arXiv subjects

Chun Hei Leung

Publications and source records attributed to Chun Hei Leung.

3 recordsLinked to original sources

arXiv2026

Engineer coherent oscillatory modes in Markovian open quantum systems

We develop a novel framework to engineer persistent oscillatory modes in Markovian open quantum systems governed by a time-independent Lindblad master equation. We show that oscillatory modes can be created when the Hamiltonian and jump operator can be expressed in the same block-diagonal form. A key feature of the framework is that the dissipator of the Lindblad master equation are generally non-zero. We identify the weak and strong conditions, where the onset of the oscillatory modes is dependent and independent of the parameters of the system, respectively. Our method extends beyond the typical decoherence-free subspace approach, in which the dissipator is zero. We demonstrate the applicability of this framework using various models, showing how carefully tailored system-environment interactions can produce sustained coherent oscillations.

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arXiv2026

Undamped Modes in an N-Qubit Heisenberg Chain with Collective Dissipation

We investigate the undamped behaviors in a spin-1/2 Heisenberg chain coupled with an environment via collective spin jump operators. Using the Bethe ansatz basis, we show that undamped modes exist for any chain length N >= 3. These modes remain robust against variations in the system parameters, including the specific form of the collective dissipation, and the external field. Exploiting the Bethe ansatz solution, we further characterize the number of undamped modes and their oscillation frequencies, uncovering long-lived coherent dynamics in open integrable quantum systems.

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arXiv2025

Hilbert space fragmentation in driven-dephasing Rydberg atom array

We investigate the onset and mechanism of Hilbert space fragmentation (HSF) in a chain of strongly interacting Rydberg atoms subject to local dephasing. It is found that the emergence of multiple long-lived metastable states is fundamentally tied to HSF of the driven-dephasing Rydberg atom system. We demonstrate that the manifesting HSF is captured by a dephasing PXP model that supports multiple degenerate zero modes. These modes form disconnected, block-diagonal subspaces of maximally mixed states, which consist of many-body spin states sharing the same symmetry. A key result is the identification of the underlying symmetry in the HSF, where conserved quantities in each subspace are defined by the consecutive double excitation addressing operator. Moreover, we show explicitly that the number of the fragmented Hilbert space grows exponentially with the chain length, following a modified Fibonacci sequence. Our work provides insights into many-body dynamics under dynamical constraints and opens avenues for controlling and manipulating HSF in Rydberg atom systems.

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