Charge-Noise Insensitive Chiral Photonic Interface for Waveguide Circuit QED

TL;DR

This paper introduces a superconducting circuit-based chiral photonic interface that is robust against charge noise, tunable, and suitable for quantum information processing, with potential for broadband microwave circulators.

Contribution

It proposes a novel superconducting circuit design for a charge-noise insensitive chiral photonic interface with tunability and wide bandwidth.

Findings

High tolerance to fabrication variations.

Decoupling of transmons from the core creates dark states.

Potential for broadband on-chip microwave circulators.

Abstract

A chiral photonic interface is a quantum system that has different probabilities for emitting photons to the left and right. An on-chip compatible chiral interface is attractive for both fundamental studies of light-matter interactions and applications to quantum information processing. We propose such a chiral interface based on superconducting circuits, which has wide bandwidth, rich tunability, and high tolerance to fabrication variations. The proposed interface consists of a core that uses Cooper-pair boxes (CPBs) to break time-reversal symmetry, and two superconducting transmons that connect the core to a waveguide in the manner reminiscent of a ``giant atom.'' The transmons form a state decoupled from the core, akin to dark states of atomic physics, rendering the whole interface insensitive to the CPB charge noise. The proposed interface can be extended to realize a broadband fully passive on-chip circulator for microwave photons.