This paper presents a comprehensive theoretical investigation of quantum information storage via the Higgs amplitude mode in superconductors. We propose a novel quantum memory mechanism based on coherent excitation and echo retrieval of the Higgs mode, exploiting the collective nature of the superconducting condensate. Through rigorous theoretical analysis combining time-dependent Ginzburg-Landau theory with quantum master equations, we demonstrate that Higgs mode excitations can store quantum information with coherence times exceeding 100 ns. We derive analytical expressions for storage fidelity as a function of temperature, gap anisotropy, and disorder, achieving theoretical fidelities above 95% for storage times up to 100 ns in clean s-wave superconductors below. Numerical simulations validate our theoretical predictions and reveal optimal parameter regimes for NbN thin films. Our findings establish fundamental bounds on Higgs-based quantum memory and propose experimental protocols compatible with current THz spectroscopy capabilities. This work opens new directions for exploiting collective modes in quantum technologies.
We demonstrate a scheme for realizing quantum-information storage (retrieval) into (from) a quantum memory using a hybrid quantum system, which consists of
N nitrogen-vacancy (N-
V) centers (as memory),
N transmission line resonators (TLRs) (as data bus), and
N current-biased Josephson-junction (CBJJ) superconducting phase qubits (as heads of read and write). By virtually exciting the vibrational modes of the TLRs, this can produce an effective coupling between the N-
V centers and the CBJJs in the system. Because the operation time ($\ensuremath{\sim}{10}^{\ensuremath{-}8}$ s) is much shorter than the decoherence time of the CBJJ ($\ensuremath{\sim}{10}^{\ensuremath{-}5}$ s), the quantum information can be transferred between the N-
V centers and the CBJJs easily. Owing to the strong-coupling condition $[\ensuremath{\lambda}/2\ensuremath{\pi}\ensuremath{\gg}({\ensuremath{\gamma}}_{eg},\ensuremath{\Gamma},{\ensuremath{\gamma}}_{\ensuremath{\phi}})]$ and the long coherence time ($\ensuremath{\sim}{10}^{\ensuremath{-}3}$ s) of the N-
V centers, the quantum information can be stored in the memory steadily, and it can be retrieved with a high fidelity (
>96). This scheme provides a scalable way of exchanging quantum information between different quantum interfaces, and has the experimental feasibility with currently available experimental technology.
A new class of quantum memory is proposed, termed the Superconducting Topological Memory State (STMS). In this framework the macroscopic phase of a superconducting condensate is not only determined by the instantaneous Hamiltonian but also encodes a history of the system's topological configuration. By coupling a superconducting circuit to a controllable topological transition, the condensate phase can lock into distinct metastable branches that are associated with different winding numbers of the superconducting order parameter. The memory is read out by measuring the persistent current or the Josephson phase across a weak link. The STMS exploits the inherent robustness of topological invariants and the dissipationless nature of superconductors to achieve long‑lived, non‑volatile quantum information. This manuscript develops the theoretical model, analyzes the dynamical conditions for memory formation, and discusses the potential for integration into hybrid quantum architectures. No experimental data are presented; the focus is on analytical and numerical insights that illuminate the feasibility and scalability of STMS as a novel quantum storage mechanism.
This work provides a novel concept for a voltage-programmable quantum memory with capability to tune superconducting qubits. Electric field-induced ion transport in Superconductor-Ionic hetero-structures programs the tunneling current and Hamiltonian [1]. This work develops a model of the field-effect in the superconducting state at resonance. We use the model to simulate designs of memory devices programmable with sub-50 milli-Volt and sub-nanosecond pulses while maintaining 1-10 year storage time [2]. Quantum Master Equation (QME) simulations [3] support tuning of the time dependent quantum coherence properties in these devices with a programmed Hamiltonian determined by unique ion energy levels. To obtain further insights, we construct Niobium/AlOx/Ionic-HfOx/AlOx/Niobium devices and characterize the effects of key experimental parameters. The work provides device technology advances applicable to cryogenic computing and quantum information [4-6].
This article reviews efforts to build a new type of quantum device, which combines an ensemble of electronic spins with long coherence times, and a small-scale superconducting quantum processor. The goal is to store over long times arbitrary qubit states in orthogonal collective modes of the spin-ensemble, and to retrieve them on-demand. We first present the protocol devised for such a multi-mode quantum memory. We then describe a series of experimental results using NV (as in nitrogen vacancy) center spins in diamond, which demonstrate its main building blocks: the transfer of arbitrary quantum states from a qubit into the spin ensemble, and the multi-mode retrieval of classical microwave pulses down to the single-photon level with a Hahn-echo like sequence. A reset of the spin memory is implemented in-between two successive sequences using optical repumping of the spins.
A quantum memory at microwave frequencies, able to store the state of multiple superconducting qubits for long times, is a key element for quantum information processing. Electronic and nuclear spins are natural candidates for the storage medium as their coherence time can be well above one second. Benefiting from these long coherence times requires to apply the refocusing techniques used in magnetic resonance, a major challenge in the context of hybrid quantum circuits. Here we report the first implementation of such a scheme, using ensembles of nitrogen-vacancy (NV) centres in diamond coupled to a superconducting resonator, in a setup compatible with superconducting qubit technology. We implement the active reset of the NV spins into their ground state by optical pumping and their refocusing by Hahn echo sequences. This enables the storage of multiple microwave pulses at the picoWatt level and their retrieval after up to
35μs, a three orders of magnitude improvement compared to previous experiments.
This paper proposes a novel approach to data storage, termed Quantum Entanglement Memory Storage (QEMS), which leverages the principles of quantum entanglement for achieving unprecedented storage density and longevity. The core concept involves encoding and storing information within multi-particle entangled states, circumventing the fundamental limitations imposed by classical physics. We detail the mechanism for creating and maintaining robust multi-body entangled states through precisely controlled superconducting qubits. The inherent coherence of entangled states is exploited to ensure long-term information preservation, while quantum measurements on these states provide a method for data retrieval. QEMS represents a paradigm shift in data storage, offering the potential for vastly increased capacity and extended data retention periods compared to conventional technologies. The theoretical framework is presented, outlining key equations and concepts, and highlighting the potential advantages of this quantum storage system. This work establishes a foundation for future research and development in the field of quantum memory. ---