def _throwExceptionIfObservableMeasurementIsNotValid(self, observable):
if self.__is_dereferenced:
raise IllegalRegisterReference("Measurement attempted on "
"dereferenced register.")
if not isinstance(observable, qOp):
raise TypeError("Argument of measure_observable() must be a qOp.")
if len(self) < observable.size():
raise WrongShapeError("Observable larger than qReg.")
def _throwExceptionIfRequestedMeasurementIsNotValid(self, target):
if self.__is_dereferenced:
raise IllegalRegisterReference('Measurement attempted on '
'dereferenced register.')
isTargetQubitIndexValid = (isinstance(target, int) and target >= 0
and target < len(self))
if not isTargetQubitIndexValid:
raise IndexError('Quantum register address must be nonnegative '
'integer less than size of register.')
def __imul__(self, some_reg):
'''
Concatentates the register with some_reg (|a_reg> *= |some_reg> stores
|a_reg>|some_reg> into ``a_reg``).
'''
if not isinstance(some_reg, qReg):
raise TypeError("Cannot concatentate a non-qReg to a qReg.")
if self.__is_dereferenced or some_reg.__is_dereferenced:
raise IllegalRegisterReference(
'Concatentation attempted on dereferenced register.')
self.__q_reg = self.__q_reg.qubit_product(some_reg._qReg__q_reg)
some_reg._qReg__is_dereferenced = True
return self
def __mul__(self, another_reg):
'''
For concatenating the register with another_reg
(|new> = |reg> * |another_reg> stores the product into ``new``).
'''
if self.__is_dereferenced or another_reg.__is_dereferenced:
raise IllegalRegisterReference(
'Concatenation attempted on dereferenced register.')
product_register = qReg()
product_qubits = self.__q_reg.qubit_product(another_reg._qReg__q_reg)
product_register._qReg__q_reg.change_state(product_qubits.state())
self.__is_dereferenced = True
another_reg._qReg__is_dereferenced = True
return product_register
def dump_state(self):
'''
Returns a copy of the state of a ``qReg`` as a numpy array. Would have
no effect on a hardware implementation of the backend. If the register
has been dereferenced, raises an exception.
Returns
-------
numpy.ndarray
The state of ``qReg`` as a vector in the computational basis. Has
no side effects.
Examples
--------
Here we get a vector corresponding to the Hadamard state:
>>> from pypsqueak.api import qReg
>>> from pypsqueak.gates import H
>>> a = qReg(3)
>>> H.on(a, 0)
>>> a.dump_state()
array([0.70710678, 0.70710678, 0. , 0. , 0. ,
0. , 0. , 0. ])
Now we dereference the ``qReg`` and run into an exception when we try
to dump its state again:
>>> a * qReg()
qReg(4)
>>> a.dump_state()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "pypsqueak/api.py", line 342, in dump_state
exception.
pypsqueak.errors.IllegalRegisterReference: Dereferenced register
encountered.
'''
if self.__is_dereferenced:
raise IllegalRegisterReference('Dereferenced register '
'encountered.')
return self.__q_reg.state()
def __iadd__(self, n_new_qubits):
'''
Prepends ``n_new_qubits`` qubits to the register in the |0> state.
Leaves register unchanged if n_new_qubits is zero.
'''
if self.__is_dereferenced:
raise IllegalRegisterReference('Attempt to add Qubits to '
'dereferenced register.')
if not isinstance(n_new_qubits, int) or n_new_qubits < 0:
raise ValueError("Can only add a nonnegative integer number of "
"qubits to qReg.")
n_qubits_in_zero_state = Qubit(
[1 if i == 0 else 0 for i in range(2**n_new_qubits)])
self.__q_reg = n_qubits_in_zero_state.qubit_product(self.__q_reg)
return self
def peek(self):
'''
Returns a ket description of the state of a ``qReg``. Would have no
effect on hardware implementations of the backend. If the register has
been dereferenced, raises an exception.
Returns
-------
str
Description of ``qReg`` state. Has no side effects.
Examples
--------
Here we peek at a register in the Hadamard state:
>>> from pypsqueak.api import qReg
>>> from pypsqueak.gates import H
>>> a = qReg(3)
>>> H.on(a, 0)
>>> a.peek()
'(7.07e-01)|000> + (7.07e-01)|001>'
After dereferencing the register via a multiplication, calling
``peek()`` raises an exception:
>>> a * qReg()
qReg(4)
>>> a.peek()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "pypsqueak/api.py", line 309, in peek
raise IllegalRegisterReference('Dereferenced register '
'encountered.')
pypsqueak.errors.IllegalRegisterReference: Dereferenced register
encountered.
'''
if self.__is_dereferenced:
raise IllegalRegisterReference('Dereferenced register '
'encountered.')
return str(self.__q_reg)
def __len__(self):
if self.__is_dereferenced:
raise IllegalRegisterReference(
'Dereferenced register encountered.')
return len(self.__q_reg)