qiskit.quantum_info.ScalarOp

class ScalarOp(dims, coeff=1)

Scalar identity operator class.

This is a symbolic representation of an scalar identity operator on multiple subsystems. It may be used to initialize a symbolic scalar multiplication of an identity and then be implicitly converted to other kinds of operator subclasses by using the compose(), dot(), tensor(), expand() methods.

Initialize an operator object.

Parameters

• dims (int or tuple) – subsystem dimensions.

• coeff (Number) – scalar coefficient for the identity operator (Default: 1).

Raises

QiskitError – If the optional coefficient is invalid.

__init__(dims, coeff=1)

Initialize an operator object.

Parameters

• dims (int or tuple) – subsystem dimensions.

• coeff (Number) – scalar coefficient for the identity operator (Default: 1).

Raises

QiskitError – If the optional coefficient is invalid.

Methods

__init__(dims[, coeff])	Initialize an operator object.
add(other)	Return the linear operator self + other.
adjoint()	Return the adjoint of the operator.
compose(other[, qargs, front])	Return the composed operator.
conjugate()	Return the conjugate of the operator.
copy()	Make a deep copy of current operator.
dot(other[, qargs])	Return the right multiplied operator self * other.
expand(other)	Return the tensor product operator other ⊗ self.
input_dims([qargs])	Return tuple of input dimension for specified subsystems.
is_unitary([atol, rtol])	Return True if operator is a unitary matrix.
multiply(other)	Return the linear operator other * self.
output_dims([qargs])	Return tuple of output dimension for specified subsystems.
power(n)	Return the power of the ScalarOp.
reshape([input_dims, output_dims])	Return a shallow copy with reshaped input and output subsystem dimensions.
set_atol(value)	Set the class default absolute tolerance parameter for float comparisons.
set_rtol(value)	Set the class default relative tolerance parameter for float comparisons.
subtract(other)	Return the linear operator self - other.
tensor(other)	Return the tensor product operator self ⊗ other.
to_matrix()	Convert to a Numpy matrix.
to_operator()	Convert to an Operator object.
transpose()	Return the transpose of the operator.

Attributes

atol	The default absolute tolerance parameter for float comparisons.
coeff	Return the coefficient
dim	Return tuple (input_shape, output_shape).
num_qubits	Return the number of qubits if a N-qubit operator or None otherwise.
qargs	Return the qargs for the operator.
rtol	The relative tolerance parameter for float comparisons.

add(other)

Return the linear operator self + other.

DEPRECATED: use operator + other instead.

Parameters

other (BaseOperator) – an operator object.

Returns

the operator self + other.

Return type

BaseOperator

adjoint()

Return the adjoint of the operator.

property atol

The default absolute tolerance parameter for float comparisons.

property coeff

Return the coefficient

compose(other, qargs=None, front=False)

Return the composed operator.

Parameters

• other (BaseOperator) – an operator object.

• qargs (list or None) – a list of subsystem positions to apply other on. If None apply on all subsystems [default: None].

• front (bool) – If True compose using right operator multiplication, instead of left multiplication [default: False].

Returns

The operator self @ other.

Return type

BaseOperator

Raises

QiskitError – if other has incompatible dimensions for specified subsystems.

Additional Information:

Composition (@) is defined as left matrix multiplication for matrix operators. That is that A @ B is equal to B * A. Setting front=True returns right matrix multiplication A * B and is equivalent to the dot() method.

conjugate()

Return the conjugate of the operator.

copy()

Make a deep copy of current operator.

property dim

Return tuple (input_shape, output_shape).

dot(other, qargs=None)

Return the right multiplied operator self * other.

Parameters

• other (BaseOperator) – an operator object.

• qargs (list or None) – a list of subsystem positions to apply other on. If None apply on all subsystems [default: None].

Returns

The operator self * other.

Return type

BaseOperator

Raises

QiskitError – if other cannot be converted to an operator, or has incompatible dimensions for specified subsystems.

expand(other)

Return the tensor product operator other ⊗ self.

Parameters

other (BaseOperator) – an operator object.

Returns

if other is an ScalarOp. BaseOperator: if other is not an ScalarOp.

Return type

ScalarOp

input_dims(qargs=None)

Return tuple of input dimension for specified subsystems.

is_unitary(atol=None, rtol=None)

Return True if operator is a unitary matrix.

multiply(other)

Return the linear operator other * self.

DEPRECATED: use other * operator instead.

Parameters

other (complex) – a complex number.

Returns

the linear operator other * self.

Return type

BaseOperator

Raises

NotImplementedError – if subclass does not support multiplication.

property num_qubits

Return the number of qubits if a N-qubit operator or None otherwise.

output_dims(qargs=None)

Return tuple of output dimension for specified subsystems.

power(n)

Return the power of the ScalarOp.

Parameters

n (Number) – the exponent for the scalar op.

Returns

the coeff ** n ScalarOp.

Return type

ScalarOp

Raises

QiskitError – if the input and output dimensions of the operator are not equal, or the power is not a positive integer.

property qargs

Return the qargs for the operator.

reshape(input_dims=None, output_dims=None)

Return a shallow copy with reshaped input and output subsystem dimensions.

Arg:

input_dims (None or tuple): new subsystem input dimensions.

If None the original input dims will be preserved [Default: None].

output_dims (None or tuple): new subsystem output dimensions.

If None the original output dims will be preserved [Default: None].

Returns

returns self with reshaped input and output dimensions.

Return type

BaseOperator

Raises

QiskitError – if combined size of all subsystem input dimension or subsystem output dimensions is not constant.

property rtol

The relative tolerance parameter for float comparisons.

classmethod set_atol(value)

Set the class default absolute tolerance parameter for float comparisons.

DEPRECATED: use operator.atol = value instead

classmethod set_rtol(value)

Set the class default relative tolerance parameter for float comparisons.

DEPRECATED: use operator.rtol = value instead

subtract(other)

Return the linear operator self - other.

DEPRECATED: use operator - other instead.

Parameters

other (BaseOperator) – an operator object.

Returns

the operator self - other.

Return type

BaseOperator

tensor(other)

Return the tensor product operator self ⊗ other.

Parameters

other (BaseOperator) – an operator object.

Returns

if other is an ScalarOp. BaseOperator: if other is not an ScalarOp.

Return type

ScalarOp

to_matrix()

Convert to a Numpy matrix.

to_operator()

Convert to an Operator object.

transpose()

Return the transpose of the operator.