qiskit.quantum_info.ScalarOp

class ScalarOp(dims=None, 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=None, 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.
adjoint()	Return the adjoint of the Operator.
compose(other[, qargs, front])	Return the operator composition with another ScalarOp.
conjugate()	Return the conjugate of the ScalarOp.
copy()	Make a deep copy of current operator.
dot(other[, qargs])	Return the right multiplied operator self * other.
expand(other)	Return the reverse-order tensor product with another ScalarOp.
input_dims([qargs])	Return tuple of input dimension for specified subsystems.
is_unitary([atol, rtol])	Return True if operator is a unitary matrix.
output_dims([qargs])	Return tuple of output dimension for specified subsystems.
power(n)	Return the power of the ScalarOp.
reshape([input_dims, output_dims, num_qubits])	Return a shallow copy with reshaped input and output subsystem dimensions.
tensor(other)	Return the tensor product with another ScalarOp.
to_matrix()	Convert to a Numpy matrix.
to_operator()	Convert to an Operator object.
transpose()	Return the transpose of the ScalarOp.

Attributes

atol	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	Default relative tolerance parameter for float comparisons.
settings	Return operator settings.

adjoint()

Return the adjoint of the Operator.

property atol

Default absolute tolerance parameter for float comparisons.

property coeff

Return the coefficient

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

Return the operator composition with another ScalarOp.

Parameters

• other (ScalarOp) – a ScalarOp object.

• qargs (list or None) – Optional, 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 composed ScalarOp.

Return type

ScalarOp

Raises

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

Note

Composition (&) by default is defined as left matrix multiplication for matrix operators, while dot() is defined as right matrix multiplication. That is that A & B == A.compose(B) is equivalent to B.dot(A) when A and B are of the same type.

Setting the front=True kwarg changes this to right matrix multiplication and is equivalent to the dot() method A.dot(B) == A.compose(B, front=True).

conjugate()

Return the conjugate of the ScalarOp.

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 (Operator) – an operator object.

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

Returns

The right matrix multiplied Operator.

Return type

Operator

expand(other)

Return the reverse-order tensor product with another ScalarOp.

Parameters

other (ScalarOp) – a ScalarOp object.

Returns

the tensor product \(b \otimes a\), where \(a\)

is the current ScalarOp, and \(b\) is the other 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.

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 (float) – the exponent for the scalar op.

Returns

the coeff ** n ScalarOp.

Return type

ScalarOp

property qargs

Return the qargs for the operator.

reshape(input_dims=None, output_dims=None, num_qubits=None)

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

Parameters

• 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].

• num_qubits (None or int) – reshape to an N-qubit operator [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

Default relative tolerance parameter for float comparisons.

property settings

Return operator settings.

tensor(other)

Return the tensor product with another ScalarOp.

Parameters

other (ScalarOp) – a ScalarOp object.

Returns

the tensor product \(a \otimes b\), where \(a\)

is the current ScalarOp, and \(b\) is the other ScalarOp.

Return type

ScalarOp

Note

The tensor product can be obtained using the ^ binary operator. Hence a.tensor(b) is equivalent to a ^ b.

to_matrix()

Convert to a Numpy matrix.

to_operator()

Convert to an Operator object.

transpose()

Return the transpose of the ScalarOp.