Projective measurement of single electron and nuclear spins has evolved from a gedanken experiment to a problem relevant for applications in atomic-scale technologies like quantum computing. Although several approaches allow for detection of a spin of single atoms and molecules, multiple repetitions of the experiment that are usually required for achieving a detectable signal obscure the intrinsic quantum nature of the spin's behavior. We demonstrated single-shot, projective measurement of a single nuclear spin in diamond using a quantum nondemolition measurement scheme, which allows real-time observation of an individual nuclear spin's state in a room-temperature solid. Such an ideal measurement is crucial for realization of, for example, quantum error correction protocols in a quantum register.
Devices that harness the laws of quantum physics hold the promise for information processing that outperforms their classical counterparts, and for unconditionally secure communication 1 . However, in particular, implementations based on condensed-matter systems face the challenge of short coherence times. Carbon materials 2,3 , particularly diamond 4-6 , however, are suitable for hosting robust solid-state quantum registers, owing to their spin-free lattice and weak spin-orbit coupling. Here we show that quantum logic elements can be realized by exploring long-range magnetic dipolar coupling between individually addressable single electron spins associated with separate colour centres in diamond. The strong distance dependence of this coupling was used to characterize the separation of single qubits (98±3 Å) with an accuracy close to the value of the crystal-lattice spacing. Our demonstration of coherent control over both electron spins, conditional dynamics, selective readout as well as switchable interaction should open the way towards a viable room-temperature solid-state quantum register. As both electron spins are optically addressable, this solid-state quantum device operating at ambient conditions provides a degree of control that is at present available only for a few systems at low temperature.One of the greatest challenges in quantum information technology is to build a room-temperature scalable quantum processor 7 . Isolated electron and nuclear spins in solids are considered to be among the most promising candidates for qubits in that respect 3,8 . Several benchmark experiments including entanglement and elements of quantum memory 9 have been achieved with spin ensembles, but ultimate functionality requires encoding quantum information into single spins. This however creates serious challenges in readout, addressing and nano-engineering single-spin arrays. The availability of photon-assisted single-spin readout 10,11 and the possibility to create single defects by ion implantation 12,13 make nitrogen-vacancy defects in diamond one of the most promising candidates in this respect. Paramagnetic nuclei in the vicinity of the electron spin can be used as auxiliary qubits with even more favourable relaxation properties 14 . As a consequence, coherence between electron and nuclear spin qubits has been exploited for showing all basic elements of a room-temperature quantum register 5,[15][16][17] . The size of these registers however is limited to a few quantum bits owing to the limited number of nuclear spins that can be addressed in frequency space 15,18 . A critical step towards scalability is to develop a technique enabling mutual coupling of individual optically addressable quantum systems. The system used in this study is a pair of single electron spins associated with separate nitrogen-vacancy defects in diamond. A single defect consists of a substitutional nitrogen atom in the diamond lattice and an adjacent vacancy (Fig. 1a,b). The electron spin triplet ground state of the defect shows a spin-depen...
The nitrogen-vacancy (NV) center in diamond is supposed to be a building block for quantum computing and nanometer-scale metrology at ambient conditions. Therefore, precise knowledge of its quantum states is crucial. Here, we experimentally show that under usual operating conditions the NV exists in an equilibrium of two charge states [70% in the expected negative (NV-) and 30% in the neutral one (NV0)]. Projective quantum nondemolition measurement of the nitrogen nuclear spin enables the detection even of the additional, optically inactive state. The nuclear spin can be coherently driven also in NV0 (T1≈90 ms and T2≈6 μs).
We present the realization of a combined trapped-ion and optical cavity system, in which a single Yb + ion is confined by a micron-scale ion trap inside a 230 µm-long optical fiber cavity. We characterize the spatial ion-cavity coupling and measure the ion-cavity coupling strength using a cavity-stimulated Λ-transition. Owing to the small mode volume of the fiber resonator, the coherent coupling strength between the ion and a single photon exceeds the natural decay rate of the dipole moment. This system can be integrated into ion-photon quantum networks and is a step towards cavity quantum-electrodynamics (cavity-QED) based quantum information processing with trapped ions.Trapped atomic ions play an important role in studies of small, isolated quantum systems, for example in quantum information processing and precision metrology. Aside from the long achievable coherence times, their success is largely based on the excellent manipulation and interrogation possibilities of their internal quantum states, which are usually performed by optical means. In order to employ the outstanding properties of trapped ions for future applications such as cavity-QED based quantum computers [1] or quantum network nodes [2][3][4], strong coupling between a single ion and a single photon is a prerequisite, i.e., the coherent coupling strength must exceed the decoherence rate of the atomic dipole moment. Unlike for neutral atoms [5,6] and solid-state emitters, such as quantum dots [7] or Cooper pairs [8], this strong coupling regime has not yet been reached for a single trapped ion despite decade-long efforts [9][10][11][12][13][14][15].The route to achieve strong light-matter coupling employs the principles of cavity-QED; a resonator changes the mode structure of the vacuum electromagnetic field in order to strongly enhance coupling to one photon mode. The coupling strength g between a single emitter and a single-photon mode depends on the mode-volume V of the cavity and on the electric dipole moment d of the transition, g ∝ d/ √ V . Owing to the large mode volumes of the cavities used in previous experiments [9][10][11][12][13][14][15], the coherent single-photon coupling rate g has been inferior to the decay rate Γ of the atomic dipole moment. The main restriction has been that the crucial ingredient to achieve strong coupling, namely placing the ion near dielectric mirror surfaces which are necessary to form an optical cavity, has been found to severely compromise the performance of a Paul trap [16]. For sizing down both the mode-volume and the amount of dielectric material, the development of cavities based on optical fibers [17] has opened a new perspective, also with respect to the integration of optical elements into microchip-based ion traps. Optical fiber cavities offer significantly smaller radii of curvature of the mirrors, which lead to a small waist of the field mode inside the optical cavity. Recently, significant experimental efforts have been devoted to integrating optical fibers with ion traps for efficient light c...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.