Fix a bug for the wrong tlist in c_ops (#107)

The get_full_tlist method only considers the tlist in the ideal pulse. If the Lindblad noise has a different time dependency, this will cause inconsistency. Use the tlist of the generated QobjEvo, which already includes all the time steps.

src/qutip_qip/device/processor.py

@@ -955,10 +955,9 @@ def get_qobjevo(self, args=None, noisy=False):
         final_qu.args.update(args)
 
         # bring all c_ops to the same tlist, won't need it in QuTiP 5
-        full_tlist = self.get_full_tlist()
         temp = []
         for c_op in c_ops:
-            temp.append(_merge_qobjevo([c_op], full_tlist))
+            temp.append(_merge_qobjevo([c_op], final_qu.tlist))
         c_ops = temp
 
         if noisy:

tests/test_noise.py

@@ -4,9 +4,9 @@
 
 from qutip import (
     tensor, qeye, sigmaz, sigmax, sigmay, destroy, identity, QobjEvo,
-    fidelity, basis
+    fidelity, basis, sigmam
     )
-from qutip_qip.device import Processor, SCQubits
+from qutip_qip.device import Processor, SCQubits, LinearSpinChain
 from qutip_qip.noise import (
     RelaxationNoise, DecoherenceNoise, ControlAmpNoise, RandomNoise,
     ZZCrossTalk, Noise)
@@ -50,6 +50,22 @@ def test_decoherence_noise(self):
         assert_allclose(c_ops[0].tlist, tlist)
         assert_allclose(c_ops[1].ops[0].qobj, tensor(qeye(2), sigmax()))
 
+    def test_collapse_with_different_tlist(self):
+        """
+        Test if there are errors raised because of wrong tlist handling.
+        """
+        qc = QubitCircuit(1)
+        qc.add_gate("X", 0)
+        proc = LinearSpinChain(1)
+        proc.load_circuit(qc)
+        tlist = np.linspace(0, 30., 100)
+        coeff = tlist * 0.1
+        noise = DecoherenceNoise(
+            sigmam(), targets=0,
+            coeff=coeff, tlist=tlist)
+        proc.add_noise(noise)
+        proc.run_state(basis(2, 0))
+
     def test_relaxation_noise(self):
         """
         Test for the relaxation noise