Energy Relaxation Time between Macroscopic Quantum Levels in a Superconducting Persistent Current Qubit

TL;DR

This paper measures the energy relaxation time in a Nb superconducting qubit, demonstrating a decoherence time over 20 microseconds, which is promising for quantum computing applications.

Contribution

It provides the first measurement of intrawell energy relaxation time in a Nb persistent-current qubit, highlighting its potential for quantum computing.

Findings

Decoherence time exceeds 20 microseconds.

Observed multi-level decay process in the qubit.

Potential for Nb-based superconducting quantum computers.

Abstract

We measured the intrawell energy relaxation time \tau_{d} between macroscopic quantum levels in the double well potential of a Nb persistent-current qubit. Interwell population transitions were generated by irradiating the qubit with microwaves. Zero population in the initial well was then observed due to a multi-level decay process in which the initial population relaxed to the lower energy levels during transitions. The qubit's decoherence time, determined from \tau_{d}, is longer than 20 microseconds, holding the promise of building a quantum computer with Nb-based superconducting qubits.