def to_quimb_tensor(g: BaseGraph) -> 'qtn.TensorNetwork':
"""Converts tensor network representing the given :func:`pyzx.graph.Graph`.
Pretty printing: to_tensor(g).draw(color = ['V', 'H'])
Args:
g: graph to be converted."""
if qu is None:
raise ImportError("quimb must be installed to use this function.")
# copying a graph guarantees consecutive indices, which are needed for the tensor net
g = g.copy()
# only Z spiders are handled below
to_gh(g)
tensors = []
# Here we have phase tensors corresponding to Z-spiders with only one output and no input.
for v in g.vertices():
if g.type(v) == VertexType.Z and g.phase(v) != 0:
tensors.append(
qtn.Tensor(data=[1, np.exp(1j * np.pi * g.phase(v))],
inds=(f'{v}', ),
tags=("V", )))
# Hadamard or Kronecker tensors, one for each edge of the diagram.
for i, edge in enumerate(g.edges()):
x, y = edge
isHadamard = g.edge_type(edge) == EdgeType.HADAMARD
t = qtn.Tensor(data=qu.hadamard()
if isHadamard else np.array([1, 0, 0, 1]).reshape(2, 2),
inds=(f'{x}', f'{y}'),
tags=("H", ) if isHadamard else ("N", ))
tensors.append(t)
# TODO: This is not taking care of all the stuff that can be in g.scalar
# In particular, it doesn't check g.scalar.phasenodes
# TODO: This will give the wrong tensor when g.scalar.is_zero == True.
# Grab the float factor and exponent from the scalar
scalar_float = np.exp(1j * np.pi * g.scalar.phase) * g.scalar.floatfactor
for node in g.scalar.phasenodes: # Each node is a Fraction
scalar_float *= 1 + np.exp(1j * np.pi * node)
scalar_exp = math.log10(math.sqrt(2)) * g.scalar.power2
# If the TN is empty, create a single 0-tensor with scalar factor, otherwise
# multiply the scalar into one of the tensors.
if len(tensors) == 0:
tensors.append(qtn.Tensor(data=scalar_float, inds=(), tags=("S", )))
else:
tensors[0].modify(data=tensors[0].data * scalar_float)
network = qtn.TensorNetwork(tensors)
# the exponent can be very large, so distribute it evenly through the TN
network.exponent = scalar_exp
network.distribute_exponent()
return network
def test_simple(self):
n = 10
d_psi = qu.computational_state('0' * n)
t_psi = Dense1D(d_psi)
assert set(t_psi.outer_inds()) == {'k{}'.format(i) for i in range(n)}
assert set(t_psi.tags) == {'I{}'.format(i) for i in range(n)}
for i in range(n):
assert t_psi.H @ t_psi.gate(qu.pauli('Z'), i) == pytest.approx(1)
for i in range(n):
t_psi.gate_(qu.hadamard(), i)
assert len(t_psi.tensors) == n + 1
# should have '++++++++++'
assert t_psi.H @ t_psi == pytest.approx(1)
for i in range(n):
assert t_psi.H @ t_psi.gate(qu.pauli('X'), i) == pytest.approx(1)
def apply_U3(psi, theta, phi, lamda, i, **gate_opts):
mtags = _merge_tags({'U3'}, gate_opts)
psi.gate_(qu.U_gate(theta, phi, lamda), int(i), tags=mtags, **gate_opts)
def apply_swap(psi, i, j, **gate_opts):
itag, jtag = map(psi.site_tag, (i, j))
psi.reindex_({itag: jtag, jtag: itag})
APPLY_GATES = {
'RX': apply_Rx,
'RY': apply_Ry,
'RZ': apply_Rz,
'U3': apply_U3,
'H': build_gate_1(qu.hadamard(), tags='H'),
'X': build_gate_1(qu.pauli('X'), tags='X'),
'Y': build_gate_1(qu.pauli('Y'), tags='Y'),
'Z': build_gate_1(qu.pauli('Z'), tags='Z'),
'S': build_gate_1(qu.S_gate(), tags='S'),
'T': build_gate_1(qu.T_gate(), tags='T'),
'X_1_2': build_gate_1(qu.Rx(math.pi / 2), tags='X_1/2'),
'Y_1_2': build_gate_1(qu.Ry(math.pi / 2), tags='Y_1/2'),
'Z_1_2': build_gate_1(qu.Rz(math.pi / 2), tags='Z_1/2'),
'IDEN': lambda *args, **kwargs: None,
'CX': build_gate_2(qu.cX(), tags='CX'),
'CY': build_gate_2(qu.cY(), tags='CY'),
'CZ': build_gate_2(qu.cZ(), tags='CZ'),
'CNOT': build_gate_2(qu.CNOT(), tags='CNOT'),
'SWAP': apply_swap,
}
