Chiral quantum optics with giant atoms

TL;DR

This paper explores how giant atoms coupled to chiral waveguides can achieve decoherence-free interactions and dark states, enabling advanced quantum simulations and networks beyond traditional small atom models.

Contribution

It demonstrates that giant atoms in chiral waveguides can form dark states without excitation and reach these states faster, expanding quantum control possibilities.

Findings

Giant atoms can interact coherently without decoherence in chiral waveguides.

Dark states can form without external excitation in giant atoms.

Population of dark states is faster in driven-dissipative regimes.

Abstract

In quantum optics, it is common to assume that atoms are point-like objects compared to the wavelength of the electromagnetic field they interact with. However, this dipole approximation is not always valid, e.g., if atoms couple to the field at multiple discrete points. Previous work has shown that superconducting qubits coupled to a one-dimensional waveguide can behave as such "giant atoms" and then can interact through the waveguide without decohering, a phenomenon that is not possible with small atoms. Here, we show that this decoherence-free interaction is also possible when the coupling to the waveguide is chiral, i.e., when the coupling depends on the propagation direction of the light. Furthermore, we derive conditions under which the giant atoms in such chiral architectures exhibit dark states. In particular, we show that unlike small atoms, giant atoms in a chiral waveguide can reach a dark state even without being excited by a coherent drive. We also show that in the driven-dissipative regime, dark states can be populated faster in giant atoms. The results presented here lay a foundation for applications based on giant atoms in quantum simulations and quantum networks with chiral settings.