.

Abstract

We have observed coherent time evolution between two quantum states of a superconducting flux qubit comprising three Josephson junctions in a loop. The superposition of the two states carrying opposite macroscopic persistent currents is manipulated by resonant microwave pulses. Readout by means of switching-event measurement with an attached superconducting quantum interference device revealed quantum-state oscillations with high fidelity. Under strong microwave driving it was possible to induce hundreds of coherent oscillations. Pulsed operations on this first sample yielded a relaxation time of 900 nanoseconds and a free-induction dephasing time of 20 nanoseconds. These results are promising for future solid-state quantum computing.