Quantum Memories. A Review based on the European Integrated Project "Qubit Applications (QAP)"
Christoph Simon, Mikael Afzelius, J. Appel, A. Boyer de la Giroday, Samuel Dewhurst, Nicolas Gisin, C. Y. Hu, Fedor Jelezko, Stefan Kröll, Jörg Helge Müller, Joshua Nunn, Eugene Simon Polzik, John Rarity, Hugues de Riedmatten, Wenjamin Rosenfeld, Andrew J. Shields, Niklas Sköld, R. M. Stevenson, Rob Thew, Ian A. Walmsley, M. C. Weber, Harald Weinfurter, Jörg Wrachtrup, Robert James Young
We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU Integrated Project "Qubit Applications". We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in "Qubit Applications" in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria.
We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU Integrated Project "Qubit Applications". We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in "Qubit Applications" in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria.
We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU integrated project Qubit Applications. We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in Qubit Applications in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria.
Quantum memory, which maps photonic quantum information into a stationary medium and retrieves it at a chosen time, plays a vital role in the advancement of quantum information science. In particular, the scalability of a quantum memory is a central challenge for quantum network that can be overcome by using integrated devices. Quantum memory with an integrated device is highly appealing since it not only expands the number of memories to increase data rates, but also offers seamless compatibility with other on-chip devices and existing fiber network, enabling scalable and convenient applications. Over the past few decades, substantial efforts have been dedicated to achieving integrated quantum memory using rare earth ions doped solid-state materials, color centers, and atomic gases. These physical platforms are the primary candidates for such devices, where remarkable advantages have been demonstrated in achieving high-performance integrated quantum memory, paving the way for efficiently establishing robust and scalable quantum network with integrated quantum devices. In this paper, we aim to provide a comprehensive review of integrated quantum memory, encompassing its background and significance, advancement with bulky memory system, fabrication of integrated device, and its memory function considering various performance metrics. Additionally, we will address the challenges associated with integrated quantum memory and explore its potential applications. By analyzing the current state of the field, this review will make a valuable contribution by offering illustrative examples and providing helpful guidance for future achievements in practical integrated quantum memory.
The approaching era will require computing resources that are future proof across various domains, extending from communications, computing and sensing. It is anticipated that quantum computing will play a major role due to limitations of classical computing. A vital factor in meeting this capability is the need of a non-classical storage unit to facilitate the quantum devices. Therefore, quantum memory becomes a necessity. This paper aims to present detailed discussion on quantum memory, which would begin from fundamental concepts and would range to a more advanced level, with the ultimate goal of identifying the most suitable method for developing quantum applications. The current protocols utilized in quantum memories rely on optically driven and photon echo based techniques. The survey will deeply analyze the processes and principles involved in storing and retrieving information using these methods. It would also assess their key features, including retention time, efficiency, measurement fidelity, bandwidth, and necessary conditions. In addition, the focus would also be on studying the neoteric realms of quantum dots and the Bose Einstein condensates. The paper concludes with challenges in building quantum memories and possible future directions.
Abstract Quantum memory devices are essential components of integrated quantum-photonic circuits with applications in quantum computing and quantum information processing. The comprehension and quantification of critical properties such as fidelity, coherence time, storage time, and efficiency of quantum memory are insufficient in the extant literature. In this review, we examine the development and characteristics of various types of quantum memories. Although diverse approaches to storing quantum information are described in detail, we emphasize solid-state quantum memory. Furthermore, we discuss the fabrication and characterization of defects of quantum materials, including two-dimensional materials, for quantum memory applications. We survey theoretical tools such as density functional theory for studying defects to evaluate quantum properties.
Abstract In order to achieve quantum computation, the qubit preparation is crucial, given that the performance relies on various gate operations, which is determined by the quality of qubit. This paper introduces many qubits, including atoms (neutral atoms and ions) and spins (quantum dots, diamond NV centers, and nuclear magnetic resonance) that depend on various systems. Moreover, they are mentioned separately in this paper due to the significance of superconducting qubits. Meanwhile, the advantages and drawbacks of these qubits are compared, e.g. their coherence (long coherence time between neutral atoms and ions), operating temperature, quantum state reading, quantum system ease of handling, and precision of handling. Challenges as well as corresponding resolved methods have been addressed and reviewed. Current gaps and limitations are also discussed.
Nitrogen-vacancy (NV) centers in diamond are a promising candidate as a solid state qubit memory for quantum information as they possess very long coherence times even at room temperature. Furthermore, NV centers are very sensitive to their electromagnetic environment and are addressable in the GHz frequency range. Here we review our progress towards the detection of single NV centers for the implementation of fast on demand coupling between NV centers and GHz electromagnetic fields. Precisely, we present efforts towards mapping NV centers with a cathodoluminescence setup. Developing such capability is important for patterning local one-qubit gates for the application of high amplitude electromagnetic fields as a tuning parameter.