Strongly driven transmon as an incoherent noise source

TL;DR

This paper investigates how strongly driven transmons can become unstable and act as incoherent noise sources in quantum circuits, affecting neighboring qubits and system stability, with modeling and spectroscopy analysis.

Contribution

It demonstrates that strongly driven transmons can induce incoherent noise in coupled elements, revealing a new source of decoherence in quantum systems.

Findings

Driven transmons exhibit chaotic behavior at high drive strengths.

A driven transmon can act as an incoherent noise source for neighboring qubits.

The interaction can be modeled as a stochastic diffusive process affecting a coupled TLS.

Abstract

Under strong drives, which are becoming necessary for fast high-fidelity operations, transmons can be structurally unstable. Due to chaotic effects, the computational manifold is no longer well separated from the remainder of the spectrum, which correlates with enhanced offset-charge sensitivity and destructive effects in readout. We show here that these detrimental effects can further propagate to other degrees of freedom, for example to neighboring qubits in a multi-qubit system. Specifically, a coherently driven transmon can act as a source of incoherent noise to another circuit element coupled to it. By using a full quantum model and a semiclassical analysis, we perform the noise spectroscopy of the driven transmon coupled to a spectator two-level system (TLS), and we show that, in a certain limit, the interaction with the driven transmon can be modeled as a stochastic diffusive process driving the TLS.