Charge-Qubit-Resonator-Interface-Based Nonlinear Circuit QED

TL;DR

This paper investigates nonlinear circuit QED systems with charge qubits, demonstrating applications in quantum optics such as Fock-state masers, microwave squeezing, and multiphoton quantum jumps, advancing quantum information processing capabilities.

Contribution

It introduces a novel charge-qubit-resonator interface enabling versatile quantum optical phenomena and control in circuit QED systems.

Findings

Arbitrary Fock-state pulsed maser achieved

Resonant pumping induces resonator squeezing

Observation of multiphoton quantum jumps in steady state

Abstract

We explore applications of nonlinear circuit QED with a charge qubit inductively coupled to a microwave LC resonator in the photonic engineering and ultrastrong-coupling multiphoton quantum optics. Simply sweeping the gate-voltage bias achieves arbitrary Fock-state pulsed maser, where the single qubit plays the role of artificial gain medium. Resonantly pumping the parametric qubit-resonator interface leads to the squeezing of resonator field, which is utilizable to the quantum-limited microwave amplification. Moreover, upwards and downwards multiphoton quantum jumps may be observed in the steady state of the driving-free system.