Superconductors as ‘giant atoms’

H. Hattermann

Da‐Wei Wang, Chengsong Zhao, Junya Yang +2 more

In this paper, we consider giant atoms coupled to a one-dimensional topological waveguide reservoir. We studied the following two cases. In the bandgap regime, where the giant-atom frequency lies outside the band, we study the generation and distribution of giant atom-photon bound states and the difference between the topological waveguide in topological and trivial phases. When the strengths of the giant atoms coupled to the two sub-lattice points are equal, the photons distribution is symmetrical and the chiral photon distribution is exhibited when the coupling is different. The coherent interactions between giant atoms are induced by virtual photons, or can be understood as an overlap of photon bound-state wave functions, and decay exponentially with increasing distance between the giant atoms. We also find that the coherent interactions induced by the topological phase are larger than those induced by the trivial phase for the same bandgap width. In the band regime, the giant-atom frequency lies in the band, under the Born-Markov approximation, we obtained effective coherence and correlated dissipative interactions between the giant atoms mediated by topological waveguide reservoirs, which depend on the giant-atom coupling nodes. We analyze the effect of the form of the giant-atom coupling point on the decay, and on the associated dissipation. The results show that we can design the coupling form as well as the frequency of the giant atoms to achieve zero decay and correlation dissipation and non-zero coherent interactions. Finally we used this scheme to realize the excitation transfer of giant atoms. Our work will promote the study of topological matter coupled to giant atoms.

Vijayalekshmi Sivakumar, V S, Amal

The simulation codes for the figures (5,6,8,9,10,11,12,13) used in our article 'Single-photon frequency comb generation in a giant-atom cavity coupled to a one-dimensional waveguide' are available here. Fig. 5: Frequency spectra of a single photon Gaussian pulse initially outside the giant-atom cavity. Fig. 6: Cavity finesse as a function of the number of giant atoms and the number of coupling points per giant atom. Fig. 8: Frequency spectra of a single photon Gaussian pulse initially inside the giant-atom cavity. Fig. 9: Spectral enhancement as a function of the number of giant atoms and the number of coupling points per giant atom.Fig 10: Number of peaks, Peak location, Peak spacing as a function of the number of giant atoms and the number of coupling points per giant atom. Fig 11: Frequency spectra of a single photon Gaussian pulse initially inside the giant-atom cavity, with reduced coupling strength.Fig 12: Number of peaks, Peak location, Peak spacing as a function of the coupling strength. Fig 13: Cavity linewidth, Spectral enhancement as a function of the coupling strength.

James F. Annett, S. P. Kruchinin

Wei Zhao, Yan Zhang, Zhihai Wang

The nonlocal emitter-waveguide coupling, which gives birth to the so called giant atom, represents a new paradigm in the field of quantum optics and waveguide QED. We investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom. Thanks to the natural interference induced by the back and forth photon transmitted/reflected between the atom-waveguide coupling points, the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom. For the two-level giant-atom setup, we demonstrate the energy shift which is dependent on the atomic size. For the driven three-level giant-atom setup, it is of great interest that, the Autler-Townes splitting is dramatically modulated by the giant atom, in which the width of the transmission valleys (reflection range) is tunable in terms of the atomic size. Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.