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A Theoretical Framework for Thermally Resilient Quantum Memory Using Engineered Lattice Structures

Yalla Jnan Devi Satya Prasad

Published Sep 25, 2025• 0 citations
Publisher

Abstract

Quantum repeaters are indispensable for extending quantum communication beyond metropolitan scales, yet their core component that is quantum memory, remains constrained by cryogenic requirements and sub-millisecond storage times. This work develops a comprehensive theoretical framework for thermally resilient quantum memory via engineered lattice structures, with the goal of identifying the design conditions under which robust room-temperature operation could be achieved. We derive closed-form Lindblad-master-equation bounds on thermal decoherence, establish coherence-time limits as functions of material parameters and temperature, and quantify classical communication capacity via Holevo-bound analysis. We propose phononic band-gap engineering criteria for crystal lattices that, under ideal assumptions, suppress spin-phonon coupling by up to two orders of magnitude, and design concatenated XY dynamical-decoupling sequences optimized for broadband thermal noise at 300 K. In addition, we outline bias-preserving quantum error-correction codes tailored to amplitude-damping and dephasing asymmetries in thermal environments. End-to-end simulations predict coherence times of 10-50 ms under realistic parameter assumptions, with optimistic projections reaching 100 ms at 300 K contingent on achieving Q mode ≳ 6×10 8 and phononic suppression factors S lat ∼ 10 −3 not yet demonstrated at room temperature. Conservative scenarios still yield entanglement-generation rate improvements of 100-1000× in two-node repeater links under the assumptions-(Q mode = 6 × 10 8 , S lat = 10 −3 , SDD = 0.1, εp = 10 −4 , σt = 0.8 ns, τcyc = 0.5 ms, τ dec = 0.2 ms). These results are predictive and simulation-based, providing scaling laws, performance bounds, and design principles that can guide future experimental efforts toward practical, room-temperature quantum memories.

DOI
10.36227/techrxiv.175877763.39188028/v1

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This paper develops a comprehensive theoretical framework for designing quantum memory systems with enhanced resilience to thermal decoherence through engineered lattice geometries and protective structures. We formulate a unified mathematical description connecting material properties, geometric configurations, and quantum information retention capabilities, establishing design principles for long-lived quantum states. The theory begins with a detailed analysis of decoherence mechanisms in structured quantum materials, deriving analytical expressions for coherence time as functions of lattice topology, defect engineering, and environmental coupling strength. We prove theoretical bounds on achievable memory lifetimes under various physical constraints and identify optimal geometric configurations that maximize information retention. The framework incorporates both passive protection mechanisms-arising from intrinsic material properties and geometric shielding-and active stabilization strategies involving periodic error detection and correction. We establish scaling laws that predict how memory performance varies with system size, temperature, and structural parameters, providing design guidelines for practical implementations. Our analysis reveals fundamental trade-offs between memory density, access time, and coherence preservation, offering a theoretical roadmap for next-generation quantum memory architectures. This work bridges quantum information theory, condensed matter physics, and materials science to advance understanding of thermally resilient quantum storage.
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Long‑lived quantum optical memories are indispensable core components for quantum communication networks and quantum relay links. This work establishes a coherence‑scale‑evolution phenomenological framework for hour‑class coherent storage in rare‑earth crystals Eu³⁺:Y₂SiO₅ and Pr³⁺:Y₂SiO₅. Theoretical characteristic constants are calibrated against published benchmark experimental observations, circumventing complex numerical solutions of ultrafast microscopic energy‑level dynamics. We provide multiple quantitatively verifiable forward‑looking predictions: storage lifetime under ultra‑low‑temperature conditions, global optimal operating window for control‑laser power, performance zoning for rare‑earth doping schemes, and the engineering trade‑off between storage duration and coherence fidelity. The model is built upon macroscopic physical constraints of lattice thermal vibration, light‑medium coupling and dopant‑mediated medium stability. Detailed microscopic mathematical derivations are omitted, and this manuscript focuses entirely on experimentally testable outputs. The results offer theoretical guidance for parameter optimization of rare‑earth‑based quantum memories, experimental workflow adjustment and novel doped‑system design, and help reduce high‑cost trial‑and‑error in low‑temperature cryogenic experiments.
Quantum communication between two remote locations often involves remote parties sharing an entangled quantum state. At present, entanglement distribution is usually performed using photons transmitted through optical fibers. However, the absorption of light in the fiber limits the communication distances to less than 200 km, even for optimal photon telecom wavelengths. To increase this distance, the quantum repeater idea was proposed. In the quantum repeater architecture, one divides communication distance into segments of the order of the attenuation length of the photons and places quantum memory nodes at the intermediate locations. Since the photon loss between intermediate locations is low, it is possible then to establish entanglement between intermediate quantum memory nodes. Once entanglement between adjacent nodes is established, one can extend it over larger distances using entanglement swapping.\n\nThe long coherence time of a quantum memory is a crucial requirement for the quantum repeater protocol. It is obvious that the coherence time of a quantum memory should be much longer that the time it takes for light to travel between remote locations. For a communication distance l = 1000 km, the corresponding time is t = l/c = 3.3 ms. One can show that for a simple repeater protocol and realistic success probabilities of entanglement generation, the required coherence time should be on the order of many seconds, while for the more complicated protocols that involve multiplexing and several quantum memory cells per intermediate node, the required coherence time is on the order of milliseconds.\n\nIn this thesis, I describe a quantum memory based on an ensemble of rubidium atoms confined in a one-dimensional optical lattice. The use of the magnetically- insensitive clock transition and suppression of atomic motion allows us to increase coherence time of the quantum memory by two-orders of magnitude compared to previous work. I also propose a method for determining the Zeeman content of atomic samples. In addition, I demonstrate the observation of quantum evolution under continuous measurement. The long quantum memory lifetime demonstrated in this work opens the way for scalable processing of quantum information and long distance quantum communication.
Developing and deploying advanced Quantum Repeater (QR) technologies will be necessary to scale quantum networks to longer distances. Depending on the error mitigation mechanisms adopted to suppress loss and errors, QRs are typically classified into memory-based or all-photonic QRs; and each type of QR may be best suited for a specific type of underlying quantum technology, a particular scale of quantum networks, or a specific regime of operational parameters. We perform theoretical analysis and simulations of quantum repeaters and networks to investigate the relative performance and resource requirements of different quantum network paradigms. Our results will help guide the optimization of quantum hardware and components and shed light on the role of a robust control plane. We present our research findings on theoretical analysis and simulations of memory-based first-generation trapped-ion quantum repeaters and networks, and all-photonic entanglement-based quantum repeaters and networks. We study the relative performance in terms of entanglement generation rate and fidelity, as well as the resource requirements of these two different quantum network paradigms.
Quantum memory is a crucial component for the development of quantum computing and quantum communication. However, the primary challenge in building a practical quantum memory lies in mitigating quantum decoherence, the loss of quantum information due to interaction with the environment. This paper proposes a novel quantum memory design leveraging the principle of quantum demixing, a phenomenon where interactions between quantum bits (qubits) can effectively slow down the decoherence rate. The design utilizes a carefully engineered architecture where qubits are coupled in a specific manner to promote entanglement and suppress unwanted dephasing. We explore the theoretical framework for this design, focusing on the mathematical models describing the decoherence process and the impact of qubit interactions. The core claim is that optimized quantum memory structures can significantly reduce decoherence, leading to enhanced storage capacity and read/write rates. This work presents a new approach to quantum memory design, addressing a fundamental limitation in the field. ---