Microwave Down-Conversion with an Impedance-Matched $\Lambda$ System in Driven Circuit QED

TL;DR

This paper demonstrates a microwave down-conversion technique using an impedance-matched $Lambda$ system in circuit QED, enabling near-perfect reflection extinction and high-efficiency frequency conversion, advancing quantum communication.

Contribution

It introduces an impedance-matched $Lambda$ system in circuit QED driven by a dispersively coupled qubit-resonator, enabling deterministic photon-induced Raman transitions and efficient microwave frequency down-conversion.

Findings

Achieved 99.7% reflection extinction.

Realized 74% microwave frequency down-conversion efficiency.

Confirmed deterministic photon-induced Raman transitions.

Abstract

By driving a dispersively coupled qubit-resonator system, we realize an "impedance-matched" $\Lambda$ system that has two identical radiative decay rates from the top level and interacts with a semi-infinite waveguide. It has been predicted that a photon input from the waveguide deterministically induces a Raman transition in the system and switches its electronic state. We confirm this through microwave response to a continuous probe field, observing near-perfect ($99.7\%$) extinction of the reflection and highly efficient ($74\%$) frequency down-conversion. These proof-of-principle results lead to deterministic quantum gates between material qubits and microwave photons and open the possibility for scalable quantum networks interconnected with waveguide photons.