class_docstr: Tests for integration with the PassthruQNode
class_docstr_tok: ["Tests","for","integration","with","the","PassthruQNode"]
docstr: Tests that the Hessian at vanishing state vector amplitudes
  is correct.
docstr_tok: ["Tests","that","the","Hessian","at","vanishing","state","vector","amplitudes","is","correct","."]
code: def test_hessian_at_zero(self, x, shift):
      """Tests that the Hessian at vanishing state vector amplitudes
      is correct."""
      dev = qml.device("default.mixed", wires=1)
  
      shift = torch.tensor(shift)
      x = torch.tensor(x, requires_grad=True)
  
      @qml.qnode(dev, interface="torch", diff_method="backprop")
      def circuit(x):
          qml.RY(shift, wires=0)
          qml.RY(x, wires=0)
          return qml.expval(qml.PauliZ(0))
  
      grad = torch.autograd.functional.jacobian(circuit, x)
      hess = torch.autograd.functional.hessian(circuit, x)
  
      assert qml.math.isclose(grad, torch.tensor(0.0))
      assert qml.math.isclose(hess, torch.tensor(-1.0))
  
imports: import pytest
  import numpy
  import pennylane
  from pennylane import numpy
  from pennylane.devices.default_mixed import DefaultMixed
label_desc: Use image node_id 11 for calling the TestPassthruIntegration obj's underlying member method code with example usage: obj.test_hessian_at_zero(x, shift) and returns: qml