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Geometry and speed of evolution for a system of arbitrary spins with long-range Ising-type interaction.

Yuri Krynytskyi, Andrij Romanovych Kuzmak

Published May 25, 2018• 0 citations
OpenAlex

Abstract

We study the evolution of N arbitrary spins described by the long-range Ising-type interaction. This fact allows us to obtain the Fubiny-Study metric of the manifold defined by this evolution. We explore the topology of this manifold and shown that it corresponds to a sphere. With the help of this fact the manifold geometry is determined. Also we calculate the Riemann curvature of manifold and represent it by means of the speed of evolution. This is important for an experimental measurement of the curvature. The conditions for achieving the minimal and maximal values of the speed of evolution are obtained. Finally, we examine the influence of an external magnetic field on the metric of manifold and on the speed of evolution. We obtain the conditions for achieving the minimal possible speed of evolution. For some predefined initial states the orientations of magnetic fields for reaching the minimal and maximal values of the speed are found.

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We study the evolution of N arbitrary spins described by the long-range Ising-type interaction. This fact allows us to obtain the Fubiny-Study metric of the manifold defined by this evolution. We explore the topology of this manifold and shown that it corresponds to a sphere. With the help of this fact the manifold geometry is determined. Also we calculate the Riemann curvature of manifold and represent it by means of the speed of evolution. This is important for an experimental measurement of the curvature. The conditions for achieving the minimal and maximal values of the speed of evolution are obtained. Finally, we examine the influence of an external magnetic field on the metric of manifold and on the speed of evolution. We obtain the conditions for achieving the minimal possible speed of evolution. For some predefined initial states the orientations of magnetic fields for reaching the minimal and maximal values of the speed are found.
Abstract The evolution of an N spin-1/2 system with all-range Ising-type interaction is considered. For this system we study the entanglement of one spin with the rest spins. It is shown that the entanglement depends on the number of spins and the initial state. Also, the geometry of the manifold, which contains entangled states, is obtained. For this case we find the dependence of entanglement on the scalar curvature of the manifold and examine it for different numbers of spins in the system. Finally we show that the transverse magnetic field leads to a change in the manifold topology.
Comprehending the connections between the geometric, topological, and dynamical structures of integrable quantum systems with quantum phenomena exploitable in quantum information tasks, such as quantum entanglement, is a major problem in geometric information science. In this work we investigate these issues in a physical system of N\mathcal{N}N interacting spin-s\mathtt{s}s under the long-range Ising model. We discover the relevant dynamics, identify the corresponding quantum phase space, and we derive the associated Fubini-Study metric. Through the application of the Gauss-Bonnet theorem and the derivation of the Gaussian curvature, we proved that the dynamics occurs on a spherical topology manifold. Afterwards, we analyze the gained geometrical phase under the arbitrary and cyclic evolution processes and solve the quantum brachistochrone problem by establishing the time-optimal evolution. Moreover, by narrowing the system to a two spin-s\mathtt{s}s system, we explore the relevant entanglement from two different perspectives. The first is geometrical in nature and involves the investigation of the interplay between the entanglement degree and the geometrical structures, such as the Fubini-Study metric, the Gaussian curvature, and the geometrical phase. The second is dynamical in nature and tackles the entanglement effect on the evolution speed and geodesic distance. Additionally, we resolve the quantum brachistochrone problem based on the entanglement degree.
We present a unified geometric and dynamical framework for a physical system consisting of nnn spin-1/21/21/2 particles with all-range Ising interaction. Using the Fubini-Study formalism, we derive the metric tensor of the associated quantum state manifold and compute the corresponding Riemann curvature. Our analysis reveals that the system evolves over a smooth, compact, two-dimensional manifold with spherical topology and a dumbbell-like structure shaped by collective spin interactions. We further investigate the influence of the geometry and topology of the resulting state space on the behavior of geometric and topological phases acquired by the system. We explore how this curvature constrains the system's dynamical behavior, including its evolution speed and Fubini-Study distance between the quantum states. Within this geometric framework, we address the quantum brachistochrone problem and derive the minimal time required for optimal evolution, a result useful for time-efficient quantum circuit design. Subsequently, we explore the role of entanglement in shaping the state space geometry, modulating geometric phase, and controlling evolution speed and brachistochrone time. Our results reveal that entanglement enhances dynamics up to a critical threshold, beyond which geometric constraints begin to hinder evolution. Moreover, entanglement induces critical shifts in the geometric phase, making it a sensitive indicator of entanglement levels and a practical tool for steering quantum evolution. This approach offers valuable guidance for developing quantum technologies that require time-efficient control strategies rooted in the geometry of quantum state space.
We consider a physical system consisting of two interacting spins governed by the [Formula: see text]-type Heisenberg Hamiltonian in an external magnetic field. We investigate the quantum evolution and the Riemannian geometry of the two-spin state space by means of the relevant Fubini–Study metric. The geometrical phase accumulated by the two-spin state is also examined under arbitrary and cyclic evolutions. By computing the evolution speed and the corresponding geodesic distance, we solve the quantum brachistochrone problem. The entanglement between the two spins is also studied via two approaches: the first one deals with the entanglement effect on the Fubini–Study metric and the geometrical phase, while the second one treats the entanglement effect on the evolution speed and the corresponding geodesic distance. Finally, we solve the quantum brachistochrone problem using the entanglement degree.
We consider a two-spin system of [Formula: see text] Heisenberg type submitted to an external magnetic field. Using the associated [Formula: see text] geometry, we investigate the dynamics of the system. We explicitly give the corresponding Fubini–Study metric. We show that for arbitrary pure initial states, the dynamics occurs on a torus. We compute the geometric phase, the dynamic phase and the topological phase. We investigate the interplay between the torus geometry and the entanglement of the two spins. In this respect, we provide a detailed analysis of the geometric phase, the dynamics velocity and the geodesic distance measured by the Fubini–Study metric in terms of the degree of entanglement between the two spins.