Scalable quantum information systems would store, manipulate, and transmit quantum information locally and across a quantum network, but no single qubit technology is currently robust enough to perform all necessary tasks. Defect centers in solid-state materials have emerged as potential intermediaries between other physical manifestations of qubits, such as superconducting qubits and photonic qubits, to leverage their complementary advantages. It remains an open question, however, how to design and to control quantum interfaces to defect centers. Such interfaces would enable quantum information to be moved seamlessly between different physical systems. Understanding and constructing the required interfaces would, therefore, unlock the next big steps in quantum computing, sensing, and communications. In this Perspective, we highlight promising coupling mechanisms, including dipole-, phonon-, and magnon-mediated interactions, and discuss how contributions from nanotechnologists will be paramount in realizing quantum information processors in the near-term.
Scalable quantum information systems would store, manipulate, and transmit quantum information locally and across a quantum network, but no single qubit technology is currently robust enough to perform all necessary tasks. Defect centers in solid-state materials have emerged as potential intermediaries between other physical manifestations of qubits, such as superconducting qubits and photonic qubits, to leverage their complementary advantages. It remains an open question, however, how to design and to control quantum interfaces to defect centers. Such interfaces would enable quantum information to be moved seamlessly between different physical systems. Understanding and constructing the required interfaces would, therefore, unlock the next big steps in quantum computing, sensing, and communications. In this Perspective, we highlight promising coupling mechanisms, including dipole-, phonon-, and magnon-mediated interactions, and discuss how contributions from nanotechnologists will be paramount in realizing quantum information processors in the near-term.
For future quantum technologies and in particular for quantum architecture systems, one needs to consider scalability and reproducibility in order to be able to handle and add easily as many qubits of information as possible on a given platform. Quantum coherence and quantum information are fragile and thus requires the need for many qubits to be created, to interact and quantum information to be preserved. Currently there are either very good qubits in terms of fidelity but poor scalability or very good scalability but poor fidelity thus requiring more qubits to compensate. Most of the current platforms are in solid-state physics such as superconducting, dopants in silicon, quantum dots in III-V semiconductors or defects in diamond. The main interest for condensed matter systems is the fact that it is potentially scalable as integration is possible in the future, already demonstrated in the ‘classical’ semiconductor industry. Nevertheless, there are some true challenges in controlling and understanding the mechanisms of decoherence, losses and unwanted effects in these ‘dirty’ systems. As quantum technologies require ultimate control of quantum effects such as maintaining quantum coherence, quantum superposition and entanglement, it pushes towards deeper knowledge of underlying material and condensed matter physics. Photons are of particular interest as they are good carriers of quantum information and one aim is to explore a fully integrated photonic quantum circuit which would be a hybrid system made of stationary solid-state qubits (we will call them quantum emitters) coupled together via single photons travelling within a common optical bus that is photonics-ready for quantum communications within a network of quantum nodes. In this presentation, we will present our latest developments and results towards the integration of quantum emitters with photonic structures with nanosize features. In the first part, our platform is described which consists of glass and thus directly compatible with optical fibres. It is based on the technique of exchanged ions within the glass in order to create locally a particular confinement of the light. The next part will concern our latest results on two different quantum emitters. The first one is based on perovskite nanocristals that can be synthetised chemically and giving rise to quantum optics-type of emitters. The second one is based on the so-called silicon-vacancy defect centre in nanodiamonds. These emitters are produced by the high-pressure/high-temperature method and lead to promising results for quantum technologies. Finally, the last part will treat the nanophotonics approaches in order to couple efficiently these emitters with our platform.
Quantum information science is entering a second phase, the Quantum Evolution 2.0, in which the challenge has shifted from demonstrating coherent control of individual quantum states to building scalable multi-qubit processors and networks. This transition places materials science at the center of the field. Across superconducting circuits, quantum defects, quantum photonic devices, and emerging materials platforms, including two-dimensional materials and heterostructures, performance is now limited less by device design than by poorly controlled surfaces, buried interfaces, and defects whose atomic identities remain incompletely known. This review surveys the materials challenges of these quantum platforms together with the characterization methods needed to resolve them. For each platform we identify the dominant decoherence mechanisms, the current state of materials understanding, and the most pressing open materials problems. A cross-platform comparison then reveals a shared structure-coherence problem. The implicated material chemistry recurs across platforms, involving light elements in disordered or buried environments, yet no platform can quantitatively connect a specific atomic-scale structure to a measured change in coherence. We close by identifying three needs, mechanistic understanding of decoherence at the atomistic level, high-throughput proxy metrics predictive of device performance, and characterization tools built for quantum materials, whose resolution would advance coherence, scalability, and integration across all platforms.
Quantum communication and quantum computation are anticipated quantum technologies which enable us to tackle problems which are hard or even impossible to solve by classical means. A major challenge in implementing real life applications for quantum communication and quantum computation is to implement efficient interfaces between different kinds of quantum systems which serve as carriers of quantum information, such as single photons and single material quantum systems (i.e. atoms, ions ...). These different kinds of quantum systems have different advantages and disadvantages if it comes to practical applications. Single photons, which may serve as flying qubits, can be transmitted over larger distances without suffering from too much decoherence while single material quantum systems may be used as matter qubits to store and process quantum information locally. For many applications, the particular advantages of both kinds of systems are needed. Hence, we require interfaces between flying qubits and matter qubits. In the first part of this thesis, we develop suitable protocols for implementing interfaces between these flying qubits and matter qubits. The key challenge is to design the interactions to allow the efficient coupling of single photons to single material quantum systems, such as atoms and ions. This is not only of interest for possible practical applications of quantum mechanics but also drives fundamental research, as it is directly connected to a precise control and enhancement of matter-field interactions. The second part of this thesis is concerned with the applications of quantum technologies for simulating complex quantum systems, which cannot be treated by classical means. In many cases, the simulation of complex quantum systems turns out to be a difficult task due to the basic structure of quantum mechanics. The same aspects of quantum mechanics, which allow us to tackle computationally hard problems by using quantum algorithms, create difficulties in understanding the behavior of complex quantum systems. However, the understanding of complex quantum systems is not only of fundamental importance but might also enable us to give answers to problems of practical significance, such as an explanation for high-temperature superconductivity. Here, we develop protocols for implementing such quantum simulations based on ions trapped in state of the art ion traps. The applications of these kinds of quantum simulations are ranging from fundamental research to process design, control, and optimization.
This monograph presents the emerging field of second-generation quantum sensing, which leverages phenomena such as superposition and entanglement, thereby offering measurement sensitivities far surpassing classical methods. In our discussion, we emphasize its potential to revolutionize various scientific and technological domains. Starting with a foundational overview of quantum sensors, distinguishing them from quantum computing and communication technologies, we then highlight the relative maturity of quantum sensing, especially in room-temperature operations, which positions it closest to market adoption. The main part of the monograph is dedicated to solid-state defects, particularly nitrogen-vacancy (NV) centers in diamond, which have emerged as promising candidates for scalable quantum sensors. The unique optical and spin properties of NV centers are explored in detail, emphasizing their possible applications in fields such as biomedical imaging, materials science, and semiconductor inspection. We delve into the technical aspects of integrating NV centers with conventional electronic and photonic systems, discussing the challenges and innovations in electronic interface circuits, photonic integration, and system-level integration technologies. Additionally, we examine gas-based quantum sensors, particularly those utilizing Rydberg atoms, which offer high precision due to their long coherence times. The challenges of integrating gas-based sensors, compared to their solid-state counterparts, are also briefly discussed. Overall, the monograph underscores the potential of second-generation quantum sensors, particularly those based on NV centers, to be the first scalable, high-volume quantum devices on the market, with applications spanning various fields due to their high sensitivity and room-temperature operation.
Solid-state quantum light sources offer a scalable pathway for interfacing stationary spin qubits with flying photonic qubits, forming the backbone of future quantum networks. Telecom-band spin-photonic qubits, operating in the 1260-1675 nm wavelength range, are particularly well-suited for long-distance quantum communication due to minimal loss in standard optical fibers. Achieving scalability, however, hinges on fulfilling several stringent criteria: coherent spin-state control, deterministic and indistinguishable single-photon emission, and integration with nanophotonic structures that enhance radiative properties, such as lifetime, coherence, and photon indistinguishability. This study explores the state-of-the-art spin-photonic qubits across solid-state platforms, including diamond color centers, silicon carbide defect centers, quantum dots, and two-dimensional materials. Special attention is given to silicon-based emitters, particularly G, T, C- and Ci-centers, which promise monolithic integration with complementary metal-oxide-semiconductor (CMOS) technology and telecom-band operation. We classify these systems based on spin-photon interface availability, CMOS process compatibility, and emitter scalability. We also discuss recent advances in cavity quantum electrodynamics (cQED), including Purcell enhancement and quality factor engineering in integrated photonic (circuits) environments. The work highlights emerging demonstrations of quantum networking over metropolitan scales and outlines the trajectory toward chip-scale quantum photonic integrated circuits (QPICs). It combines deterministic emitter creation, coherent spin manipulation, and quantum information processing. These developments pave the way for global quantum networks, enabling secure communication, distributed quantum computing, and quantum-enhanced sensing.
This talk will focus on the development of material platforms and physical mechanisms for high-fidelity control, storage, and transmission of quantum information. In particular, emerging quantum materials - novel diamond impurities - featuring long-lived, optically addressable quantum states are promising candidates fulfilling most of these requirements. We will discuss possible mechanisms for efficient interfacing of these novel solid-state qubits, in particular allowing for high-fidelity quantum-state transduction to superconducting qubits or to the long-lived nuclear spins. Finally, the physical phenomena enabling local quantum control in these materials, including strain-mediated or optically mediated state-transfer and two-qubit gates, will be discussed.