Direct Observation of Coherent Population Trapping in a Superconducting Artificial Atom

TL;DR

This paper reports the first observation of Coherent Population Trapping in a superconducting artificial atom, demonstrating quantum interference effects and enabling characterization of quantum coherence times in such systems.

Contribution

The study demonstrates CPT in a superconducting phase qubit using a three-level system, with experimental data matching theoretical models, and introduces a method to measure dephasing times.

Findings

60% suppression of excited state population under CPT conditions

Development of time-resolved CPT observation in a superconducting qubit

Characterization of quantum dephasing times using CPT dynamics

Abstract

The phenomenon of Coherent Population Trapping (CPT) of an atom (or solid state "artificial atom"), and the associated effect of Electromagnetically Induced Transparency (EIT), are clear demonstrations of quantum interference due to coherence in multi-level quantum systems. We report observation of CPT in a superconducting phase qubit by simultaneously driving two coherent transitions in a $\Lambda$-type configuration, utilizing the three lowest lying levels of a local minimum of a phase qubit. We observe $60(\pm 7)%$ suppression of excited state population under conditions of CPT resonance. We present data and matching theoretical simulations showing the development of CPT in time. Finally, we used the observed time dependence of the excited state population to characterize quantum dephasing times of the system.