Waveguide Quantum Electrodynamics with Giant Superconducting Artificial Atoms

TL;DR

This paper demonstrates a novel waveguide quantum electrodynamics architecture using giant superconducting artificial atoms, enabling tunable couplings and decoherence-free interactions for advanced quantum information processing.

Contribution

It introduces a new architecture for giant atoms with multiple coupling points, allowing tunable interactions and decoherence-free coupling, surpassing previous single-frequency studies.

Findings

Achieved tunable atom-waveguide coupling with high on-off ratios.

Demonstrated decoherence-free interactions between multiple giant atoms.

Enabled in situ switching between protected and emissive qubit states.

Abstract

Models of light-matter interactions typically invoke the dipole approximation, within which atoms are treated as point-like objects when compared to the wavelength of the electromagnetic modes that they interact with. However, when the ratio between the size of the atom and the mode wavelength is increased, the dipole approximation no longer holds and the atom is referred to as a "giant atom". Thus far, experimental studies with solid-state devices in the giant-atom regime have been limited to superconducting qubits that couple to short-wavelength surface acoustic waves, only probing the properties of the atom at a single frequency. Here we employ an alternative architecture that realizes a giant atom by coupling small atoms to a waveguide at multiple, but well separated, discrete locations. Our realization of giant atoms enables tunable atom-waveguide couplings with large on-off ratios and a coupling spectrum that can be engineered by device design. We also demonstrate decoherence-free interactions between multiple giant atoms that are mediated by the quasi-continuous spectrum of modes in the waveguide-- an effect that is not possible to achieve with small atoms. These features allow qubits in this architecture to switch between protected and emissive configurations in situ while retaining qubit-qubit interactions, opening new possibilities for high-fidelity quantum simulations and non-classical itinerant photon generation.