Remove reset from beginning of tomography experiments

Some backends do not implement reset but can be treated as having reset
the qubits between circuits. It is also possible some backends implement
reset but have a slower, higher fidelity reset between circuits than the
in-circuit reset.

qiskit_experiments/library/tomography/tomography_experiment.py

@@ -207,7 +207,6 @@ def circuits(self):
             if prep_element:
                 # Add tomography preparation
                 prep_circ = self._prep_circ_basis.circuit(prep_element, self._prep_physical_qubits)
-                circ.reset(self._prep_indices)
                 circ.compose(prep_circ, self._prep_indices, inplace=True)
                 circ.barrier(*self._prep_indices)
 

releasenotes/notes/remove-tomo-reset-3f21ec4d0dacba91.yaml

@@ -0,0 +1,8 @@
+---
+other:
+  - |
+    Removed the reset instruction from the beginning of tomography experiments.
+    Since qubits are usually reset between circuits, this change should have no
+    impact on tomography experiments, but it should allow backends that do not
+    provide a reset instruction to run tomography experiments. `#1250
+    <https://github.com/Qiskit-Extensions/qiskit-experiments/issues/881>`