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The article focuses on photon entanglement in quantum optics. It is stated that semiconductor quantum dots offer a solid-state platform for generating single and entangled photons. It is mentioned that quantum dots are compatible with modern semiconductor device technology, due to which they can be artificially developed through crystal growth and nanofabrication techniques.

[Display omitted] Semiconductor quantum dots, as promising solid-state platform, have exhibited deterministic photon pair generation with high polarization entanglement fidelity for quantum information applications. However, due to temporal correlation from inherently cascaded emission, photon indistinguishability is limited, which restricts their potential scalability to multi-photon experiments. Here, by utilizing quantum interferences to decouple polarization entanglement from temporal correlation, we improve four-photon Greenberger–Horne–Zeilinger (GHZ) state entanglement fidelity from (58.7 ± 2.2) % to (75.5 ± 2.0) %. Our work paves the way to realize scalable and high-quality multi-photon states from quantum dots. [ABSTRACT FROM AUTHOR]

Layered nanomaterial has become a popular hierarchical material for amplifying chemiluminescence (CL) in recent years, mainly because of its ease of preparation and modification, large specific surface area, and high catalytic activity. In this review, we mainly discuss layered-nanomaterial-amplified CL systems based on graphene and its derivatives, layered double hydroxides, and clay. Detection mechanisms and strategies of layered-nanomaterial-amplified CL systems are provided to show the basic concepts for designing sensitive and selective sensing systems. Strategies for expanding the applications of layered-nanomaterial-amplified CL systems by combination with surfactants, quantum dots, organic dyes, and nanoparticles are introduced for the analysis of various analytes in real samples. The challenges and future trends of layered-nanomaterial-amplified CL systems are discussed at the end of the review. [ABSTRACT FROM AUTHOR]

Highlights: [•] The complete ligand transformation of CdTe QDs from thiolglycolic acid to citrate. [•] Negligible differences are observed between original QDs and new-born QDs. [•] The new-born CdTe QDs can induce minimal cytotoxicity against HepG2 cells. [Copyright &y& Elsevier]

Abstract: In this study, the directional luminescent quantum dot (QD)-layered double hydroxide (LDH) assembly was fabricated by embedding the trace QDs onto the exterior surface of the organo-modified LDHs. It was found that this novel nanomaterial was able to extraordinarily improve an ultra-weak chemiluminescence (CL) emission from peroxynitrous acid (ONOOH). The enhanced CL emission was attributed to the electrostatic concentration of peroxynitrite (ONOO−) onto the orderly surface of the QD-organo-modified LDHs as well as the hydrophobic microenvironment of the organo-LDHs, facilitating the production of superoxide radical ( O2 −) and hydroxyl radical ( OH). In addition, the CL intensity increased with increasing the concentration of nitrite in a wide range of 1.0–1000μM with a detection limit of 0.3μM (S/N=3). Therefore, the proposed method was applied for the selective and sensitive detection of nitrite in sausage samples. Recoveries from spiked real samples were in the range of 96–103%. The results of the proposed method for sensing nitrite in real samples were agreed with those obtained by the standard spectrophotometric method. [Copyright &y& Elsevier]

Memristor characteristics have been reported to be enhanced by inserting graphene oxide quantum dots (GOQDs) in oxide layers. However, it has not been studied how the density of GOQDs affects the resistive switching behavior of memristor devices. In this work, memristor devices in the structure of Ag/Zr0.5Hf0.5O2 (ZHO)/GOQDs/ZHO/Pt are fabricated and tested. The device measurement results show that as the applied voltage is scanned, if the density of GOQDs increases, the resistance adjustment of fabricated memristor devices shifts from abruptly to gradually. Moreover, the resistance of a high-GOQD-density device is modulated by controlling the amplitude, width, polarity, and number of applied voltage pulses. Furthermore, the fabricated memristor device demonstrates basic synaptic behavior, including tunable conductance, short-term plasticity, long-term plasticity, spike-timing-dependent facilitation, and paired-pulse facilitation. These phenomena are attributed to the high density of GOQDs, which prevents Ag+ from migrating through the switching layers, and hence, the formation of Ag conductive filaments is slower. This study reveals that the proposed memristor device with an appropriate density of GOQDs has great potential in artificial electronic synaptic applications. [ABSTRACT FROM AUTHOR]

Abstract: Memristors as electronic artificial synapses have attracted increasing attention in neuromorphic computing. Emulation of both “learning” and “forgetting” processes requires a bidirectional progressive adjustment of memristor conductance, which is a challenge for cutting‐edge artificial intelligence. In this work, a memristor device with a structure of Ag/Zr0.5Hf0.5O2:graphene oxide quantum dots/Ag is presented with the feature of bidirectional progressive conductance tuning. The conductance of proposed memristor is adjusted through voltage pulse number, amplitude, and width. A series of voltage pulses with an amplitude of 0.6 V and a width of 30 ns is enough to modulate conductance. The impacts of pulses with different parameters on conductance modulation are investigated, and the potential relationship between pulse amplitude and energy is revealed. Furthermore, it is proved that the pulse with low energy can realize the almost linear conductance regulation, which is beneficial to improve the accuracy of pattern recognition. The bidirectional progressive conduction modulation mimics various plastic synapses, such as spike‐timing‐dependent plasticity and paired‐pulse facilitation. This progressive conduction tuning mechanism might be attributed to the coexistence of tunneling effect and extrinsic electrochemical metallization effect. This work provides one way for memristor to attain attractive features such as bidirectional tuning, low‐power consumption, and fast speed switching that is in urgent demand for further evolution of neuromorphic chips. [ABSTRACT FROM AUTHOR]

Single photon sources, which are compatible with quantum memories, are important components of quantum networks. In this article, we show optical investigations on isolated GaAs/Al0.25Ga0.75As quantum dots grown via droplet epitaxy, which emit single photons on resonance with the Rb-87-D2 line (780 nm). Under continuous wave resonant excitation conditions, we observe bright, clean, and narrowband resonance fluorescence emission from such a droplet quantum dot. Furthermore, the second-order correlation measurement clearly demonstrates the single photon emission from this resonantly driven transition. Spectrally resolved resonance fluorescence of a similar quantum dot yields a linewidth as narrow as 660 MHz (2.7 μeV), which corresponds to a coherence time of 0.482 ns. The observed linewidth is the smallest reported so far for strain free GaAs quantum dots grown via the droplet method. We believe that this single photon source can be a prime candidate for applications in optical quantum networks. [ABSTRACT FROM AUTHOR]

Developing probes for sensitive H 2 O 2 detection is critical for understanding its related physiological and pathological processes. In this study, novel carbon quantum dot-gold nanocluster (CQD-AuNC) nanosatellite with high fluorescence energy transfer efficiency (∼40%) and dual-emission fluorescent properties have been exploited for fluorescence ratiometric sensing of H 2 O 2 . The sensing mechanism was based on the fact that H 2 O 2 can quench the red emission of AuNCs. Under the optimal conditions, the CQD-AuNC nanosatellite probe was sensitive to H 2 O 2 in the range from 5.0 nM to 80 nM with a limit of detection of 2.9 nM. The practicality of the proposed CQD-AuNC nanosatellite probe was validated by imaging H 2 O 2 in living cells. [ABSTRACT FROM AUTHOR]

The ratio of reduced and oxidized glutathione (GSH/GSSG ratio) is a greater first indication of disease risk than the total concentration of GSH. However, the interferences from thiolated biomolecules, especially cysteine (Cys), make the accurate detection of GSH/GSSG ratio a technical problem. In this work, we successfully used a mixture of quantum dots (QDs) and ZnAl-LDH nanosheets to fabricate a high electrochemiluminescence resonance energy transfer (ERET) efficiency sensor for GSH from the disturbances of amino acids, especially Cys and GSSG. The mechanisms of high ERET efficiency and selectivity were well investigated with spectroscopy analysis and theoretical calculation. The results showed that the interaction force between ZnAl-LDH nanosheets and molecules proved a long-range-ordered space and selective transmission for molecules. On the basis of these interesting phenomena, we successfully measured the GSH/GSSG ratio in whole blood and serum samples. [ABSTRACT FROM AUTHOR]

The utilization of semiconductor quantum dots (QDs) as optical labels for biosensing and biorecognition has made substantial progress. However, the development of a suitable QD-based luminescent probe that is capable of detecting individual reactive oxygen species (ROS) represents a great challenge, mainly because the fluorescence of QDs is quenched by a wide variety of ROS. To overcome this limitation, a novel QD-based turn-on luminescent probe for the specific detection of .OH has been designed, and its application in monitoring the endogenous release of .OH species in living cells is demonstrated. Metal citrate complexes on the surfaces of the QDs can act as electron donors, injecting electrons into the LUMO of the QDs, while .OH can inject holes into the HOMO of the QDs. Accordingly, electron-hole pairs are produced, which could emit strong luminescence by electron-hole recombination. Importantly, this luminescent probe does not respond to other ROS. [ABSTRACT FROM AUTHOR]

Wereport a new type of single InAs quantum dot (QD) embedded atthe junction of gold-free branched GaAs/AlGaAs nanowire (NW) grownon silicon substrate. The photoluminescence intensity of such QD is∼20 times stronger than that from randomly distributed QD grownon the facet of straight NW. Sharp excitonic emission is observedat 4.2 K with a line width of 101 μeV and a vanishing two-photonemission probability of g2(0) = 0.031(2).This new nanostructure may open new ways for designing novel quantumoptoelectronic devices. [ABSTRACT FROM AUTHOR]

Single-photon sources based on semiconductor quantum dots offer distinct advantages for quantum information, including a scalable solid-state platform, ultrabrightness and interconnectivity with matter qubits. A key prerequisite for their use in optical quantum computing and solid-state networks is a high level of efficiency and indistinguishability. Pulsed resonance fluorescence has been anticipated as the optimum condition for the deterministic generation of high-quality photons with vanishing effects of dephasing. Here, we generate pulsed single photons on demand from a single, microcavity-embedded quantum dot under s-shell excitation with 3 ps laser pulses. The π pulse-excited resonance-fluorescence photons have less than 0.3% background contribution and a vanishing two-photon emission probability. Non-postselective Hong-Ou-Mandel interference between two successively emitted photons is observed with a visibility of 0.97(2), comparable to trapped atoms and ions. Two single photons are further used to implement a high-fidelity quantum controlled-NOT gate. [ABSTRACT FROM AUTHOR]

In this work, different types of Mn-doped ZnS QDs were prepared and applied to study of the chemiluminescence reaction of hydrogen peroxide and periodate. The effects of the size of nanoparticles, shell protection and the stabilizing agents on chemiluminescence intensity were studied. The results indicated that the size of quantum dots was not the only factor to enhance the intensity of chemiluminescence system. Different stabilizing agents and the silica film protection will also influence the performance of the quantum dots in the chemiluminescence reaction. A CL spectrum was examined by using a series of high-energy cut-off optical filters and a possible mechanism of the CL was also proposed. [ABSTRACT FROM AUTHOR]