TrotterQRTE

class qiskit.algorithms.time_evolvers.trotterization.TrotterQRTE(product_formula=None, estimator=None, num_timesteps=1)

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Bases: RealTimeEvolver

Quantum Real Time Evolution using Trotterization. Type of Trotterization is defined by a ProductFormula provided.

Examples

from qiskit.opflow import PauliSumOp
from qiskit.quantum_info import Pauli, SparsePauliOp
from qiskit import QuantumCircuit
from qiskit.algorithms import TimeEvolutionProblem
from qiskit.algorithms.time_evolvers import TrotterQRTE
from qiskit.primitives import Estimator
 
operator = PauliSumOp(SparsePauliOp([Pauli("X"), Pauli("Z")]))
initial_state = QuantumCircuit(1)
time = 1
evolution_problem = TimeEvolutionProblem(operator, time, initial_state)
# LieTrotter with 1 rep
estimator = Estimator()
trotter_qrte = TrotterQRTE(estimator=estimator)
evolved_state = trotter_qrte.evolve(evolution_problem).evolved_state

Parameters

product_formula (ProductFormula | None) – A Lie-Trotter-Suzuki product formula. If None provided, the Lie-Trotter first order product formula with a single repetition is used. reps should be 1 to obtain a number of time-steps equal to num_timesteps and an evaluation of TimeEvolutionProblem.aux_operators at every time-step. If reps is larger than 1, the true number of time-steps will be num_timesteps * reps.
num_timesteps (int) – The number of time-steps the full evolution time is devided into (repetitions of product_formula)
estimator (BaseEstimator | None) – An estimator primitive used for calculating expectation values of TimeEvolutionProblem.aux_operators.

Attributes

estimator

Returns an estimator.

num_timesteps

Returns the number of timesteps.

product_formula

Returns a product formula.

Methods

evolve

evolve(evolution_problem)

Evolves a quantum state for a given time using the Trotterization method based on a product formula provided. The result is provided in the form of a quantum circuit. If auxiliary operators are included in the evolution_problem, they are evaluated on the init_state and on the evolved state at every step (num_timesteps times) using an estimator primitive provided.

Parameters

evolution_problem (TimeEvolutionProblem) - Instance defining evolution problem. For the included Hamiltonian, Pauli or PauliSumOp are supported by TrotterQRTE.

Returns

Evolution result that includes an evolved state as a quantum circuit and, optionally, auxiliary operators evaluated for a resulting state on an estimator primitive.

Raises

ValueError – If t_param is not set to None in the TimeEvolutionProblem (feature not currently supported).
ValueError – If aux_operators provided in the time evolution problem but no estimator provided to the algorithm.
ValueError – If the initial_state is not provided in the TimeEvolutionProblem.
ValueError – If an unsupported Hamiltonian type is provided.

Return type

TimeEvolutionResult

supports_aux_operators

classmethod supports_aux_operators()

Whether computing the expectation value of auxiliary operators is supported.

Returns

True if aux_operators expectations in the TimeEvolutionProblem can be evaluated, False otherwise.

Return type

bool

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