def init_from_mul(cls, qu_gates):
""" Create a quantum gate by multiplying existing gates
The multiplication will be done from left to right starting zeroth
element of the qu_gates list. For example:
qu_gates = [H, X, H] will be H * X * H
Args:
qu_gates: a list of QuGates to multiply
Raises:
InvalidQuGateError: if the result of the multiplication is
not unitary or if the shape of the
matrices does not match
"""
if qu_gates:
matrix = qu_gates[0].matrix
for i in range(1, len(qu_gates)):
if matrix.shape != qu_gates[i].matrix.shape:
message = "The matrices supplied have different shapes"
raise errors.InvalidQuGateError(message)
matrix = matrix * qu_gates[i].matrix
return QuGate(matrix)
else:
raise errors.InvalidQuGateError("No gates specified")
def __init__(self, matrix, multiplier=0):
"""Create a quantum gate from a numpy matrix.
Note that if the matrix dtype is not complex it will be converted
to a complex matrix.
Args:
matrix: a complex typed numpy matrix
multiplier: if supplied all the elements of the matrix will
be multiplied by the multiplier
Raises:
InvalidQuGateError: if the gate is not unitary
"""
if matrix.dtype == np.dtype('complex128'):
self._matrix = matrix
else:
self._matrix = matrix.astype('complex128')
shape = self._matrix.shape
if shape[0] != shape[1]:
raise errors.InvalidQuGateError("Gate is not a square matrix")
if multiplier:
self._matrix = self._matrix * multiplier
#TODO: choose and configure project wide tolerance value
is_unitary = np.allclose(self._matrix.H * self._matrix,
np.eye(shape[0]))
if not is_unitary:
raise errors.InvalidQuGateError("Gate is not unitary")
def init_control_gate(cls,
qu_gate,
control_qubit=1,
target_qubit=2,
num_qubits=2):
""" Creates a CONTROL-U gate where qu_gate is U
Note we use the handy formula for control-U gates in
Rieffel/Polak page 78:
|0><0| x I + |1><1| x U
where x is the tensor product
Args:
qu_gate: a QuGate which acts as your U in control-U
control_qubit: the index of the control bit, default is 1
target_qubit: the index of the target bit, default is 2
num_qubits: total number of qubits, default is 2
"""
if num_qubits < 2:
msg = "control gates must operate on at least 2 qubits"
raise errors.InvalidQuGateError(msg)
if control_qubit == target_qubit:
msg = "control qubit must be different than target qubit"
raise errors.InvalidQuGateError(msg)
if control_qubit > num_qubits:
msg = "control qubit cannot be greater than total number of qubits"
raise errors.InvalidQuGateError(msg)
if target_qubit > num_qubits:
msg = "target qubit cannot be greater than total number of qubits"
raise errors.InvalidQuGateError(msg)
index = 1
# start with 1x1 matrix, a.k.a a number
control_mat = 1
target_mat = 1
# build control and target matrices
while index <= num_qubits:
if index == control_qubit:
control_mat = np.kron(control_mat, ZERO.ket * ZERO.bra)
target_mat = np.kron(target_mat, ONE.ket * ONE.bra)
elif index == target_qubit:
control_mat = np.kron(control_mat, np.eye(2))
target_mat = np.kron(target_mat, qu_gate.matrix)
else:
control_mat = np.kron(control_mat, np.eye(2))
target_mat = np.kron(target_mat, np.eye(2))
index += 1
control_gate = control_mat + target_mat
return QuGate(control_gate)
def apply_control_gate(self, qu_gate, control_qubit, target_qubit):
"""Apply a control gate to the state.
Args:
qu_gate: the U gate in a control-U operation
control_qubit: the control qubit
target_qubit: the target qubit
Raises:
InvalidQuGateError: if control or target qubits are out of range
"""
if control_qubit <= 0 or control_qubit > self.num_qubits:
raise errors.InvalidQuGateError("control qubit out of range")
if target_qubit <= 0 or target_qubit > self.num_qubits:
raise errors.InvalidQuGateError("target qubit out of range")
control_qugate = QuGate.init_control_gate(qu_gate, control_qubit,
target_qubit,
self.num_qubits)
self.apply_gate(control_qugate)
def init_from_tensor_product(cls, qu_gates):
""" Create a quantum gate by the tensor product of other gates
The tensor product will be done from left to right starting zeroth
element of the qu_gates list. For example:
qu_gates = [H, X, H] will be H tensor X tensor H
Args:
qu_gates: a list of QuGates to tensor
Raises:
InvalidQuGateError: if the result is not unitary
"""
if qu_gates:
matrix = np.matrix([1], dtype="complex128")
for i in range(len(qu_gates) - 1, -1, -1):
matrix = np.kron(qu_gates[i].matrix, matrix)
return QuGate(matrix)
else:
raise errors.InvalidQuGateError("No gates specified")