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class VarQRTE(ansatz, initial_parameters, variational_principle=None, estimator=None, ode_solver=<class 'qiskit.algorithms.time_evolvers.variational.solvers.ode.forward_euler_solver.ForwardEulerSolver'>, lse_solver=None, num_timesteps=None, imag_part_tol=1e-07, num_instability_tol=1e-07)

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Bases: qiskit.algorithms.time_evolvers.variational.var_qte.VarQTE, qiskit.algorithms.time_evolvers.real_time_evolver.RealTimeEvolver

Variational Quantum Real Time Evolution algorithm.


  • ansatz – Ansatz to be used for variational time evolution.
  • initial_parameters – Initial parameter values for an ansatz.
  • variational_principle – Variational Principle to be used. Defaults to RealMcLachlanPrinciple.
  • estimator – An estimator primitive used for calculating expectation values of TimeEvolutionProblem.aux_operators.
  • ode_solver – ODE solver callable that implements a SciPy OdeSolver interface or a string indicating a valid method offered by SciPy.
  • lse_solver – Linear system of equations solver callable. It accepts A and b to solve Ax=b and returns x. If None, the default np.linalg.lstsq solver is used.
  • num_timesteps – The number of timesteps to take. If None, it is automatically selected to achieve a timestep of approximately 0.01. Only relevant in case of the ForwardEulerSolver.
  • imag_part_tol – Allowed value of an imaginary part that can be neglected if no imaginary part is expected.
  • num_instability_tol – The amount of negative value that is allowed to be rounded up to 0 for quantities that are expected to be non-negative.




Apply Variational Quantum Time Evolution to the given operator.


evolution_problem (TimeEvolutionProblem) – Instance defining an evolution problem.

Return type



Result of the evolution which includes a quantum circuit with bound parameters as an evolved state and, if provided, observables evaluated on the evolved state.


ValueError – If initial_state is included in the evolution_problem.

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