arXiv subjects

Yuval Idan

Publications and source records attributed to Yuval Idan.

6 recordsLinked to original sources

arXiv2026

Quantum Error Mitigation with Diffusion-Like Models

Coupling between a quantum system and its environment causes decoherence by transferring information from the system to environmental degrees of freedom. When discretized in time, such interactions can be interpreted as sequences of weak measurements that provide an effective model of noisy quantum dynamics. Motivated by this picture, we propose an AI-assisted error-mitigation framework for quantum diffusion processes generated by sequential local weak measurements. The forward process progressively erases information from the input state through weak measurements performed in randomly selected Pauli bases, producing basis-dependent local dephasing and locally depolarizing dynamics on average. Machine-learning models are trained on exact synthetic density matrices to learn a channel- and distribution-specific denoising map and estimate the corresponding pre-noise state. We benchmark the approach on single-qubit states and separable and entangled multi-qubit registers. We also study distribution-dependent local-to-global reconstruction, in which local reduced density matrices are used to reconstruct the global state. This experimentally motivated setting relies on locally accessible information and is therefore compatible with noisy and distributed quantum systems. More broadly, the framework provides a hybrid classical-quantum approach for approximating non-unitary dynamics and mitigating coherence loss.

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arXiv2026

Quantum Circuit Cutting: Complexity and Optimization

The current noisy intermediate-scale quantum (NISQ) era is characterized by substantial errors and noise, which limit the practical feasibility of deep, many-qubit circuits. To address these constraints, quantum circuit cutting has emerged as a promising tool. Recently, there has been significant research on methods for performing such cutting effectively. In this work, the duality between quantum circuits and classical graphs - specifically, directed acyclic graphs (dags) - is leveraged to analyze the complexity of finding an optimal circuit-cutting configuration that minimizes the number of cuts. After developing a rigorous graph-theoretic framework, the complexity of identifying cut locations that partition a given quantum circuit into smaller fragments is characterized. The corresponding graph-combinatorial task is then defined, and the resulting partition problem is shown to be NP-complete. Furthermore, even a simplified version of the problem, restricted to circuits composed only of one- and two-qubit gates, is shown to be NP-complete. Finally, based on these constraints, an algorithm grounded in satisfiability modulo theories (SMT) is proposed to find optimal cuts when the number of qubits per partition is bounded. This work therefore provides a complexity-theoretic characterization of cut placement and a practical solver for bounded-size decompositions.

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arXiv2025

Implementation and Analysis of Quantum Majority Rules under Noisy Conditions

Quantum voting, inspired by quantum game theory, provides a framework in which the quantum majority rule (QMR) constitution of Bao and Yunger Halpern [Phys. Rev. A 95, 062306 (2017)] violates the quantum analogue of Arrow's impossibility theorem. We evaluate this QMR constitution analytically on classical profile data and implement its final measurement stage as a quantum circuit, running on both noiseless simulators and noisy IBM quantum hardware to map how realistic noise deforms the resulting societal ranking distribution. Moderate-high single-qubit noise does not change the qualitative behavior of QMR, whereas strong noise shifts the distribution toward other dominant winners than the classical one. We quantify this behavior using winner-agreement rates, Condorcet-winner flip rates, and Jensen-Shannon divergence between societal ranking distributions. In a second, exploratory component, we demonstrate an explicitly entanglement-based variant of the QMR constitution that serves as a testbed for multi-voter quantum correlations under noise, which we refer to as the QMR2-inspired variant. There, GHZ-type and separable superpositions over opposite rankings have the same expectation values but respond very differently to noise. Taken together, these two components connect the abstract QMR constitution to concrete implementations on noisy intermediate-scale quantum (NISQ) devices and highlight design considerations for future quantum voting protocols.

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arXiv2025

Probeless vs Probe-Based Variable-Strength Eavesdropping in Quantum Key Distribution

Quantum key distribution (QKD) is a provably secure way of generating a secret key, which can later be used for encoding and decoding information. In this paper we analyze the effects of an eavesdropper's variable-strength measurements on QKD. Two types of measurements have been considered: (i) a probe-based model, commonly referred to as a "weak measurement", in which each qubit is weakly coupled to a continuous variable probe which is later projectively measured (ii) a probeless model, usually referred to as a "partial measurement", where only a small (tunable) part of all transmitted photons is projectively measured and the rest are transmitted with no disturbance. The information gain of the eavesdropper and the quantum-bit-error-rate (QBER) are computed for each case. An experimental realization of an intercept-and-resend attack based on variable-strength partial measurements is demonstrated in a time-bin-encoded, fiber-based simplified Bennett-Brassard 1984 (BB84) protocol, which is compatible with data centers. It is shown that the measured information gain and QBER follow the theoretical curves across the full coupling range, validating the partial-measurement model and clarifying its relation to the well-known monitoring channel. Further attacks involving photon number splitting and noise injection during the calibration stage are also analyzed. The results highlight the theoretical differences between weak and partial measurements, while also demonstrating the practicality of probeless eavesdropping in the case of real-world QKD systems.

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arXiv2024

A Review of Quantum communication using high-dimensional Hilbert spaces

In this project we examine several different quantum key distribution protocols which we divide into ones utilizing qubits whose Hilbert spaces are two dimensional and ones whose Hilbert space dimension is greater than two, these units of data in quantum computers are known as qudits and in the papers we'll examine are implemented using the orbital angular momentum of twisted photons. In sections [3] and [4] the specific procedures of each protocol are briefly described and followed by an examination of the theoretical and experimental merits of each protocol. These merits are measured in the bit error rate tolerance $e_b$, which quantifies the maximum channel noise and the key rate $R$ which quantifies the rate at which data is transferred in the protocol. In section [7] we present a unified view of all the relevant data for the different protocols, and argue for the benefits and drawbacks of the different protocols for different applications.

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arXiv2023

Variational Quantum Algorithm based circuit that implements the Toffoli gate with multi inputs

The prime objective of this study is to seek a circuit diagram for a multi-inputs Toffoli gate including only single qubit gates and CNOTs. In this regard, we have developed two variational quantum algorithms that can be used to implement a multi-inputs Toffoli gate. The cost functions of these two VQAs are derived by using the Hilbert Schmidt inner product and the expected value of an observable that can capture the difference between the inputs and outputs of a Toffoli gate. We employ two ansatz circuit architectures and use the PennyLane package to execute the optimization.

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