Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Here, we report a storage efficiency greater than 28% in a Tm3+:YAG crystal (where YAG is yttrium a...
Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Here, we report a storage efficiency greater than 28% in a Tm3+:YAG crystal (where YAG is yttrium aluminum garnet) at elevated temperatures, achieving this milestone without relying on optical cavities and without compromising memory bandwidth. We introduce different pumping techniques for Tm-based memories that enable multifrequency-window storage and high memory bandwidth reaching 630 MHz, significantly surpassing previous Tm-based memory demonstrations, considering the operating temperature of 3.5 K. Furthermore, we propose a general method for large-bandwidth atomic frequency memory using non-Kramers rare-earth ions (REIs) in solids, paving the way for storage efficiencies and bandwidths approaching fundamental limits. The compatibility of Tm memories with neutral-atom quantum processors and their seamless integration with scalable photonic platforms, such as lithium niobate on insulator, underscore their potential for distributed quantum computing, hybrid quantum networks, and space-based quantum communication. Our study represents a significant advancement toward practical high-performance quantum memories based on REI-doped crystals, where we predict that gigahertz bandwidth and storage efficiencies exceeding 30% are achievable at lower temperatures.
We describe a fiber-optic-based confocal fluorescence spectrometer for obtaining depth-resolved, attenuated fluorescence emission spectra with lateral resolution of several microns and depth resolution of tens of micr...
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We describe a fiber-optic-based confocal fluorescence spectrometer for obtaining depth-resolved, attenuated fluorescence emission spectra with lateral resolution of several microns and depth resolution of tens of microns. The confocal optics of the spectrometer are small, inexpensive, and easy to construct and to interface to existing spectrometers. We compare the performance of this system to that of conventional fluorescence spectrometers for nonscattering homogeneous and inhomogeneous samples. We demonstrate that the confocal measurements readily provide information about the sample geometry and optical properties not available from nonconfocal measurements. Potential applications of the technique are discussed.
Two methods for the analysis of the acoustic transmission of the respiratory system are presented. Continuous speech utterance is used as acoustic stimulation. The transmitted acoustic signal is recorded from various ...
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Two methods for the analysis of the acoustic transmission of the respiratory system are presented. Continuous speech utterance is used as acoustic stimulation. The transmitted acoustic signal is recorded from various sites over the chest wall. The AR method analyzes the power spectral density function of the transmitted sound, which heavily depends on the microphone assembly and the utterance. The method was applied to a screening problem and was tested on a small database that consisted of 19 normal and five abnormal patients. Using the first five AR coefficients and the prediction error of an AR(10) model, as discriminating features, the system screened all abnormals. An ARMA method is suggested, which eliminates the dependence on microphone and utterance. In this method, the generalized least squares identification algorithm is used to estimate the ARMA transfer function of the respiratory system. The normal transfer function demonstrates a peak at the range of 130-250 Hz and sharp decrease in gain for higher frequencies. A pulmonary fibrotic patient demonstrated a peak at the same frequency range, a much higher gain in the high frequency range with an additional peak at about 700 Hz.
The feasibility of real-time digital filtering using dedicated state-of-the-art microcomputers of 8-bit wordlength is demonstrated. Implementations of Lynn's integer filter structures by means of wrap-around queue...
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The feasibility of real-time digital filtering using dedicated state-of-the-art microcomputers of 8-bit wordlength is demonstrated. Implementations of Lynn's integer filter structures by means of wrap-around queue data structures are shown to operate at sampling rates of over 8 kHz. An initial condition constraint unique to this filter class which must be satisfied to prevent inadvertent overflows or oscillations in microcomputers is discussed. The fast-filtering techniques are applied to the problem of calculating the average absolute value of a fast signal in real time.
Recent studies of genotype-phenotype maps have reported universally enhanced phenotypic robustness to genotype mutations, a feature essential to evolution. Virtually all of these studies make a simplifying assumption ...
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Recent studies of genotype-phenotype maps have reported universally enhanced phenotypic robustness to genotype mutations, a feature essential to evolution. Virtually all of these studies make a simplifying assumption that each genotype—represented as a sequence—maps deterministically to a single phenotype, such as a discrete structure. Here we introduce probabilistic genotype-phenotype (PrGP) maps, where each genotype maps to a vector of phenotype probabilities, as a more realistic and universal language for investigating robustness in a variety of physical, biological, and computational systems. We study three model systems to show that PrGP maps offer a generalized framework which can handle uncertainty emerging from various physical sources: (1) thermal fluctuation in RNA folding, (2) external field disorder in the spin-glass ground state search problem, and (3) superposition and entanglement in quantum circuits, which are realized experimentally on IBM quantum computers. In all three cases, we observe a biphasic robustness scaling which is enhanced relative to random expectation for more frequent phenotypes and approaches random expectation for less frequent phenotypes. We derive an analytical theory for the behavior of PrGP robustness, and we demonstrate that the theory is highly predictive of empirical robustness.
InGaN red micro-LEDs were fabricated with indium tin oxide (ITO) and metal n-electrode designs. Micro-LEDs with ITO electrodes achieved a peak on-wafer external quantum efficiency of 2.1% (at 1.25 A cm−2) and wall-plu...
InGaN red micro-LEDs were fabricated with indium tin oxide (ITO) and metal n-electrode designs. Micro-LEDs with ITO electrodes achieved a peak on-wafer external quantum efficiency of 2.1% (at 1.25 A cm−2) and wall-plug efficiency of 1.7% (at 0.64 A cm−2), representing 1.6 times and 1.5 times improvements compared to metal-based electrodes. Improved performance was attributed to the transparency of ITO, enabling light extraction, while metal electrodes block emission. Both configurations achieved a low leakage current density (≤ 10–7 A cm−2) and a high peak emission wavelength around 650 nm. These results represent a strong potential for low-power consumption required/area-limited AR/VR applications.
作者：
PAKZAD, SComputer Engineering Program
Department of Electrical Engineering The Pennsylvania State University University Park Pennsylvania 16802 USA
The issue of the fault tolerance of interconnection networks has received considerable attention since the last decade. The theoretical framework developed by J. P. Shen and J. P. Hays ( IEEE Trans. Comput. C-33 , 3 (...
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The issue of the fault tolerance of interconnection networks has received considerable attention since the last decade. The theoretical framework developed by J. P. Shen and J. P. Hays ( IEEE Trans. Comput. C-33 , 3 (Mar. 1984), 241–248) and extended by S. Pakzad and S. Lakshmivarahan ( Internat. J. Comput. Syst. Sci. Engrg. 3 , 2 (April 1988), 91–99) can be used as a guideline to analyze the fault tolerance behavior of the interconnection networks in a multicomputer environment. This paper analyzes the fault tolerance characteristics of a range of rearrangeable β-networks based on the concepts and the framework developed by S. Pakzad and S. Lakshmivarahan (cited earlier). These rearrangeable β-networks include the Benes network, the Waksman network, the Joel network, and the serial network. In addition, this paper presents a comparative analysis of the aforementioned networks according to their hardware cost, performance, and degree of fault tolerance.
This paper addresses a set-theoretic method for the detection of data corruption cyber-attacks on the load frequency control loop of a networked power system. The system consists of several interconnected control area...
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This paper addresses a set-theoretic method for the detection of data corruption cyber-attacks on the load frequency control loop of a networked power system. The system consists of several interconnected control areas forming a power grid. Based on the overall discrete-time network dynamics, a convex and compact polyhedral robust invariant set is extracted and is used as a set-induced anomaly detector. If the state vector exits the invariant set,then an alarm will be activated, and the potential threat is considered disclosed. The attack scenario used to assess the efficiency of the proposed anomaly detector concerns corrupted frequency sensor measurements transmitted to the automatic generation control unit of a compromised control area. Simulation studies highlight the ability of a set-theoretic approach to disclose persistent and intermittent attack patterns even when they occur at the same time with changes in the power load demand.
Measurement of small currents is often impeded by a suboptimal signal-to-noise ratio, largely due to background noise. This background noise significantly constrains the range of catalysts accessible for interrogation...
Measurement of small currents is often impeded by a suboptimal signal-to-noise ratio, largely due to background noise. This background noise significantly constrains the range of catalysts accessible for interrogation via micro- and nanoscale electrochemistry. In response, this work reveals how background noise scales in the presence of induced Faradaic reactions. We measured noise under a series of electrochemical conditions and discovered that the induced noise from a Faradaic reaction scales directly with current. Complementary electrochemical impedance spectroscopy measurements demonstrated that diffusional resistance dictates the noise of Faradaic reactions, independent of the electrochemical mechanism. The noise source is thermal in origin and propagates in a predictable trend, which is inversely proportional to the equivalent diffusional resistance of the analyte. The universality of the observed phenomenon allows for better deconvolution of measured charge from background noise, thus assisting in achieving higher resolution and measurement precision, which is a key in micro- and nanoscale electrochemical measurements.
The relationship between optical properties and image contrast in confocal imaging is investigated. A Monte Carlo simulation has been developed to analyze the effects of changes in scattering, index of refraction, and...
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The relationship between optical properties and image contrast in confocal imaging is investigated. A Monte Carlo simulation has been developed to analyze the effects of changes in scattering, index of refraction, and absorption in a three-layer medium. Contrast was calculated from the computed signal-to-background ratios for changes in tissue optical properties. Results show that the largest source of contrast is changes in refractive index. (C) 1996 Optical Society of America
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