Engineering entangled microwave photon states via multiphoton interactions between two cavity fields and a superconducting qubit

TL;DR

This paper presents a universal algorithm for generating arbitrary entangled two-mode microwave photon states in superconducting circuits using multiphoton interactions and longitudinal couplings, enabling efficient state creation in the ultrastrong coupling regime.

Contribution

The authors introduce a novel algorithm leveraging multiphoton processes and longitudinal couplings to produce arbitrary entangled microwave states, including NOON states, in superconducting qubit-resonator systems.

Findings

Efficient generation of entangled microwave states in ultrastrong coupling regime.

Analysis of evenly-populated and NOON state generation.

Comparison showing advantages over single-photon process methods.

Abstract

It has been shown that there are not only transverse but also longitudinal couplings between microwave fields and a superconducting qubit with broken inversion symmetry of the potential energy. Using multiphoton processes induced by longitudinal coupling fields and frequency matching conditions, we design a universal algorithm to produce arbitrary superpositions of two-mode photon states of microwave fields in two separated transmission line resonators, which are coupled to a superconducting qubit. Based on our algorithm, we analyze the generation of evenly-populated states and NOON states. Compared to other proposals with only single-photon process, we provide an efficient way to produce entangled microwave states when the interactions between superconducting qubits and microwave fields are in the ultrastrong regime.