Abstract The development of single‐platform qubits, predominant for most of the last few decades, has driven the progress of quantum information technologies but also highlighted the limitations of various platforms. Some inherent issues, such as charge/spin noise in materials hinder certain platforms, while increased decoherence upon attempts to scale up severely impacts qubit quality and coupling on others. In addition, a universal solution for coherent information transfer between quantum systems remains lacking. By combining one or more qubit platforms, one could potentially create new hybrid platforms that might alleviate significant issues that current single‐platform qubits suffer from, and in some cases, even facilitate the conversion of static to flying qubits on the same hybrid platform. While nascent, this is an area of rising importance that could shed new light on robust and scalable qubit development and provide new impetus for research directions. Here, the requirements for hybrid systems are defined with artificial atoms in the solid state, exemplified with systems that are proposed or attempted, and conclude with the outlook for such hybrid quantum systems.
Abstract The development of single‐platform qubits, predominant for most of the last few decades, has driven the progress of quantum information technologies but also highlighted the limitations of various platforms. Some inherent issues, such as charge/spin noise in materials hinder certain platforms, while increased decoherence upon attempts to scale up severely impacts qubit quality and coupling on others. In addition, a universal solution for coherent information transfer between quantum systems remains lacking. By combining one or more qubit platforms, one could potentially create new hybrid platforms that might alleviate significant issues that current single‐platform qubits suffer from, and in some cases, even facilitate the conversion of static to flying qubits on the same hybrid platform. While nascent, this is an area of rising importance that could shed new light on robust and scalable qubit development and provide new impetus for research directions. Here, the requirements for hybrid systems are defined with artificial atoms in the solid state, exemplified with systems that are proposed or attempted, and conclude with the outlook for such hybrid quantum systems.
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.
Abstract As a foundational technology in quantum information science (QIS), the manipulation and detection of quantum spins enable precise control, opening new avenues for significant advancements. Early research focused on macroscopic ensemble quantum systems, where electron spin resonance is used to coherently address electron spins within different ensembles. However, the low initialization efficiency and readout sensitivity of such systems hinder their further development. Unlocking the full potential of quantum technology, it is essential to achieve single‐spin precision. Various quantum systems, including color centers, quantum dots, atoms, and molecules, have been demonstrated the capability for single‐spin manipulation. The successful control of spin quantum states in these systems through diverse techniques has paved the way for new ideas and boundless possibilities in QIS. This review provides a comprehensive overview of recent significant advances in the field and explores future development directions, aiming to shed light on the ongoing evolution of QIS.
Abstract Spanning a range of hardware platforms, the building-blocks of quantum processors are today sufficiently advanced to begin work on scaling-up these systems into complex quantum machines. A key subsystem of all quantum machinery is the interface between the isolated qubits that encode quantum information and the classical control and readout technology needed to operate them. As few-qubit devices are combined to construct larger, fault-tolerant quantum systems in the near future, the quantum-classical interface will pose new challenges that increasingly require approaches from the engineering disciplines in combination with continued fundamental advances in physics, materials and mathematics. This review describes the subsystems comprising the quantum-classical interface from the viewpoint of an engineer, experimental physicist or student wanting to enter the field of solid-state quantum information technology. The fundamental signalling operations of readout and control are reviewed for a variety of qubit platforms, including spin systems, superconducting implementations and future devices based on topological degrees-of-freedom. New engineering opportunities for technology development at the boundary between qubits and their control hardware are identified, transversing electronics to cryogenics.
Abstract Scalable quantum computing and communication systems strictly require the development of highly integrated quantum hardware. While prominent implementations like superconducting and semiconductor spin qubits show integration progress, their reliance on extreme cryogenic conditions raises substantial sustainability concerns, especially given global helium depletion. In contrast, solid-state quantum devices, such as nitrogen-vacancy (NV) centers, offer room-temperature operation. Although ensemble solid-state defects have been successfully utilized in quantum sensing, the realization of complex quantum registers requires highly precise arrays of single, coupled qubits. Currently, their practical integration into scalable multi-qubit arrays is fundamentally limited by the technical challenge of achieving deterministic, ultra-precise atomic injection at the angstrom scale. This Perspective examines the current state of solid-state quantum system integration, identifying recent advances and persistent bottlenecks, particularly focusing on the limitations of cooling ion sources based on Paul traps. We then propose a novel architecture combining established neutral-particle decelerator techniques with deterministic ionization to overcome these fundamental operational hurdles. This analysis aims to present a viable path for advanced integrated solid-state quantum platform development, fostering broader adoption and sustainable evolution.
As work progresses towards a useful quantum computer using various physical implementations, it seems likely that no single physical system can fully realize all necessary requirements for a large scale, interfaced, stable quantum computer. Instead, it seems various systems are more predisposed for use as computational qubits while others to acting as “flying” qubits. The nitrogen vacancy center in diamond is a physical system of numerous applications, of which significant interest has been towards the NV’s role in quantum computation. The center’s impressive spin coherence as well as its coupling to magnetic fields, strain fields and nuclear spins suggests the role of the NV in hybrid quantum systems will be critical. In this dissertation, I will report on progress made towards the use of the NV in various hybrid quantum systems, including the coupling of the NV between optical, microwave and strain fields.
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.