Fixed the random unitary generation from the Haar measure (#760) (#760)

* fix #519 use scipy.stats.unitary_group * Update CHANGELOG
Qiskit · Aug 9, 2018 · b2c5251 · b2c5251
1 parent 5c418c5
commit b2c5251
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diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -49,6 +49,7 @@ Fixed
 - Fixed swap mapper using qubits after measurement (#691).
 - Fixed error in cpp simulator for 3+ qubit operations (#698).
 - Fixed issue with combining or extending circuits that contain CompositeGate (#710).
+- Fixed the random unitary generation from the Haar measure (#760).
 
 `0.5.6`_ - 2018-07-06
 =====================

diff --git a/qiskit/tools/qi/qi.py b/qiskit/tools/qi/qi.py
@@ -18,6 +18,7 @@
 
 import numpy as np
 import scipy.linalg as la
+from scipy.stats import unitary_group
 
 from qiskit import QISKitError
 from qiskit.tools.qi.pauli import pauli_group
@@ -335,8 +336,7 @@ def random_unitary_matrix(length):
     Returns:
         ndarray: U (length, length) unitary ndarray.
     """
-    q_matrix = la.qr(__ginibre_matrix(length))[0]  # Get only the first element
-    return q_matrix
+    return unitary_group.rvs(length)
 
 
 def random_density_matrix(length, rank=None, method='Hilbert-Schmidt'):