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Mohammadreza Khellat edited this page Dec 16, 2025 · 1 revision

FAQ and Troubleshooting

Frequently asked questions and troubleshooting guide for openqcp-lab.

Table of Contents

  1. Setup and Installation
  2. Framework-Specific Issues
  3. Execution Problems
  4. Mathematical and Conceptual Questions
  5. Performance Issues
  6. Platform-Specific Notes

Setup and Installation

Q: How do I set up the environment?

A: See the Getting Started guide for detailed instructions. Quick setup:

git clone https://codeberg.org/mkhellat/openqcp-lab.git
cd openqcp-lab
./setup_env.sh
source venv/bin/activate

Q: Which Python version should I use?

A: Python 3.9 or later is recommended. Check your version:

python3 --version

Q: I get "command not found: python3" on Windows

A: On Windows, try python instead of python3. Also ensure Python is installed and added to your PATH.

Q: Permission denied when running setup_env.sh

A: Make the script executable:

chmod +x setup_env.sh
./setup_env.sh

Q: ModuleNotFoundError for specific packages

A:

  1. Ensure virtual environment is activated
  2. Reinstall dependencies: pip install -r requirements.txt
  3. For Qiskit (optional): pip install qiskit qiskit-optimization

Q: Jupyter doesn't open in browser

A:

  1. Check terminal for URL (usually http://localhost:8888)
  2. Copy URL and paste in browser manually
  3. Or use: jupyter notebook --no-browser

Framework-Specific Issues

Classiq

Q: Classiq import errors

A:

  • Install: pip install classiq
  • Update: pip install --upgrade classiq
  • Check Python version (3.8+ required)

Q: Classiq authentication errors

A: Some features require API authentication. See Classiq Documentation for authentication setup. Most tutorials work without authentication for basic usage.

Q: Circuit synthesis errors

A:

  • Check function definitions
  • Verify quantum function syntax
  • Review Classiq documentation for correct usage

PennyLane

Q: PennyLane import errors

A:

  • Install: pip install pennylane
  • Check version: python -c "import pennylane as qml; print(qml.__version__)"
  • Update: pip install --upgrade pennylane

Q: Backend not found

A:

  • Install specific backend plugin if needed
  • Check device name spelling
  • Verify backend is available

Q: Gradient computation errors

A:

  • Ensure differentiable operations
  • Check parameter shapes
  • Verify circuit structure

Qiskit

Q: Qiskit not installed

A: Qiskit is an optional dependency. Install manually:

pip install qiskit qiskit-optimization

Or the notebook will install it automatically if needed.

Q: IBM Quantum access errors

A:

Q: VQE execution errors

A:

  • Verify Hamiltonian format
  • Check ansatz compatibility
  • Ensure Qiskit version is compatible

Execution Problems

Q: Notebooks run slowly

A:

  • Reduce number of shots in quantum simulations
  • Use smaller problem sizes for initial testing
  • Check if using quantum hardware (slower than simulators)
  • Use faster simulator backends if available

Q: Optimization not converging

A:

  • Increase maximum iterations
  • Adjust optimizer parameters (learning rate, etc.)
  • Try different initial parameter values
  • Check that problem is well-posed

Q: Results differ from tutorial

A: Some variation is expected:

  • Quantum measurement randomness is normal
  • Optimization may converge differently
  • Numerical precision variations occur

If results are significantly different, check:

  • Parameters match tutorial
  • Package versions are compatible
  • Random seeds are set (if applicable)

Q: LaTeX errors in plots (Tutorial 05)

A:

  • Install LaTeX distribution (TeX Live, MiKTeX, or MacTeX)
  • Install cm-super package
  • Or disable LaTeX: plt.rcParams['text.usetex'] = False

Q: Figures not displaying

A:

  • Ensure matplotlib is installed
  • Use %matplotlib inline in Jupyter
  • Check that cells executed successfully
  • Verify plt.show() is called

Q: Quantum model files not generated

A:

  • Ensure write permissions in directory
  • Check that write_qmod cell executed without errors
  • Verify Classiq authentication if required
  • Check file paths are correct

Mathematical and Conceptual Questions

Q: What mathematical background do I need?

A: See Getting Started for prerequisites. Key areas:

  • Linear algebra (vectors, matrices, eigenvalues)
  • Complex numbers
  • Probability theory
  • Basic calculus (for optimization)

Q: Where can I learn quantum computing basics?

A: Recommended resources:

Q: What is the notation used in tutorials?

A: See Theory and Background for notation guide. Common notation:

  • $| \psi \rangle$ - Quantum state (ket)
  • $\langle \psi |$ - Dual state (bra)
  • $H$ - Hamiltonian or Hermitian operator
  • $\theta$ - Parameters

Q: How do I understand the mathematical foundations?

A:

Q: What's the difference between unitary and non-unitary operations?

A:

  • Unitary: Reversible quantum operations (most quantum gates)
  • Non-unitary: Operations that are not reversible (requires special techniques like LCU)
  • See Tutorial 03 for non-unitary implementation

Performance Issues

Q: How can I speed up execution?

A:

  • Reduce number of shots
  • Use smaller problem sizes
  • Use simulators instead of hardware
  • Optimize code (profile slow sections)
  • Use faster backends if available

Q: How long should tutorials take?

A: Estimated times:

  • Tutorial 00: ~2 hours
  • Tutorial 01: ~1.5 hours
  • Tutorial 02: ~2-3 hours
  • Tutorial 03: ~2-3 hours
  • Tutorial 04: ~3-4 hours
  • Tutorial 05: ~4-5 hours

Actual time depends on your background and system.

Q: My computer is slow, can I still run tutorials?

A: Yes, but:

  • Use smaller problem sizes
  • Reduce number of shots
  • Be patient with longer execution times
  • Consider using cloud resources if needed

Q: Memory errors during execution

A:

  • Reduce problem size
  • Close other applications
  • Use more efficient data structures
  • Consider using cloud resources

Platform-Specific Notes

Linux

Q: LaTeX installation

A:

sudo apt-get install texlive-latex-base cm-super
# Or for full installation:
sudo apt-get install texlive-full

Q: Permission issues

A: Use sudo for system-wide installations, or use virtual environments (recommended).

macOS

Q: LaTeX installation

A:

Q: Python version

A: macOS may have system Python. Use Homebrew to install Python 3.9+:

brew install python3

Windows

Q: Python installation

A:

  • Download from python.org
  • Ensure "Add Python to PATH" is checked
  • Use python instead of python3

Q: LaTeX installation

A:

Q: Virtual environment activation

A:

venv\Scripts\activate

Instead of source venv/bin/activate.

General Questions

Q: Which tutorial should I start with?

A: See Learning Paths for guidance:

  • Beginner: Start with Tutorial 00
  • Some experience: Start with Tutorial 02
  • Experienced: Start with Tutorial 04 or 05

Q: Can I skip tutorials?

A: Yes, but:

  • Check prerequisites for each tutorial
  • Some tutorials build on previous ones
  • See Learning Paths for dependencies

Q: How do I contribute?

A: See Contributing guide. You can:

  • Improve documentation
  • Add new tutorials
  • Fix bugs
  • Report issues

Q: Where can I get help?

A:

Q: Are there video tutorials?

A: Not currently, but the written tutorials are comprehensive. Check individual tutorial pages for detailed guidance.

Q: Can I use these tutorials for teaching?

A: Yes! The project is licensed under GNU GPL v3+. See the LICENSE file. Please cite appropriately (see Academic Resources).

Q: How do I cite this project?

A: See Academic Resources for citation information and formats.

Still Need Help?

If you can't find an answer here:

  1. Check Documentation:

  2. Search Issues:

  3. Report Issues:

    • Open a new issue with:
      • Error messages
      • System information
      • Steps to reproduce
      • Which tutorial/cell

  4. Community:

    • Check framework communities (Classiq, PennyLane, Qiskit)
    • Quantum computing forums and communities

Return to: Home | Getting Started | Tutorial Catalog

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