qrunch.quantum.algorithms.second_quantization.quantum_selected_configuration_interaction.krylov_subspace_state_generator

Krylov subspace state generator for quantum-selected configuration interaction.

Classes

KrylovSubspaceStateGenerator

Generate Krylov subspace states for quantum-selected configuration interaction.
class KrylovSubspaceStateGenerator

Bases: SubspaceStateGenerator

Generate Krylov subspace states for quantum-selected configuration interaction.

For each Krylov order \(k = 1, \ldots, d\) (with \(d\) the maximum order) and each randomization, this generator produces a state preparing (an approximation of) the Krylov vector

\[\ket{\Psi_k} = e^{-iH k \tau} \ket{\Psi_\text{ref}} ,\]

where \(\tau\) is the time step and \(\ket{\Psi_\text{ref}}\) is prepared by the reference circuit. Each time-evolution operator \(e^{-iH k \tau}\) is compiled by the injected HamiltonianTimeEvolution strategy, once the caller realizes the state.

__init__(time_evolution: HamiltonianTimeEvolution, *, maximum_krylov_order: int = 3, time_step: float = 1.0, number_of_randomizations: int = 1) → None

Initialize the Krylov subspace state generator.

Parameters:

  • time_evolution (HamiltonianTimeEvolution) – Strategy compiling each time-evolution operator into a circuit.

  • maximum_krylov_order (int) – The largest Krylov order \(d\); states are generated for every order \(k = 1, \ldots, d\).

  • time_step (float) – The reference time step \(\tau\); the evolution time for order \(k\) is \(k \tau\).

  • number_of_randomizations (int) – Number of states generated per Krylov order.

Return type:

None

generate() → Iterator[SubspaceState]

Yield the Krylov subspace states.

Return type:

Iterator[SubspaceState]