Deterministic single-photon source in the ultrastrong coupling regime

TL;DR

This paper proposes a novel deterministic single-photon source in circuit QED capable of operating in the ultrastrong coupling regime, enabling sequential emission of two photons with high efficiency and purity.

Contribution

It introduces a new scheme for generating deterministic single photons in the ultrastrong coupling regime using adiabatic transfers along one-photon solutions.

Findings

Achieves near-unity single-photon efficiency

Enables sequential photon emission with arbitrary time separation

Operates effectively in the ultrastrong coupling regime

Abstract

Deterministic single-photon sources are important and ubiquitous in quantum information protocols. However, to the best of our knowledge, none of them work in the ultrastrong light-matter coupling regime, and each excitation process can only emit one photon. We propose a deterministic single-photon source in circuit QED which can work in the ultrastrong coupling regime. Here, two qubits are excited simultaneously in one process and two deterministic single photons can be sequentially emitted with an arbitrary time separation. This happens through two consecutive adiabatic transfers along the one-photon solutions of the two-qubit Rabi and Jaynes-Cummings model, which has constant eigenenergy in the whole coupling regime. Unlike the stimulated Raman adiabatic passage, the system goes back to the initial state of another period automatically after photon emission. Our scheme can approach unity single-photon efficiency, indistinguishability, and purity simultaneously. With the assistance of the Stark shift, a deterministic single photon can be generated within a time proportional to the inverse of the resonator frequency.