openfermion.circuits.trotter.algorithms.low_rank.LowRankTrotterStep

A method for performing a Trotter step.

Inherits From: TrotterStep

openfermion.circuits.trotter.algorithms.low_rank.LowRankTrotterStep(
    hamiltonian: 'ops.InteractionOperator',
    truncation_threshold: Optional[float] = 1e-08,
    final_rank: Optional[int] = None,
    spin_basis=True
) -> None

This class assumes that Hamiltonian evolution using a Trotter-Suzuki product formula is performed in the following steps:

1. Perform some preparatory operations (for instance, a basis change).
2. Perform a number of Trotter steps. Each Trotter step may induce a
   permutation on the ordering in which qubits represent fermionic
   modes.
3. Perform some finishing operations.

hamiltonian The Hamiltonian being simulated.

Methods

finish

View source

finish(
    qubits: Sequence[cirq.Qid],
    n_steps: int,
    control_qubit: Optional[cirq.Qid] = None,
    omit_final_swaps: bool = False
) -> cirq.OP_TREE

Operations to perform after all Trotter steps are done.

Args
qubits The qubits on which to perform operations.
hamiltonian The Hamiltonian to simulate.
n_steps The total number of Trotter steps that have been performed.
control_qubit The control qubit, if the algorithm is controlled.
omit_final_swaps Whether or not to omit swap gates at the end of the circuit.

prepare

View source

prepare(
    qubits: Sequence[cirq.Qid], control_qubit: Optional[cirq.Qid] = None
) -> cirq.OP_TREE

Operations to perform before doing the Trotter steps.

Args
qubits The qubits on which to perform operations. They should be sorted so that the j-th qubit in the Sequence holds the occupation of the j-th fermionic mode.
hamiltonian The Hamiltonian to simulate.
control_qubit The control qubit, if the algorithm is controlled.

step_qubit_permutation

View source

step_qubit_permutation(
    qubits: Sequence[cirq.Qid], control_qubit: Optional[cirq.Qid] = None
) -> Tuple[Sequence[cirq.Qid], Optional[cirq.Qid]]

The qubit permutation induced by a single Trotter step.

Returns
A tuple whose first element is the new list of system qubits and second element is the new control qubit

trotter_step

View source

@abc.abstractmethod
trotter_step(
    qubits: Sequence[cirq.Qid],
    time: float,
    control_qubit: Optional[cirq.Qid] = None
) -> cirq.OP_TREE

Yield operations to perform a Trotter step.

Args
qubits The qubits on which to apply the Trotter step.
hamiltonian The Hamiltonian to simulate.
time The evolution time.
control_qubit The control qubit, if the algorithm is controlled.