Achieving decoherence-free quantum state manipulation is a paramount goal in modern quantum technologies. To this end, we demonstrate its implementation in a two-dimensional dissipative photonic graphene featuring exceptional rings. Employing the resolvent method, we analytically explore the quantum dynamics of emitters coupled to photonic graphene. In the thermodynamic limit, our analysis predicts a dissipation-dependent logarithmic relaxation for a single quantum emitter, alongside a pronounced quantum Zeno effect that slows the decay with increased dissipation. Notably, within a finite lattice, the excitation of single quantum emitter stabilizes in a decoherence-protected quantum state, which is identified as a dissipation-robust quasilocalized state. Interestingly, this state, together with a dark state, facilitates decoherence-free interactions between quantum emitters. This capability can be extended to topological graphenic platforms, where edge states mediate analogous protected interactions among giant atoms. Our findings highlight a promising path toward protecting quantum coherence in practical, high-dimensional photonic environment through dissipation engineering.
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42 pages, 18 figures. Comments and suggestions are welcome
Achieving decoherence-free quantum state manipulation is a paramount goal in modern quantum technologies. To this end, we demonstrate its implementation in a two-dimensional dissipative photonic graphene featuring exceptional rings. Employing the resolvent method, we analytically explore the quantum dynamics of emitters coupled to photonic graphene. In the thermodynamic limit, our analysis predicts a dissipation-dependent logarithmic relaxation for a single quantum emitter, alongside a pronounced quantum Zeno effect that slows the decay with increased dissipation. Notably, within a finite lattice, the excitation of single quantum emitter stabilizes in a decoherence-protected quantum state, which is identified as a dissipation-robust quasilocalized state. Interestingly, this state, together with a dark state, facilitates decoherence-free interactions between quantum emitters. This capability can be extended to topological graphenic platforms, where edge states mediate analogous protected interactions among giant atoms. Our findings highlight a promising path toward protecting quantum coherence in practical, high-dimensional photonic environment through dissipation engineering.
Abstract We investigate qubits coupled to the boundary of a two-dimensional photonic lattice that supports dispersionless edge modes—unlike conventional edge modes that sustain propagating photons. As a case study, we consider a honeycomb lattice ( photonic graphene ) of coupled resonators with a zigzag edge, where the edge modes form a flat band defined only over a restricted region of momentum space. We show that light–matter interactions are effectively captured by a dissipative cavity-QED model, wherein the emitter coherently couples to a localized mode emerging as a superposition of edge modes. This mode has support on only one sublattice and displays an unconventional power-law localization around the qubit—yet remaining normalizable in the thermodynamic limit—with a spatial range that can be tuned by introducing lattice anisotropy. We predict the occurrence of vacuum Rabi oscillations and state transfer between distant emitters. An experimental demonstration using superconducting circuits is proposed.
Abstract This review discusses how nanophotonic architectures—including plasmonic nanostructures, dielectric resonators, optical cavities, and multi-emitter assemblies—provide powerful platforms for engineering light–matter interactions and controlling decoherence, dissipation, and collective mode formation. Within the framework of open quantum systems, decoherence arises from the coupling of a quantum system to its environment, suppressing phase coherence and transforming quantum superpositions into effectively classical statistical mixtures. Rather than representing an unavoidable limitation, decoherence can be deliberately tailored through the design of structured photonic reservoirs. We examine how the spectral density, symmetry, and coupling topology of these reservoirs govern the emergence of preferred pointer states and collective excitations. In contrast to the far-field geometry of the canonical double-slit experiment, nanophotonic platforms operate in the near-field regime, where localized, collective, and hybridized excitations coexist and interact. We further discuss how nanoparticle dimers, cavity-coupled emitters, and exciton–plasmon systems function as nanoscale which-path discriminators, enabling environmentally driven selection and stabilization of robust eigenmodes, including subradiant states, dark modes, and symmetry-protected excitations. By viewing decoherence as a mechanism for basis selection rather than solely a source of quantum information loss, this review highlights emerging opportunities for quantum state preparation, mode engineering, photonic logic, and scalable light–matter interfaces, providing a unified perspective on harnessing engineered nanophotonic environments to direct quantum dynamics.
The coherent light-matter interaction at the single-photon and electronic qubit level promises to be a remarkable potential for nonclassical information processing. Besides the efforts of improving the figure of merit of the cavities, here we demonstrate strong anharmonicity in the polariton dressed states via dark state resonances in a highly dissipative cavity. It is shown that the vacuum Rabi oscillation occurs for a single quantum emitter inside a cavity even with the bosonic decay-to-interaction rate ratio exceeding 102, when the photon field is coupled to an auxiliary high-Q cavity. Moreover, photon blockade is observable in such a highly dissipative cavity quantum electrodynamics system. This study provides a promising platform for overcoming decoherence and advancing the coherent manipulation of polariton qubits.
Weyl photons appear when two three-dimensional photonic bands with linear dispersion are degenerate at a single momentum point, labeled as Weyl point. These points have remarkable properties such as being robust topological monopoles of Berry curvature as well as an associated vanishing density of states. Here, we study the quantum optical consequences of such topological Weyl photons by characterizing the individual and collective dynamics of quantum emitters close to resonance with these points. Using an exact non-perturbative treatment, we predict the development of non-exponential decay dynamics due to the emergence of localized photonic states around the emitters. We find that these bound states, whose wavefunction displays power-law spatial decay, can mediate coherent and topological long-range interactions when many emitters exchange energy through Weyl photons. Furthermore, by exploiting the topological protection of Weyl points, we provide a recipe to tune the range of the mediated interactions while keeping their power-law nature, something not possible in any other photonic platform. Thus, Weyl photons enable coherent, tunable, long-range interactions between emitters, and therefore can become a very valuable platform in the context of quantum simulation.
Reduced abstract. This Thesis explores emergent cooperative phenomena in collective light-matter systems. We study ensembles of interacting quantum emitters coherently driven by a laser field and coupled to photonic structures, focusing on the hybrid description of emitters dressed by light. The interplay among quantum emitters, coherent driving, and photonic environments reveals a rich landscape of cooperative effects. While single-emitter dressing has been widely studied, we address collective phenomena in two non-identical emitters modelled as two-level systems. Strong interaction forms a dimer exhibiting superradiant and subradiant states, with two-photon resonances directly connecting ground and doubly excited states. This nonlinear process, central to the Thesis, enables new regimes of cooperative light-matter physics. Analytical studies show how interactions reshape observables such as emission intensity, photon statistics, and spectra, offering implications for quantum metrology. The sensitivity of two-photon processes to emitter distance and driving strength enables high-precision sensing and sub-wavelength imaging. Unexpectedly, we find that off-resonant virtual states may gain population through dissipation, redefining their role in open systems. To capture this, we develop a hierarchical adiabatic elimination method for metastable dynamics. We also analyze entanglement in emitters coupled to a lossy cavity, identifying five mechanisms, including the frequency-resolved Purcell effect introduced here. This selective enhancement stabilizes cooperative states and enables scalable entanglement. Our models, tailored to solid-state platforms such as quantum dots and molecular aggregates, address challenges like inhomogeneous broadening and decoherence, demonstrating the feasibility of harnessing cooperative light-matter effects for quantum technologies.
This work studies the absorption spectrum of a two-level quantum emitter coupled to a photonic environment modified by the plasmon modes of a graphene nanodisk. Using macroscopic quantum electrodynamics and a Lorentzian mapping, the system is described within an effective cavity quantum electrodynamics framework. Analytical expressions are derived for the linear susceptibility, and three distinct spectral regimes are identified. In vacuum induced transparency, destructive quantum interference opens a narrow transparency window in the absorption spectrum. In vacuum Rabi splitting, coherent energy exchange between the emitter and the plasmonically modified photonic mode produces a well-resolved doublet. When plasmon losses are large, the required interference is suppressed, leading to the absence of induced optical transparency. It is shown that the transitions between these regimes are strictly determined by the exceptional points of the system's effective non-Hermitian Hamiltonian, and a complete phase diagram is provided as a function of the emitter-nanodisk distance and the free-space decay rate. The results highlight graphene nanodisks as a highly tunable platform for the dynamic control of quantum interference, offering potential applications in reconfigurable nanophotonic spectral switching and transparency-window engineering.