Merge pull request #528 from qiboteam/fixprobs

Fix probabilities do not sum to 1
qiboteam · Dec 27, 2021 · 5ebf0d1 · 5ebf0d1
2 parents 20fb08d + 9c81b47
commit 5ebf0d1
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diff --git a/src/qibo/backends/numpy.py b/src/qibo/backends/numpy.py
@@ -63,7 +63,7 @@ def cast(self, x, dtype='DTYPECPX'):
         if isinstance(dtype, str):
             dtype = self.dtypes(dtype)
         if isinstance(x, self.backend.ndarray):
-            return x.astype(dtype)
+            return x.astype(dtype, copy=False)
         return self.backend.array(x, dtype=dtype)
 
     def diag(self, x, dtype='DTYPECPX'):

diff --git a/src/qibo/core/states.py b/src/qibo/core/states.py
@@ -93,7 +93,7 @@ def probabilities(self, qubits=None, measurement_gate=None):
         unmeasured_qubits = tuple(i for i in range(self.nqubits)
                                   if i not in qubits)
         state = K.reshape(K.square(K.abs(K.cast(self.tensor))), self.nqubits * (2,))
-        return K.sum(state, axis=unmeasured_qubits)
+        return K.sum(K.cast(state, dtype="float64"), axis=unmeasured_qubits)
 
     def measure(self, gate, nshots, registers=None):
         self.measurements = gate(self, nshots)