operators

Module for representing operators of quantum states.

An Operator is constructed as a sum of BaseState and in turn State

The BaseOperator-class represents a single term of the form |left><right|, where left and right are BaseState’s. The BaseOperator is agnostic to which subclass of BaseState is used.

The Operator-class is then a sum of BaseOperator.

class qualg.operators.BaseOperator(left, right)
__init__(left, right)

Represents a single term of an operator, i.e. |left><right|, where left and right are BaseState’s.

Parameters

  • left (BaseState) – Left side of operator.

  • right (BaseState) – Right side of operator.

property shape

Returns the shape of the operator, e.q. (2, 2) for a single-qubit operator.

None means that the shape is undefined, e.g. if the state is infinite-dimensional.

to_operator()

Converts the base operator to an Operator with a single term.

replace_var(old_variable, new_variable)

Replaces a variable with another.

get_variables()

Returns the variable of this operator.

class qualg.operators.Operator(base_ops=None, scalars=None)
__init__(base_ops=None, scalars=None)

An operator represented as a sum of BaseOperator of a subclass thereof.

Parameters

  • base_ops (None or list of BaseOperator) – The base operators that sums up to this operator. If None, then the operator is “zero”, i.e. no terms.

  • scalar (None or list of Scalar) – The amplitudes used when taking the sum of base operators. If None, then all operators have amplitude 1.

property shape

Returns the shape of the operator, e.q. (2, 2) for a single-qubit operator.

None means that the shape is undefined, e.g. if the state is infinite-dimensional.

get_scalar(base_op)

Returns the scalar of the given base_op

dagger()

Complex conjugate of the operator.

simplify()

Tries to simplify the operator, returning a new one.

replace_var(old_variable, new_variable)

Replaces a variable with another.

get_variables()

Returns the variable of this operator.

to_numpy_matrix(convert_scalars=None, **kwargs)

Converts the operator to a numpy matrix.

If there are non-number scalars then the provided function convert_scalars is used to convert a non-number scalar to a number. This function should then take a scalar (plus optional keyword arguments) and return a number.

Parameters

  • convert_scalars (function) – Function to convert a non-number scalar to a number.

  • **kwargs – Keyword-arguments to be passed to convert_scalars.

Returns

The operator in numerical matrix form.

Return type

numpy.ndarray

qualg.operators.outer_product(left, right)

Creates an opertor based on the outer product of left and right, i.e. |left><right|.

Parameters

  • left (BaseState) – Left side of operator.

  • right (BaseState) – Right side of operator.

Returns

The new operator.

Return type

Operator