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Hadamard transform efficient #1688

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merged 4 commits into from Oct 13, 2021
Merged

Hadamard transform efficient #1688

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4456bea
More efficient creation of the hadamard matrix.
AGaliciaMartinez Oct 13, 2021
0afc6ae
Merge branch 'hadamard_transform_efficient' of github.com:AGaliciaMar…
AGaliciaMartinez Oct 13, 2021
ede4a5b
Update qutip/qip/operations/gates.py
AGaliciaMartinez Oct 13, 2021
311ba24
Update qutip/qip/operations/gates.py
AGaliciaMartinez Oct 13, 2021
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6 changes: 2 additions & 4 deletions qutip/qip/operations/gates.py
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Expand Up @@ -892,11 +892,9 @@ def hadamard_transform(N=1):
Quantum object representation of the N-qubit Hadamard gate.

"""
data = 2 ** (-N / 2) * np.array([[(-1) ** _hamming_distance(i & j)
for i in range(2 ** N)]
for j in range(2 ** N)])
H = Qobj([[1, 1], [1, -1]]) / np.sqrt(2)

return Qobj(data, dims=[[2] * N, [2] * N])
return tensor([H] * N)


def _flatten(lst):
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14 changes: 14 additions & 0 deletions qutip/tests/test_gates.py
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Expand Up @@ -299,6 +299,20 @@ def test_cnot_explicit(self):
[0, 0, 0, 1, 0, 0, 0, 0]])
np.testing.assert_allclose(test, expected, atol=1e-15)


def test_hadamard_explicit(self):
test = gates.hadamard_transform(3).full()
expected = np.array([[ 1, 1, 1, 1, 1, 1, 1, 1],
[ 1, -1, 1, -1, 1, -1, 1, -1],
[ 1, 1, -1, -1, 1, 1, -1, -1],
[ 1, -1, -1, 1, 1, -1, -1, 1],
[ 1, 1, 1, 1, -1, -1, -1, -1],
[ 1, -1, 1, -1, -1, 1, -1, 1],
[ 1, 1, -1, -1, -1, -1, 1, 1],
[ 1, -1, -1, 1, -1, 1, 1, -1]])
expected = expected/np.sqrt(8)
np.testing.assert_allclose(test, expected)

def test_cyclic_permutation(self):
operators = [qutip.sigmax(), qutip.sigmaz()]
test = gates.expand_operator(qutip.tensor(*operators), N=3,
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