Landau-Zener interference at bichromatic driving

TL;DR

This paper explores how bichromatic driving influences Landau-Zener interference patterns in a charge qubit, revealing the effects of frequency commensurability and phase relations on interference symmetry.

Contribution

It provides a combined experimental and theoretical analysis of bichromatic driving effects on quantum interference in a charge qubit system.

Findings

Symmetry of interference patterns depends on frequency commensurability.

Relative phase affects interference symmetry in commensurable frequencies.

Incommensurable frequencies restore monochromatic symmetry.

Abstract

We investigate experimentally and theoretically the interference at avoided crossings which are repeatedly traversed as a consequence of an applied ac field. Our model system is a charge qubit in a serial double quantum dot connected to two leads. Our focus lies on effects caused by simultaneous driving with two different frequencies. We work out how the commensurability of the driving frequencies affects the symmetry of the interference patterns both in real space and in Fourier space. For commensurable frequencies, the symmetry depends sensitively on the relative phase between the two modes, whereas for incommensurable frequencies the symmetry of monochromatic driving is always recovered.