Name: Nadav Eliran Rosenthal. Supervisor: Prof. Joseph Tabrikian. Degree: PhD Seminar title: MCRB for Parameter Estimation from One-Bit Quantized and Oversampled Measurements. Name: Ayush Mehra Supervisor Name: Prof Shlomi Arnon Degree Program: PhD Seminar Topic: Analyzing Beams carrying Orbital Angular Momentum in Optical Communication Systems

Abstract: One-bit quantization has garnered significant attention in recent years for various signal processing and communication applications. Estimating model parameters from one-bit quantized data can be challenging, particularly when the quantization process is explicitly accounted for in the estimator. In many cases, the estimator disregards quantization effects, leading to model misspecification. Consequently, estimation errors arise from both quantization and misspecification. Traditional performance bounds, such as the Cramér-Rao bound (CRB), fail to capture the impact of misspecification on estimation performance. To address this limitation, we derive the misspecified CRB (MCRB) for parameter estimation in a quantized data model consisting of a signal component in additive Gaussian noise. We apply this bound to direction-of-arrival estimation using quantized measurements from a sensor array and to frequency estimation with oversampled quantized data. The simulations show that the MCRB is asymptotically achieved by the mean-squared-error of the misspecified maximum-likelihood estimator. Our results demonstrate that, unlike in finely quantized scenarios, oversampling can significantly enhance the estimation performance in the presence of misspecified one-bit quantized Seminar Abstract: Optical wireless communication (OWC) is being actively explored for next-generation (B5G/6G) systems because it can support very high data rates with low latency. One promising approach within OWC is the use of beams carrying orbital angular momentum (OAM), which have a helical phase structure . Since different OAM modes are orthogonal, they can be used to carry multiple data streams simultaneously, increasing the overall channel capacity. However, in practice, several challenges arise. Beam divergence over long distances causes the beam to spread significantly, while atmospheric turbulence and misalignment between the transmitter and receiver introduce distortions and crosstalk between modes. As a result, a large receiver aperture is often required to capture the full beam, which is not always practical. To overcome this limitation, an alternative approach is to analyze only a small portion of the received beam instead of capturing it entirely. By extracting relevant features from this localized region, it is still possible to identify the transmitted OAM mode, reducing both system complexity and receiver size. More recently, this work has been extended beyond communication toward quantum information processing. In this context, Laguerre-Gaussian (LG) modes offer a natural high-dimensional basis. Using Multi-Plane Light Conversion (MPLC), it becomes possible to perform programmable transformations between these modes. The current focus is on designing high-fidelity quantum gates using LG modes within an MPLC framework. The primary aim of this research is to develop efficient methods for utilizing structured light, particularly beams carrying orbital angular momentum (OAM), in both optical communication and quantum information processing. Initially, the work focuses on addressing a key practical limitation in OAM-based communication systems, namely, the requirement of capturing the entire received beam. The objective is to develop a mathematical framework and experimental approach that enables reliable detection of OAM modes using only a small portion of the beam, while accounting for real-world impairments such as beam divergence, atmospheric turbulence, and transmitter–receiver misalignment. The goal is to optimize system performance in terms of signal-to-noise ratio and bit-error rate under these constraints. Building on this foundation, the research extends toward high-dimensional quantum information processing using spatial modes of light. In this direction, the aim is to design and implement quantum gate operations using Laguerre–Gaussian (LG) modes within a Multi-Plane Light Conversion (MPLC) framework. Key research questions include identifying optimal mode sets for high-fidelity transformations, minimizing modal crosstalk in finite-plane systems, and developing scalable architectures for implementing multi-dimensional quantum logic. Ultimately, the work seeks to bridge classical OAM communication techniques with emerging photonic quantum technologies.