Algorithm classes

QDK/Chemistry provides a comprehensive set of algorithm classes which express core methodological primitives for quantum and classical chemistry calculations. All algorithms follow a factory pattern design, allowing you to create instances by name and configured through a unified settings interface.

Quick reference

The following table summarizes the available algorithm classes in QDK/Chemistry and their purposes. For detailed documentation, refer to the linked pages.

Algorithm Class	Purpose	Input → Output
ScfSolver	Mean-field (HF/DFT) calculations	Structure → Orbitals
OrbitalLocalizer	Orbital transformations	Orbitals → Orbitals
ActiveSpaceSelector	Active space identification	Wavefunction → Wavefunction
HamiltonianConstructor	Molecular Hamiltonian construction	Orbitals → Hamiltonian
MultiConfigurationCalculator	Many-body wavefunction calculations	Hamiltonian → Wavefunction
MultiConfigurationScf	Coupled Orbital-Wavefunction calculations.	Orbitals → Wavefunction
QubitMapper	Fermion-to-qubit mapping	Hamiltonian → QubitHamiltonian
StatePreparation	Quantum state preparation	Wavefunction → Circuit
EnergyEstimator	Quantum energy expectation values	Circuit + QubitHamiltonian → Energy
StabilityChecker	SCF stability analysis	Orbitals → Stability

Discovering implementations

Each algorithm class exposes multiple implementations that can be discovered at runtime. Use available() to list registered implementations:

C++ API

#include <qdk/chemistry/algorithms/scf.hpp>

// List all registered SCF solver implementations
auto names = qdk::chemistry::algorithms::ScfSolver::available();
for (const auto& name : names) {
  std::cout << name << std::endl;
}

// Create a specific implementation
auto solver = qdk::chemistry::algorithms::ScfSolver::create("pyscf");

Python API

from qdk_chemistry.algorithms import available, create  # noqa: E402

# List all registered SCF solver implementations
print(available("scf_solver"))  # ['qdk', 'pyscf']

# Create a specific implementation
solver = create("scf_solver", "qdk")

# Inspect available settings
print(solver.settings())

For details on creating, loading, and using custom algorithm implementations, see the plugin system and factory pattern documentation.