Threshold-independent method for single-shot readout of spin qubits in semiconductor quantum dots

The single-shot readout data process is essential for the realization of high-fidelity qubits and fault-tolerant quantum algorithms in semiconductor quantum dots. However, the fidelity and visibility of the readout process are sensitive to the choice of the thresholds and limited by the experimental hardware. By demonstrating the linear dependence between the measured spin state probabilities and readout visibilities along with dark counts, we describe an alternative threshold-independent method for the single-shot readout of spin qubits in semiconductor quantum dots. We can obtain the extrapolated spin state probabilities of the prepared probabilities of the excited spin state through the threshold-independent method. We then analyze the corresponding errors of the method, finding that errors of the extrapolated probabilities cannot be neglected with no constraints on the readout time and threshold voltage. Therefore, by limiting the readout time and threshold voltage, we ensure the accuracy of the extrapolated probability. We then prove that the efficiency and robustness of this method are 60 times larger than those of the most commonly used method. Moreover, we discuss the influence of the electron temperature on the effective area with a fixed external magnetic field and provide a preliminary demonstration for a single-shot readout of up to 0.7K/1.5T in the future.

Advantageous properties of halide perovskite quantum dots towards energy-efficient sustainable applications

As lead halide perovskite(LHP)semiconductors have shown tremendous promise in many application fields,and particularly made strong impact in the solar photovoltaic area,low dimensional quantum dot forms of these perovskites are showing the potential to make distinct marks in the fields of electronics,optoelectronics and photonics.The so-called perovskite quantum dots(PQDs)not only possess the most important features of LHP materials,i.e.,the unusual high defect tolerance,but also demonstrate clear quantum size effects,along with exhibiting desirable optoelectronic properties such as near perfect photoluminescent quantum yield,multiple exciton generation and slow hot-carrier cooling.Here,we review the advantageous properties of these nanoscale perovskites and survey the prospects for diverse applications which include lightemitting devices,solar cells,photocatalysts,lasers,detectors and memristors,emphasizing the distinct superiorities as well as the challenges.

Experimental and computational study of annealed nickel sulfide quantum dots for catalytic and antibacterial activity

This research investigates the hydrothermal synthesis and annealing duration effects on nickel sulfide(NiS_(2) quantum dots(QDs)for catalytic decolorization of methylene blue(MB)dye and antimicrobial efficacy.QD size increased with longer annealing,reducing catalytic activity.UV–vis,XRD,TEM,and FTIR analyses probed optical structural,morphological,and vibrational features.XRD confirmed NiS2's anorthic structure,with crystallite size growing from 6.53 to 7.81 nm during extended annealing.UV–Vis exhibited a bathochromic shift,reflecting reduced band gap energy(Eg)in NiS_(2).TEM revealed NiS_(2)QD formation,with agglomerated QD average size increasing from 7.13 to 9.65 nm with prolonged annealing.Pure NiS_(2) showed significant MB decolorization(89.85%)in acidic conditions.Annealed NiS_(2) QDs demonstrated notable antibacterial activity,yielding a 6.15mm inhibition zone against Escherichia coli(E.coli)compared to Ciprofloxacin.First-principles computation supported a robust interaction between MB and NiS_(2),evidenced by obtained adsorption energies.This study highlights the nuanced relationship between annealing duration,structural changes,and functional properties in NiS_(2)QDs,emphasizing their potential applications in catalysis and antibacterial interventions.

Temperature-controlled DCP Fluorescent Probe Based on Hydrogel-immobilized Quantum Dots Composite

A composite was created by incorporating the quantum dot-enhanced SiO_(2)nanoparticles within this hydrogel.Based on this composite,a temperature-controlled fluorescent probe for DCP was developed.A meticulous examination of this probe revealed its attributes and factors affecting its performance.By using temperature modulation,the probe was adept at detecting DCP concentrations ranging between 1.0×10^(-6)and 9.0×10^(-6)mol/L.Such a probe offers remarkable selectivity,repeatability,and robust stability,so that the detection of DCP can be carried out at different temperatures,and a fast,reliable,sensitive and low-cost intelligent detection method is realized.

Majorana tunneling in a one-dimensional wire with non-Hermitian double quantum dots

The combination of non-Hermitian physics and Majorana fermions can give rise to new effects in quantum transport systems. In this work, we investigate the interplay of PT-symmetric complex potentials, Majorana tunneling and interdot tunneling in a non-Hermitian double quantum dots system. It is found that in the weak-coupling regime the Majorana tunneling has pronounced effects on the transport properties of such a system, manifested as splitting of the single peak into three and a reduced 1/4 peak in the transmission function. In the presence of the PT-symmetric complex potentials and interdot tunneling, the 1/4 central peak is robust against them, while the two side peaks are tuned by them. The interdot tunneling only induces asymmetry, instead of moving the conductance peak, due to the robustness of the Majorana modes. There is an exceptional point induced by the union of Majorana tunneling and interdot tunneling. With increased PT-symmetric complex potentials, the two side peaks will move towards each other. When the exceptional point is passed through, these two side peaks will disappear. In the strong-coupling regime, the Majorana fermion induces a 1/4 conductance dip instead of the three-peak structure. PT-symmetric complex potentials induce two conductance dips pinned at the exceptional point. These effects should be accessible in experiments.

NbN quantum dots anchored hollow carbon nanorods as efficient polysulfide immobilizer and lithium stabilizer for Li-S full batteries

The shuttle effect of lithium polysulfides(LiPSs)and uncontrollable lithium dendrite growth seriously hinder the practical application of lithium-sulfur(Li-S)batteries.To simultaneously address such issues,monodispersed Nb N quantum dots anchored on nitrogen-doped hollow carbon nanorods(NbN@NHCR)are elaborately developed as efficient Li PSs immobilizer and Li stabilizer for high-performance Li-S full batteries.Density functional theory(DFT)calculations and experimental characterizations demonstrate that the sulfiphilic and lithiophilic NbN@NHCR hybrid can not only efficiently immobilize the soluble Li PSs and facilitate diffusion-conversion kinetics for alleviating the shuttling effect,but also homogenize the distribution of Li+ions and regulate uniform Li deposition for suppressing Li-dendrite growth.As a result,the assembled Li-S full batteries(NbN@NHCR-S||Nb N@NHCR-Li)deliver excellent long-term cycling stability with a low decay rate of 0.031%per cycle over 1000 cycles at high rate of 2 C.Even at a high S loading of 5.8 mg cm^(-2)and a low electrolyte/sulfur ratio of 5.2μL mg^(-1),a large areal capacity of 6.2 mA h cm^(-2)can be achieved in Li-S pouch cell at 0.1 C.This study provides a new perspective via designing a dual-functional sulfiphilic and lithiophilic hybrid to address serious issues of the shuttle effect of S cathode and dendrite growth of Li anode.

Small but mighty:Empowering sodium/potassium-ion battery performance with S-doped SnO_(2) quantum dots embedded in N,S codoped carbon fiber network

SnO_(2) has been extensively investigated as an anode material for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs)due to its high Na/K storage capacity,high abundance,and low toxicity.However,the sluggish reaction kinetics,low electronic conductivity,and large volume changes during charge and discharge hinder the practical applications of SnO_(2)-based electrodes for SIBs and PIBs.Engineering rational structures with fast charge/ion transfer and robust stability is important to overcoming these challenges.Herein,S-doped SnO_(2)(S-SnO_(2))quantum dots(QDs)(≈3 nm)encapsulated in an N,S codoped carbon fiber networks(S-SnO_(2)-CFN)are rationally fabricated using a sequential freeze-drying,calcination,and S-doping strategy.Experimental analysis and density functional theory calculations reveal that the integration of S-SnO_(2) QDs with N,S codoped carbon fiber network remarkably decreases the adsorption energies of Na/K atoms in the interlayer of SnO_(2)-CFN,and the S doping can increase the conductivity of SnO_(2),thereby enhancing the ion transfer kinetics.The synergistic interaction between S-SnO_(2) QDs and N,S codoped carbon fiber network results in a composite with fast Na+/K+storage and extraordinary long-term cyclability.Specifically,the S-SnO_(2)-CFN delivers high rate capacities of 141.0 mAh g^(−1) at 20 A g^(−1) in SIBs and 102.8 mAh g^(−1) at 10 A g^(−1) in PIBs.Impressively,it delivers ultra-stable sodium storage up to 10,000 cycles at 5 A g^(−1) and potassium storage up to 5000 cycles at 2 A g^(−1).This study provides insights into constructing metal oxide-based carbon fiber network structures for high-performance electrochemical energy storage and conversion devices.

Embedded high-quality ternary GaAs_(1−x)Sb_(x) quantum dots in GaAs nanowires by molecular-beam epitaxy

Semiconductor quantum dots are promising candidates for preparing high-performance single photon sources.A basic requirement for this application is realizing the controlled growth of high-quality semiconductor quantum dots.Here,we report the growth of embedded GaAs_(1−x)Sb_(x) quantum dots in GaAs nanowires by molecular-beam epitaxy.It is found that the size of the GaAs_(1−x)Sb_(x) quantum dot can be well-defined by the GaAs nanowire.Energy dispersive spectroscopy analyses show that the antimony content x can be up to 0.36 by tuning the growth temperature.All GaAs_(1−x)Sb_(x) quantum dots exhibit a pure zinc-blende phase.In addition,we have developed a new technology to grow GaAs passivation layers on the sidewalls of the GaAs_(1−x)Sb_(x) quantum dots.Different from the traditional growth process of the passivation layer,GaAs passivation layers can be grown simultaneously with the growth of the embedded GaAs_(1−x)Sb_(x) quantum dots.The spontaneous GaAs passivation layer shows a pure zinc-blende phase due to the strict epitaxial relationship between the quantum dot and the passivation layer.The successful fabrication of embedded high-quality GaAs_(1−x)Sb_(x) quantum dots lays the foundation for the realization of GaAs_(1−x)Sb_(x)-based single photon sources.

A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection

Ratiometric fluorescent detection of iron(Ⅲ)(Fe^(3+))offers inherent self-calibration and contactless analytic capabilities.However,realizing a dual-emission near-infrared(NIR)nanosensor with a low limit of detection(LOD)is rather challenging.In this work,we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots(Si QDs:Er),which emit NIR light at the wavelengths of 810 and 1540 nm.A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe^(3+)detection with a very low LOD(0.06μM).The effects of pH,recyclability,and the interplay between static and dynamic quenching mechanisms for Fe^(3+)detection have been systematically studied.In addition,we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Temperature-dependent photoluminescence of highly luminescent water-soluble CdTe quantum dots

Highly luminescent water-soluble CdTe quantum dots （QDs） have been synthesized with an electrogenerated precursor. The obtained CdTe QDs can possess good crystallizability, high quantum yield （QY） and favorable stability. Furthermore, a detection system is designed firstly for the investigation of the temperature-dependent PL of the QDs. ？2009 Yu Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals （nc-Si） by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 〈 S nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence （I3L） intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Water-soluble CdSe/ZnS quantum dots passivated by poly(glycino amino acid) phosphazenes

Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs of red emission were prepared. Subsequently the trioctylphosphine oxide-stabilized CdSe/ZnS QDs were transferred from chloroform into water through a ligand exchange process with poly(glycino amino acid)phosphazenes, which can be obtained from the saponification of poly (glycino amino ester)phosphazenes at room temperature. The resulting QDs-polymer nanocomposite particles can form colloidally stable suspensions in water and exhibit good photostability.

N-doped graphene quantum dot-decorated N-TiO2/P-doped porous hollow g-C_(3)N_(4) nanotube composite photocatalysts for antibiotic photodegradation and H2 production

Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

Luminescent properties dependence of water-soluble CdTe quantum dots on stabilizing agents and reaction time

The influence of stabilizing agents and reaction time on the luminescent properties of water-soluble CdTe quantum dots(QDs) was discussed.The thioglycolic acid(TGA)-CdTe ODs were characterized by TEM,XRD and FTIR.It is found that larger-size QDs can be synthesized more easily when L-cysteine(Cys) or golutathione(GSH) is chosen as stabilizing agent and TGA is proper to prepare highly luminescent QDs because of the effect between Cd2+ and sulfhydryl group.Furthermore,the absorption wavelength,full width at half maximum(FWHM),stokes shift,photoluminescence(PL) quantum yield and PL stability of TGA-CdTe are strongly dependent on reaction time,in which the absorption wavelength changes against reaction time with an exponential function.The TGA-CdTe QDs prepared at 2 h possess more excellent luminescent properties.

Manipulation of internal blockage in triangular triple quantum dot

We utilize the calculation of hierarchical equations of motion to demonstrate that the spin-dependent properties between adjacent quantum dots(QDs)can be changed by breaking the internal symmetry configuration,corresponding to the inversion of dominant chiral states.In the linear triple quantum dots(LTQDs)connected to two electron reservoirs,we can observe that the blockage appears at the triangle triple quantum dots(TTQDs)by gradually increasing the coupling strength between next-nearest double QDs.When the initial coupling between LTQDs has altered,the internal chiral circulation also undergoes the corresponding transform,thus achieving qualitative regulation and detection of the blocking region.We also investigate the response of the chiral circulation to the dot–lead coupling strength,indicating the overall robust chiral circulation of the TTQDs frustration.

Defect engineering of ternary Cu-In-Se quantum dots for boosting photoelectrochemical hydrogen generation

Heavy-metal-free ternary Cu–In–Se quantum dots(CISe QDs)are promising for solar fuel production because of their low toxicity,tunable band gap,and high light absorption coefficient.Although defects significantly affect the photophysical properties of QDs,the influence on photoelectrochemical hydrogen production is not well understood.Herein,we present the defect engineering of CISe QDs for efficient solar-energy conversion.Lewis acid–base reactions between metal halide–oleylamine complexes and oleylammonium selenocarbamate are modulated to achieve CISe QDs with the controlled amount of Cu vacancies without changing their morphology.Among them,CISe QDs with In/Cu=1.55 show the most outstanding photoelectrochemical hydrogen generation with excellent photocurrent density of up to 10.7 mA cm-2(at 0.6 VRHE),attributed to the suitable electronic band structures and enhanced carrier concentrations/lifetimes of the QDs.The proposed method,which can effectively control the defects in heavy-metal-free ternary QDs,offers a deeper understanding of the effects of the defects and provides a practical approach to enhance photoelectrochemical hydrogen generation.

Proton‑Prompted Ligand Exchange to Achieve High‑Efficiency CsPbI_(3) Quantum Dot Light‑Emitting Diodes

CsPbI_(3)perovskite quantum dots(QDs)are ideal materials for the next generation of red light-emitting diodes.However,the low phase stability of CsPbI_(3)QDs and long-chain insulating capping ligands hinder the improvement of device performance.Traditional in-situ ligand replacement and ligand exchange after synthesis were often difficult to control.Here,we proposed a new ligand exchange strategy using a proton-prompted insitu exchange of short 5-aminopentanoic acid ligands with long-chain oleic acid and oleylamine ligands to obtain stable small-size CsPbI_(3)QDs.This exchange strategy maintained the size and morphology of CsPbI_(3)QDs and improved the optical properties and the conductivity of CsPbI_(3)QDs films.As a result,high-efficiency red QD-based light-emitting diodes with an emission wavelength of 645 nm demonstrated a record maximum external quantum efficiency of 24.45%and an operational half-life of 10.79 h.

MXene Quantum Dots/Copper Nanocomposites for Synergistically Enhanced N_(2)Electroreduction

Electrocatalytic N_(2) reduction reaction(NRR)represents an appealing solution for sustainable ammonia production,whereas exploring high-efficiency NRR catalysts is highly desired but extremely challenging.Herein,we combine Ti_(3) C_(2)T_(x)-MXene quantum dots(MQDs)with porous Cu nanosheets to design a novel heterostructured MQDs/Cu as an effective and durable NRR catalyst.Impressively,MQDs/Cu showed a synergistically enhanced NRR activity with an NH_(3) yield of 78.5 lg h^(-1) mg^(-1)(-0.5 V)and a Faradaic efficiency of 21.3%(-0.4 V),far superior to pure MQDs and Cu,and outperforming the majority of the state-of-the-art NRR catalysts.Density function theory computations demonstrated that the synergy of MQDs and Cu enabled the creation of interfacial Cu-Ti dimer as dual-active-centers to strongly activate the absorbed N 2 and promote the*N_(2)H formation,consequently resulting in the much reduced energy barriers and greatly enhanced NRR performance.

Inorganic Halide Perovskite Quantum Dots:A Versatile Nanomaterial Platform for Electronic Applications

Metal halide perovskites have generated significant attention in recent years because of their extraordinary physical properties and photovoltaic performance.Among these,inorganic perovskite quantum dots(QDs)stand out for their prominent merits,such as quantum confinement effects,high photoluminescence quantum yield,and defect-tolerant structures.Additionally,ligand engineering and an all-inorganic composition lead to a robust platform for ambient-stable QD devices.This review presents the state-of-the-art research progress on inorganic perovskite QDs,emphasizing their electronic applications.In detail,the physical properties of inorganic perovskite QDs will be introduced first,followed by a discussion of synthesis methods and growth control.Afterwards,the emerging applications of inorganic perovskite QDs in electronics,including transistors and memories,will be presented.Finally,this review will provide an outlook on potential strategies for advancing inorganic perovskite QD technologies.

Passivation engineering via silica‐encapsulated quantum dots for highly sensitive photodetection

Organometal halide perovskites are promising semiconducting materials for photodetectors because of their favorable optoelectrical properties.Although nanoscale perovskite materials such as quantum dots(QDs)show novel behavior,they have intrinsic stability issues.In this study,an effectively silane barrier-capped quantum dot(QD@APDEMS)is thinly applied onto a bulk perovskite photosensitive layer for use in photodetectors.QD@APDEMS is synthesized with a silane ligand with hydrophobic CH_(3)-terminal groups,resulting in excellent dispersibility and durability to enable effective coating.The introduction of the QD@APDEMS layer results in the formation of a lowdefect perovskite film with enlarged grains.This is attributed to the grain boundary interconnection effect via interaction between the functional groups of QD@APDEMS and uncoordinated Pb^(2+)in grain boundaries.By passivating the grain boundaries,where various trap sites are distributed,hole chargecarrier injection and shunt leakage can be suppressed.Also,from the energy point of view,the deep highest occupied molecular orbital(HOMO)level of QD@APDEMS can work as a hole charge injection barrier.Improved charge dynamics(generation,transfer,and recombination properties)and reduced trap density of QD@APDEMS are demonstrated.When this perovskite film is used in a photodetector,the device performance(especially the detectivity)stands out among existing perovskites evaluated for energy sensing device applications.