def pauli_gadget(alpha, s, n_qubits):
c1 = U(s, n_qubits)
c2 = phi([x for x in range(n_qubits) if s[x] != "I"], alpha, n_qubits)
c = Circuit(n_qubits)
c.add_circuit(c1, list(range(n_qubits)))
c.add_circuit(c2, list(range(n_qubits)))
c.add_circuit(c1.dagger(), list(range(n_qubits)))
return c
def approximate_with_cnots(unitary):
n_qubits = int(math.log(unitary.shape[0], 2))
mnots = function_to_mnots(
matrix_to_function(suggest_cnot_unitary(unitary), n_qubits), n_qubits)
circs = mnot_templates(n_qubits)
c = Circuit(n_qubits)
for mnot in mnots:
n_controls = len(mnot[0])
c.add_circuit(circs[n_controls - 1], mnot[0] + [mnot[1]])
return c
def mnot_templates(n_controls):
if n_controls == 0:
return Circuit(1)
c1 = Circuit(2)
c1.CX(0, 1)
c1.add_circuit(c1.copy(), [0, 1])
if n_controls == 1:
return c1
c2 = Circuit(3)
c2.CX(1, 2)
c2.CX(0, 1)
c2.CX(1, 2)
c2.CX(0, 1)
c2.CX(0, 2)
circs = [c1, c2]
for i in range(3, n_controls + 1):
c = Circuit(i + 1)
c.CX(i - 1, i)
c.CX(i - 1, i)
c.add_circuit(circs[-1], list(range(i)))
c.CX(i - 1, i)
c.CX(i - 1, i)
c.add_circuit(circs[-1], list(range(i)))
c.add_circuit(circs[-1], list(range(i - 1)) + [i])
c.add_circuit(circs[-1], list(range(i - 1)) + [i])
circs.append(c)
return circs
def random_gadget_circuit(n_qubits, n_gadgets):
c = Circuit(n_qubits)
for _ in range(n_gadgets):
c.add_circuit(random_pauli_gadget(n_qubits), list(range(n_qubits)))
return c