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Strongly anisotropic spin relaxation in the neutral silicon vacancy center in diamond
摘要： Color centers in diamond are a promising platform for quantum technologies, and understanding their interactions with the environment is crucial for these applications. We report a study of spin-lattice relaxation (T1) of the neutral charge state of the silicon vacancy center in diamond. Above 20 K, T1 decreases rapidly with a temperature-dependence characteristic of an Orbach process and is strongly anisotropic with respect to magnetic-field orientation. As the angle of the magnetic field is rotated relative to the symmetry axis of the defect, T1 is reduced by over three orders of magnitude. The electron spin coherence time (T2) follows the same temperature dependence but is drastically shorter than T1. We propose that these observations result from phonon-mediated transitions to a low-lying excited state that are spin conserving when the magnetic field is aligned with the defect axis, and we discuss likely candidates for this excited state.
关键词： anisotropy,spin relaxation,quantum technologies,diamond,silicon vacancy center,Orbach process
更新于2025-09-23 15:23:52
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[Springer Theses] Quantum Confined Excitons in 2-Dimensional Materials || Introduction: 2d-Based Quantum Technologies
摘要： Framed within the growing giant of quantum technologies, with billions in expenditure world-wide and rapidly growing, we harness the exciting physics and technological promise of 2-dimensional materials to create atomically-thin quantum devices capable of emitting single photons and capturing single spins. In this thesis we present the alliance of 2d and quantum information technology - the first steps towards hybrid light-matter quantum networks set in a low power, scalable on-chip platform.
关键词： quantum technologies,single spins,single photons,quantum networks,2-dimensional materials
更新于2025-09-23 15:21:21
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Multi-Qubit Registers of Individually Addressable Solid-State Defect Centers
摘要： Mesoscopic ensembles of qubits offer a platform for near-term applications in quantum technologies, as well as for studying many-body physics. Key in exploiting these systems is the ability to coherently control constituent qubits in a manner that leaves the quantum states of neighboring qubits unperturbed. Atom-like emitters in solids have emerged as a promising platform for computing, communications, and sensing. In particular, their long coherence times, coherent optical transitions, and the ability to couple to nearby long-lived nuclear spins make them excellent candidates for building medium-scale registers of coupled qubits. Here, we present progress towards producing and controlling such individually addressable ensembles. Our approach relies on the natural inhomogeneous distribution of optical transitions for solid-state color centers. This distribution allows us to excite individual centers even in tightly-grouped clusters. With this, we first demonstrate super-resolution localization and readout of individual nitrogen vacancy (NV) centers in diamond. We probe a system of three NV centers, demonstrating localization with a mean precision of 0.74 nm. While super-resolution imaging of NV centers has been achieved with other techniques, our approach uniquely allows for individual readout of single NVs in a cluster in a manner that maintains the states of nearby spins. We perform simultaneous control of two spin populations in a cluster of NVs, demonstrating preservation of coherence of one population during the optical readout of another. Lastly, we discuss recent work towards scalable creation of such clusters and techniques for producing systems of coupled spins with various defect centers.
关键词： spin-spin coupling,quantum technologies,super-resolution localization,qubits,solid-state color centers,nitrogen vacancy centers,many-body physics,atom-like emitters
更新于2025-09-16 10:30:52
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Large‐Scale Fabrication of Highly Emissive Nanodiamonds by Chemical Vapor Deposition with Controlled Doping by SiV and GeV Centers from a Solid Source
摘要： A new strategy to produce loose chemical vapor deposited nanodiamonds (ND) without the need of a seeded substrate, and that are intentionally doped by silicon vacancy and GeV centers from a solid source is presented. The addition of a low amount of gases such as N2 or O2 during growth is used as a control knob to finely tune the emission intensity of embedded color centers. NDs with a high brightness and a controllable amount of group IV color centers are eventually obtained. Their optical properties at low temperature indicate that this approach can usefully produce dispersed NDs that can deliver suitable optical performance for quantum technologies.
关键词： nanodiamond,color centers,quantum technologies,spectroscopy,chemical vapor deposition
更新于2025-09-12 10:27:22
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Optical remote control of a single charge qubit
摘要： Both the electron transport-based qubits, implemented through double quantum dots, and the sources of indistinguishable single photons like self-assembled quantum dots are strong candidates for the implementation of quantum technologies, such as quantum computers and quantum repeaters. Here, we demonstrate a reliable way of coupling these two types of qubits, uncovering the possibility of controlling and reading out the population of the double quantum dot via optical excitation. It is also shown that, in spite of the decoherence mechanisms affecting the qubits, the entanglement between them is achievable and, consequently, the implementation of the suggested system in quantum technologies is feasible.
关键词： quantum technologies,quantum dots,entanglement,optical excitation,qubits
更新于2025-09-11 14:15:04
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Entanglement activation from quantum coherence and superposition
摘要： Quantum entanglement and coherence are two fundamental features of nature, arising from the superposition principle of quantum mechanics. While considered as puzzling phenomena in the early days of quantum theory, it is only very recently that entanglement and coherence have been recognized as resources for the emerging quantum technologies, including quantum metrology, quantum communication, and quantum computing. In this work we study the limitations for the interconversion between coherence and entanglement. We prove a fundamental no-go theorem, stating that a general resource theory of superposition does not allow for entanglement activation. By constructing a quantum controlled-NOT gate as a free operation, we experimentally show that such activation is possible within the more constrained framework of quantum coherence. By using recent results from coherence theory, we further show that the trace norm entanglement is not a strong entanglement monotone.
关键词： quantum technologies,entanglement activation,quantum entanglement,quantum coherence,trace norm entanglement,no-go theorem,superposition principle
更新于2025-09-09 09:28:46
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Two-level system damping in a quasi-one-dimensional optomechanical resonator
摘要： Nanomechanical resonators have demonstrated great potential for use as versatile tools in a number of emerging quantum technologies. For such applications, the performance of these systems is restricted by the decoherence of their fragile quantum states, necessitating a thorough understanding of their dissipative coupling to the surrounding environment. In bulk amorphous solids, these dissipation channels are dominated at low temperatures by parasitic coupling to intrinsic two-level system (TLS) defects; however, there remains a disconnect between theory and experiment on how this damping manifests in dimensionally reduced nanomechanical resonators. Here, we present an optomechanically mediated thermal ringdown technique, which we use to perform simultaneous measurements of the dissipation in four mechanical modes of a cryogenically cooled silicon nanoresonator, with resonant frequencies ranging from 3–19 MHz. Analyzing the device’s mechanical damping rate at fridge temperatures between 10 mK and 10 K, we demonstrate quantitative agreement with the standard tunneling model for TLS ensembles con?ned to one dimension. From these ?ts, we extract the defect density of states (P0 ～ 1?4 × 1044 J?1 m?3) and deformation potentials (γ ～ 1–2 eV), showing that each mechanical mode couples on average to less than a single thermally active defect at 10 mK.
关键词： Quantum technologies,Nanomechanical resonators,Optomechanical,Mechanical damping rate,Deformation potentials,Tunneling model,Defect density of states,Two-level system (TLS) defects,Silicon nanoresonator
更新于2025-09-09 09:28:46
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Delivering on a quantum promise
摘要： With the European Commission investing €1bn over 10 years in quantum technologies, Karl Svozil warns against overselling many of the initiative’s longer-term goals. Unlike modern-day politicians, scientists have great authority regarding the pursuit of truth. As a consequence, many members of the public – as well as political bodies and institutions – tend to uncritically take science as a matter of fact. Yet there are some occasions where the benefits and risks of science need to be communicated carefully. A striking example is nuclear energy and the bold claims made by some that nuclear-fission technology is “safe beyond doubt”. One only has to look at the nuclear power plants at Three Mile Island, Chernobyl and Fukushima to know that such claims can prove spurious. In a similar fashion, I believe that the alleged applications of quantum physics are, in some cases, being oversold to the public. The “quantum mechanics is magic” tour – expressed through European physicists’ “quantum manifesto” – has resulted in the European Commission launching a €1bn quantum-technologies flagship initiative in quantum technology. The campaign promises to deliver nothing less than a “second quantum revolution”.
关键词： quantum computing,quantum manifesto,quantum cryptography,quantum technologies,quantum revolution
更新于2025-09-04 15:30:14
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Entanglement certification from theory to experiment
摘要： Entanglement is an important resource for quantum technologies. There are many ways quantum systems can be entangled, ranging from the two-qubit case to entanglement in high dimensions or between many parties. Consequently, many entanglement quantifiers and classifiers exist, corresponding to different operational paradigms and mathematical techniques. However, for most quantum systems, exactly quantifying the amount of entanglement is extremely demanding, if at all possible. Furthermore, it is difficult to experimentally control and measure complex quantum states. Therefore, there are various approaches to experimentally detect and certify entanglement when exact quantification is not an option. The applicability and performance of these methods strongly depend on the assumptions regarding the involved quantum states and measurements, in short, on the available prior information about the quantum system. In this Review, we discuss the most commonly used quantifiers of entanglement and survey the state-of-the-art detection and certification methods, including their respective underlying assumptions, from both a theoretical and an experimental point of view.
关键词： Entanglement classifiers,Quantum technologies,Entanglement quantifiers,Experimental detection,Quantum states,Certification methods,Entanglement
更新于2025-09-04 15:30:14