fixed partial trace constraint in cvx fitting routine (#438) (#440)

(cherry picked from commit 3b72172) Co-authored-by: Christophe Piveteau <cpivetea@student.ethz.ch>
qiskit-community · Jun 24, 2020 · f0e1021 · f0e1021
1 parent 6579e61
commit f0e1021
Showing 1 changed file with 1 addition and 0 deletions.
diff --git a/qiskit/ignis/verification/tomography/fitters/cvx_fit.py b/qiskit/ignis/verification/tomography/fitters/cvx_fit.py
@@ -155,6 +155,7 @@ def cvx_fit(data: np.array,
         sdim = int(np.sqrt(dim))
         ptr = partial_trace_super(sdim, sdim)
         cons.append(ptr @ cvxpy.vec(rho_r) == np.identity(sdim).ravel())
+        cons.append(ptr @ cvxpy.vec(rho_i) == np.zeros(sdim*sdim))
 
     # Rescale input data and matrix by weights if they are provided
     if weights is not None: