# Advances in quantum control of three-level superconducting circuit architectures

## TL;DR

This paper introduces new control schemes for three-level superconducting circuits that enable quantum state manipulation despite constraints like always-on fields, with applications demonstrated in ultrastrong coupling regimes.

## Contribution

The paper proposes two novel control protocols for Lambda schemes in circuit-QED, accommodating always-on fields and adapting quantum optics techniques to solid-state systems.

## Key findings

- New control schemes for Lambda systems with always-on fields
- Protocols adapted for circuit-QED architectures
- Application demonstrated in ultrastrong coupling spectroscopy

## Abstract

Advanced control in Lambda ($\Lambda$) scheme of a solid state architecture of artificial atoms and quantized modes would allow the translation to the solid-state realm of a whole class of phenomena from quantum optics, thus exploiting new physics emerging in larger integrated quantum networks and for stronger couplings. However control solid-state devices has constraints coming from selection rules, due to symmetries which on the other hand yield protection from decoherence, and from design issues, for instance that coupling to microwave cavities is not directly switchable. We present two new schemes for the $\Lambda$-STIRAP control problem with the constraint of one or two classical driving fields being always-on. We show how these protocols are converted to apply to circuit-QED architectures. We finally illustrate an application to coherent spectroscopy of the so called ultrastrong atom-cavity coupling regime.