AdaptVQE¶
- class AdaptVQE(solver, *, gradient_threshold=1e-05, eigenvalue_threshold=1e-05, max_iterations=None, threshold=None)[source]¶
Bases:
VariationalAlgorithm
,MinimumEigensolver
The Adaptive Variational Quantum Eigensolver algorithm.
AdaptVQE is a quantum algorithm which creates a compact ansatz from a set of evolution operators. It iteratively extends the ansatz circuit, by selecting the building block that leads to the largest gradient from a set of candidates. In chemistry, this is usually a list of orbital excitations. Thus, a common choice of ansatz to be used with this algorithm is the Unitary Coupled Cluster ansatz implemented in Qiskit Nature. This results in a wavefunction ansatz which is uniquely adapted to the operator whose minimum eigenvalue is being determined. This class relies on a supplied instance of
VQE
to find the minimum eigenvalue. The performance of AdaptVQE significantly depends on the minimization routine.from qiskit.algorithms.minimum_eigensolvers import AdaptVQE, VQE from qiskit.algorithms.optimizers import SLSQP from qiskit.primitives import Estimator from qiskit.circuit.library import EvolvedOperatorAnsatz # get your Hamiltonian hamiltonian = ... # construct your ansatz ansatz = EvolvedOperatorAnsatz(...) vqe = VQE(Estimator(), ansatz, SLSQP()) adapt_vqe = AdaptVQE(vqe) eigenvalue, _ = adapt_vqe.compute_minimum_eigenvalue(hamiltonian)
The following attributes can be set via the initializer but can also be read and updated once the AdaptVQE object has been constructed.
- solver¶
a
VQE
instance used internally to compute the minimum eigenvalues. It is a requirement that theansatz
of this solver is of typeEvolvedOperatorAnsatz
.
- gradient_threshold¶
once all gradients have an absolute value smaller than this threshold, the algorithm has converged and terminates.
- eigenvalue_threshold¶
once the eigenvalue has changed by less than this threshold from one iteration to the next, the algorithm has converged and terminates. When this case occurs, the excitation included in the final iteration did not result in a significant improvement of the eigenvalue and, thus, the results from this iteration are not considered.
- max_iterations¶
the maximum number of iterations for the adaptive loop. If
None
, the algorithm is not bound in its number of iterations.
Deprecated since version 0.24.0_pending:
qiskit.algorithms.minimum_eigensolvers.adapt_vqe.AdaptVQE.__init__()
’s argumentthreshold
is pending deprecation as of qiskit-terra 0.24.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, use the argumentgradient_threshold
, which behaves identically.- Parameters
solver (VQE) – a
VQE
instance used internally to compute the minimum eigenvalues. It is a requirement that theansatz
of this solver is of typeEvolvedOperatorAnsatz
.gradient_threshold (float) – once all gradients have an absolute value smaller than this threshold, the algorithm has converged and terminates.
eigenvalue_threshold (float) – once the eigenvalue has changed by less than this threshold from one iteration to the next, the algorithm has converged and terminates. When this case occurs, the excitation included in the final iteration did not result in a significant improvement of the eigenvalue and, thus, the results from this iteration are not considered.
max_iterations (int | None) – the maximum number of iterations for the adaptive loop. If
None
, the algorithm is not bound in its number of iterations.threshold (float | None) – once all gradients have an absolute value smaller than this threshold, the algorithm has converged and terminates. Defaults to
1e-5
.
Methods
Computes the minimum eigenvalue.
Whether computing the expectation value of auxiliary operators is supported.
Attributes
- threshold¶
The threshold for the gradients.
Once all gradients have an absolute value smaller than this threshold, the algorithm has converged and terminates.
Deprecated since version 0.24.0_pending: The property
qiskit.algorithms.minimum_eigensolvers.adapt_vqe.AdaptVQE.threshold
is pending deprecation as of qiskit-terra 0.24.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, use the gradient_threshold attribute.