Single Atom Detection Research Articles

N -body antibunching in a degenerate Fermi gas of He*3 atoms

A key set of observables for investigating quantum systems are the n-body correlation functions, which provide a powerful tool for experimentally determining coherence and directly probing the many-body wave function. While the (bosonic) correlations of photonic systems are well explored, the correlations present in matter-wave systems, particularly for fermionic atoms, are still an emerging field. In this work, we use the unique single-atom detection properties of He*3 atoms to perform simultaneous measurements of the n-body quantum correlations, up to the fifth order, of a degenerate Fermi gas. In a direct demonstration of the Pauli exclusion principle, we observe clear antibunching at all orders and find good agreement with predicted correlation volumes. Our results pave the way for using correlation functions to probe some of the rich physics associated with fermionic systems. Published by the American Physical Society 2024

Scalable Multipartite Entanglement Created by Spin Exchange in an Optical Lattice.

Ultracold atoms in optical lattices form a competitive candidate for quantum computation owing to the excellent coherence properties, the highly parallel operations over spins, and the ultralow entropy achieved in qubit arrays. For this, a massive number of parallel entangled atom pairs have been realized in superlattices. However, the more formidable challenge is to scale up and detect multipartite entanglement, the basic resource for quantum computation, due to the lack of manipulations over local atomic spins in retroreflected bichromatic superlattices. In this Letter, we realize the functional building blocks in quantum-gate-based architecture by developing a cross-angle spin-dependent optical superlattice for implementing layers of quantum gates over moderately separated atoms incorporated with a quantum gas microscope for single-atom manipulation and detection. Bell states with a fidelity of 95.6(5)% and a lifetime of 2.20±0.13 s are prepared in parallel, and then connected to multipartite entangled states of one-dimensional ten-atom chains and two-dimensional plaquettes of 2×4 atoms. The multipartite entanglement is further verified with full bipartite nonseparability criteria. This offers a new platform toward scalable quantum computation and simulation.

Observation of in-plane oriented Guinier-Preston zones in Al-Cu

Known for a long time, the first metastable precipitate which forms in Al-Cu alloys during natural ageing are the so-called Guinier-Preston zones (GPZ), platelets of Cu on {100} planes of only one atomic layer thickness. Only with the development of aberration corrected transmission electron microscopes (TEM), direct observation and imaging of these platelets was possible, but with the restriction, that only edge view was possible. Here we show that under appropriate conditions an observation in a plan-view is possible and allows further insight into the shape and arrangement of the GP-zones. Furthermore, this demonstrates that single atom detection of one Cu atom in a column of Al atoms is possible.

Automated Image Analysis for Single-Atom Detection in Catalytic Materials by Transmission Electron Microscopy

Single-atom catalytic sites may have existed in all supported transition metal catalysts since their first application. Yet, interest in the design of single-atom heterogeneous catalysts (SACs) only really grew when advances in transmission electron microscopy (TEM) permitted direct confirmation of metal site isolation. While atomic-resolution imaging remains a central characterization tool, poor statistical significance, reproducibility, and interoperability limit its scope for deriving robust characteristics about these frontier catalytic materials. Here, we introduce a customized deep-learning method for automated atom detection in image analysis, a rate-limiting step toward high-throughput TEM. Platinum atoms stabilized on a functionalized carbon support with a challenging irregular three-dimensional morphology serve as a practically relevant test system with promising scope in thermo- and electrochemical applications. The model detects over 20,000 atomic positions for the statistical analysis of important properties for establishing structure-performance relations over nanostructured catalysts, like the surface density, proximity, clustering extent, and dispersion uniformity of supported metal species. Good performance obtained on direct application of the model to an iron SAC based on carbon nitride demonstrates its generalizability for single-atom detection on carbon-related materials. The approach establishes a route to integrate artificial intelligence into routine TEM workflows. It accelerates image processing times by orders of magnitude and reduces human bias by providing an uncertainty analysis that is not readily quantifiable in manual atom identification, improving standardization and scalability.

Evolution in X-ray analysis from micro to atomic scales in aberration-corrected scanning transmission electron microscopes.

X-ray analysis is one of the most robust approaches to extract quantitative information from various materials and is widely used in various fields ever since Raimond Castaing established procedures to analyze electron-induced X-ray signals for materials characterization '70 years ago'. The recent development of aberration-correction technology in a (scanning) transmission electron microscopes (S/TEMs) offers refined electron probes below the Å level, making atomic-resolution X-ray analysis possible. In addition, the latest silicon drift detectors allow complex detector arrangements and new configurational designs to maximize the collection efficiency of X-ray signals, which make it feasible to acquire X-ray signals from single atoms. In this review paper, recent progress and advantages related to S/TEM-based X-ray analysis will be discussed: (i) progress in quantification for materials characterization including the recent applications to light element analysis, (ii) progress in analytical spatial resolution for atomic-resolution analysis and (iii) progress in analytical sensitivity toward single-atom detection and analysis in materials. Both atomic-resolution analysis and single-atom analysis are evaluated theoretically through multislice-based calculation for electron propagation in oriented crystalline specimen in combination with X-ray spectrum simulation.

Quantum gas microscopy for single atom and spin detection

A particular strength of ultracold quantum gases are the versatile detection methods available. Since they are based on atom-light interactions, the whole quantum optics toolbox can be used to tailor the detection process to the specific scientific question to be explored in the experiment. Common methods include time-of-flight measurements to access the momentum distribution of the gas, the use of cavities to monitor global properties of the quantum gas with minimal disturbance and phase-contrast or high-intensity absorption imaging to obtain local real space information in high-density settings. Even the ultimate limit of detecting each and every atom locally has been realized in two-dimensions using so-called quantum gas microscopes. In fact, these microscopes not only revolutionized the detection, but also the control of lattice gases. Here we provide a short overview of this technique, highlighting new observables as well as key experiments that have been enabled by quantum gas microscopy.

Development of Highly Sensitive Raman Spectroscopy for Subnano and Single-Atom Detection

Direct detection and characterisation of small materials are fundamental challenges in analytical chemistry. A particle composed of dozens of metallic atoms, a so-called subnano-particle (SNP), and a single-atom catalyst (SAC) are ultimate analysis targets in terms of size, and the topic is now attracting increasing attention as innovative frontier materials in catalysis science. However, characterisation techniques for the SNP and SAC adsorbed on substrates requires sophisticated and large-scale analytical facilities. Here we demonstrate the development of an ultrasensitive, laboratory-scale, vibrational spectroscopic technique to characterise SNPs and SACs. The fine design of nano-spatial local enhancement fields generated by the introduction of anisotropic stellate-shaped signal amplifiers expands the accessibility of small targets on substrates into evanescent electromagnetic fields, achieving not only the detection of isolated small targets but also revealing the effects of intermolecular/interatomic interactions within the subnano configuration under actual experimental conditions. Such a development of “in situ subnano spectroscopy” will facilitate a comprehensive understanding of subnano and SAC science.

Trapping, detection and manipulation of single Rb atoms in an optical dipole trap using a long-focus objective lens

Single alkali-metal atoms in arrays of optical dipole traps represent a quantum register that can be used for quantum computation and simulation based on short-term Rydberg excitations, which switch the interactions between qubits. To load single atoms into optical dipole traps and then detect them by resonance fluorescence, lenses with a large numerical aperture (NA > 0.5) inside a vacuum chamber and expensive EMCCD cameras are commonly used. We present our recent experimental results on demonstrating the trapping of single 87Rb atoms using a long-focus objective lens with a low numerical aperture (NA = 0.172) placed outside the vacuum chamber, and detecting single atoms with a low-cost sCMOS camera. We also present our current results on implementing a single-qubit gate based on optical pumping and subsequent microwave transition between two hyperfine sublevels of a single 87Rb atom with fidelity near 95%.

Single-site-resolved imaging of ultracold atoms in a triangular optical lattice

We demonstrate single-site-resolved fluorescence imaging of ultracold 87Rb atoms in a triangular optical lattice by employing Raman sideband cooling. Combining a Raman transition at the D1 line and a photon scattering through an optical pumping of the D2 line, we obtain images with low background noise. The Bayesian optimisation of 11 experimental parameters for fluorescence imaging with Raman sideband cooling enables us to achieve single-atom detection with a high fidelity of (96.3 ± 1.3)%. Single-atom and single-site resolved detection in a triangular optical lattice paves the way for the direct observation of spin correlations or entanglement in geometrically frustrated systems.

Visualizing single atom dynamics in heterogeneous catalysis using analytical in situ environmental scanning transmission electron microscopy.

Progress is reported in analytical in situ environmental scanning transmission electron microscopy (ESTEM) for visualizing and analysing in real-time dynamic gas-solid catalyst reactions at the single-atom level under controlled reaction conditions of gas environment and temperature. The recent development of the ESTEM advances the capability of the established ETEM with the detection of fundamental single atoms, and the associated atomic structure of selected solid-state heterogeneous catalysts, in catalytic reactions in their working state. The new data provide improved understanding of dynamic atomic processes and reaction mechanisms, in activity and deactivation, at the fundamental level; and in the chemistry underpinning important technological processes. The benefits of atomic resolution-E(S)TEM to science and technology include new knowledge leading to improved technological processes, reductions in energy requirements and better management of environmental waste. This article is part of a discussion meeting issue 'Dynamic in situ microscopy relating structure and function'.

Doublon-Hole Correlations and Fluctuation Thermometry in a Fermi-Hubbard Gas.

We report on the single atom and single site-resolved detection of the total density in a cold atom realization of the 2D Fermi-Hubbard model. Fluorescence imaging of doublons is achieved by splitting each lattice site into a double well, thereby separating atom pairs. Full density readout yields a direct measurement of the equation of state, including direct thermometry via the fluctuation-dissipation theorem. Site-resolved density correlations reveal the Pauli hole at low filling, and strong doublon-hole correlations near half filling. These are shown to account for the difference between local and nonlocal density fluctuations in the Mott insulator. Our technique enables the study of atom-resolved charge transport in the Fermi-Hubbard model, the site-resolved observation of molecules, and the creation of bilayer Fermi-Hubbard systems.

Evaluation of Confocal X-ray Analysis for Single-Atom Detection in a Thin Specimen by an Advanced Analytical Electron Microscope

Journal Article Evaluation of Confocal X-ray Analysis for Single-Atom Detection in a Thin Specimen by an Advanced Analytical Electron Microscope Get access Masashi Watanabe, Masashi Watanabe Lehigh University, Bethlehem, Pennsylvania, United States Search for other works by this author on: Oxford Academic Google Scholar Ray Egerton Ray Egerton Department of Physics, University of Alberta, Edmonton, Alberta, Canada Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 1512–1514, https://doi.org/10.1017/S143192762001836X Published: 01 August 2020

Methods for Gibbs triple junction excess determination: Ti segregation in $$\hbox {CoSi}_2$$ thin film

Methods are presented determining the Gibbs triple junction excess ( $${\varGamma }^{\text{TJ}}$$ ) of solute segregation in polycrystalline materials from single atom counting in 3D volumes. One method bases on cumulative profile analysis, while two further methods use radial integration of solute atoms. The methods are demonstrated and compared on simulated model volumes which include three grain boundaries joining together at a triple junction with set values for Gibbs grain boundary and triple junction excess. An experimental technique that provides 3D volumes with single atom detection and spatial resolution close to atomic scale is atom probe tomography. An atom probe tomography volume of a $$\hbox {CoSi}_2$$ thin film that contains three grain boundaries and a triple junction has been acquired. Ti segregation is found qualitatively at the grain boundaries and triple junction. The quantification of the Ti excess at the investigated $$\hbox {CoSi}_2$$ triple junction reveals for the three introduced methods positive Gibbs triple junction excess values. It demonstrates that there is an excess of Ti at $$\hbox {CoSi}_2$$ triple junctions and provides opportunities for its quantification.

Trapping and detection of single rubidium atoms in an optical dipole trap using a long-focus objective lens

The trapping of single atoms in optical dipole traps is widely used in experiments on the implementation of quantum processors based on neutral atoms, and studying interatomic interactions. Typically, such experiments employ lenses with a large numerical aperture (NA > 0.5), highly sensitive EMCCD cameras, or photon counters. In this work, we demonstrate trapping and detection of single rubidium atoms using a long-focus objective lens with a numerical aperture NA = 0.172 and a FLir Tau CNV sCMOS camera.

Robust ultraclean atomically thin membranes for atomic-resolution electron microscopy

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.

Interference effects due to nuclear motion of the hydrogen molecule

We show that two-particle interferences can be used to probe the nuclear motion in a doubly excited hydrogen molecule. The dissociation of molecular hydrogen by electron impact involves several decay channels, associated with different molecular rotational states, which produce quantum interferences in the detection of the atomic fragments. Thanks to the correlations between the angular momentum and the vibrational states of the molecule, the fragments arising from each dissociation channel carry out a phase shift which is a signature of the molecule rotation. These phase shifts, which cannot be observed in a single-atom detection scheme, may be witnessed under realistic experimental conditions in a time-of-flight coincidence measurement. We analyze the interferences arising from the two lowest-energy rotational states of a parahydrogen molecule. Our result shows the relevance of two-fragment correlations to track the molecular rotation.

Single Atom Detection from Low Contrast-to-Noise Ratio Electron Microscopy Images.

Single atom detection is of key importance to solving a wide range of scientific and technological problems. The strong interaction of electrons with matter makes transmission electron microscopy one of the most promising techniques. In particular, aberration correction using scanning transmission electron microscopy has made a significant step forward toward detecting single atoms. However, to overcome radiation damage, related to the use of high-energy electrons, the incoming electron dose should be kept low enough. This results in images exhibiting a low signal-to-noise ratio and extremely weak contrast, especially for light-element nanomaterials. To overcome this problem, a combination of physics-based model fitting and the use of a model-order selection method is proposed, enabling one to detect single atoms with high reliability.

Fluorescence detection of single lithium atoms in an optical lattice using Doppler-cooling beams

We demonstrate in situ fluorescence detection of 7Li atoms in a 1D optical lattice with single atom precision. Even though illuminated lithium atoms tend to boil out, when the lattice is deep, red-detuned probe beams without extra cooling retain the atoms while producing sufficient fluorescent photons for detection. When the depth of the potential well at an antinode is 1.6 mK, an atom remains trapped for longer than 20 s while scattering probe photons at the rate of 5.3 × 104 s−1. We propose a simple model that describes the dependence of the lifetime of an atom on well depth. When the number of trapped atoms is reduced, a clear stepwise change in integrated fluorescence is observed, indicating the detection of a single atom. The presence or absence of an atom is determined within 300 ms with an error of less than 5 × 10−4 at a photon-collecting efficiency of 1%, which is limited by the small numerical aperture.

Zeptomolar detection of Hg2 + based on label-free electrochemical aptasensor: One step closer to the dream of single atom detection

An ultra-sensitive and highly selective electrochemical label-free aptasensor is proposed for the quantitation of Hg2+ based on the hybridization/dehybridization of double-stranded DNA (dsDNA) on a gold electrode. Thiol-substituted single-stranded DNA (ssDNA) is self-assembled on the gold electrode surface through the SAu interaction. The hybridization of ssDNA with complementary DNA (cDNA) and the consequences of dehybridization in the presence of mercury ions are followed through differential pulse voltammetry (DPV) responses using a [Fe(CN)6]3−/4− redox probe. The formation of a thymine–Hg2+–thymine (T–Hg2+–T) complex is the key to producing a highly selective and sensitive aptasensor for Hg2+ determination. Specifically, the present electrochemical aptasensor is able to quantify Hg2+ ions in concentrations from 5zeptomolar (zM) to 55picomolar (pM) with a limit of detection of 0.6zM, close to the dream of single atom detection, without requiring a complicated procedure or expensive materials.

Single-atom detection of light elements: Imaging or spectroscopy?

Single-atom imaging and spectroscopy at a lower accelerating voltage (~60kV) has been largely facilitated by the development of aberration correctors for transmission electron microscopy (TEM)/ scanning TEM (STEM). Such an STEM condition will reduce beam damage and has therefore been demonstrated capable of detecting individual atoms of light elements including B, C, and N in mono-layered materials. However, other light elements such as Li, O, or F are still difficult to visualise as individual atoms by using conventional STEM/TEM imaging because their extremely weak contrast can be often smeared out by the other atoms nearby. In this paper, we demonstrate the successful detection of these ‘hardly visible’ atoms in the spectroscopy mode.