Resonant excitation of single and coupled qubits for coherent quantum control and microwave detection

TL;DR

This paper investigates resonant multiphoton excitations in coupled qubits, revealing phenomena like the Bloch-Siegert shift and population inversion, with implications for quantum control and microwave photon detection.

Contribution

It provides a theoretical analysis of multiphoton resonances in coupled qubits, including analytical solutions for single-qubit cases and insights into collective excitation dynamics.

Findings

Identification of multiphoton resonances in coupled qubits

Analysis of the Bloch-Siegert shift in quantum dynamics

Conditions for population inversion in qubit systems

Abstract

Resonant driving enables coherent control of quantum systems, including single and coupled qubits. From a complementary perspective, transitions of a quantum system can be exploited for the detection of microwave photons. In this work, we theoretically investigate resonant multiphoton excitations in a system of qubits. When the energy of K photons matches the energy splitting of the qubit system, the absorption of these photons leads to collective excitation of the qubits. We focus on the case of two coupled qubits and analyze the quantum dynamics of both excitation and relacation processes. In the particular case where only a single qubit is relevant and the remaining qubits can be neglected, the dynamics admits an analytical treatment. We examine multiphoton resonances, the Bloch-Siegert shift, and population inversion, phenomena that are central to both coherent quantum control and microwave photon detection.