Multiple Coherent Finite Time Landau-Zener Transitions Interference

by Mr. Yosef Sitton

BGU

at Condensed Matter Seminar

Mon, 19 Jun 2023, 11:10
***Change of venue***: Nano building (51) auditorium

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 a broad distribution of energies, existing in disordered dielectrics and on surfaces. We study the dielectric loss of superconducting microwave 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(LZ) transitions.

We examine the effect of sweeping amplitude versus Rabi gap ratio on the TLS relaxation rate at high sweep rates. We relax the approximation of the infinite period and establish a formalism to evaluate the dielectric loss tangent in a finite maximal to minimal detuning ratio.
Considering finite-time LZ transitions, we show that smaller time constants T1, reflecting the averaged relaxation time of the TLS by phonon emission, result in larger minimal dielectric loss tangent value at high sweep rates.

The regime of short sweep times is discussed, and the discrepancy in this regime between experiment and theory, as it appears in
previous works, is specifically addressed. We suggest that reduction in the dielectric loss tangent under the saturation value (the value at zero bias sweep rate), due to LZ transitions interference, is impossible.

Created on 16-06-2023 by Meidan, Dganit (dganit)
Updaded on 18-06-2023 by Meidan, Dganit (dganit)