Programmable preparation of entangled quantum states is a central requirement for scalable quantum information processing, quantum networking and photonic quantum computing. Topological photonic platforms offer an attractive route towards robust quantum-state generation by encoding information in symmetry- protected optical modes, yet the generated entangled states are typically dictated by the lattice geometry and therefore lack programmability. Here we demonstrate programmable preparation of topological entangled states by inverse engineering the nonlinear optical pump profile of an integrated photonic lattice. Our approach enables deterministic control over both the dimensionality and modal structure of the generated entangled state while preserving its topological character. We experimentally realize silicon photonic topological superlattices in which the nonlinear generation pathway itself becomes programmable via tailored excitations. The superlattices host a multiband manifold of co localized topological interface modes, while coherently controlled inputs synthesize pump superpositions within this protected basis. We showcase this principle by selectively addressing topological biphoton eigenstates, steering correlations to produce a desired target state in a high-dimensional Hilbert space, and inverse-designing pump states that generate targeted Schmidt dimensionalities. Site-resolved two-photon correlation measurements remain reproducible across nominally identical fabricated devices, demonstrating robustness to realistic nanofabrication-induced disorder. Programmable preparation of topological entangled states establishes a pathway towards exploiting topological photonic modes as application-specific quantum resources, enabling tailored input states for high-dimensional quantum communication, quantum networking and photonic quantum computing.
Programmable preparation of entangled quantum states is a central requirement for scalable quantum information processing, quantum networking and photonic quantum computing. Topological photonic platforms offer an attractive route towards robust quantum-state generation by encoding information in symmetry- protected optical modes, yet the generated entangled states are typically dictated by the lattice geometry and therefore lack programmability. Here we demonstrate programmable preparation of topological entangled states by inverse engineering the nonlinear optical pump profile of an integrated photonic lattice. Our approach enables deterministic control over both the dimensionality and modal structure of the generated entangled state while preserving its topological character. We experimentally realize silicon photonic topological superlattices in which the nonlinear generation pathway itself becomes programmable via tailored excitations. The superlattices host a multiband manifold of co localized topological interface modes, while coherently controlled inputs synthesize pump superpositions within this protected basis. We showcase this principle by selectively addressing topological biphoton eigenstates, steering correlations to produce a desired target state in a high-dimensional Hilbert space, and inverse-designing pump states that generate targeted Schmidt dimensionalities. Site-resolved two-photon correlation measurements remain reproducible across nominally identical fabricated devices, demonstrating robustness to realistic nanofabrication-induced disorder. Programmable preparation of topological entangled states establishes a pathway towards exploiting topological photonic modes as application-specific quantum resources, enabling tailored input states for high-dimensional quantum communication, quantum networking and photonic quantum computing.
The generation and manipulation of high-dimensional quantum states lies at the heart of modern quantum computation. The use of topology to resiliently encode and transport quantum information has been widely investigated in condensed matter and has recently penetrated quantum photonics. However, a route to scale up to a large number of entangled topological photonic modes has been missing. In this work, we demonstrate a method to generate high-dimensional topological photonic entanglement. Our platform relies on designed silicon photonic waveguide topological superlattices, which support nonlinear generation of energy-time-entangled photon pairs on a superposition of multiple topological modes. We show strong signatures of entanglement of up to five topological modes with resilience to nanofabrication imperfections, providing a route toward scalable, fault-tolerant quantum photonic states.
This paper explores the novel concept of programmable spatiotemporal entanglement, realized through engineered disordered photonic crystals (DPhCs). We propose a theoretical framework that leverages the unique light-matter interaction within these disordered photonic structures. This interaction is characterized by phenomena such as Anderson localization and can be effectively described using random matrix theory. Our goal is to generate and control highly complex entangled states, addressing limitations of traditional methods. Conventional approaches for entanglement generation often struggle with scalability, robust control, and high-dimensional encoding across both spatial and temporal degrees of freedom simultaneously. By introducing controlled disorder into photonic crystal designs, we aim to harness the rich scattering phenomena to tailor the correlations between entangled photons across their spatiotemporal wavefronts. The proposed methodology involves embedding nonlinear optical elements within these disordered structures to facilitate spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (SFWM). In such environments, the localized modes and the modified density of states profoundly influence the properties of the emitted photon pairs. Programmability is envisioned through external control mechanisms, such as adaptive wavefront shaping of the pump light or tunable disorder elements. These mechanisms would allow for dynamic manipulation of entanglement properties like dimensionality, purity, and Schmidt mode distributions. We discuss the potential for robust, high-dimensional quantum states and their implications for advanced quantum communication, quantum imaging, and novel quantum computing architectures. This work lays the groundwork for a new paradigm in quantum state engineering, exploiting complexity to achieve unprecedented control over multiphoton entanglement.
Quantum skyrmions are topological structures that have garnered significant interest due to their demonstrated robustness and versatility across diverse optical platforms. However, existing approaches for their generation are limited to producing pre-determined two dimensional qubit states with a single topology. Here we create multi-dimensional topological states by introducing a non-local interaction between high-dimensional photonic entanglement and a metasurface, where the topological transformation induced by the metasurface is made non-deterministic by the probabilistic nature of the interfacing entangled state. Within this framework, we demonstrate that individual quantum states can host multiple co-existing topologies that are only revealed upon measurement, allowing for their parallel transport within distinct spatial mode channels. We confirm this by revealing the rich topological landscape within our modified Hilbert space while controlling the desired output topology by orbital angular momentum (OAM) projections on one of the entangled photons, producing multiple non-local polarization-OAM entangled states characterized by distinct topological classes, all from a single metasurface device. Our results reveal new capability when structured high-dimensional entanglement is interfaced with structured matter capable of coupling photonic degrees of freedom, establishing a new pathway for the compact generation of complex quantum states.
Abstract Based on a coupled resonator array, we theoretically construct and numerically simulate a nonlinear quantum optics platform to dynamically control the Bloch wavevector. By scanning the modulation parameters ( α , k y ), we reproduce the Hofstadter’s butterfly structure in the biphoton energy spectrum and reveal clear correspondences among the eigenenergy spectrum, transmission spectrum, and biphoton joint spectral intensity (JSI). Further research demonstrates that screening the pump wavelength can effectively tailor the JSI profile and the Schmidt number of the quantum state, enabling flexible manipulation of frequency entanglement characteristics. This work provides a theoretical framework for exploring quantum state generation and manipulation in nonlinear topological photonic systems and demonstrates the potential for realizing programmable quantum light sources in integrated quantum photonic circuits.
Biphoton states have shown promising applications in quantum information processing, including quantum communications, quantum metrology, and quantum imaging. The generation and manipulation of biphoton entanglement in topologically distinct modes paves the way in this direction. Here we present a comprehensive method for regulating the topological properties of the system by combining the nonlinearity in waveguides, i.e., nonlinearity in the waveguide coupling materials, and the waveguide lattice structure. Our method enables the generation of topological biphoton states with injected pump activation on the topologically trivial modes. This is realized through self-induced manipulation on pump-dependent nonlinear couplings on the defects, which is unable to be realized while there are no such nonlinear couplings. Specifically, by including the nonlinear gain/loss mechanism in the coupling between the nearest-neighbor waveguides and the third-order Kerr nonlinearity effect along the waveguides, the injected pump power will be the controllable parameter for the manipulation of the topology in the defect states and the generation of biphoton entanglement states. We also present an experimental proposal to realize our scheme and its generalization in the contemporaneous "active" topological photonics time-bin platforms. Our method can be used in other Su-Schrieffer-Heeger (SSH) models with various defect configurations. Our method enables the reusability and versatility of SSH lattice chips and their application for fault-tolerant quantum information processing, promoting the industrialization process of quantum technology.
Photon entanglement is a fundamental resource for quantum technologies, yet it is extremely fragile especially in large quantum circuitry, which is necessary for quantum information processing and computing. We propose an integrated scheme for direct topological protection of entanglement, enabling robust transport of entangled photonic states, even when the photon dynamically evolves during propagation. Our platform relies on a two-dimensional discrete-time quantum walks in synthetic dimensions, supporting topological edge states at the interface between distinct domains. Thus far, in all previous approaches for exploiting topology to protect entanglement, the protection was linked to the position of the photon in the actual structure. In contrast, our scheme relies on a synthetic temporal dimension (time bins) where the entangled state is always reproduced, despite fluctuations or variations that may emerge in the system. Thus, our scheme provides precise temporal control important for synchronization and timing in quantum computation. By suppressing phase-sensitive errors—the most critical noise source in photonic platforms—our approach can lower the physical error rate below fault-tolerance thresholds and reduce the overhead typically required for scalable quantum information processing. The robustness to errors arises from the fact that the entangled state is preserved through correlations in the synthetic (temporal) dimension. As a result, we ensure that at specific designated times, the emergent state faithfully reproduces the initial entangled state, despite the photon having taken any dynamically evolving paths. This approach establishes a robust framework for directly protecting entanglement.