Zi-Min Li | 李梓民 Zi-Min Li

A New Course: Quantum Optics, from Physical Intuition to Quantum Information

Sun, 20 Sep 2026 00:00:00 +0000

I recently began teaching a new course in Quantum Optics.

The course is primarily intended for third- and fourth-year physics undergraduates. Participants also include undergraduates from different years undertaking research training in our group, as well as our graduate students. I hope it will offer an accessible introduction to quantum optics while building a shared foundation for research.

Given these varied backgrounds, no prior knowledge of quantum mechanics is assumed, although students should have a foundation in university physics. We will begin with physical stories and concrete questions, gradually developing the concepts and mathematical tools needed for a rigorous understanding. Intuition and calculation will go hand in hand: stories motivate the questions, while derivations help us answer them precisely.

The interaction between light and atoms will provide the central thread of the course. Starting with the essential foundations of quantum mechanics, we will work toward quantum optics and its applications in quantum information science. Rather than treating the prerequisites as a separate introductory block, we will develop them as they become relevant to the physics.

My aim is to make this a course where students can both follow the physical ideas and work through the necessary derivations. For those encountering quantum theory for the first time, I hope it will build confidence and intuition. For those who have already studied quantum mechanics or begun research, I hope it will offer a fresh perspective on light-matter interaction.

Time: Mondays, starting at 10:00 a.m.
Location: Room 125, School of Physics, Xiaoxiang Campus, Central South University
Course website: Quantum Optics

Entanglement and Bell-State Preparation in the Tripartite Quantum Rabi Model

Sat, 11 Jul 2026 00:00:00 +0000

How can a simple light-matter interaction reorganize two-qubit entanglement, and can that structure be used to prepare a useful quantum state? Our recent preprint studies these questions in the tripartite quantum Rabi model, where two qubits interact collectively with a single bosonic mode.

In the zero-detuning limit, the spectrum separates into branches with sharply different entanglement properties. Some triplet states carry no two-qubit entanglement, while others are maximally entangled; the antisymmetric singlet ladder remains decoupled. Finite detuning turns selected crossings into avoided crossings, allowing entanglement to move between eigenbranches.

This spectral picture suggests a state-preparation strategy. Starting from a nearly separable state at weak coupling, one can slowly increase the collective coupling and follow an eigenbranch that becomes dominated by a Bell-state component. A compact three-state model explains the relevant mixing, while finite-time simulations identify the coupling strength and ramp duration needed for high final fidelity.

The work links a static question, the organization of entanglement in the spectrum, to a dynamical one, the preparation of a Bell state within a finite time.

Read the preprint on arXiv

How Topology and Non-Hermiticity Enhance a Quantum Battery

Wed, 15 Apr 2026 00:00:00 +0000

A quantum battery stores energy in quantum degrees of freedom. The central question is not only how much energy it can store, but also how rapidly and robustly it can be charged. In our recent work, we investigate a quantum battery built from a Su-Schrieffer-Heeger chain and driven by an alternating gain-loss protocol.

The SSH lattice has alternating strong and weak couplings. In its topological regime, states can become localized near the boundary rather than spread throughout the bulk. The gain and loss make the charging dynamics non-Hermitian and introduce exceptional points, where both eigenvalues and eigenstates coalesce.

The key result is that topology and non-Hermiticity do not simply contribute two separate effects. Their interplay creates an edge-state exceptional point at a weaker gain-loss strength than the bulk exceptional-point thresholds. This boundary mode provides a distinct route for controlling the transient and long-time charging behavior.

The model offers a clear setting for understanding how band topology, boundary localization, and non-Hermitian dynamics can be combined in quantum energy devices.

Read the paper in Physical Review A

Research Directions and Our Group

Sat, 13 Apr 2024 00:00:00 +0000

Our group is based in the School of Physics at Central South University. We study how quantum systems exchange energy and information with light fields and their surrounding environments. Our work combines analytical methods, numerical calculations, and physically transparent models.

Our current research has four closely connected themes:

Quantum Rabi models and light-matter interaction. We develop exact and approximate methods for strongly coupled qubit-oscillator systems and investigate their spectra, eigenstates, and dynamics.
Open quantum systems. We study how relaxation, dissipation, and environmental noise reshape quantum dynamics and steady states.
Non-Hermitian physics. We explore parity-time symmetry, exceptional points, and the interplay between gain, loss, and quantum coherence.
Quantum information and energy science. We are interested in entanglement generation, state preparation, and quantum batteries.

Graduate and undergraduate students participate in different parts of these projects, from analytical derivations and numerical simulations to literature review and scientific visualization. We welcome discussions and collaborations in quantum optics and related areas.