Qubit-oscillator dynamics in the dispersive regime: analytical theory beyond rotating-wave approximation

TL;DR

This paper develops an analytical theory for qubit-oscillator dynamics beyond the rotating-wave approximation, revealing new interaction regimes and implications for quantum information processing.

Contribution

It extends the dispersive Jaynes-Cummings model beyond RWA, showing how non-RWA effects alter qubit interactions and entanglement.

Findings

Diagonalization of non-RWA Hamiltonian in the dispersive regime

Emergence of Ising-type qubit-qubit interactions

Extended regime for dispersive qubit readout

Abstract

We generalize the dispersive theory of the Jaynes-Cummings model beyond the frequently employed rotating-wave approximation (RWA) in the coupling between the two-level system and the resonator. For a detuning sufficiently larger than the qubit-oscillator coupling, we diagonalize the non-RWA Hamiltonian and discuss the differences to the known RWA results. Our results extend the regime in which dispersive qubit readout is possible. If several qubits are coupled to one resonator, an effective qubit-qubit interaction of Ising type emerges, whereas RWA leads to isotropic interaction. This impacts on the entanglement characteristics of the qubits.