We investigate the entanglement dynamics of two giant atoms coupled to a one-dimensional photonic lattice with synthetic chirality. The atoms are connected to multiple lattice sites in a braided configuration and interact with a structured photonic reservoir featuring direction-dependent hopping phases. By tuning the atomic detuning and the synthetic gauge phase, we identify distinct dynamical regimes characterized by decoherence-free population exchange, damped oscillations, long-lived revivals, and excitation trapping. Using a combination of time-domain simulations and resolvent-based analysis, we show how interference and band structure effects lead to the emergence of bound states, quasi-bound states, and phase-dependent entanglement dynamics. We compare the initial states with localized and delocalized atomic excitations, demonstrating that pre-existing entanglement can enhance the robustness against decoherence or accelerate its loss, depending on the system parameters. These results highlight the utility of synthetic photonic lattices and nonlocal emitter configurations in tailoring quantum coherence, entanglement, and information flows in structured environments.
We investigate the entanglement dynamics of two giant atoms coupled to a one-dimensional photonic lattice with synthetic chirality. The atoms are connected to multiple lattice sites in a braided configuration and interact with a structured photonic reservoir featuring direction-dependent hopping phases. By tuning the atomic detuning and the synthetic gauge phase, we identify distinct dynamical regimes characterized by decoherence-free population exchange, damped oscillations, long-lived revivals, and excitation trapping. Using a combination of time-domain simulations and resolvent-based analysis, we show how interference and band structure effects lead to the emergence of bound states, quasi-bound states, and phase-dependent entanglement dynamics. We compare the initial states with localized and delocalized atomic excitations, demonstrating that pre-existing entanglement can enhance the robustness against decoherence or accelerate its loss, depending on the system parameters. These results highlight the utility of synthetic photonic lattices and nonlocal emitter configurations in tailoring quantum coherence, entanglement, and information flows in structured environments.
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 explore the spontaneous emission dynamics of a giant atom coupled to a photonic Creutz ladder, focusing on how flat-band frustration and synthetic gauge fields shape atom–photon interactions. The Creutz ladder exhibits perfectly flat bands, Aharonov–Bohm caging, and topological features arising from its nontrivial hopping structure. By embedding the giant atom at multiple spatially separated sites, we reveal interference-driven emission control and the formation of nonradiative bound states. Using both spectral and time-domain analyses, we uncover strong non-Markovian dynamics characterized by persistent oscillations, long-lived entanglement, and recoherence cycles. The emergence of bound-state poles in the spectral function is accompanied by spatially localized photonic profiles and directionally asymmetric emission, even in the absence of band dispersion. Calculations of von Neumann entropy and atomic purity confirm the formation of coherence-preserving dressed states in the flat-band regime. Furthermore, the spacetime structure of the emitted field displays robust zig-zag interference patterns and synthetic chirality, underscoring the role of geometry and topology in photon transport. Our results demonstrate how flat-band photonic lattices can be leveraged to engineer tunable atom–photon entanglement, suppress radiative losses, and create structured decoherence-free subspaces for quantum information applications.
Nonlocal light-matter interactions with giant atoms in high-dimensional environments are not only fundamentally intriguing for testing quantum electrodynamics beyond the dipole approximation but also crucial for building high-dimensional quantum networks and engineering multipartite entangled states. Given the enigmatic and largely uncharted collective signatures exhibited by multiple giant atoms within two-dimensional optical baths, we delve into their nonperturbative collective dynamics within the single-excitation subspace, focusing on the case where they are coupled to a common two-dimensional photonic reservoir and employing a resolvent operator approach. We demonstrate that precisely engineered atomic arrangements lead to unconventional quantum dynamics, featuring non-Markovianity-induced beats and long-lived bound states in the continuum, thereby providing a versatile platform for implementing two-dimensional quantum memory. Phenomenologically, we observe the emergence of exotic photon emission patterns in both two- and three-dimensional (3D) baths. The emission directions are shown to be precisely controllable on demand through exact phase engineering of the coupling parameters, enabling a highly efficient chiral light-matter interface. Moreover, our generalization to a 3D bath reveals that coherent dipole-dipole interactions can survive despite the coupling to a continuum of modes, a finding that challenges conventional wisdom regarding decoherence.
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.
Engineering the on-site frequencies of a photonic lattice provides a powerful route to endow emitted photons with non-trivial dynamical and topological properties, reshaping the way a coupled qubit decays. This thesis investigates the emission dynamics of a qubit weakly coupled to photonic lattices hosting such synthetic potentials, showing how the resulting band structure dictates qualitatively distinct regimes of light-matter interaction.In the first part, we study a qubit coupled to a one-dimensional coupled-cavity array with a linear gradient in the cavity frequencies, which acts on photons as a synthetic force F. For strong F, emission becomes reversible and is captured by an effective Jaynes--Cummings model, producing a chiral, time-periodic excitation of an extended region of the array, either to the right or to the left of the qubit depending on its frequency. For weak F, the decay is non-Markovian and exhibits revivals reminiscent of atoms between mirrors, even though no mirrors are present: the finite bandwidth confines the emitted photon, and the dynamics is well described by a delay differential equation in which the amplitude and period of Bloch oscillations play the role of cavity length and round-trip time.In the second part, we move to two dimensions and couple a giant atom, a qubit with multiple, spatially separated coupling points, non-locally to a honeycomb lattice of resonators with detuned sublattice frequencies. By suitably arranging the coupling points, the giant atom selectively addresses a single valley, a capability unattainable with a local emitter. This valley-selective coupling endows the emitted photons with an effective valley-polarized Berry curvature, giving rise to valley-polarized edge modes at domain walls between regions of opposite sublattice detuning. As a consequence, a giant atom placed near such a domain wall exhibits chiral emission of valley-polarized photons without breaking time-reversal symmetry, suggesting a natural implementation in circuit QED.Together, these results establish synthetic potentials in photonic lattices as a versatile tool for controlling qubit emission, linking waveguide QED to Bloch-oscillation physics and to valleytronics.
Abstract We investigate the dynamics of two two-level giant atoms coupled to a one-dimensional waveguide in separate and braided configurations. Using the resolvent method, the quantum dynamics are determined by the poles of the Green’s function. We identify conditions under which three real poles with distinct eigenfrequencies emerge, corresponding to three bound states in the continuum (BICs). Their superposition gives rise to oscillating BICs. In this regime, the atomic excitation oscillates between the two atoms, while the photon field remains confined between the coupling points and exhibits persistent oscillations. The maxima of the photon field distribution coincide with those of the atomic excitations, reflecting the atom-photon bound-state nature. The revival of the photon distribution reveals the coherent interaction between the two giant atoms mediated by the BICs. This work broadens the fields of quantum information storage and manipulation by leveraging larger Hilbert spaces enabled by multiple nonradiative BICs.