Dynamical decoupling of quantum two-level systems by coherent multiple Landau\u2013Zener transitions

Shlomi Matityahu,Alexander Bilmes,Georg Weiss,Alexander Shnirman,Hartmut Schmidt,Alexey V. Ustinov,Moshe Schechter,Jürgen Lisenfeld

doi:10.1038/s41534-019-0228-x

Abstract

Increasing and stabilizing the coherence of superconducting quantum circuits and resonators is of utmost importance for various technologies, ranging from quantum information processors to highly sensitive detectors of low-temperature radiation in astrophysics. A major source of noise in such devices is a bath of quantum two-level systems (TLSs) with broad distribution of energies, existing in disordered dielectrics and on surfaces. Here we study the dielectric loss of superconducting resonators in the presence of a periodic electric bias field, which sweeps near-resonant TLSs in and out of resonance with the resonator, resulting in a periodic pattern of Landau–Zener transitions. We show that at high sweep rates compared to the TLS relaxation rate, the coherent evolution of the TLS over multiple transitions yields a significant reduction in the dielectric loss relative to the intrinsic value. This behavior is observed both in the classical high-power regime and in the quantum single-photon regime, possibly suggesting a viable technique to dynamically decouple TLSs from a qubit.

Highlights

Superconducting quantum devices are nowadays at the heart of many physical platforms exploring both foundations and applications of quantum mechanics
Postulated in the 1970s to explain the lowtemperature properties of amorphous solids,[9,10] tunneling two-level systems (TLSs) have attracted a lot of renewed interest in the field of superconducting quantum devices, where such defects residing in the amorphous oxides of the microfabricated circuits form a major energy relaxation and decoherence channel.[11]
Since the physics of the single-photon regime corresponds to that of a qubit coupled to a resonant TLS, the results suggest a technique to effectively decouple near-resonant TLSs from a qubit without affecting the qubit state

Summary

Introduction

Superconducting quantum devices are nowadays at the heart of many physical platforms exploring both foundations and applications of quantum mechanics. Note that for the triangular bias field shown, the maximum sweep rate is jv0j 1⁄4 4pEmax=Tsw. To obtain the dielectric loss due to TLSs, we calculate the counting statistics of the number of photons absorbed by a single

Results

Conclusion