Abstract
Conventional nonlinear spectroscopy, which use classical probes, can only access a limited set of correlations in a quantum system. Here we demonstrate that quantum nonlinear spectroscopy, ...in which a quantum sensor and a quantum object are first entangled and the sensor is measured along a chosen basis, can extract arbitrary types and orders of correlations in a quantum system. We measured fourth-order correlations of single nuclear spins that cannot be measured in conventional nonlinear spectroscopy, using sequential weak measurement via a nitrogen-vacancy center in diamond. The quantum nonlinear spectroscopy provides fingerprint features to identify different types of objects, such as Gaussian noises, random-phased AC fields, and quantum spins, which would be indistinguishable in second-order correlations. This work constitutes an initial step toward the application of higher-order correlations to quantum sensing, to examining the quantum foundation (by, e.g., higher-order Leggett-Garg inequality), and to studying quantum many-body physics.
The silicon-vacancy centre ( ) in diamond has exceptional spectral properties for single-emitter quantum information applications. Most of the fluorescence is concentrated in a strong zero phonon ...line (ZPL), with a weak phonon sideband extending for 100 nm that contains several clear features. We demonstrate that the ZPL position can be used to reliably identify the silicon isotope present in a single centre. This is of interest for quantum information applications since only the 29Si isotope has nuclear spin. In addition, we show that the sharp 64 meV phonon peak is due to a local vibrational mode of the silicon atom. The presence of a local mode suggests a plausible origin of the measured isotopic shift of the ZPL.
Magnetic field sensors that exploit quantum effects have shown that they can outperform classical sensors in terms of sensitivity enabling a range of novel applications in future, such as a brain ...machine interface. Negatively charged nitrogen‐vacancy (NV) centers in diamond have emerged as a promising high sensitivity platform for measuring magnetic fields at room temperature. Transferring this technology from laboratory setups into products and applications, the total size of the sensor, the overall power consumption, and the costs need to be reduced and optimized. Here, a fiber‐based NV magnetometer featuring a complete integration of all functional components is demonstrated without using any bulky laboratory equipment. This integrated prototype allows portable measurement of magnetic fields with a sensitivity of 344 pT Hz−1/2.
Negatively charged nitrogen‐vacancy centers in diamond are a promising candidate for high sensitive magnetometers enabling wide range of applications. Transferring this technology into products, this sensor needs to be miniaturized and integrated such that it can be portably used without the requirement of bulky laboratory equipment. A portable prototype of a fiber‐integrated magnetometer with sub‐nanotesla sensitivity is demonstrated.
A versatile biopolymer platform for advancing nanodiamonds (NDs) as unique magnetooptic materials for biomedical applications is presented here. Precision biopolymer coatings are designed by chemical ...reprogramming the functionalities of serum albumin via a straightforward synthesis protocol. Such biopolymers offer high biocompatibility and precise modification with various functional entities due to the large number of available reactive amino acid residues. Premodification of these biopolymers provides a convenient approach to customized surface functionalization of NDs. As an example, the anticancer drug doxorubicin (DOX) is conjugated to the biopolymer with high reproducibility and full characterization. The biopolymer‐coated NDs reveal excellent colloidal stabilities in all physiological media tested, even after loading with high numbers of hydrophobic DOX. The intracellular distribution of NDs and DOX is analyzed in living cells by recording the fluorescence spectra in different cellular compartments, which proves efficient intracellular release of DOX from the carrier. Studies in vitro as well as in a chick tumor xenograft model reveal efficient antitumor effects. The facile and versatile biopolymer coating strategy reported herein will greatly accelerate the availability of customized NDs with reliable and reproducible features to exploit their great potential in single molecular bioimaging, in vivo biosensing, and high resolution quantum optics.
A versatile biopolymer platform for advancing fluorescent nanodiamonds as unique magnetooptic materials for biomedical applications is reported. The biopolymer coatings are designed by chemical reprogramming the functionalities of albumin, which offer high biocompatibility and precise modification with various functional entities. The biopolymer coated nanodiamonds reveal excellent colloidal stabilities even after loading high numbers of hydrophobic doxorubicin for drug delivery.
Abstract
Quantum sensors are known for their high sensitivity in sensing applications. However, this sensitivity often comes with severe restrictions on other parameters which are also important. ...Examples are that in measurements of arbitrary signals, limitation in linear dynamic range could introduce distortions in magnitude and phase of the signal. High frequency resolution is another important feature for reconstructing unknown signals. Here, we demonstrate a distortion-free quantum sensing protocol that combines a quantum phase-sensitive detection with heterodyne readout. We present theoretical and experimental investigations using nitrogen-vacancy centers in diamond, showing the capability of reconstructing audio frequency signals with an extended linear dynamic range and high frequency resolution. Melody and speech based signals are used for demonstrating the features. The methods could broaden the horizon for quantum sensors towards applications, e.g. telecommunication in challenging environment, where low-distortion measurements are required at multiple frequency bands within a limited volume.
With optical/electronic devices of the next generation in mind, we provide a guideline for the growth of homoepitaxial diamond films that possess higher crystalline quality, higher chemical purity, ...and a higher carbon isotopic ratio. A custom‐built microwave plasma‐assisted chemical vapor deposition system was constructed to achieve these requirements. To improve both the purity and crystalline quality of homoepitaxial diamond films, an advanced growth condition was applied: higher oxygen concentration in the growth ambient. Under this growth condition for high‐quality diamond, a thick diamond film of ≥30 μm was deposited reproducibly while maintaining high purity and a flat surface. Then, combining this advanced growth condition for non‐doped diamond with a unique doping technique that provides parts‐per‐billion order doping, single‐color centers of either nitrogen‐vacancy or silicon‐vacancy centers that show excellent properties were formed. The new idea of using these color centers as a probe for detecting tiny amounts of impurities was presented. These advanced growth and characterization techniques are expected to open up new fields of diamond research that require extremely low‐impurity concentration, for use in power devices and quantum information devices.
Teraji et al. present recent research progress achieved in high‐quality and high‐purity diamond growth. To improve both the purity and crystalline quality of homoepitaxial diamond films, an advanced growth condition was applied: higher oxygen concentration in the growth ambient. With increasing film thickness, morphological patterns (A and B in the images) move to the crystallographic off direction of the substrate. Isotopic enrichment and extremely low concentration doping, which are linked to the study of quantum information devices, are also discussed in this Feature Article.
We investigated the charge state stability and coherence properties of near-surface single nitrogen vacancy (NV) centers in 12C-enriched diamond for potential use in nanoscale magnetic field sensing ...applications. The stability of charge states in negatively charged NV centers (NV−) was evaluated using one of the pulsed optically detected magnetic resonance measurements, Rabi oscillation measurements. During the accumulation of Rabi oscillations, an unstable shallow NV− was converted to a neutral state. As a result, the contrast of Rabi oscillations degraded, depending on charge state stability. We stabilized the NV− state of very shallow NV centers (∼2.6 ± 1.1 nm from the surface) created by 1.2 keV nitrogen ion implantation by diamond surface modification, UV/ozone exposure, and oxygen annealing. This improvement indicates that we can suppress the upward surface band bending and surface potential fluctuations through Fermi level pinning originating from oxygen-terminated diamond surfaces.
Abstract
A nitrogen vacancy (NV) center in diamond is known as a solid-state spin qubit at room temperature. NV centers coherently coupled by dipole–dipole interactions have a potential to accomplish ...quantum registers at room temperature. This study reports to develop a phthalocyanine ion implantation technique to fabricate multiple dipole-coupled NV centers. Photon counts and optically detected magnetic resonance spectra show that up to four NV centers were successfully created in a confocal spot. The histogram of photon counts is fitted by a Poisson distribution, and the ratio of multiple NV spots suggests the potential for a five NV centers creation.
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