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[ACM Press the 14th IEEE/ACM International Symposium - Athens, Greece (2018.07.17-2018.07.19)] Proceedings of the 14th IEEE/ACM International Symposium on Nanoscale Architectures - NANOARCH '18 - Signal Synchronization in Large Scale Quantum-dot Cellular Automata Circuits
摘要： Quantum-dot fabrication is a well-established nanotechnology, which have many applications in many different scientific fields. By placing four quantum-dots on the corners of a square, a cell is formed, in which the digital information can be stored. This cell serves as the structural device of Quantum-dot Cellular Automata (QCA) circuits. After QCA presentation, several digital circuits and systems have been designed and proposed in the literature. However, one of the biggest problems QCA designers have to face to pave the successful design of functional and large scale QCA circuits is signal synchronization. In this paper, a novel approach of the aforementioned problem is presented. This approach is inspired by the well known computational problem of Firing Squad Synchronization (FSS). FSS problem has many similarities with large scale QCA circuits synchronization problem. In addition, FSS problem has been studied by many researchers and many efficient solutions have been proposed in the literature.
关键词： Synchronization,Firing Squad Synchronization problem,Quantum-dot Cellular Automata (QCA),Large Scale Circuits,Nanoelectronics
更新于2025-09-23 15:22:29
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An efficient quantum photonic phase shift in a low Q-factor regime
摘要： Solid-state quantum emitters have long been recognised as the ideal platform to realize integrated quantum photonic technologies. We demonstrate that a self-assembled negatively charged quantum dot (QD) in a low Q-factor photonic micropillar is a suitable design for deterministic polarisation switching and spin-photon entanglement. We show this by measuring a shift in phase of an input single photon of at least 2π/3. As we explain in the text, this is strong experimental proof that input photons can interact with the emitter deterministically. A deterministic photon-emitter interaction is a viable and scalable means to achieve several vital functionalities such as single photon switches and entanglement gates. Our experimentally determined value is limited by mode mismatch between the input laser and the cavity, QD spectral fluctuations and spin relaxation. When on-resonance we estimate that up to ～ 80% of the collected photons couple into the cavity mode and have interacted with the QD and undergone a phase shift of π.
关键词： micropillar cavity,quantum dot,cavity QED
更新于2025-09-23 15:22:29
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An Efficient Clocking Scheme for Quantum-dot Cellular Automata
摘要： Fast pace growth in the IC industry is facing the challenges of feature size reduction which in turn demands an alternative to current CMOS VLSI. Quantum-dot cellular automata is emerging as one of the viable alternative nanotechnologies with high device density, high operating frequency and low power characteristics. Information transition and propagation in QCA take place with the underlying clocking circuitry. Thus, clocking is the main source of power of the QCA circuit as well as play the vital role of information synchronization in QCA circuit. For efficient design and to provide routing option, a regular, scalable clocking structure becomes the utmost necessity of QCA circuit. In this context, a robust, efficient and scalable (RES) clocking scheme for QCA circuit is proposed which can facilitate three directional information flow within a single clock zone. Also, it can facilitate the feedback path without extra layer (unlike 2DDwave scheme) and overcome the complex multilayer wire crossing (unlike USE scheme) with most promising coplanar crossover. Simulation results underpin the significant improvement in terms of clocking zone, area and cells.
关键词： Coplanar Wire Crossing,Quantum-dot Cellular Automata (QCA),Clocking Circuitry,Clocking,Feedback Path
更新于2025-09-23 15:22:29
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Quantum-dot circuit-QED thermoelectric diodes and transistors
摘要： Recent breakthroughs in quantum-dot circuit-quantum-electrodynamics systems are promising both from fundamental perspectives and from the point of view of quantum photonic devices. However, understanding such setups as potential thermoelectric devices has been missing. In this paper, via the Keldysh nonequilibrium Green’s function approach, we show that cavity-coupled double quantum-dots can serve as excellent quantum thermoelectric diodes and transistors. Using an enhanced perturbation approach based on the exact polaron transformation, we find dependencies of thermoelectric transport properties on the electron-photon interaction beyond the predictions from the conventional second-order perturbation theory. In particular, strong light-matter interaction leads to pronounced rectification effects for both charge and heat, as well as thermal transistor effects in the linear transport regime, which opens up a cutting-edge frontier for quantum thermoelectric devices.
关键词： rectification,light-matter interaction,circuit-QED,diode,transistor,thermoelectric,thermal transistor,quantum-dot
更新于2025-09-23 15:22:29
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Theoretical study on optical response in nanostructures in the Born–Markov regime: The role of spontaneous emission and dephasing
摘要： We theoretically study the linear and nonlinear optical susceptibility in a nanostructure that interacts with a classical monochromatic optical field, by means of the solution of a Born-Markov master equation in the Lindblad form, considering as environment for the system the quantum vacuum of the continuum of modes of the external electromagnetic field. The processes of spontaneous emission and dephasing between two levels of the nanostructured quantum system are studied formally, within the framework of the quantum theory of open systems. It was found that the phenomenological master equation corresponds to a Born-Markov master equation in the Lindblad form that considers only the dissipative terms of spontaneous emission and dephasing, provided that the transverse coherence time is smaller than spontaneous emission time . Finally, comparative results are presented between the proposed methodology and the conventional method for: optical rectification, optical absorption, generation of second harmonic and generation of third harmonic in a cylindrical quantum dot (CQD) of with a hydrogen-like impurity inside it and under the action of a uniform magnetic field.
关键词： Lindblad,quantum dot,Optical susceptibility,Born-Markov,open quantum systems
更新于2025-09-23 15:21:21
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Charge qubit under optical control in a thin semiconductor slab
摘要： The dynamics of a single-electron double quantum dot (charge qubit) in an optical microcavity has been theoretically analysed taking into account the influence of optical and acoustic phonons. The Lamb modes of a two-dimensional mechanical resonator (thin slab) are considered as an example of an acoustic phonon subsystem. It is found that an optical phonon mode can be used as a qubit control tool, similar to the microcavity photon one. The probability of the quantum operation ‘NOT’ has been calculated for two qubit control scenarios: in the microcavity photon field and in the combined photon – phonon field of a microcavity and slab. It is shown that the coherent energy exchange between a qubit and a set of acoustic phonon modes reduces this probability, which depends on the number of modes, the initial state of the phonon field, and the decay rate of modes.
关键词： acoustic phonons,quantum dot,microcavity,quantum computer,qubit
更新于2025-09-23 15:21:21
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Fluorescence Imaging for Ultrafiltration of Individual Nanoparticles from a Colloidal Solution in Track Membranes
摘要： We have used ? uorescence nanoscopy for direct imaging of adsorption of individual colloidal quantum dots of diameter ~10 nm (spherical core/shell CdSeS/ZnS semiconductor nanocrystals, functionalized by organic oleic acid ligands) in nanopores of a nuclear ? lter (a polypropylene track membrane with pores of diameter ~500 nm). We have shown that when a colloidal toluene solution passes through the pores of the membrane, the nanoparticles are completely retained at a depth of 10 μm.
关键词： nanopore,single-photon source,CdSe,membrane,nanoscopy,entangled-photon source,quantum dot,colloidal solution,microscopy,nanoparticles,ultra? ltration,oleic acid,nuclear ? lter,luminescence,polymer
更新于2025-09-23 15:21:21
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Bi-Exciton Dissociation Dynamics in Nano-Hybrid Au-CuInS <sub/>2</sub> Nanocrystals
摘要： Multiexciton harvesting from semiconductor quantum dot has been a new approach for improving the solar cell efficiency in Quantum Dot Sensitized Solar Cells (QDSC). Till date, relation between multiexciton dissociation in metal?semiconductor nanohybrid system and boosting the power conversion efficiency (PCE) of QDSC were never discussed. Herein we report a detailed spectroscopic investigation of biexciton dissociation dynamics in copper indium sulfide (CuInS2, also referred as CIS) and Au-CIS nanohybrid, utilizing both time-resolved PL and ultrafast transient absorption (TA) techniques. Ultrafast transient absorption suggests the formation of bi-exciton in CIS NCs which efficiently dissociates in Au-CIS nanohybrids. Maximum multiexciton dissociation (MED) efficiency is determined to be ~ 80% at higher laser fluency, however it was observed to be 100% at lower laser fluency. Prior to exciton dissociation electrons are captured by Au NP in the nanohybrid from the conduction band of CIS NCs which is energetically higher than Fermi level of Au. Here we demonstrate the proof-of-concept in multi-electron dissociation which may provide a new approach for improving the efficiency in QDSSCs, where we found power conversion efficiency (PCE) of Au-CIS nanohybrids up to 2.49% as compared to ~1.06% ~for pure CIS NCs in similar condition. This finding can be an efficient approach towards the design and development of efficient solar cell and optoelectronic devices using the principles of multiexciton generation and extracting multiexcitons in metal-semiconductor nanohybrid system.
关键词： copper indium sulfide,biexciton dissociation dynamics,Quantum Dot Sensitized Solar Cells,power conversion efficiency,ultrafast transient absorption,Multiexciton harvesting,Au-CIS nanohybrid
更新于2025-09-23 15:21:21
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Effect of PbS quantum dot-doped polysulfide nanofiber gel polymer electrolyte on efficiency enhancement in CdS quantum dot-sensitized TiO2 solar cells
摘要： Quantum dot-sensitized solar cells (QDSSCs) are among the most promising low cost third generation solar cells. Semiconductor quantum dots have unique properties such as high molar extinction coefficients, tunable energy gap by the quantum confinement effect and the ability of multiple exciton generation. In this study, stable CdS QDSSCs were fabricated by using polysulfide liquid electrolytes and also by using cellulose acetate nanofiber-based gel electrolytes. Incorporation of PbS Q dots to the liquid or gel electrolyte showed a significant enhancement in solar cell efficiency. Under the simulated light of 100 mW cm-1 the efficiency of the polysulfide liquid electrolyte based CdS QD solar cells increased from 1.19% to 1.51% and the efficiency of the nanofibre gel electrolyte based CdS QD solar cells increased from 0.94 % to 1.46% due to the incorporation of 5% (wt/wt) PbS Q dots into the respective electrolytes. The efficiency increase has been attributed to the increase in short circuit photocurrent density due to increased sulfide ion (S2-) conductivity evidently caused by indirect ionic dissociation facilitated by PbS QDs.
关键词： Sulfide ion conductivity,Nanofibre gel electrolyte,Efficiency enhancement,Quantum dot sensitized solar cells,Quantum dot doped electrolyte
更新于2025-09-23 15:21:01
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Hybrid of quantum dots for interfacial tension reduction and reservoir alteration wettability for enhanced oil recovery (EOR)
摘要： Nanoparticle stabilized emulsions in enhanced oil recovery are more attractive and practical than conventional emulsions which stabilized by colloidal particles and different surfactants due to their advantages and special characteristics such as high stability in harsh condition, move long distance in reservoirs without high retention due to small size of nanoparticles. Only one third of original oil in place (OIP) is usually produced and two third of oil in place will be trapped to reservoir rockthus suitable chemical enhanced oil recovery (C-EOR) methods should be used. In this research, we have suggested a novel, economical and commercial method for synthesis N-doped graphene quantum dots (N-GQDs)/MoS2 quantum dots (MQDs) nanohybrids for preparing different percentage of Nanoemulsions which can reduce alterfacial tension significantly so it can used for Enhanced Oil Recovery (EOR) application. MoO3 material was used as a base of MQDs. MQDs was synthesized via exfoliation of MoS2 nanoparticles by Butyl lithium under N2 atmosphere condition. N-GQDs were synthesized by citric acid and urea materials via hydrothermal method. GQDs/MQDs were prepared via a simple sol-gel method for 5 h string. Synthetic materials were characterized with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV–visible absorption, Scanning Microscopic Electron (SEM), EDX profile and mapping, Transmission electron microscopy (TEM), High Resolution Transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). Then, emulsions were prepared with two different cationic and anionic surfactants and the stability and morphology of emulsion droplets were investigated in condition close to reservoir environment. Our results show that 10% GQDs/MQDs in cationic surfactant and 50% GQDs/MQDs in anionic surfactant have good stability and very small and fine emulsion droplets in simulated reservoir conditions in laboratory. The Interfacial Tension (IFT) measurement shows N70% improvement which indicates the high ability of these nanohybrids in reducing the surface tension than previous nanohybrids. Contact angle values show that these nanohybrids can alter the wettability of reservoir rock from oil-wet to water-wet so the trapped oil in the porous region of rock can be easily extracted in the presence of a layer of these nanohybrids. Furthermore, according to the results of altering the density and viscosity of nanohybrids, these are not as limiting parameters and only about 1% increasing observed for density and viscosity, respectively. Coreflooding test revealed the high oil recovery efficiency (22%) at very low nanofluid concentration (0.01 wt%).
关键词： Molybdenum disulfide quantum dots,Graphene quantum dots,Nanohybrids emulsion,Enhanced oil recovery (EOR),Quantum dot hybrids,Rock reservoir alteration wettability
更新于2025-09-23 15:21:01