Bloch-Redfield Educational Repository

This mini-project provides pedagogical Jupyter notebooks illustrating the Bloch-Redfield (redfield) master equation using QuTiP's brmesolve and comparisons to Lindblad (mesolve) where appropriate.

Goals

• Show simple canonical open quantum system examples.
• Visualize dynamical maps and identify when redfield breaks CP (negative density matrix eigenvalues).
• Demonstrate the secular approximation: Redfield vs Secular Redfield vs Lindblad.
• Explore multiple bath spectral densities (DrudeLorentzEnvironment, OhmicEnvironment, UnderDampedEnvironment).

Notebooks

1. 01_qubit_dephasing.ipynb: Pure dephasing qubit: analytical vs redfield vs Lindblad.
2. 02_qubit_relaxation_drude_lorentz.ipynb: Energy relaxation & temperature dependence.
3. 03_harmonic_oscillator_ohmic.ipynb: Damped quantum oscillator & approach to thermal state.
4. 04_coupled_qubits_secular_breakdown.ipynb: Breakdown of secular approximation when splittings comparable to rates.
5. 05_negative_eigenvalues_explorer.ipynb: Scan parameter regimes to locate positivity violations.

Structure

src/ contains small reusable helpers (bath factory, diagnostics, plotting helpers). tests/ minimal sanity tests (import & a short evolution) to ensure environment reproducibility.

Install

Option 1: Using conda environment file (Recommended)

# Create and activate environment from environment.yml
conda env create -f environment.yml
conda activate redfield-education

# Install this package in editable mode (optional)
pip install -e .

Option 2: Manual environment creation

# Create environment manually
conda create -n redfield-ed python=3.11 -y
conda activate redfield-ed
pip install qutip numpy scipy matplotlib jupyter pytest black ruff tqdm

# Install this package in editable mode (optional)
pip install -e .

Updating the environment

# Update environment from environment.yml
conda env update -f environment.yml --prune

License

MIT (add if desired).