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A theoretical–experimental approach is proposed to convert the photoluminescence spectra of colloidal perovskite quantum dot ensembles into accurate estimates for their intrinsic particle size distribution functions. Two main problems were addressed and properly correlated: the size dependence of the first excitonic transition in a single cube-shaped quantum dot and the inhomogeneous broadening of the fluorescence line shape due to the size nonuniformity of the chemically prepared quantum dot suspension in addition to the single-dot homogeneous broadening. By applying the reported methodology to CsPbBr3 quantum dot samples belonging to the strong and intermediate confinement regimes, the calculated size distributions exhibited close agreement with those obtained from transmission electron microscopy, with precise estimates for the average particle size and standard deviation. Specifically for strongly confined ultrasmall CsPbBr3 quantum dots, the presented spectroscopic model for size distribution computation is based on a new analytical expression for the size-dependent bandgap, which was developed within the framework of the finite-depth square-well effective mass approximation accounting for band nonparabolicity effects. Such a quantum mechanical approach correctly predicts the expected transition to the intermediate confinement regime in sufficiently large quantum dots, which are traditionally described by the well-known bandgap equation in the infinite potential barrier limit with a spatially correlated electron–hole wavefunction and nonparabolic carrier effective masses. The proposed calculation scheme originates from general theoretical considerations so that it can be readily adapted to semiconductor quantum dots of many other systems, from all inorganic metal halides to hybrid perovskite materials, regardless of the adopted chemical synthesis route. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots are favorable candidates for quantum information processing due to their long coherence time and potential scalability. However, the calibration and characterization of interconnected quantum dot arrays have proven to be challenging tasks. One method to characterize the configuration of such an array involves using the Hubbard model. In this paper, we present an efficient characterization algorithm that efficiently extracts the Hubbard model parameters, including tunnel coupling and capacitive coupling energy, from experimental stability diagrams. Leveraging the dual-annealing optimizer, we determine the set of Hubbard parameters that best characterize the experimental data. We compare our method with an alternate, well-established measure of tunnel coupling and find good agreement within the investigated regime. Our extracted tunnel couplings range from 69 to 517 μ eV, and we discuss the limiting factors of our method. [ABSTRACT FROM AUTHOR]

Quantum Dot Cellular Automata (QCA) is an emerging trend in the field of nanoelectronics, and computing can be regarded as an alternative to the traditional complementary metal–oxide–semiconductor technology. The paper is devoted to the study of the key functional properties of the cells for molecular QCA based on mixed valence molecules. The theoretical results for the heat dissipation under the conditions of the fast nonadiabatic switching event and cell–cell response function are obtained in the framework of the quantum-mechanical vibronic approach. These results are parameterized using the previous reliable ab initio calculations performed for oxidized norbornadiene and its polycyclic derivatives with variable lengths of the bridge. The comparative analysis of the dimeric and bidimeric molecular cells composed of these compounds is given. It is underlined that the conditions of a strong non-linear response and a low heat release are contradictory. However, despite this problem, a parametric regime is proposed, which provides a low heat release in combination with a strong nonlinear response of the working cell to the electric field induced by the polarized driver cell. [ABSTRACT FROM AUTHOR]

The efficient conversion of solar energy to chemical energy represents a critical bottleneck to the energy transition. Photocatalytic splitting of water to generate solar fuels is a promising solution. Semiconductor quantum dots (QDs) are prime candidates for light-harvesting components of photocatalytic heterostructures, given their size-dependent photophysical properties and band-edge energies. A promising series of heterostructured photocatalysts interface QDs with transition-metal oxides which embed midgap electronic states derived from the stereochemically active electron lone pairs of p-block cations. Here, we examine the thermodynamic driving forces and dynamics of charge separation in Sb2VO5/CdSe QD heterostructures, wherein a high density of Sb 5s2-derived midgap states are prospective acceptors for photogenerated holes. Hard-x-ray valence band photoemission spectroscopy measurements of Sb2VO5/CdSe QD heterostructures were used to deduce thermodynamic driving forces for charge separation. Interfacial charge transfer dynamics in the heterostructures were examined as a function of the mode of interfacial connectivity, contrasting heterostructures with direct interfaces assembled by successive ion layer adsorption and reaction (SILAR) and interfaces comprising molecular bridges assembled by linker-assisted assembly (LAA). Transient absorption spectroscopy measurements indicate ultrafast (<2 ps) electron and hole transfer in SILAR-derived heterostructures, whereas LAA-derived heterostructures show orders of magnitude differentials in the kinetics of hole (<100 ps) and electron (∼1 ns) transfer. The interface-modulated kinetic differentials in electron and hole transfer rates underpin the more effective charge separation, reduced charge recombination, and greater photocatalytic efficiency observed for the LAA-derived Sb2VO5/CdSe QD heterostructures. [ABSTRACT FROM AUTHOR]

A unique on-chip method for the direct correlation of optical properties, with atomic-scale chemical–structural characteristics for a single quantum dot (QD), is developed and utilized in various examples. This is based on performing single QD optical characterization on a modified glass substrate, followed by the extraction of the relevant region of interest by focused-ion-beam–scanning electron microscope processing into a lamella for high resolution scanning transmission electron microscopy (STEM) characterization with atomic scale resolution. The direct correlation of the optical response under an electric field with STEM analysis of the same particle allows addressing several single particle phenomena: first, the direct correlation of single QD photoluminescence (PL) polarization and its response to the external field with the QD crystal lattice alignment, so far inferred indirectly; second, the identification of unique yet rare few-QD assemblies, correlated directly with their special spectroscopic optical characteristics, serving as a guide for future designed assemblies; and third, the study on the effect of metal island growth on the PL behavior of hybrid semiconductor–metal nanoparticles, with relevance for their possible functionality in photocatalysis. This work, therefore, establishes the use of the direct on-chip optical–structural correlation method for numerous scenarios and timely questions in the field of QD research. [ABSTRACT FROM AUTHOR]

This article discusses a new fabrication process for colloidal silicon quantum dots (SiQDs) that allows for the tuning of their luminescence color from red to green. The process involves low-temperature thermal cracking of electrochemically prepared meso-porous silicon flakes in a mixture of 10-undecen-1-ol and aqueous hydrogen fluoride solution. The size of the SiQDs and their luminescence color can be controlled by adjusting the content of hydrogen fluoride. The article also explores the properties and potential applications of SiQDs in various fields, such as photovoltaic devices, light emitting devices, bio-imaging, and sensing. The document discusses the size-dependent radiative recombination processes of SiQDs, including factors that can affect their photoluminescence properties. It also explains the formation mechanisms of SiQDs and how they can result in different photoluminescence colors and peak wavelengths. The document concludes by discussing the relationship between the size of SiQDs and their photoluminescence peak energies, as well as the effect of surface passivation on quantum confinement. The article presents a novel method for producing SiQDs with tunable emission colors and suggests potential applications for SiQD devices. [Extracted from the article]

Semiconductor quantum dots (QDs) are one of the leading candidates for realizable qubits, as well as for many other advances in quantum computing and quantum communication. The spatial overlapping of wavefunctions describing each single electron in these nanoscale devices results in tunable spatial entanglement. In this article, we explore the case of two electrons in two-dimensional double quantum dot systems. We compute the two-particle wavefunction through a variational method combined with Hermite finite elements and study the spatial entanglement of electrons. We show that symmetry in the geometry of the double quantum dots plays a role in obtaining optimal entanglement, while a broken symmetry can lead to additional resonances in entanglement that are associated with the crossings of states. We also show that one can finely tune the level of spatial entanglement by altering the geometry of the quantum dots or by applying external fields, which corresponds to an "entanglement spectroscopy." Finally, we study how impurities in the potential profile of the QDs affect the level of entanglement. [ABSTRACT FROM AUTHOR]

We investigate the optical properties appearing in a nanostructure that is composed of an asymmetric double semiconductor quantum dot (SQD) molecule and a metal nanoparticle (MNP). The profile of the total linear absorption spectrum is proportional to the SQD contribution, while the MNP contribution is important. The profile of the doublet of resonances detected on the total linear absorption spectrum creates a transparency window. The doublet is asymmetric for small SQD-MNP distances and has a narrow peak and a wide peak. The width of the transparency window is increased, either with the enhancement of the rate at which the electron tunneling effect takes place within the double SQD molecule or with the decrease of the distance that separates the SQD molecule from the center of the MNP. The steep slope detected on the linear dispersion spectrum for frequencies laying within the transparency window owes its presence to the tunneling induced transparency and leads to slow light production. The corresponding value of the slow down factor is maximized for low values of the electron tunneling rate as well as for low center-to-center distances between the components of the hybrid nanostructure. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are important luminescent structures with applications in wide‐color‐gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs are expected to serve as eco‐friendly materials to replace conventional QDs owing to the narrow spectral widths and tunable bandgaps of these QDs. However, the application of multinary QDs, which tend to exhibit defect‐related emissions, to QD light‐emitting diode (QLED) displays will require electroluminescence to be obtained from QLEDs incorporating inkjet‐printed emitting layers. The present work examines QLEDs exhibiting vibrant color emissions based on blue‐emitting Zn–Se–Te QDs, green‐emitting Ag–In–Ga–S QDs, and red‐emitting Ag–Cu–In–Ga–S QDs. Each such QLED contains QD emitting layers comprising a mixture of charge transport materials. The spectra obtained from these RGB QLEDs fabricated by spin‐coating show very high color purity. Passive matrix QLED displays incorporating these QDs are also fabricated by inkjet printing to demonstrate the high color purity that can be obtained from multinary QDs in displays. In conjunction with passive matrix driving, these displays produce clear moving images with vibrant electroluminescence originating from the multinary QDs. The present results indicate that these QDs have significant potential for utilization in wide‐color‐gamut displays. [ABSTRACT FROM AUTHOR]

Quantum devices such as spin qubits have been extensively investigated in electrostatically confined quantum dots using high-quality semiconductor heterostructures like GaAs and Si. Here, we present a demonstration of electrostatically forming the quantum dots in ZnO heterostructures. Through the transport measurement, we uncover the distinctive signature of the Kondo effect independent of the even-odd electron number parity, which contrasts with the typical behavior of the Kondo effect in GaAs. By analyzing temperature and magnetic field dependences, we find that the absence of the even-odd parity in the Kondo effect is not straightforwardly interpreted by the considerations developed for conventional semiconductors. We propose that, based on the unique parameters of ZnO, electron correlation likely plays a fundamental role in this observation. Our study not only clarifies the physics of correlated electrons in the quantum dot but also holds promise for applications in quantum devices, leveraging the unique features of ZnO. To date, semiconductor quantum dots have been studied in heterostructures of materials such as GaAs and Si. Here the authors report the formation of electrostatically defined quantum dots in ZnO heterostructures with correlated electrons and observe a unique Kondo effect independent of even-odd electron parity. [ABSTRACT FROM AUTHOR]

The first part of this work evaluates Al-doped ZnO (AZO) as an optically transparent top-gate material for studies on semiconductor quantum dots. In comparison with conventional Ti gates, samples with AZO gates demonstrate a more than three times higher intensity in the quantum dot emission under comparable excitation conditions. On the other hand, charges inside a process-induced oxide layer at the interface to the semiconductor cause artifacts at gate voltages above  U ≈  1 V. The second part describes an optical and simulation study of a vertical electric-field (F)-induced switching from a strong to an asymmetric strong–weak confinement in GaAs cone-shell quantum dots (CSQDs), where the charge carrier probability densities are localized on the surface of a cone. These experiments are performed at low U and show no indications of an influence of interface charges. For a large F, the measured radiative lifetimes are substantially shorter compared with simulation results. We attribute this discrepancy to an F-induced transformation of the shape of the hole probability density. In detail, an increasing F pushes the hole into the wing part of a CSQD, where it forms a quantum ring. Accordingly, the confinement of the hole is changed from strong, which is assumed in the simulations, to weak, where the local radius is larger than the bulk exciton Bohr radius. In contrast to the hole, an increasing F pushes the electron into the CSQD tip, where it remains in a strong confinement. This means the radiative lifetime for large F is given by an asymmetric confinement with a strongly confined electron and a hole in a weak confinement. To our knowledge, this asymmetric strong–weak confinement represents a novel kind of quantum mechanical confinement and has not been observed so far. Furthermore, the observed weak confinement for the hole represents a confirmation of the theoretically predicted transformation of the hole probability density from a quantum dot into a quantum ring. For such quantum rings, application as storage for photo-excited charge carriers is predicted, which can be interesting for future quantum photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots, with their size-tunable optoelectronic properties and scalable synthesis, enable applications in which inexpensive high-performance semiconductors are needed. Synthesis science breakthroughs have been key to the realization of quantum dot technologies, but important group III-group V semiconductors, including colloidal gallium arsenide (GaAs), still cannot be synthesized with existing approaches. The high-temperature molten salt colloidal synthesis introduced in this work enables the preparation of previously intractable colloidal materials. We directly nucleated and grew colloidal quantum dots in molten inorganic salts by harnessing molten salt redox chemistry and using surfactant additives for nanocrystal shape control. Synthesis temperatures above 425°C are critical for realizing photoluminescent GaAs quantum dots, which emphasizes the importance of high temperatures enabled by molten salt solvents. We generalize the methodology and demonstrate nearly a dozen III-V solid-solution nanocrystal compositions that have not been previously reported. [ABSTRACT FROM AUTHOR]

Multiplexed fluorescence in vivo imaging remains challenging due to the attenuation and scattering of visible and traditional near infrared (NIR‐I, 650–950 nm) wavelengths. Fluorescence imaging using shortwave infrared (SWIR, 1000–1700 nm, a.k.a. NIR‐II) light enables deeper tissue penetration due to reduced tissue scattering as well as minimal background autofluorescence. SWIR‐emitting semiconductor quantum dots (QDs) with tunable emission peaks and optical stability are powerful contrast agents, yet few imaging demonstrations exclusively use SWIR emission beyond two‐color imaging schemes. In this study, we engineered three high quality lead sulfide/cadmium sulfide (PbS/CdS) core/shell QDs with distinct SWIR emission peaks ranging from 1100–1550 nm for simultaneous three‐color imaging in mice. We first use the exceptional photostability of QDs to non‐invasively track lymphatic drainage with longitudinal imaging, highlighting the detailed networks of lymphatic vessels with widefield imaging over a 2 hr period. We then perform multiplexed imaging with all three QDs to distinctly visualize the lymphatic system and spatially overlapping vasculature networks, including clearly distinguishing the liver and spleen. This work establishes optimized SWIR QDs for next generation multiplexed and longitudinal preclinical imaging, unlocking numerous opportunities for preclinical studies of disease progression, drug biodistribution, and cell trafficking dynamics in living organisms. [ABSTRACT FROM AUTHOR]

A derivation of a tight-binding model from Schrödinger formalism for various topologies of position-based semiconductor qubits is presented in the case of static and time-dependent electric fields. The simplistic tight-binding model enables the description of single-electron devices at a large integration scale. The case of two electrostatically Wannier qubits (also known as position-based qubits) in a Schrödinger model is presented with omission of spin degrees of freedom. The concept of programmable quantum matter can be implemented in the chain of coupled semiconductor quantum dots. Highly integrated and developed cryogenic CMOS nanostructures can be mapped to coupled quantum dots, the connectivity of which can be controlled by a voltage applied across the transistor gates as well as using an external magnetic field. Using the anti-correlation principle arising from the Coulomb repulsion interaction between electrons, one can implement classical and quantum inverters (Classical/Quantum Swap Gate) and many other logical gates. The anti-correlation will be weakened due to the fact that the quantumness of the physical process brings about the coexistence of correlation and anti-correlation at the same time. One of the central results presented in this work relies on the appearance of dissipation-like processes and effective potential renormalization building effective barriers in both semiconductors and in superconductors between not bended nanowire regions both in classical and in quantum regimes. The presence of non-straight wire regions is also expressed by the geometrical dissipative quantum Aharonov–Bohm effect in superconductors/semiconductors when one obtains a complex value vector potential-like field. The existence of a Coulomb interaction provides a base for the physical description of an electrostatic Q-Swap gate with any topology using open-loop nanowires, with programmable functionality. We observe strong localization of the wavepacket due to nanowire bending. Therefore, it is not always necessary to build a barrier between two nanowires to obtain two quantum dot systems. On the other hand, the results can be mapped to the problem of an electron in curved space, so they can be expressed with a programmable position-dependent metric embedded in Schrödinger's equation. The semiconductor quantum dot system is capable of mimicking curved space, providing a bridge between fundamental and applied science in the implementation of single-electron devices. [ABSTRACT FROM AUTHOR]

Actuators containing sensors are developed for various applications. However, it is still challenging to equip miniaturized high‐precision sensors with actuators at the micrometer scale to achieve micro‐environment detection. Here, a two‐in‐one processing strategy to construct a sensor‐equipped magnetic actuator (SEMA) is proposed. The design of magnetic actuators is continuously optimized to achieve less resistance and faster acceleration. Besides, the temperature‐dependent properties of semiconductor quantum dots (QDs) are used to fabricate the temperature‐sensitive unit (TSU), with a sensitivity of up to 111 pm °C−1. Finally, as a proof of concept, the real‐time temperature detection of arbitrary micro‐area in microchannels is achieved. This method of equipping sensors with microactuators will bring many potential applications in microenvironment sensing, micro‐mechanical manipulating, and microcargo transporting. [ABSTRACT FROM AUTHOR]

The development of optoelectronic devices based on III–V semiconductor colloidal quantum dots (CQDs) is highly sought after due to their reduced toxicity. While devices based on conventional CQDs (II–VI semiconductors, halide perovskites) have achieved impressive technological leaps since their discovery, the most mature of these compounds contain toxic heavy metal elements (Cd, Hg, or Pb), which are highly undesirable for safe industrial scale applications. The strong covalent bonds of III–V compounds like InP, InAs, or InSb prevent the release of their toxic atoms, making them safer. However, these same bonds create severe material constraints. Namely, their harsher reaction conditions and increased sensitivity to oxidation have kept most of the research focused on material development. Meanwhile, their integration into devices and their coupling to photonic structures lag behind. Here, the integration of InAs/ZnSe core‐shell CQDs is advanced. First, the material parameters necessary to design plasmonic gratings coupled to the CQDs are elucidated and those gratings are fabricated. Angle‐resolved spectroscopy shows that the plasmon modes successfully couple to the CQD layer's emission leading to a tunable directivity with a 15° linewidth. A 3‐fold increase of the PL signal is achieved at normal incidence, thus advancing toward the goal of efficient outcoupling in LEDs. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution has attracted tremendous interest as it offers a process for generation of green hydrogen based on solar radiation. But the process is extremely complex as many factors influence photocatalytic hydrogen evolution. While novel photocatalysts such as MOFs, perovskites, conjugated polymers, carbon-based materials, quantum dots, and others face challenges such as stability and scalability, semiconductor photocatalysts and cocatalysts such as TiO 2 /Pt, Ni–CdS, CdS/ZnO, CdS/ZnS have the advantages of simplicity in synthesis, stability, and scalability. Despite decades of research, challenges such as charge separation, spectrum usage, low hydrogen generation efficiency, photocatalyst stability and scalability persist. This review discusses what has been achieved so far in the domain of photocatalytic hydrogen evolution and presents a critical analysis of challenges to be addressed in developing a robust and practical photocatalytic hydrogen generation system based on efficiency of photocatalysts and their stability and the extreme importance of efficient reactor designs. [Display omitted] • Challenges associated with photocatalytic hydrogen generation systems. • Photocatalysts, cocatalysts and their stability challenges in hydrogen evolution. • Potential of semiconductor nanostructures, plasmonic nanoparticles and QDs. • Importance of reactor designs in enhancing photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Holes in silicon quantum dots are promising for spin qubit applications due to the strong intrinsic spin-orbit coupling. The spin-orbit coupling produces complex hole-spin dynamics, providing opportunities to further optimise spin qubits. Here, we demonstrate a singlet-triplet qubit using hole states in a planar metal-oxide-semiconductor double quantum dot. We demonstrate rapid qubit control with singlet-triplet oscillations up to 400 MHz. The qubit exhibits promising coherence, with a maximum dephasing time of 600 ns, which is enhanced to 1.3 μs using refocusing techniques. We investigate the magnetic field anisotropy of the eigenstates, and determine a magnetic field orientation to improve the qubit initialisation fidelity. These results present a step forward for spin qubit technology, by implementing a high quality singlet-triplet hole-spin qubit in planar architecture suitable for scaling up to 2D arrays of coupled qubits. Hole-spin qubits based on semiconductor quantum dots offer potential advantages over their electron-spin counterparts, such as fast qubit control and enhanced coherence times. Liles et al. report a hole-based singlet-triplet spin qubit in planar Si MOS device and develop a model to describe its dynamics. [ABSTRACT FROM AUTHOR]

A brief overview is presented of results obtained at the Rzhanov Institute of Semiconductor Physics in the development of photon detectors and emitters promising for use in quantum cryptography systems, along with miniature quantum frequency standards based on the effect of coherent population trapping. [ABSTRACT FROM AUTHOR]

Conventional chemotherapy lacks insolubility, selective targeting and bio-imaging of the chemotherapeutics aggravating the diseased state with developed drug resistant toxicity in the biological system. To overcome these obstacles and other biological barriers, nano-sized semiconductor quantum dots (QDs) having the unique photoluminescence and electronic physicochemical properties such as size-tunable light emission, narrow emission range, high brightness and photo-stability for making them the suitable diagnostic probe materials in bio/immune -sensing platform have attracted attention for targeted theranostic photodynamic therapy to bridge nanotechnology and cargo therapy assay. In general, QDs, linked to photoluminescence, induce generation of free radicals, disrupt cell walls/membranes and arrest gene expression as antimicrobial/anti-cancer agents in nano theranostic platform for concomitant sensing, imaging and therapy in the biological system. QDs may be conjugated with polymers, ligands, cargos and other biomolecules through covalent and non-covalent bonds for different specific targeting and controlled liberation of cargos to the diseased site/s of concern to get higher theranostic efficacy. This review focuses mainly the physicochemical characteristics of QDs, their synthesized methods, surface functionalizations, mechanism of action, biomedical applications, toxicity, biodistribution, pharmacokinetics and elimination as nano delivery system. [ABSTRACT FROM AUTHOR]

Hydrophilic semiconductor quantum dots (QDs) with emission in the second near-infrared window (NIR-II) have been widely studied in bioimaging applications. In such cases, QDs are usually dispersed in water. As is known, water has strong absorbance in the NIR-II region. However, investigations on the interaction between NIR-II emitters and water molecules are ignored in previous studies. Herein, we synthesized a series of mercaptoundecanoic acid-coated silver sulfide (Ag2S/MUA) QDs with various emissions that partially or completely overlapped with the absorbance of water at 1200 nm. By constructing a hydrophobic interface of cetyltrimethylammonium bromide (CTAB) with MUA on the Ag2S QDs surface via forming an ionic bond, significant enhancement of Ag2S QDs photoluminescence (PL) intensity was observed, as well as a prolonged lifetime. These findings suggest that there is an energy transfer between Ag2S QDs and water in addition to the classical resonance absorption. Transient absorption and fluorescence spectra results revealed that the increased PL intensities and lifetime of Ag2S QDs originated from the suppressed energy transfer from Ag2S QDs to the water due to the CTAB bridged hydrophobic interfaces. This discovery is important for a deeper understanding of the photophysical mechanisms of QDs and their applications. [ABSTRACT FROM AUTHOR]

Frequency encoded reconfigurable logic gates OR and AND are designed using interferometric switch based on quantum dot semiconductor optical amplifier (QDSOA) and simulated using MATLAB for the first time as far as our knowledge goes. The amplitude modulation (AM) and quality factor ( Q fe ) are calculated using numerical simulations confirming practical feasibility of the logic gates. This paper also investigates the effect of amplified spontaneous emission (ASE) noise on AM, Q fe and signal-to-noise ratio (SNR) values. AM below 0.005 dB and Q fe more than 30 dB ensure error free operation of the logic gates. [ABSTRACT FROM AUTHOR]

We theoretically study the optical bistability assisted by multipole polarizations in a semiconductor quantum dot (SQD)/metal nanoparticle (MNP) hybrid molecule. We map out bistability phase diagrams within the parameter subspace spanned by (the pumping intensity Ipu, interparticle distance, d) under dipole and multipole approximations. It is shown that the Ipu-correlated bistable region will be broadened greatly in the strong exciton–plasmon coupling regime, and the corresponding lower (upper) bistable threshold is enlarged significantly due to multipole polarization (N = 10) in comparison to that in the dipole approximation (N = 1). However, under the same conditions, the d-correlated bistable region is shrunk at high pump intensities. Our contribution not only offers a better understanding of exciton–plasmon coupling systems but also expands the application of SQD/MNP hybrid molecules in the field of optical bistable nanodevices. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots (QDs) are efficient organic photoredox catalysts due to their high extinction coefficients and easily tunable band edge potentials. Despite the majority of the surface being covered by ligands, our understanding of the effect of the ligand shell on organic photocatalysis is limited to steric effects. We hypothesize that we can increase the activity of QD photocatalysts by designing a ligand shell with targeted electronic properties, namely, redox-mediating ligands. Herein, we functionalize our QDs with hole-mediating ferrocene (Fc) derivative ligands and perform a reaction where the slow step is hole transfer from QD to substrate. Surprisingly, we find that a hole-shuttling Fc inhibits catalysis, but confers much greater stability to the catalyst by preventing a build-up of destructive holes. We also find that dynamically bound Fc ligands can promote catalysis by surface exchange and creation of a more permeable ligand shell. Finally, we find that trapping the electron on a ligand dramatically increases the rate of reaction. These results have major implications for understanding the rate-limiting processes for charge transfer from QDs and the role of the ligand shell in modulating it. [ABSTRACT FROM AUTHOR]

In this study, we developed very simple and ULSI (ultra large scale integration) compatible fabrication processes for group-IV (Si1–xGex and Si) semiconductor quantum dots (QDs) to apply hybrid ULSIs with photonic and electron devices, using double Ge+/Si+ hot-ion implantation into a SiO2 layer with larger bandgap EG and the post-furnace annealing. We successfully demonstrated the near-infrared (IR) photoluminescence (PL) from Si1–xGex-QDs. Transmission electron microscopy observations of single-crystallized Si1–xGex-QDs revealed that the diameter and the QD density were 3.6 ± 0.9 nm and (2.6 ± 0.4) × 1012 cm−2, respectively. In addition, Ge atoms were detected in the Si1–xGex-QDs by the energy dispersive x-ray spectroscopy analysis, and the Ge fraction of Si1–xGex-QDs was varied from 0.06 to 0.26 by changing the Ge ion dose. The increase in the PL intensity by forming gas annealing was attributed to the dangling-bond reduction by the H-atom termination method. The PL spectrum of Si1–xGex-QDs was fitted by PL components of two QD structures containing Si1–xGex and Si materials. The PL intensity and PL-peak photon energy of Si1–xGex-QDs strongly depended on the Ge fraction. The Si1–xGex-QDs achieved the maximum PL intensity at x ≈ 0.13. High PL-peak photon energy (∼1.31 eV) of Si1–xGex-QDs is attributed to the quantum confinement effect of carriers in QDs. Consequently, group-IV semiconductor QDs including Si1–xGex, Si, SiC, and C, through the simple hot-ion implantation into the SiO2 layer, exhibited a wide range of PL emissions from the near-IR to ultraviolet regions. [ABSTRACT FROM AUTHOR]

Semiconductor nanocrystals with an anisotropic morphology exhibit unique properties, most notably their linear polarization. The colloidal growth of semiconductor nanorods with core dots inside, also referred to as dot-in-rod (DIR) structure, has enabled the synthesis of anisotropic nanocrystals with better stability and controllable fluorescence polarization. In this study, we synthesize CdSe/CdS DIR nanocrystals, in which the position of the CdSe core particle can be controlled by using different ligand compositions during the CdS growth. Varying the core position within the DIR structure, e.g., from the center to the end of the DIR particles, results in a change in the degree of linear polarization. When the core is positioned at the center of the nanorod, the linear polarization turns out to be higher compared with tip-core DIRs. Time-resolved photoluminescence analysis reveals that the center-core DIRs have higher electron–hole interaction than tip-core DIRs because of weak uniaxial strain in center-core DIR that arises from lattice dislocations at the interface to relieve accumulated strain. [ABSTRACT FROM AUTHOR]

The adaptively compressed exchange (ACE) operator combined with interpolative separable density fitting (ISDF) decomposition has been utilized to accelerate plane-wave hybrid functional calculations for restricted Kohn–Sham density functional theory (DFT), but the neglect of spin degree of freedom has limited its application in the exploration of systems where the spin property of the electron is critical. Herein, we derive the ACE-ISDF formulation for hybrid functional calculations in both unrestricted and noncollinear spin DFT with plane waves and periodic boundary conditions. We proposed an improved ISDF algorithm for the sum of Kohn–Sham orbital pairs to further reduce the computational cost for the spin-noncollinear case. Numerical results demonstrate that these improved ACE-ISDF low-rank approximations can not only significantly reduce the computational time by two orders of magnitude compared with conventional plane-wave hybrid functional calculations but also lead to a good convergence behavior when a moderate rank parameter is set, even for complex periodic magnetic systems. By using these ACE-ISDF approximations, we investigate the electronic and magnetic properties of two-dimensional periodic ferromagnetic semiconductors consisting of triangular zigzag graphene quantum dots and transition metal atoms. Our computational results showcase that hybrid functional calculations in spin DFT can provide not only accurate electronic structures but also accurate magnetic order temperature of ferromagnetic semiconductors compared to local or semilocal functional calculations. [ABSTRACT FROM AUTHOR]

We investigate experimentally and theoretically the impact of valence band mixing and spectrum of confined states on the polarization of light emitted from or absorbed by GaAs/AlGaAs semiconductor quantum dots and quantum wires with tailored heterostructure potential. In particular, such nanostructures with parabolic-profile confinement potentials, realized by organometallic vapor phase epitaxy inside pyramidal pits, served as model systems for the study. Different degrees of linear polarization (DOLP) of emitted light, depending on the confinement potential profile, the specific excitonic transition, and the level of excitation, are observed. A theoretical model shows that, besides the impact of valence band mixing, the overlap of conduction and valence band wavefunctions as well as state occupation probability and broadening of transitions determine the DOLP. The conclusions are useful for the design of quantum light emitters with controlled polarization properties. [ABSTRACT FROM AUTHOR]

We theoretically study the polarization of plasmonic fields in a hybrid nanosystem composed of three different metallic nano ellipsoid and a semiconductor quantum dot. The components of the hybrid nanosystem interact with three electromagnetic fields and one another via dipole-dipole interactions. We derive the density matrix equations at a steady state for the description of the optical properties of the hybrid nanosystem. The polarization of the plasmonic fields induced on the prolate, spherical, and oblate nano ellipsoid is calculated. We find that the polarization of the plasmonic fields depends on the number of the metallic nanoparticles (ellipsoid), the depolarization factor of the metallic nano ellipsoid, the direction of the plasmonic field, and the metallic nano ellipsoid parameters of the hybrid nanosystem. The phenomena of electromagnetically induced transparency (EIT) and electromagnetically induced transparency with amplification (EITA) are obtained in this work. [ABSTRACT FROM AUTHOR]

The physical mechanism of the quantum size effect, which determines the main feature of the size dependence of absorption and photoluminescence spectra of nanoparticles of semiconductor materials, is outlined, and the effects of multiexciton generation and luminescence blinking of colloidal quantum dots are discussed. [ABSTRACT FROM AUTHOR]

Three‐photon‐pumped (3PP) excitonic lasing in inorganic semiconductor quantum dots (QDs) is of particular importance for near‐infrared biophotonics and optical communications. However, the implementation of such lasers has been hindered severely by the required high pump thresholds. Here, 3PP excitonic lasing of all‐inorganic cesium lead bromide perovskite QDs (CsPbBr3 PQDs) embedded in a whispering‐gallery microcavity is demonstrated, and achieving a record low threshold of 3 mJ cm−2 by tuning the 3P pump energy in resonance with the S exciton state. Wavelength‐dispersive Z‐scan spectroscopy reveals that such reduced lasing threshold is attributed to the exciton resonance enhanced multiphoton absorption, which, as disclosed by the kinetics analysis of transient absorption spectroscopy (TAS), leads to the appearance of net gain at a pump fluence as low as 2.2 mJ cm−2, corresponding to an average S exciton population of 1.5. A microscopic model incorporating the quantum master equation reproduces the TAS results and provides the intrinsic parameters of biexciton relaxation for lasing. The 3PP resonant excitonic transition is the most favored multiphoton pumping process that minimizes quantum defect (6.8% of the pump photon energy) to realize optical gain at low threshold, marking a major step toward using all‐inorganic perovskite QDs for on‐chip integrated microlasers and multiphoton bioimaging. [ABSTRACT FROM AUTHOR]

Controlling large-scale many-body quantum systems at the level of single photons and single atomic systems is a central goal in quantum information science and technology. Intensive research and development has propelled foundry-based silicon-on-insulator photonic integrated circuits to a leading platform for large-scale optical control with individual mode programmability. However, integrating atomic quantum systems with single-emitter tunability remains an open challenge. Here, we overcome this barrier through the hybrid integration of multiple InAs/InP microchiplets containing high-brightness infrared semiconductor quantum dot single photon emitters into advanced silicon-on-insulator photonic integrated circuits fabricated in a 300 mm foundry process. With this platform, we achieve single-photon emission via resonance fluorescence and scalable emission wavelength tunability. The combined control of photonic and quantum systems opens the door to programmable quantum information processors manufactured in leading semiconductor foundries. Integrating tunable quantum emitters with commercial photonic circuits is promising for quantum information applications but remains a challenge. Here the authors report integration of InAs/InP microchiplets containing quantum dot single photon emitters into a large-scale foundry silicon platform. [ABSTRACT FROM AUTHOR]

The construction of a large-scale quantum internet requires quantum repeaters containing multiple entangled photon sources with identical wavelengths. Semiconductor quantum dots can generate entangled photon pairs deterministically with high fidelity. However, realizing wavelength-matched quantum-dot entangled photon sources faces two difficulties: the non-uniformity of emission wavelength and exciton fine-structure splitting induced fidelity reduction. Typically, these two factors are not independently tunable, making it challenging to achieve simultaneous improvement. In this work, we demonstrate wavelength-tunable entangled photon sources based on droplet-etched GaAs quantum dots through the combined use of AC and quantum-confined Stark effects. The emission wavelength can be tuned by ~1 meV while preserving an entanglement fidelity f exceeding 0.955(1) in the entire tuning range. Based on this hybrid tuning scheme, we finally demonstrate multiple wavelength-matched entangled photon sources with f > 0.919(3), paving the way towards robust and scalable on-demand entangled photon sources for quantum internet and integrated quantum optical circuits. Realising scalable entangled photon sources with quantum dots requires compensating for both wavelength mismatches and exciton fine-structure splitting (FSS). So far, multiple QDs with the same emission wavelength and near-zero FSS have not been demonstrated. Here, the authors fill this gap, reaching high entanglement fidelity for multiple QDs tuned into resonance with each other or with Rb atoms. [ABSTRACT FROM AUTHOR]

Quantum links can interconnect qubit registers and are therefore essential in networked quantum computing. Semiconductor quantum dot qubits have seen significant progress in the high-fidelity operation of small qubit registers but establishing a compelling quantum link remains a challenge. Here, we show that a spin qubit can be shuttled through multiple quantum dots while preserving its quantum information. Remarkably, we achieve these results using hole spin qubits in germanium, despite the presence of strong spin-orbit interaction. In a minimal quantum dot chain, we accomplish the shuttling of spin basis states over effective lengths beyond 300 microns and demonstrate the coherent shuttling of superposition states over effective lengths corresponding to 9 microns, which we can extend to 49 microns by incorporating dynamical decoupling. These findings indicate qubit shuttling as an effective approach to route qubits within registers and to establish quantum links between registers. Spin shuttling is a promising technique for establishing a quantum link between qubit registers and has been studied in several quantum dot qubit platforms. Here the authors realize coherent shuttling of a hole spin qubit in a minimal quantum dot chain in germanium despite strong spin-orbit coupling. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots, composed of elements from groups II–VI (CdSe, CdTe, CdS, ZnTe, ZnO), III–V (InAs, GaSb, InP) and IV (Si, Ge), are nanoscale particles attracting significant research interest. The focus of current studies lies predominantly on II–VI group quantum dots like CdS, CdSe, and CdTe, known for their narrow band gaps and exceptional fluorescent properties intrinsically related to quantum size effects. In this study, a straightforward aqueous reflux method was employed, using thioglycolic acid as a stabilizer, and NaHTe as a Te precursor. Over a period of 3 h, CdTe semiconductor quantum dots of various colors were prepared, addressing and mitigating the issue of oxidation susceptibility during NaHTe transfer. The fluorescence luminescence properties of the product were meticulously analyzed, yielding a series of CdTe quantum dots with an impressive quantum efficiency of 48%. This experimental approach is notable for its simplicity, minimal reagent consumption, and distinct fluorescence characteristics, making it highly operable and replicable. It is well-suited for undergraduate education in inorganic chemistry, instrumental analysis, and comprehensive professional experiments. [ABSTRACT FROM AUTHOR]

As excellent functional materials, the composite materials based on graphene and its derivatives (GNDs) have lots of important application values in the emerging fields such as solar energy conversion, and the exploration of electron (or energy) transfer properties of those composites is the key for revealing their further applications. In this review, femtosecond transient absorption spectroscopy (TAS) has been introduced as an essential technique to understand the carrier behaviors in GNDs composites, as well as the advancements of TAS. The specific examples of electron transport in various composite materials characterized by TAS are summarized and discussed, which consist of GNDs with semiconductor quantum dots (QDs), organic dyes, organic polymers, perovskites and other materials, respectively. This review provides a deep insight into the electron transfer (ET) kinetics of various GNDs composites from the perspective of TAS. [ABSTRACT FROM AUTHOR]

Modern industry actively uses metal structural materials to create innovative devices and components. In order to prevent emergency situations in production, nondestructive testing methods are used to detect defects on the surface of the material being developed. Among the methods of nondestructive testing, one can highlight the method of luminescent magnetic flaw detection, which allows identifying defects on the surface and under the surface of the test sample with minimal effort. It is known that in some cases, the magnetic‐powder method cannot achieve the required sensitivity due to the shape and location of defects themselves or due to certain conditions of object operation. To increase the visibility and sensitivity, magnetic nano‐ and microparticles can be conjugated with the dyes. Iron oxide nanoparticles (Fe3O4, γ‐Fe2O3) can be used as such magnetic particles, since they are quite easy to obtain and have low toxicity, high chemical stability, and a wide variety of magnetic properties. To ensure fluorescence of magnetic particles, a wide variety of fluorescent dyes associated with such particles are used. The dyes can include morin, naphthalimide derivatives, as well as semiconductor quantum dots. This article provides a review of fluorescent composite micro‐ and nanoparticles based on xanthene dyes (rhodamine, fluorescein, and pyronine). Such dyes are economically available luminophores, have good binding to the surface of magnetic particles, and therefore can be suitable for luminescent magnetic flaw detection. This review article discusses methods for producing composite nano‐ and microparticles of iron oxides with xanthene dyes and provides prospects of using composite nano‐ and microparticles in nondestructive testing methods. [ABSTRACT FROM AUTHOR]

We investigate three-dimensional (3D) probe absorption spectrum in a three-level ladder-type quantum dot nanostructure, which is driven by a superposition of three mutually perpendicular standing-wave fields and a traveling- wave field. Due to the position-dependent light-matter interaction, the probe absorption is sensitive to the position in 3D space. It is found that the 3D distribution of the probe absorption spectrum can be easily controlled via adjusting the detuning of the probe field and the intensity of the position-dependent control field. More importantly, the maximal probe absorption can be localized in different positions via tuning the phases of the three standing-wave fields. The scheme may provide some technological applications in solid-state optoelectronics. [ABSTRACT FROM AUTHOR]

Structural deformation modifies the bandgap, exciton fine structure and phonon energy of semiconductors, providing an additional knob to control their optical properties. The impact can be exploited in colloidal semiconductor quantum dots (QDs), wherein structural stresses can be imposed in three dimensions while defect formation is suppressed by controlling surface growth kinetics. Yet, the control over the structural deformation of QDs free from optically active defects has not been reached. Here, we demonstrate strain-graded CdSe-ZnSe core-shell QDs with compositionally abrupt interface by the coherent pseudomorphic heteroepitaxy. Resulting QDs tolerate mutual elastic deformation of varying magnitudes at the interface with high structural fidelity, allowing for spectrally stable and pure emission of photons at accelerated rates with near unity luminescence efficiency. We capitalize on the asymmetric strain effect together with the quantum confinement effect to expand emission envelope of QDs spanning the entire visible region and exemplify their use in photonic applications. Structural deformation can modify the optical properties of quantum dots. Here, the author report strain-graded CdSe-ZnSe quantum dots, allowing for spectrally stable and pure emission of photons at accelerated rates with near unity luminescence efficiency. [ABSTRACT FROM AUTHOR]

With the increasing emphasis on ecological safety and physical health, the detection and treatment of harmful substances and diseases are becoming more and more prevalent. Therefore, efficiently monitoring these biological behaviors with high accuracy and sensitivity in real-time has shown prominent research significance. The use of fluorescent probes to analyze organisms has gained momentum in recent years, especially in the field of organ imaging and assisted cancer therapy, where fluorescent bioanalysis demonstrates significant advantageous. In this review, we explored the latest advancements in fluorescent molecular probes (e.g., small-molecule, macro-molecule, supramolecule) and fluorescent nanoparticle probes (e.g., quantum dots or nanoclusters, metal-organic frameworks, polymers, complexes) used as bioanalytical tools in various assays over the last three years. We also delved into their detective mechanisms, specific application areas, and characterization tools for responsive behavior. This review aims to showcase the most recent and comprehensive research progress in fluorescent bioanalysis based on molecular and nanoparticle probes, offering guidance for future developments in the design and fabrication of fluorescent probes and their potential applications. [ABSTRACT FROM AUTHOR]

Photoluminescent carbon dots (CDs) have garnered significant interest owing to their distinctive optical and electronic properties. In contrast to semiconductor quantum dots, which incorporated toxic elements in their composition, CDs have emerged as a promising alternative, rendering them suitable for both environmental and biological applications. CDs exhibit astonishing features, including photoluminescence, charge transfer, quantum confinement effect, and biocompatibility. Recently, CDs derived from green sources have drawn a lot of attention due to their strong photostability, reduced toxicity, better biocompatibility, enhanced fluorescence, and simplicity. These attributes have shown great promise in the areas of LED technology, bioimaging, photocatalysis, drug delivery, biosensing, and antibacterial activity. In contrast, this review offers a comprehensive overview of various green sources utilized to produce CDs and methodologies, along with their merits and demerits, with a notable emphasis on physiochemical properties. Additionally, the paper provides insight into the bibliometric analysis and recent advancements of CDs in sensing, photocatalysis, and antibacterial activity. In this field, extensive research is underway, and a total of 7,438 articles have been identified. Among these, 4242 articles are dedicated to sensing applications, while 1518 and 1678 focus on adsorption and degradation. Carbon dots demonstrate exceptional sensing capabilities within the nanomolar range with a selectivity of up to 95% for pollutants. They exhibit excellent degradation efficiency exceeding 90% within 10–130 min and possess an adsorption capacity from 100 to 800 mg/g. These fascinating qualities render them suitable for diverse applications. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are recognized as the most promising functional nanotechnology, for which its discoverers are awarded the Nobel Prize in 2023. Their remarkable tunability of optoelectronic properties has attracted significant interest from both researchers and industries, placing QDs at the forefront of developing cutting‐edge technologies. This comprehensive review aims to explore the exciting results in terms of fundamental science, present and forthcoming applications. Beyond their contributions to biomedicine, energy, environmental science, quantum sensing, and quantum information processing, QDs have brought important results due to their integration into micro/nanorobotic systems, self‐propelled materials representing the state of the art research at the micro and nanoscale. These hybrid systems have demonstrated noteworthy outcomes, unlocking novel possibilities in biomedicine, quantum sensing, and environmental science, accurately reviewed in this article. In conclusion, this review addresses current challenges, offering insights to facilitate further research, stimulate new developments, and enhance the comprehension of the full potential of QDs. [ABSTRACT FROM AUTHOR]

The 2023 Nobel Prize in Chemistry was awarded to Aleksey I. Ekimov (prize share 1/3), Louis E. Brus (prize share 1/3), and Moungi G. Bawendi (prize share 1/3) for groundbreaking inventions in the field of nanotechnology, i.e., for the discovery and synthesis of semiconductor nanocrystals, also termed quantum dots, that exhibit size-dependent physicochemical properties enabled by quantum size effects. This feature article summarizes the main milestones of the discoveries and developments of quantum dots that paved the road to their versatile applications in solid-state lighting, display technology, energy conversion, medical diagnostics, bioimaging, and image-guided surgery. [ABSTRACT FROM AUTHOR]

Heterojunctions of perovskite quantum dots (QDs) and organic semiconductors (OSCs) can synergistically leverage the unique optoelectronic properties of different functional components to fabricate advanced optoelectronic devices, such as neuromorphic photosensors, by low‐cost solution processes. However, a long‐lasting challenge remains in micropatterning high‐density perovskite QDs/polymer OSCs heterojunction array with high yield and reliability due to the fragility of functional layers to organic solvents. High‐density and micro‐structure patterned organic neuromorphic photosensor arrays based on OSCs and QDs are thus rarely reported. Here, an effective cross‐linking microlithography strategy is reported to fabricate perovskite QDs/OSCs microstructure arrays. The fabricated CsPbBr3 QDs/(poly(2,5‐(2‐octyldodecyl)−3,6‐diketopyrrolopyrrole‐alt‐5,5‐(2,5‐di(thien‐2‐yl) thieno [3,2‐b] thiophene) (DPPDTT) planer heterojunctions phototransistor array presents minor device‐to‐device variation, high density (6500 devices cm−2), and high yield (almost 100%). The device array exhibits impressive merits as a neuromorphic photosensor, including a photosensitivity of 3.02 × 107, a responsivity up to 1.92 × 104 A W−1, a detectivity exceeding 1014 Jones, and a persistent photoconductivity. Moreover, an energy consumption as low as 27.9 aJ is achieved at an operating voltage of −0.0001 V. The potential application of the heterojunction neuromorphic photosensor array in motion perception is demonstrated in conjunction with a neural network. [ABSTRACT FROM AUTHOR]

Semiconductor nanorods (NRs) have great potential in optoelectronic devices for their unique linearly polarized luminescence which can break the external quantum efficiency limit of light-emitting diodes (LEDs) based on spherical quantum dots. Significant progress has been made for developing red, green, and blue light-emitting NRs. However, the synthesis of NRs emitting in the deep red region, which can be used for accurate red LED displays and promoting plant growth, is currently less explored. Here, we report the synthesis of deep red CdSeTe/CdZnS/ZnS dot-in-rod core/shell NRs via a seeded growth method, where the doping of Te in the CdSe core can extend the NR emission to the deep red region. The rod-shaped CdZnS shell is grown over CdSeTe seeds. By growing a ZnS passivation shell, the CdSeTe/CdZnS/ZnS NRs exhibit a photoluminescence emission peak at 670 nm, a full width at a half maximum of 61 nm and a photoluminescence quantum yield of 45%. The development of deep red NRs can greatly extend the applications of anisotropic nanocrystals. [ABSTRACT FROM AUTHOR]

Small-size gold nanoparticles (AuNPs) are showing large potential in various fields, such as photothermal conversion, sensing, and medicine. However, current synthesis methods generally yield lower, resulting in a high cost. Here, we report a novel uni-micelle method for the controlled synthesis of monodisperse gold nanocrystals, in which there is only one kind micelle containing aqueous solution of reductant while the dual soluble Au (III) precursor is dissolved in oil phase. Our synthesis includes the reversible phase transfer of Au (III) and "uni-micelle" synthesis, employing a Au (III)-OA complex as an oil-soluble precursor. Size-controlled monodisperse AuNPs with a size of 4–11 nm are synthesized by tuning the size of the micelles, in which oleylamine (OA) is adsorbed on the shell of micelles and enhances the rigidity of the micelles, depressing micellar coalescence. Monodisperse AuNPs can be obtained through a one-time separation process with a higher yield of 61%. This method also offers a promising way for the controlled synthesis of small-size alloy nanoparticles and semiconductor heterojunction quantum dots. [ABSTRACT FROM AUTHOR]

Since their first demonstration in 2001 [Gol'tsman et al., Appl. Phys. Lett. 79, 705–707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as "binary" detectors, meaning that they could only distinguish between 0 and > = 1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2–5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong–Ou–Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850–950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613–738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication. [ABSTRACT FROM AUTHOR]

Augmented reality smart glasses, in general, have highest requirements as compared with smart phones and watches. Its display must be of light weight (a few grams), tremendous brightness (millions of nits), low power consumption (hundreds of milliwatts), and extremely small volume (a small fraction of cubic centimeter) to allow fashionable smart glass designs that would be socially and aesthetically favored by consumers. We have been focusing on micrometer‐scale native semiconductor MicroLED integration, to create miniaturized panels and projectors, which can be seamlessly integrated into the frames of the smart glasses. Among many technical aspects of microLED displays, two key parameters will be emphasized here. First, a microLED panel must be bright and efficient at the same time, especially for red microLED panel with small pixel pitch, such as 2.5 µm. Second, a microLED technology must enable reasonable reliability at a high energy density of, such as 10 watts per square centimeter. Vertically stacked native semiconductors monolithic integration, quantum dots conversion, perovskites, etc., will be discussed, in a context of facing challenges in materials and device physics and fulfilling the two requirements. In addition, an image quality correction method on the waveguide‐microLED display module will be proposed. [ABSTRACT FROM AUTHOR]