# Mark A. Neifeld's research while affiliated with The University of Arizona and other places

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## Publications (302)

Combinatorial optimization problems over large and complex systems have many applications in social networks, image processing, artificial intelligence, computational biology and a variety of other areas. Finding the optimized solution for such problems in general are usually in non-deterministic polynomial time (NP)-hard complexity class. Some NP-...

We are presenting a tabletop radar range with a scale factor of 100,000. This scale reduction allows to use near IR wavelength instead of radio frequency to determine the radar cross section of complex objects. Scale models are manufactured using a 3D printer with nanometric resolution. Interferometric time-of-flight gives the system depth resoluti...

We are presenting a compact radar range system with a scale factor of 105. Replacing the radio frequency (RF) by optical wavelength (300 THz), the system easily fit on a tabletop. We used interferometric time-of-flight to reproduce radar ranging measurements. Sub-micron range accuracy was achieved with a 100 fs laser pulse, which correspond to 3 cm...

The probabilistic inference model has been widely used in various areas such as error-control coding, machine learning, speech recognition, artificial intelligence and statistics. In this paper, we study both computation and communications power consumption of optical-based and electronic-based implementations of the probabilistic inference algorit...

The probabilistic graphical models (PGMs) are tools that are used to compute probability
distributions over large and complex interacting variables. They have applications in social
networks, speech recognition, artificial intelligence, machine learning, and many more areas.
Here, we present an all-optical implementation of a PGM through the sum-pr...

Non-destructive testing (NDT) by x-ray imaging is commonly used for finding manufacturing defects, cargo inspection, or security screening. These tasks can be regarded as examples of a detection problem where a target is either present or not. Task-specific information (TSI) [J. Opt. Soc. Am. A 24, B25 (2007); Appl. Opt. 47, 4457 (2008)] bounds, an...

The radar cross section of an object is an important electromagnetic property that is often measured in anechoic chambers. However, for very large and complex structures such as ships or sea and land clutters, this common approach is not practical. The use of computer simulations is also not viable since it would take many years of computational ti...

It is well known that a translating mask can optically encode low-resolution measurements from which higher resolution images can be computationally reconstructed. We experimentally demonstrate that this principle can be used to achieve substantial increase in image resolution compared to the size of the focal plane array (FPA). Specifically, we de...

Here, we present the engineering trade studies of a free-space optical communication system operating over a 30 km maritime channel for the months of January and July. The system under study follows the BB84 protocol with the following assumptions: a weak coherent source is used, Eve is performing the intercept resend attack and photon number split...

In the first part of this work, we present two methods for improving the shape-threat detection performance of x-ray computed tomography. Our work uses a fixed-gantry system employing 25 x-ray sources. We first utilize Kullback-Leibler divergence and Mahalanobis distance to determine the optimal single-source single-exposure measurement. The second...

We theoretically investigate and experimentally demonstrate a RF-assisted four-state continuous-variable quantum key distribution (CV-QKD) system. Classical coherent detection is implemented with a simple digital phase noise cancelation scheme. In the proposed system, there is no need for frequency and phase locking between the quantum signals and...

Adaptive compressive measurements can offer significant system performance advantages due to online learning over non-adaptive or static compressive measurements for a variety of applications, such as image formation and target identification. However, such adaptive measurements tend to be sub-optimal due to their greedy design. Here, we propose a...

We investigate a multiple spatial modes based quantum key distribution (QKD) scheme that employs multiple independent parallel beams through a marine free-space optical channel over open ocean. This approach provides the potential to increase secret key rate (SKR) linearly with the number of channels. To improve the SKR performance, we describe a b...

We are investigating the use of optics to solve highly connected graphical models by probabilistic inference, and more specifically the sum-product message passing algorithm. We are examining the fundamental limit of size and power requirement according to the best multiplexing strategy we have found. For a million nodes, and an alphabet of a hundr...

We optimize secret key rates (SKRs) of weak coherent pulse (WCP)-based quantum key distribution (QKD) over time-varying free-space optical channels affected by atmospheric turbulence. The random irradiance fluctuation due to scintillation degrades the SKR performance of WCP-based QKD, and to improve the SKR performance, we propose an adaptive schem...

X-ray Computed Tomography (CT) is used widely for screening purposes. Conventional x-ray threat detection systems employ image reconstruction and segmentation algorithms prior to making threat/no-threat decisions. We ﬁnd that in many cases these pre-processing steps can degrade detection performance. Therefore in this work we will investigate metho...

We present capacity bounds of an optical system that communicates using electromagnetic waves between a transmitter and a receiver. The bounds are investigated in conjunction with a rigorous theory of degrees of freedom (DOF) in the presence of noise. By taking into account the different signal-to-noise ratio (SNR) levels, an optimal number of DOF...

Free-space optical (FSO) channels can be characterized by random power fluctuations due to atmospheric turbulence, which is known as scintillation. Weak coherent source based FSO quantum key distribution (QKD) systems suffer from the scintillation effect because during the deep channel fading the expected detection rate drops, which then gives an e...

We experimentally demonstrate and characterize the performance of a 400-Gbit/s orbital angular momentum (OAM) multiplexed free-space optical link over 120 m on the roof of a building. Four OAM beams, each carrying a 100-Gbit/s quadrature-phase-shift-keyed channel are multiplexed and transmitted. We investigate the influence of channel impairments o...

We study large-alphabet quantum key distribution (QKD) based on the use of weak-coherent states and the time–frequency uncertainty relation. The large alphabet is achieved by dividing time and spectrum into M bins resulting in a frame similar to traditional pulse-position modulation (in time domain). However, the non-uniform occurrence of a photon...

Compressive sensing is a novel sampling/sensing paradigm that enables significant sampling and computation cost reduction for signals with sparse or compressible representation. With compressive sensing technique, the number of measurements needed for accomplishing a specific task can be greatly reduced compared to traditional methods when the sign...

We investigate the sensing of a data-carrying Gaussian beacon on a separate wavelength as a means to provide the information necessary to compensate for the effects of atmospheric turbulence on orbital angular momentum (OAM) and polarization-multiplexed beams in a free-space optical link. The influence of the Gaussian beacon's wavelength on the com...

We simulate and study various computational techniques for image reconstruction applied to a multiplexed Mid-wave-IR Imager. The imager consists of two arms where one is dedicated to high resolution imaging using a lower resolution Focal Plane Array and the other is a single measurement Multispectral imager which uses dispersive optics. We exploit...

We experimentally demonstrate a 400-Gbit/s free-space optical communications link over 120 meters on the building roof by multiplexing four orbital angular momentum(OAM)modes (OAM l = ±1, ±3) each carrying a 100-Gbit/s data channel.

On 10-11 April 2014, the Optical Society of America (OSA) hosted an incubator on compressive sensing at its Washington, D.C., headquarters.

In this paper, we propose several entanglement assisted QKD protocols based on time-energy encoding with the number of mutually unbiased bases (MUBs) larger than two. We describe how to implement these protocols based on: (i) optical FFT device implemented in integrated optics with the help of Franson interferometers and (ii) Weyl gate. We also des...

We study the performance of the BB84 quantum key distribution technique in a marine environment. We quantify effects of loss, scattering, and turbulence on secret key rate and extend single channel results to multi-mode encodings.

We describe an adaptive computed tomography imaging system based on sequential hypotheses testing and apply it to a detection problem. It outperforms non-adaptive computed tomography imaging in terms of decision error rate with same SNR.

We examine the information-theoretical limits for a two-class material classification problem with x-ray pencil beam illumination and energy-resolved diffraction imaging. The materials under study are two liquids: water and diesel.

We study SKRs of QKD systems over time-varying FSO channels under strong turbulence. A channel predictive method is proposed to improve corresponding SKRs. The results show that the higher SKR can be obtained for better prediction accuracy.

This letter presents a design of a principal component analysis (PCA)-based microwave compressive sensing system using reconfigurable array. An iterative beam synthesis process is used to realize the required radiation patterns obtained from PCA. In this letter, a human body scanning system is studied as an example to investigate the compressive se...

As a recently explored property of light, orbital angular momentum (OAM) has potential in enabling multiplexing of multiple data-carrying beams, to increase the transmission capacity and spectral efficiency of a communication system. For the use of OAM multiplexing in free-space optical (FSO) communications, atmospheric turbulence presents a critic...

We investigate the influence of wavelength dependence of turbulence on the compensation performance of OAM beams in a beacon beam-based compensation scheme. We then implement this scheme and demonstrate a 1-Tbit/s OAM-multiplexed free space optical link through emulated turbulence.

Pulse-position modulation (PPM) is a promising technique that can be used to improve the efficiency of quantum key distribution (QKD) based on a Poisson photon source. In this paper, we first investigate a simple entanglement-and- PPM-based QKD protocol and demonstrate the improvement in secret key rate. However, such a PPM-based QKD protocol that...

While the theory of compressive sensing has been very well investigated in the literature, comparatively little attention has been given to the issues that arise when compressive measurements are made in hardware. For instance, compressive measurements are always corrupted by detector noise. Further, the number of photons available is the same whet...

We demonstrate crosstalk mitigation using 4 x 4 multiple-input-multiple-output (MIMO) equalization on an orbital angular momentum (OAM) multiplexed free-space data link with heterodyne detection. Four multiplexed OAM beams, each carrying a 20 Gbit/s quadrature phase-shift keying signal, propagate through weak turbulence. The turbulence induces inte...

We propose an adaptive optics compensation scheme to simultaneously compensate multiple orbital angular momentum (OAM) beams propagating through atmospheric turbulence. A Gaussian beam on one polarization is used to probe the turbulence-induced wavefront distortions and derive the correction pattern for compensating the OAM beams on the orthogonal...

We present a non-greedy adaptive compressive measurement design for application to an M-class recognition task. Unlike a greedy strategy which sequentially optimizes the immediate performance conditioned on previous measurement, a non-greedy adaptive design determines the optimal measurement vector by maximizing the expected final performance. Gaus...

We experimentally investigate the performance of an orbital angular momentum (OAM) multiplexed free space optical (FSO) communication link through emulated atmospheric turbulence. The turbulence effects on the crosstalk and system power penalty of the FSO link are characterized. The experimental results show that the power of the transmitted OAM mo...

The simultaneous pre-and post-turbulence compensation of multiple orbital-angular-momentum (OAM) modes propagating through turbulent channel is experimentally demonstrated in a bidirectional free-space optical (FSO) link by using a single adaptive-optics system.

We design an adaptive compressive imager by maximizing mutual information between measurements and the object. Simulation result shows that the proposed design requires 1.5 times fewer measurements relative to a static information-optimal design.

In contrast with previous compressive light field imagers, we propose an optical architecture that jointly encodes both angular and spatial structure using a 2D random mask. This joint modulation is shown to outperform other compressive LF cameras.

Compressive imaging employs the direct measurement of object features and has been shown to offer both performance (e.g., improved reconstructed image fidelity) and cost (e.g., reduced number of measurements relative to the native dimensionality) advantages. We examine compressive imaging within a stereo vision application in which a traditional co...

Despite the promise of higher performance and/or lower cost cameras, compressive imaging has not yet seen widespread use in either commercial or military applications. This presentation will discuss some possible reasons (both fundamental and practical) for the observed disconnect. Recent results related to compressive 3D imaging will also be prese...

The compressive sensing paradigm exploits the inherent sparsity/compressibility of signals to reduce the number of measurements required for reliable reconstruction/recovery. In many applications additional prior information beyond signal sparsity, such as structure in sparsity, is available, and current efforts are mainly limited to exploiting tha...

The simultaneous compensation of multiple orbital angular momentum (OAM) modes propagating through turbulent channel is experimentally demonstrated by using a Gaussian probe beam for wavefront sensing. The experimental results indicate that the turbulence-induced crosstalk and power penalty could be efficiently mitigated by ~12.5 dB and ~11 dB resp...

We demonstrate crosstalk degradation mitigation using 4×4 MIMO equalization on an orbital-angular-momentum-multiplexed free-space data link with heterodyne detection. 20-Gbit/s QPSK signal with up to -4.8 dB crosstalk is recovered and the BER is reduced by two orders of magnitude.

We present an information-theoretic framework for measurement basis design in compressive imaging. Simulation results show that the reconstruction error obtained with information-optimal projections is nearly an order of magnitude lower than that for random projections.

Compressive imaging systems typically exploit the spatial correlation of the scene to facilitate a lower dimensional measurement relative to a conventional imaging system. In natural time-varying scenes there is a high degree of temporal correlation that may also be exploited to further reduce the number of measurements. In this work we analyze spa...

We use an information-theoretic method developed by Neifeld and Lee [J. Opt. Soc. Am. A 25, C31 (2008)] to analyze the performance of a slow-light system. Slow-light is realized in this system via stimulated Brillouin scattering in a 2 km-long, room-temperature, highly nonlinear fiber pumped by a laser whose spectrum is tailored and broadened to 5...

We adopt a sequential Bayesian experiment design framework for compressive imaging wherein the measurement basis is data dependent and therefore adaptive. The criteria for measurement basis design employs the task-specific information (TSI), an information theoretic metric, that is conditioned on the past measurements. A Gaussian scale mixture prio...

Traditional light field imagers do not exploit the inherent spatio-angular correlations in light field of natural scenes towards reducing the number of measurements and minimizing the spatio-angular resolution trade-off. Here we describe a compressive light field imager that utilizes the prior knowledge of sparsity/compressibility along the spatial...

Difference images quantify changes in the object scene over time. In this paper, we use the feature-specific imaging paradigm to present methods for estimating a sequence of difference images from a sequence of compressive measurements of the object scene. Our goal is twofold. First is to design, where possible, the optimal sensing matrix for takin...

We describe a compressive imager that adapts the measurement basis based on past measurements within a sequential Bayesian estimation framework. Simulations show a 7% improvement in reconstruction performance compared to a static measurement basis.

The inherent redundancy in natural scenes forms the basis of compressive imaging where the number of measurements is less than the dimensionality of the scene. The compressed sensing theory has shown that a purely random measurement basis can yield good reconstructions of sparse objects with relatively few measurements. However, additional prior kn...

Feature-specific imaging (FSI) or compressive imaging involves measuring relatively few linear projections of a scene compared to the dimensionality of the scene. Researchers have exploited the spatial correlation inherent in natural scenes to design compressive imaging systems using various measurement bases such as Karhunen-Lo`eve (KL) transform,...

A block-wise motion detection strategy based on compressive imaging, also referred to as feature-specific imaging (FSI), is described in this work. A mixture of Gaussian distributions is used to model the background in a scene. Motion is detected in individual object blocks using feature measurements. Gabor, Hadamard binary and random binary featur...

We demonstrate a 5-GHz-broadband tunable slow-light device based on stimulated Brillouin scattering in a standard highly-nonlinear optical fiber pumped by a noise-current-modulated laser beam. The noisemodulation waveform uses an optimized pseudo-random distribution of the laser drive voltage to obtain an optimal flat-topped gain profile, which min...

In this chapter we will study a FSO MISO system. Section 2 describes the components of single beam and multi-beam FSO communication links. Because spatial correlation among the propagating beams in a MISO link plays a key role in the system performance, this correlation structure must quantified as a function of turbulence strength, beam separation...

Static feature-specific imaging (SFSI), where the measurement basis remains fixed/static during the data measurement process, has been shown to be superior to conventional imaging for reconstruction tasks. Here, we describe an adaptive approach that utilizes past measurements to inform the choice of measurement basis for future measurements in an F...

Traditional approaches to wide field of view (FoV) imager design usually lead to overly complex optics with high optical mass and/or pan-tilt mechanisms that incur significant mechanical/weight penalties, which limit their applications, especially on mobile platforms such as unmanned aerial vehicles (UAVs).We describe a compact wide FoV imager desi...

Static Feature-specific imaging (SFSI) employing a fixed/static measurement basis has been shown to achieve superior reconstruction performance to conventional imaging under certain conditions.1-5 In this paper, we describe an adaptive FSI system in which past measurements inform the choice of measurement basis for future measurements so as to maxi...

Compressive imaging/sensing employing a random measurement basis does not incorporate the specific object prior information available for natural images. An alternate hybrid measurement basis is proposed that yields improved reconstruction performance for natural images.

Undersampling in the detector array degrades the performance of iris-recognition imaging systems. We find that an undersampling of 8 x 8 reduces the iris-recognition performance by nearly a factor of 4 (