While ideal lattice models have been widely used to study giant-atom systems, fabrication-induced defects inevitably introduce disorder in realistic platforms. Here, we study non-Markovian dynamics of a giant atom coupled to a discrete photonic lattice with on-site frequency disorder. Using time-domain and spectral analyses, we show that the overall population-decay envelope and global photon-transport patterns remain robust against moderate lattice disorder, while the quantified non-Markovian memory can be significantly enhanced within the explored disorder range. We characterize the memory using a normalized geometrical non-Markovianity measure tailored to delayed giant-atom feedback and demonstrate how the coupling-point separation and the disorder strength serve as complementary parameters that shape the delay timescale and the complexity of coherent-feedback interference. Spectral analysis reveals that scattering-band transport is relatively insensitive to disorder, whereas disorder-sensitive bound-state branches and localization features reshape revival windows and promote information backflow. Our results establish a disorder-aware framework for understanding and engineering non-Markovian feedback effects of giant atoms in structured reservoirs.
While ideal lattice models have been widely used to study giant-atom systems, fabrication-induced defects inevitably introduce disorder in realistic platforms. Here, we study non-Markovian dynamics of a giant atom coupled to a discrete photonic lattice with on-site frequency disorder. Using time-domain and spectral analyses, we show that the overall population-decay envelope and global photon-transport patterns remain robust against moderate lattice disorder, while the quantified non-Markovian memory can be significantly enhanced within the explored disorder range. We characterize the memory using a normalized geometrical non-Markovianity measure tailored to delayed giant-atom feedback and demonstrate how the coupling-point separation and the disorder strength serve as complementary parameters that shape the delay timescale and the complexity of coherent-feedback interference. Spectral analysis reveals that scattering-band transport is relatively insensitive to disorder, whereas disorder-sensitive bound-state branches and localization features reshape revival windows and promote information backflow. Our results establish a disorder-aware framework for understanding and engineering non-Markovian feedback effects of giant atoms in structured reservoirs.
It is known that the superposition of two bound states in the continuum (BICs) leads to the phenomenon of an oscillating bound state, where excitations mediated by the continuum modes oscillate persistently. We perform exact calculations for the oscillating BICs in a one-dimensional photonic lattice coupled to a ``giant atom'' at multiple points. Our work is significantly distinct from previous proposals of oscillating BICs in continuous waveguide systems due to the presence of a finite energy band contributing band-edge effects. In particular, we show that the bound states outside the energy band are detrimental to the oscillating BIC phenomenon, and can be suppressed by increasing either the number of coupling points or the separation between each coupling point. Crucially, non-Markovianity is necessary for the existence of oscillating BICs, and the oscillation amplitude increases with the characteristic delay time of the giant atom interactions. We also propose an initialization scheme in the BIC subspace. Our work be experimentally implemented on current photonic waveguide array platforms and opens up prospects in utilizing reservoir engineering for the storage of quantum information in photonic lattices.
The study of giant atoms goes beyond the local interaction paradigm in the conventional quantum optics, and predicts novel phenomena, such as oscillating bound states in the continuum (BICs) and decoherence-free interaction (DFI) that do not exist in small atoms, for some particular parameter settings of coupling positions and strengths. However, in the realistic experiments to implement giant-atom systems, there is always some level of disorder both in coupling positions and strengths. In this work, we investigate the effects of disorder on the phenomena related to giant atoms. We find that the giant-atom related phenomena are robust to both disorders of coupling positions and strengths in the Markovian regime, but more sensitive to the disorder of coupling positions in the non-Markovian regime. Our work shows that, to observe the non-Markovian phenomenon such as (oscillating) BICs in giant-atom systems, more precision is needed to control the disorder of coupling positions than that of the coupling strengths in the experiments.
In this paper we investigate the non-Markovian dynamics of a giant atom coupled to a one-dimensional photonic lattice with synthetic gauge fields. By engineering a complex-valued hopping amplitude, we break reciprocity and explore how chiral propagation and phase-induced interference affect spontaneous emission, bound-state formation, and atom–field entanglement. The giant atom interacts with the lattice at multiple, spatially separated sites, leading to rich interference effects and decoherence-free subspaces. We derive an exact expression for the self-energy and perform real-time Schrödinger simulations in the single-excitation subspace, for the atomic population, von Neumann entropy, field localization, and asymmetry in emission. Our results show that the hopping phase ϕ governs not only the directionality of emitted photons but also the degree of atom–bath entanglement and photon localization. Remarkably, we observe robust bound states inside the photonic band and directional asymmetry, due to interference from spatially separated coupling points. These findings provide a basis for engineering non-reciprocal, robust, and entangled light–matter interactions in structured photonic systems.
We study the non-Markovian dynamics of a giant artificial atom coupled to a one-dimensional acoustic waveguide beyond the rotating-wave and weak-coupling approximations. By combining an optimized ESPRIT-based decomposition of the bath correlation function with the hierarchical equations of motion (HEOM), we achieve numerically exact simulations in regimes with long memory times, finite temperature, and strong system-bath coupling. Benchmarking against analytical results reveals the breakdown of perturbative non-Markovian approaches such as Redfield theory even at weak coupling in the presence of delay-induced memory. We further show that non-Markovian features, including excitation revivals, remain robust at finite temperature and can be enhanced by increasing the system-bath coupling strength. Our approach provides a versatile framework for studying non-Markovian quantum dynamics in structured environments relevant to giant-atom platforms.
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.
Giant artificial atoms are promising and flexible building blocks for the implementation of analog quantum simulators. They are realized via a multilocal pattern of couplings of two-level systems to a waveguide, or to a two-dimensional photonic bath. A hallmark of giant-atom physics is their non-Markovian character in the form of self-coherent feedback, leading, e.g., to nonexponential atomic decay. The timescale of their non-Markovianity is essentially given by the time delay proportional to the distance between the various coupling points. In parallel, with the state-of-the-art experimental setups, it is possible to engineer complex phases in the atom-light couplings. Such phases simulate an artificial magnetic field, yielding a chiral behavior of the atom-light system. Here, we report a surprising connection between these two seemingly unrelated features of giant atoms, showing that the chirality of a giant atom controls its Markovianity. In particular, by adjusting the couplings' phases, a giant atom can, counterintuitively, enter an exact Markovian regime, irrespectively of any inherent time delay. We illustrate this mechanism as an interference process and via a collision model picture. Our findings significantly advance the understanding of giant atom physics, and open new avenues for the control of quantum nanophotonic networks.