arXiv subjects

Yun-Yan Lee

Publications and source records attributed to Yun-Yan Lee.

3 recordsLinked to original sources

arXiv2024

Generation of Maximally Entangled States by Lyapunov Control Based on Entanglement Measure

Maximally entangled states (MES) are highly valued in quantum information processing. In quantum control, the creation of MES is typically treated as a state transfer problem with a predefined MES as the target. However, this approach is limited by the requirement to predetermine the MES structure. This paper introduces an improved quantum Lyapunov control approach that relies on the quantum entanglement measure to construct the Lyapunov function, instead of using the distance between quantum states. This strategy enables the preparation of any MES, regardless of whether its structure is known beforehand, using a single control scheme. The proposed entanglement control technique is unaffected by the number of entangled subsystems since it targets the entanglement measure as a scalar. Initially applied to bipartite pure states, this method demonstrates its capability to generate Bell states and their equivalents. Subsequent applications to bipartite mixed states and multipartite systems illustrate that the technique can produce MES with unspecified structures.

quant-ph↗

arXiv2024

The initial state of Pluto-Charon with Tidal Evolution

This study explores the gravitational interaction between Pluto and its moon Charon, which has led to their synchronous orbit, where they consistently show the same face to each other. This process is known as tidal evolution, which explains how the gravitational pull between two celestial bodies can adjust their spinning speeds until they match their orbital speed. By simulating various initial conditions, we aim to understand the specific paths Pluto and Charon might have taken to reach their current stage. We observe that the tilt of their orbits has a negligible long-term effect, typically stabilizing quickly. In our analysis, we examine a scenario when the orbital size initially increases, leading to an increased orbit and a high eccentricity, a phenomenon attributed to the dissipation of tidal energy.

astro-ph.EP↗

arXiv2022

Quantum Chaos Control by Complex Trajectories

In recent years, analysis and control of quantum chaos are increasingly important, but the lack of the concept of trajectory makes it impossible to analyze quantum chaos by the methods used in classical chaos. This research aims to connect Newton's world to the quantum world by the complex mechanics so that quantum chaos can be analyzed and controlled by the complex-extended Newtonian mechanics. Through the bridge of complex mechanics, in this article, we model quantum motions for 2D charged anisotropic harmonic oscillator by complex-valued dynamic equations, based on which quantum chaos can be analyzed by using well-known methods used in classical chaos. With the established quantum dynamic model, we then apply the sliding-mode control method to control the chaotic quantum behavior of the considered quantum system. The simulation results show that chaotic motions can be changed into periodic motions by the proposed chaos control and meanwhile, chaos synchronization can be achieved in the presence of variations of initial conditions. Several signatures of chaos are introduced here to justify the chaos of the periodicity process under the sliding-mode control law.

quant-ph↗