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Quantum dot (QD) light-emitting diodes (QLEDs) are promising candidates for next-generation displays because of their high efficiency, brightness, broad color gamut, and solution-processability. Large-scale solution-processing of electroluminescent QLEDs poses significant challenges, particularly concerning the precise control of the active layer's thickness and uniformity. These obstacles directly impact charge transport, leading to current leakage and reduced overall efficiency. Blade-coating is a prevalent and scalable solution processing technique known for its speed and minimal waste. Additionally, it allows for continuous "roll-to-roll" processing, making it highly adaptable in various applications. In this study, we demonstrate the precise control of blade speed in the Landau-Levich regime to create a uniform QD emission layer, using a commercial CdSe/ZnS QD as a representative example. QDs assemble into different morphologies on glass and the underlying layers of the QLED device due to variations in interaction energy. The QD film thickness can be modified from monolayer to multilayer by adjusting blade speed, which can be predicted by fitting the Landau-Levich-Derjaguin theory. The optimal speed at 7 mm/s results in a QD film with a surface coverage of around 163% and low roughness (1.57 nm mean square height). The QLED external quantum efficiency (EQE) of approximately 1.5% was achieved using commercially available CdSe/ZnS QDs with low photoluminescence quantum yield (PLQY), and an EQE of around 7% has been obtained using lab-made InP/ZnSe/ZnS QDs having a solution PLQY of 74%. All-blade-coated CdSe-QLEDs are further demonstrated by adopting the optimized speed for the QD layer. This method demonstrates significant potential for developing low-cost, reproducible, and scalable QLED technologies with uniform emission characteristics and low-waste production., Comment: 36 pages, 17 figures

The quantum dynamics of a compound sample consisting from a semiconductor double quantum dot (DQD) system non-linearly coupled with a leaking single-mode micro-resonator is theoretically investigated. The focus is on the resonance condition when the transition frequency of the double quantum dot equals to the doubled resonator frequency, respectively, and the resulting interplay among the involved phonon or photon channels. As a result, the steady-state quantum dynamics of this complex non-linear system exhibits a variety of possible effects that have been demonstrated here. Particularly, we have found the relationship among the electrical current through the double quantum dot and the microwave field inside the resonator that is nonlinearly coupled to it, with a corresponding emphasizing on their critical behaviors. Additionally, the quantum correlations of the photon flux generated into the resonator mode vary from super-Poissonian to Poissonian photon statistics, leading to single-qubit lasing phenomena at microwave frequencies., Comment: 10 pages, 3 figures

We investigate the thermoelectric properties of a double quantum dot system coupled to two metallic reservoirs, focusing on two main effects: (i) the influence of coupling asymmetry between the quantum dot and the reservoirs on the Seebeck coefficient, and (ii) the impact of asymmetry in the energy levels of the dots on current rectification. In the first case, we find that introducing moderate asymmetry significantly enhances the Seebeck coefficient. In the second case, while rectification vanishes when the energy levels are degenerate, substantial rectification is achieved when one energy level lies below and the other above the Fermi level. We further interpret the dependence of rectification magnitude and shape on system parameters using analytical results from a spinless model., Comment: 9 pages, 6 figures, accepted in Phys. Rev. B

In this paper, we investigate the thermal quantum correlations in a semiconductor double quantum dot system. The device comprises a single electron in a double quantum dot subjected to a longitudinal magnetic field and a transverse magnetic field gradient. The thermal entanglement of the single electron is driven by the charge and spin qubits. Utilizing the density matrix formalism, we derive analytical expressions for thermal concurrence and correlated coherence. The main goal of this work is to provide a good understanding of the effects of temperature and various parameters on quantum coherence. Additionally, our findings indicate that the transverse magnetic field can be employed to adjust the thermal entanglement and quantum coherence of the system. We also highlight the roles of thermal entanglement and correlated coherence in generating quantum correlations, noting that thermal correlated coherence is consistently more robust than thermal entanglement. This suggests that quantum algorithms based solely on correlated coherence might be more resilient than those relying on entanglement., Comment: 8 pages, 7 figures

A model of the non-concentric spherical core-shell quantum dot under the influence of an externally applied electric field was proposed. It was established that the energy spectrum of both the electron and the hole depends on the intensity of the electric field as well as on the specific location of the core within the quantum dot. The phenomenon of energy level splitting and degeneration was analyzed in detail. Additionally, the variations in the optical gap were determined and expressed as a function of the applied electric field strength and the position of the core in the quantum dot., Comment: 8 pages, 5 figures (Published version)

We describe here a theory of a quantum dot in an electrically tunable MoSe$_2$/WSe$_2$ heterostructure. Van der Waals heterostructures allow for tuning their electronic properties beyond their monolayer counterparts. We start by determining their electronic structure using density functional theory. We obtain the type-II band alignment and close in energy conduction band minima (valleys) at the $K$ and $Q$ points in the Brillouin zone. The valence band maxima, also energetically close, are located at the $K$ and $\Gamma$ points. By analyzing the Kohn-Sham wavefunctions, we describe the layer, spin, and orbital contributions. Next, we construct an \textit{ab initio}-based tight-binding model, which helps us to better understand the complexity of the interlayer interactions. We determine the effect of a vertical electric field, showing that vertical gating enables control of valleys extrema and their occupancy. Finally, we employ the tight-binding model to investigate laterally gated quantum dots and analyze the influence of a perpendicular electric field on their energy spectrum. Our results demonstrate that tuning the electric field enables control over the valley character of the quantum dot states, selectively localizing them in either the $K$ or $Q$ valleys, as evidenced by their characteristic degeneracies and wavefunctions.

We studied time-dependent features of high-frequency fluorescent radiation from a two-level quantum system with broken inversion spatial symmetry. The system in question was modelled after a one-electron two-level asymmetric polar semiconductor quantum dot whose electric dipole moment operator has permanent unequal diagonal matrix elements. The dot was permanently excited by incoherent pumping of some sort. Our attention was focused on the evolution of the fluorescence spectrum following abrupt switching on of an additional driving monochromatic field, which frequency is much lower than the optical transition frequency of the quantum dot. An analytical expression for the fluorescence spectrum as a function of the amplitude, initial phase and frequency of the monochromatic driving field, as well as of the pumping intensity and the elapsed time, was derived., Comment: 14 pages, 11 figures

We propose a nested quantum dot structure for improved control of entanglement induced by the Heisenberg exchange between an electron and a qubit with relative motion. The entanglement is quantified by the mutual information (MI). The electron, initially prepared in the ground state, generally produces greater entanglement when excited to the scattering state compared to remaining in the bound state. In the bound state, the final entanglement oscillates as a function of the qubit speed and can be tuned accordingly. In the case of long-range interaction, the normalized exchange distribution leads to substantial final entanglement, independent of the qubit moving direction, indicating that even very weak but prolonged exchange can still generate significant entanglement. In the case of short-range interaction, different moving directions lead to varying MI values. We also consider the scenario without the nested dot and find that the same maximum (among all times) MI is pre-determined solely by the initial angle between the spins. In this case, the entanglement exhibits different growth characteristics during different phases. The saturation of the MI mimics that of a strict zero-dimensional quantum dot, where exchange and time are combined into a single parameter, the amount of interaction., Comment: 7 pages, 3 figures

Transformers are widely used for their ability to capture data relations in sequence processing, with great success for a wide range of static tasks. However, the computational and memory footprint of their main component, i.e., the Scaled Dot-product Attention, is commonly overlooked. This makes their adoption in applications involving stream data processing with constraints in response latency, computational and memory resources infeasible. Some works have proposed methods to lower the computational cost of transformers, i.e. low-rank approximations, sparsity in attention, and efficient formulations for Continual Inference. In this paper, we introduce a new formulation of the Scaled Dot-product Attention based on the Nystr\"om approximation that is suitable for Continual Inference. In experiments on Online Audio Classification and Online Action Detection tasks, the proposed Continual Scaled Dot-product Attention can lower the number of operations by up to three orders of magnitude compared to the original Transformers while retaining the predictive performance of competing models., Comment: 11 pages, 7 figures

The study investigates and compares the impact of intense, non-diffractive, non-resonant structured laser beams with various intensity profiles on the properties of InAs/GaAs cylindrical quantum dot. The comparative study demon-strates that the different structured beams, having unique symmetries and hence properties, have significant effects on the confinement potentials and electron probability densities of the quantum dot. It is shown that the system is most sensitive to the intensity and peak position changes of the zeroth order Bessel beam. Drastic changes in the dressed confinement potentials and electron probability densities under the impact of the above-mentioned beams were demonstrated, which can lead to the usage of the following method in such applications, where the precise manipulation of the charge carrier location is required. This study provides new insights into the role of structured laser fields in quantum dot systems, offering possibilities for their use in advanced nanophotonics and quantum information technologies.

Semiconductor nanowires can be utilized to create quantum dot qubits. The formation of quantum dots is typically achieved by means of bottom gates created by a lift-off process. As an alternative, we fabricated flat buried bottom gate structures by filling etched trenches in a Si substrate with sputtered TiN, followed by mechanical polishing. This method achieved gate line pitches as small as 60 nm. The gate fingers have low gate leakage. As a proof of principle, we fabricated quantum dot devices using InAs nanowires placed on the gate fingers. These devices exhibit single electron tunneling and Coulomb blockade., Comment: 7 pages main manuscript, 5 pages supplementary material, 6 figures in main manuscript, 6 supplementary figures

Dense arrays of semiconductor quantum dots are currently employed in highly efficient quantum dot lasers for data communications and other applications. Traditionally, the electronic properties of such quantum nanostructures have been treated as isolated objects, with the degree of hybridization between neighboring quantum dots and the wetting layer left unexplored. Here, we use atom probe tomography and transmission electron microscopy to uncover the three-dimensional composition profile of a high-density ensemble of epitaxial InAs/GaAs quantum dots. The sub-nanometer compositional data is used to construct the 3D local band structure and simulate the electronic eigenstates within the dense quantum dot ensemble using finite element method. This in situ electronic simulation reveals a high degree of hybridization between neighboring quantum dots and the wetting layer, in stark contrast to the usual picture of isolated quantum nanostructures. The simulated transition energies are compared with low temperature photoluminescence. This work has important applications for quantum dot laser design and paves the way to engineering ensemble effects in quantum dot lasers and other quantum nanostructures., Comment: 26 pages, 10 figures

We investigate chiral quantum dot (QD)-based Josephson junction and show the correlation-induced Josephson diode effect (JDE) in it. The presence of electron-electron interaction spontaneously creates an imbalance between up- and down-spin electrons during the non-equilibrium transport making the QD effectively magnetic. The simultaneous presence of the chirality and the interaction eventually results in the field-free JDE in our chiral QD junction. We employ the Keldysh non-equilibrium Green's function technique to study the behavior of the Josephson current (JC) and the rectification coefficient (RC) of our Josephson diode (JD). We show a sign-changing behavior of the RC with the Coulomb correlation and the lead-to-dot coupling strength and find the maximum magnitude of the RC $\sim 72\%$ for moderate interaction strength. Our proposed field-free Josephson diode (JD) based on interacting chiral QD may be a potential switching component in superconductor based devices., Comment: 14 pages; 8 figures; comments are welcome

Recent advances in semiconductor spin qubits have achieved linear arrays exceeding ten qubits. Moving to two-dimensional (2D) qubit arrays is a critical next step to advance towards fault-tolerant implementations, but it poses substantial fabrication challenges, particularly because enabling control of nearest-neighbor entanglement requires the incorporation of interstitial exchange gates between quantum dots in the qubit architecture. In this work, we present a 2D array of silicon metal-oxide-semiconductor (MOS) quantum dots with tunable interdot coupling between all adjacent dots. The device is characterized at 4.2 K, where we demonstrate the formation and isolation of double-dot and triple-dot configurations. We show control of all nearest-neighbor tunnel couplings spanning up to 30 decades per volt through the interstitial exchange gates and use advanced modeling tools to estimate the exchange interactions that could be realized among qubits in this architecture. These results represent a significant step towards the development of 2D MOS quantum processors compatible with foundry manufacturing techniques., Comment: 9 pages, 5 figures

Arrays of gate-defined semiconductor quantum dots are among the leading candidates for building scalable quantum processors. High-fidelity initialization, control, and readout of spin qubit registers require exquisite and targeted control over key Hamiltonian parameters that define the electrostatic environment. However, due to the tight gate pitch, capacitive crosstalk between gates hinders independent tuning of chemical potentials and interdot couplings. While virtual gates offer a practical solution, determining all the required cross-capacitance matrices accurately and efficiently in large quantum dot registers is an open challenge. Here, we establish a Modular Automated Virtualization System (MAViS) -- a general and modular framework for autonomously constructing a complete stack of multi-layer virtual gates in real time. Our method employs machine learning techniques to rapidly extract features from two-dimensional charge stability diagrams. We then utilize computer vision and regression models to self-consistently determine all relative capacitive couplings necessary for virtualizing plunger and barrier gates in both low- and high-tunnel-coupling regimes. Using MAViS, we successfully demonstrate accurate virtualization of a dense two-dimensional array comprising ten quantum dots defined in a high-quality Ge/SiGe heterostructure. Our work offers an elegant and practical solution for the efficient control of large-scale semiconductor quantum dot systems., Comment: 14 pages, 5 figures, 8 pages of supplemental material