InQuanto: Quantum Chemistry Simulation Tutorials (Quantinuum)

InQuanto is Quantinuum’s Python framework for quantum chemistry simulation, built on top of the TKET circuit compiler. The tutorial library is one of the most technically detailed collections of quantum chemistry content available for free, covering the full range from introductory VQE to advanced research-level molecular simulation on Quantinuum’s Helios and H-Series hardware.

What the tutorials cover

Beginner level:

• A basic VQE simulation: computing the ground state energy of a simple molecule end to end
• Molecular visualization with inquanto-nglview
• Backends overview: setting up classical simulators and quantum hardware connections

Intermediate level:

• Extended VQE: more sophisticated variational approaches and convergence techniques
• Variational Quantum Deflation (VQD): computing excited state energies, not just ground states
• Hamiltonian averaging with the Aer simulator: shot-based sampling and stochastic expectation value estimation
• Accessing backends through Quantinuum Nexus cloud platform
• Submitting jobs to Quantinuum Helios (trapped ion) and Selene (error-corrected emulator)
• Circuit compilation within VQE protocols: optimizing circuits for specific hardware

Advanced level:

• Quantum Subspace Expansion (QSE) on real hardware: improving energy accuracy beyond VQE
• Fe4N2 molecular simulation series (3 tutorials): active space construction using AVAS and CASSCF, ADAPT-VQE for adaptive ansatz generation, and full execution on Quantinuum trapped ion hardware — the nitrogen activation problem
• Density Matrix Embedding Theory (DMET): partitioning large systems into quantum-tractable fragments
• Projection-based embedding: combining wave function and DFT methods
• NEVPT2 and AC0 energy corrections: post-processing techniques for improved accuracy

Who is this for?

Chemists, materials scientists, and quantum computing researchers who want to use quantum hardware for molecular simulation. The tutorials assume familiarity with quantum chemistry concepts (molecular orbitals, Hamiltonians, DFT limitations) and Python programming. This is not an introduction to quantum computing — it is an introduction to doing real chemistry on real quantum hardware.

Framework and hardware

InQuanto uses pytket (Quantinuum’s quantum circuit compiler) as its backend. Circuits can be run on classical simulators (Qiskit Aer, pytket simulators) for development and on Quantinuum’s H-Series trapped ion hardware for production. A free Quantinuum Nexus account provides access to the Selene emulator; H-Series QPU access requires a separate arrangement.

Context: why Quantinuum for quantum chemistry?

Quantinuum’s H-Series trapped ion systems have among the highest gate fidelities available commercially. For quantum chemistry, where deep circuits and high precision matter, this hardware advantage is significant. The Fe4N2 tutorials in particular represent state-of-the-art quantum chemistry research, not textbook examples.