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Physical Review A

Single-photon trapping in a giant-atom cavity coupled to a one-dimensional waveguide

Amal Vijayalekshmi Sivakumar, Jiru Liu, Muhammad Suhail Zubairy

Published Mar 26, 2025• 3 citations
Publisher

Abstract

Giant atoms introduce promising avenues for enhancing light-matter interaction in waveguides, which plays a crucial role in quantum information processing and quantum state control. In this work, we study the dynamics of a system comprising a single-photon Gaussian pulse initially inside a cavity with giant-atom mirrors coupled to a one-dimensional waveguide. The decay rate of the photon pulse can be significantly minimized by using giant atoms instead of point atoms and by carefully selecting the spacing between the coupling points of the giant atom to the waveguide. The quality factor for the cavity is analyzed by varying the number of atoms, coupling points, and coupling point spacing in each mirror to find the optimal parameters for a high $Q$-factor cavity. Our work contributes to the design of more efficient, high-quality quantum devices such as integrated quantum photonic circuits.

DOI
10.1103/physreva.111.033714

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Giant atoms introduce promising avenues for enhancing light-matter interaction in waveguides, which plays a crucial role in quantum information processing and quantum state control. In this work, we study the dynamics of a system comprising a single-photon Gaussian pulse initially inside a cavity with giant-atom mirrors coupled to a one-dimensional waveguide. The decay rate of the photon pulse can be significantly minimized by using giant atoms instead of point atoms and by carefully selecting the spacing between the coupling points of the giant atom to the waveguide. The quality factor for the cavity is analyzed by varying the number of atoms, coupling points, and coupling point spacing in each mirror to find the optimal parameters for a high QQQ-factor cavity. Our work contributes to the design of more efficient, high-quality quantum devices such as integrated quantum photonic circuits.
We study the decay of a single-photon pulse inside a cavity consisting of two atomic mirrors coupled to a one-dimensional waveguide. The finesse of the cavity can be increased with proper choice of coupling strength, cavity length, spontaneous decay rate, and separation between atoms. The loss rate of a single-photon pulse inside the cavity can be decreased with narrower spectrum width and smaller detuning between the photon pulse and the atomic resonance. The decay of a single-photon pulse in the atomic cavity can be significantly slowed down with proper parameters and the increase of the number of atoms within the atomic mirrors.
Giant atoms, quantum emitters that couple to light at multiple discrete points, are emerging as a new paradigm in quantum optics due to their many promising properties, such as decoherence-free interaction. While most previous work has considered giant atoms coupled to open continuous waveguides or a single giant atom coupled to a structured bath, here we study the interaction between two giant atoms mediated by a structured waveguide, e.g., a photonic crystal waveguide. This environment is characterized by a finite energy band and a band gap, which affect atomic dynamics beyond the Markovian regime. Here we show that, inside the band, decoherence-free interaction is possible for different atom-cavity detunings, but is degraded from the continuous-waveguide case by time delay and other non-Markovian effects. Outside the band, where atoms interact through the overlap of bound states, we find that giant atoms can interact more strongly and over longer distances than small atoms for some parameters, for instance, when restricting the maximum coupling strength achievable per coupling point. The results presented here may find applications in quantum simulation and quantum gate implementation.
Abstract The phase-controlled single-photon transport properties of a giant atom coupled to a one-dimensional waveguide are investigated. The coupling between the giant atom and the waveguide is modeled as a multi-point interaction. The coupling strengths between the giant atom and the waveguide are represented as complex numbers with associated phases. Analytical expressions for the scattering amplitudes are obtained using the real-space Hamiltonian method. The results show that the characteristics of the scattering spectra, including the positions of peaks (or dips) and the full width at half maximum, can be tuned by adjusting the phase difference between the coupling strengths. Further calculations reveal that the scattering spectra can be either super-broadened or sub-broadened. The conditions for achieving perfect nonreciprocal single-photon transport in the Markovian regime are also discussed. Moreover, we demonstrate the control of single-photon transport through phase differences in the non-Markovian regime. Our results may find applications in the design of quantum devices operating at the single-photon level, based on waveguide quantum electrodynamics.
We theoretically investigate coherent controlling single photon transport in one-dimensional waveguide coupled to a giant atom interacting with a resonator. The giant atom is considered as a Λ-type system. One transition of the atom couples to the waveguide and the other one is driven by the resonator. Single photon scattering amplitudes are calculated for three kinds of coupling schematics, respectively. Both the analytical and numerical results show that single photon scattering properties can be manipulated by adjusting the size of the giant atom, the coupling strengths of the waveguide-resonator and resonator-giant atom. Specifically, the transmission spectra exhibit two Rabi-splitting dips and the locations of the dips are strongly dependent on the size of the giant atom (GA). It also shows that the resonant single photon can be tuned from being transmitted to being reflected by controlling the coupling strength. Our results may find applications in designing quantum devices based on giant atom at single-photon level.
We propose a frequency-controllable single-photon router in a giant atom waveguide QED system, in which two linear waveguides are mediately by two coupled giant atoms. Since each giant atom has two coupling points, a pair of giant atoms can be arranged as three different topologies: separated, braided, and nested. The exact analytical expressions of the four scattering amplitudes for the three different topologies are obtained with the real-space approach. We find that the deterministic routing scheme is strongly relevant to the energy and the decay rates of the collective states of the two coupled giant atoms. In particular, only if the two scattering states degenerate in energy and decay rates, the frequency-tunable router with 100% efficiency can be achieved in the three different topologies. Moreover, our numerical results show that the single-photon routing scheme in the current model is more tunable and robust than that in the normal atom waveguide QED system. The physics behind the complete routing scheme is also illuminated. Our results pave the way for the study of controllable single-photon router devices involving giant atoms.
We examine a quantum routing mechanism utilizing a giant-atom-like array coupled to two one-dimensional waveguides. The giant-atom-like array is formed by a one-dimensional array of three-level-systems. In the regime of strong atom-waveguide coupling and weak inter-atomic interactions, this system functions as an efficient and directionally controllable single-photon router. Our analysis shows that the routing behavior is influenced by effective phase accumulation and interference effects, which can be adjusted by varying the number of coupling sites NNN, the photon energy EEE, and the inter-atomic coupling strength JJJ. Importantly, we identify configurations that enable perfect photon transfer (100%100 \%100% efficiency) over a wide range of energies and that provide dynamic control over the output channel. In addition, we investigate how the system responds to changes in its internal parameters, demonstrating the robustness and scalability of routing performance. These findings underscore the potential of this setup for implementation in reconfigurable and integrated quantum photonic networks.