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arXiv · 2502.08156

Chirality, Nonreciprocity and Symmetries for a Giant Atom

Luting Xu·Lingzhen Guo
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Abstract

Chiral and nonreciprocal quantum devices are crucial for signal routing and processing in a quantum network. In this work, we study the chirality and nonreciprocity of a giant atom coupled to a one-dimensional waveguide. We clarify that the chiral emission of the giant atom is not directly related to the time-reversal symmetry breaking but to the mirror-symmetry breaking. We propose a passive scheme to realize the chiral emission of a giant atom without breaking time-reversal symmetry by extending the legs of the giant atom. We find the time-reversal symmetry breaking via nonuniform coupling phases is artificial and thus cannot result in nonreciprocal single-photon scattering for the giant atom. The nonreciprocity of the giant atom can be obtained by the external dissipation of the giant atom that truly breaks the time-reversal symmetry. Our work clarifies the roles of symmetries in the chirality and nonreciprocity of giant-atom systems and paves the way for the design of on-chip functional devices with superconducting giant atoms.

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Luting Xu, Lingzhen Guo. 2025-02-12. Chirality, Nonreciprocity and Symmetries for a Giant Atom. https://doi.org/10.1007/s11433-025-2854-8

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