The study of non-Hermitian systems has attracted more and more attention, because physical properties in many real systems should be described by non-Hermitian Hamiltonians. Due to the existence of absorption and dissipation, transmission and transformation of entangled states with high fidelity are very difficult to realize in the non-Hermitian systems. How to realize transmission and transformation of entangled states with high fidelity in these dissipative systems becomes an open problem. Here we provide an inverse design scheme for topologically protected channels to solve such a problem. From our scheme, topologically protected channels can be designed according to the requirements for the overlap integrals among the initial states, target states, and eigenstates of the system. As a result, robust transmission and transformation of entangled states with high fidelity can be achieved in the non-Hermitian systems. Our proposed scheme has been demonstrated experimentally using the constructed non-Hermitian quantum walk platform. This work interconnects topology, quantum physics, and non-Hermitian systems, and opens up an avenue for quantum engineering in real systems.
The study of non-Hermitian systems has attracted more and more attention, because physical properties in many real systems should be described by non-Hermitian Hamiltonians. Due to the existence of absorption and dissipation, transmission and transformation of entangled states with high fidelity are very difficult to realize in the non-Hermitian systems. How to realize transmission and transformation of entangled states with high fidelity in these dissipative systems becomes an open problem. Here we provide an inverse design scheme for topologically protected channels to solve such a problem. From our scheme, topologically protected channels can be designed according to the requirements for the overlap integrals among the initial states, target states, and eigenstates of the system. As a result, robust transmission and transformation of entangled states with high fidelity can be achieved in the non-Hermitian systems. Our proposed scheme has been demonstrated experimentally using the constructed non-Hermitian quantum walk platform. This work interconnects topology, quantum physics, and non-Hermitian systems, and opens up an avenue for quantum engineering in real systems.
Abstract Realization of robust transmission and transformation of entangled states with high fidelity is crucial for the applications in quantum information, computing, and communications. However, it is hard to achieve currently because of scattering loss and disorder. Here, an inverse‐design scheme is theoretically proposed and experimentally demonstrated to realize nearly perfect transmission and transformation of entangled photon states. The scheme is based on the determination of the transmission and transformation properties of entangled states, which depends on the overlap integrals among the initial states, eigenmodes of the system and target states. Thus, topologically protected channels are designed according to the requirements for the overlap integrals of these states. As a result, robust transmission and transformation of entangled states are achieved with high fidelity. The proposed scheme has been demonstrated experimentally using the constructed quantum walk platform. This work interconnects topology, quantum physics, and inverse design, and opens up a new avenue for quantum engineering.
This paper investigates the protection of quantum entanglement states through topological principles. The core claim is that embedding entangled states within systems exhibiting non-trivial topological properties can lead to enhanced long-term fidelity. The fundamental mechanism involves leveraging the topological robustness of these structures to suppress the detrimental effects of local perturbations on the delicate entangled correlations. We explore various topological systems, focusing on their ability to shield entangled states from decoherence. The theoretical framework presented here offers a novel approach to building robust quantum information processing architectures, particularly for quantum computing applications. We demonstrate, through mathematical analysis, that the topological protection significantly improves the preservation of entanglement against environmental noise. Specifically, we consider a model system—a chain of interacting spin-1/2 particles—and derive the equations governing the evolution of the entangled state under the influence of both Hamiltonian terms and external perturbations. Our results highlight the potential of topological protection for achieving high-fidelity quantum entanglement over extended periods. The key equation governing the evolution of the entangled state is given by: ψ(t) = U(t)ψ(0) where ψ(t) is the state vector at time t, ψ(0) is the initial state vector, and U(t) is the time-evolution operator. We also explore the concept of topological invariants, such as the braid group, to characterize the topological properties of the system. The braiding of these topological elements can be used to manipulate the entangled state without destroying the entanglement. The preservation of entanglement is quantified by the fidelity, defined as: F(t) = |⟨ψ(t)|ψ(0)⟩|2 where ⟨ψ(t)|ψ(0)⟩ represents the overlap between the final and initial states. Our analysis demonstrates that the fidelity decays much slower in topological systems compared to non-topological systems. Furthermore, we investigate different types of topological protection, including chiral edge states and non-abelian braiding. We present a general framework for assessing the topological protection of any quantum system, emphasizing the importance of understanding the interplay between the topological structure and the quantum state. Finally, we discuss the challenges and future directions in realizing topological quantum computation. ---
Robust quantum state transfer (QST) is the foundation for information exchange among nodes in quantum networks. In this paper, we propose a robust QST protocol that utilizes topological edge modes in the qubit chains to encode (decode) quantum states (flying qubits). By employing qubits with tunable couplings, we construct Su-Schrieffer-Heeger (SSH) chains as the nodes of a quantum network. The end qubit of each SSH chain is dissipatively coupled to a chiral waveguide, and the dissipative strength is a constant. We refer to the SSH chain with a dissipation channel at the end qubit as the non-Hermitian SSH chain. Comparing the symmetry and energy spectra of the non-Hermitian SSH chain with those of the SSH chain, our analysis reveals that the dissipative dynamics of the topological edge state in the non-Hermitian SSH chain are governed by its imaginary spectra. The edge mode with the imaginary spectrum can be used to encode (decode) quantum states (flying qubits), thereby enabling robust QST between two remote mirrored non-Hermitian SSH chains. Our numerical simulations demonstrate that high-fidelity QST can be achieved even in the presence of coupling errors. Furthermore, we extend our analysis to consider QST in imperfect chiral waveguides, providing insights into the robustness of our protocol under realistic conditions. Our discussion is applicable to various quantum platforms and holds significant implications for constructing large-scale quantum networks.
Engineering quantum bath networks through non-Hermitian subsystem Hamiltonians has recently emerged as a promising strategy for qubit cooling, state stabilization, and fault-tolerant quantum computation. However, scaling these systems while maintaining precise control over their complex interconnections, especially in the optical domain, poses significant challenges in both theoretical modeling and physical implementation. In this work, drawing on principles from quantum and mathematical physics, we introduce a systematic framework for constructing non-Hermitian subsystems within entirely Hermitian photonic platforms. In particular, controlled exponential decay without actual absorption loss is realized in finite 1-D waveguide chains through discrete-to-continuum coupling and Lanczos transformations. Using this new methodology, we implement parity-time symmetric quantum systems and experimentally demonstrate that these artificial bath environments accurately replicate the dynamics of non-Hermitian arrangements in both single- and multi-photon excitation regimes. Since the non-Hermitian subsystem response deterministically arises from an artificially built Hermitian bath, the quantum evolution can be monitored via post-selection in this fully conservative configuration. This approach bridges the gap between theoretical models and experimental realizations, thus paving the way for exploiting quantum bath engineering in advanced information processing and emerging quantum technologies.
Dissipation always exists in real environments, and it can cause decoherence during transfer of quantum states. To avoid decoherence, dissipation is usually shielded. However, dissipation is difficult to avoid in real cases. Thus, how to achieve efficient quantum state transfer in dissipation environments, although it will receive great attention, remains a challenge. Here we demonstrate that dissipation can be utilized to realize robust control of quantum state transfer instead of being avoided. Our scheme is realized by constructing Liouvillian exceptional point (LEP). By tuning dissipation, the exchange of eigenvectors and nonadiabatic transition near the LEP can be modulated, thereby controlling transfer and chirality of topological quantum state. Furthermore, we have experimentally validated such a scheme on a quantum walk platform. Our work opens up a different avenue for quantum information process in real systems.
This paper presents a novel approach to quantum information storage and transmission leveraging the principles of quantum entanglement and topological protection. The core idea centers around constructing topologically protected quantum bits (QBs) based on non-Abelian entangled states. These states, shielded by topological defects, provide inherent robustness against local perturbations, leading to enhanced stability and fidelity in quantum information storage and transmission. We detail the theoretical framework, focusing on the manipulation and control of these entangled states. The proposed system offers a pathway to mitigate the detrimental effects of environmental noise, a significant hurdle in the practical realization of quantum technologies. Specifically, we explore the encoding scheme using the braiding of quasiparticles in a topological superconductor to generate and maintain non-Abelian anyons, which are the building blocks of our QBs. We examine the key metrics – fidelity and error rates – and demonstrate a potential for achieving high-fidelity, fault-tolerant quantum information processing. This research contributes to the burgeoning field of topological quantum computing, offering a promising route toward scalable and reliable quantum devices. ---