Abstract In this paper, the unconventional light‐matter interactions between giant atoms and structured baths (i.e., lattices) are studied with either Hermitian or non‐Hermitian next‐nearest‐neighbor coupling terms. Essentially different dynamics of the atoms and the propagating field in the Hermitian and non‐Hermitian cases is revealed, which can be further engineered by tuning parameters such as the atomic transition frequency and the (synthetic) magnetic field associated to the coupling terms. The next‐nearest‐neighbor couplings play an important role in controlling the emission direction and the field distribution in the lattice, thus providing opportunities for tailoring exotic dipole–dipole interactions. The results in this paper have potential applications in, e.g., engineering unconventional quantum networks and simulating quantum many‐body systems.
Abstract In this paper, the unconventional light‐matter interactions between giant atoms and structured baths (i.e., lattices) are studied with either Hermitian or non‐Hermitian next‐nearest‐neighbor coupling terms. Essentially different dynamics of the atoms and the propagating field in the Hermitian and non‐Hermitian cases is revealed, which can be further engineered by tuning parameters such as the atomic transition frequency and the (synthetic) magnetic field associated to the coupling terms. The next‐nearest‐neighbor couplings play an important role in controlling the emission direction and the field distribution in the lattice, thus providing opportunities for tailoring exotic dipole–dipole interactions. The results in this paper have potential applications in, e.g., engineering unconventional quantum networks and simulating quantum many‐body systems.
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.
Lattice models featuring the non-Hermitian skin effect have attracted rapidly growing interest due to their nontrivial spectral topology and the exotic field dynamics they enable. Such non-Hermitian lattices provide a promising paradigm for engineering exotic light-matter interactions which benefit from the intrinsic chirality and unconventional (non-Bloch) band theory. Here we study a series of unconventional light-matter interactions between quantum emitters and the prototypical Hatano-Nelson model, and briefly discuss the case with an extended lattice model dubbed the bosonic Kitaev chain. We focus on the robustness of the dynamics against various imperfections and elucidate the underlying mechanisms. We consider both small emitters, which interact with the lattice at single sites, and giant emitters, coupling at multiple sites. The latter exhibit an exclusive amplification mechanism, which we find enables decoherence-free dynamics even in the presence of extra dissipation in the system. The protection from dissipation arises from the cooperation of the non-Hermiticity and the self-interference effect, and is therefore lacking for small emitters. These results not only provide deeper insights into the interplay of non-Hermiticity and various interference effects, but also have potential applications in engineering exotic spin Hamiltonians and quantum networks.
Emitters coupled simultaneously to distant positions of a photonic bath, the so-called giant atoms, represent a new paradigm in quantum optics. When coupled to one-dimensional baths, as recently implemented with transmission lines or SAW waveguides, they lead to striking effects such as chiral emission or decoherence-free atomic interactions. Here, we show how to create giant atoms in dynamical state-dependent optical lattices, which offers the possibility of coupling them to structured baths in arbitrary dimensions. This opens up new avenues to a variety of phenomena and opportunities for quantum simulation. In particular, we show how to engineer unconventional radiation patterns, like multidirectional chiral emission, as well as collective interactions that can be used to simulate nonequilibrium many-body dynamics with no analog in other setups. Additionally, the recipes we provide to harness giant atoms in high dimensions can be exported to other platforms where such nonlocal couplings can be engineered.
To go beyond quantum optics in free-space setups, atom-light interfaces with structured photonic environments are often employed to realize unconventional quantum electrodynamics (QED) phenomena. However, when employed as quantum buses, those long-distance nanostructures are limited by fabrication disorders. In this work, we alternatively propose to realize structured light-matter interactions by engineering multiple coupling points of hybrid giant atom--conventional environments without any periodic structure. We present a general optimization method to obtain the real-space coupling sequence for multiple coupling points. We report a broadband chiral emission for frequency-tunable giant emitters, with no analog in other quantum setups. Moreover, we show that the QED phenomena in the band-gap environment, such as fractional atomic decay and dipole-dipole interactions mediated by a bound state, can be observed in our setup. Numerical results indicate that our proposal is robust against fabrication disorders of the coupling sequence. Our work opens up a route for realizing unconventional light-matter interactions.
Photon-mediated interaction between quantum emitters in engineered photonic baths is an emerging area of quantum optics. At the same time, non-Hermitian (NH) physics is currently thriving, spurred by the exciting possibility to access new physics in systems ruled by non-trivial NH Hamiltonians—in particular, photonic lattices—which can challenge longstanding tenets such as the Bloch theory of bands. Here, we combine these two fields and study the exotic interaction between emitters mediated by the photonic modes of a lossy photonic lattice described by a NH Hamiltonian. We show in a paradigmatic case study that structured losses in the field can seed exotic emission properties. Photons can mediate dissipative, fully non-reciprocal interactions between emitters with range critically dependent on the loss rate. When this loss rate corresponds to a bare-lattice exceptional point, the effective couplings are exactly nearest neighbor, implementing a dissipative, fully non-reciprocal Hatano–Nelson model. Counterintuitively, this can occur irrespective of the lattice boundary conditions. Thus photons can mediate an effective emitter’s Hamiltonian which is translationally invariant despite the fact that the field is not. We interpret these effects in terms of metastable atom–photon dressed states, which can be exactly localized on only two lattice cells or extended across the entire lattice. These findings introduce a paradigm of light-mediated interactions with unprecedented features such as non-reciprocity, non-trivial dependence on field boundary conditions, and range tunability via a loss rate.
Simulating photonic lattices remains to be an interesting and important goal for quantum technologies. Here, we propose several simulation schemes of one- and quasi-one-dimensional photonic lattices based on arrays of diverse three-level giant-atom dimers. The resulting models, including diamond, Su-Schrieffer-Heeger, and ladder lattices, exhibit protected nearest-neighbor and greatly inhibited next-nearest-neighbor interactions, which are challenging with most state-of-the-art experimental platforms. Our proposals based on circuit quantum electrodynamics are tunable, scalable, and reconfigurable, thus providing opportunities for simulating more advanced photonic lattices and exploring unprecedented phenomena with no counterparts in conventional condensed matter physics.