WeightedAdder¶

class
WeightedAdder
(num_state_qubits=None, weights=None, name='adder')[source]¶ Bases:
qiskit.circuit.library.blueprintcircuit.BlueprintCircuit
A circuit to compute the weighted sum of qubit registers.
Given \(n\) qubit basis states \(q_0, \ldots, q_{n1} \in \{0, 1\}\) and nonnegative integer weights \(\lambda_0, \ldots, \lambda_{n1}\), this circuit performs the operation
\[q_0 \ldots q_{n1}\rangle 0\rangle_s \mapsto q_0 \ldots q_{n1}\rangle \sum_{j=0}^{n1} \lambda_j q_j\rangle_s\]where \(s\) is the number of sum qubits required. This can be computed as
\[s = 1 + \left\lfloor \log_2\left( \sum_{j=0}^{n1} \lambda_j \right) \right\rfloor\]or \(s = 1\) if the sum of the weights is 0 (then the expression in the logarithm is invalid).
For qubits in a circuit diagram, the first weight applies to the uppermost qubit. For an example where the state of 4 qubits is added into a sum register, the circuit can be schematically drawn as
┌────────┐ state_0: ┤0 ├  state_0 * weights[0] │ │  state_1: ┤1 ├  + state_1 * weights[1] │ │  state_2: ┤2 ├  + state_2 * weights[2] │ │  state_3: ┤3 ├  + state_3 * weights[3] │ │ sum_0: ┤4 ├  │ Adder │  sum_1: ┤5 ├  = sum_0 * 2^0 + sum_1 * 2^1 + sum_2 * 2^2 │ │  sum_2: ┤6 ├  │ │ carry_0: ┤7 ├ │ │ carry_1: ┤8 ├ │ │ control_0: ┤9 ├ └────────┘
Computes the weighted sum controlled by state qubits.
 Parameters
num_state_qubits (
Optional
[int
]) – The number of state qubits.weights (
Optional
[List
[int
]]) – List of weights, one for each state qubit. If none are provided they default to 1 for every qubit.name (
str
) – The name of the circuit.
Attributes

ancillas
¶ Returns a list of ancilla bits in the order that the registers were added.

calibrations
¶ Return calibration dictionary.
 The custom pulse definition of a given gate is of the form
{‘gate_name’: {(qubits, params): schedule}}

clbits
¶ Returns a list of classical bits in the order that the registers were added.

data
¶

extension_lib
= 'include "qelib1.inc";'¶

global_phase
¶ Return the global phase of the circuit in radians.

header
= 'OPENQASM 2.0;'¶

instances
= 16¶

metadata
¶ The user provided metadata associated with the circuit
The metadata for the circuit is a user provided
dict
of metadata for the circuit. It will not be used to influence the execution or operation of the circuit, but it is expected to be passed between all transforms of the circuit (ie transpilation) and that providers will associate any circuit metadata with the results it returns from execution of that circuit.

num_ancilla_qubits
¶ Deprecated. Use num_ancillas instead.
 Return type
int

num_ancillas
¶ Return the number of ancilla qubits.

num_carry_qubits
¶ The number of carry qubits required to compute the sum.
Note that this is not necessarily equal to the number of ancilla qubits, these can be queried using
num_ancilla_qubits
. Return type
int
 Returns
The number of carry qubits required to compute the sum.

num_clbits
¶ Return number of classical bits.

num_control_qubits
¶ The number of additional control qubits required.
Note that the total number of ancilla qubits can be obtained by calling the method
num_ancilla_qubits
. Return type
int
 Returns
The number of additional control qubits required (0 or 1).

num_parameters
¶  Return type
int

num_qubits
¶ Return number of qubits.

num_state_qubits
¶ The number of qubits to be summed.
 Return type
int
 Returns
The number of state qubits.

num_sum_qubits
¶ The number of sum qubits in the circuit.
 Return type
int
 Returns
The number of qubits needed to represent the weighted sum of the qubits.

parameters
¶  Return type
ParameterView

prefix
= 'circuit'¶

qregs
¶ A list of the quantum registers associated with the circuit.

qubits
¶ Returns a list of quantum bits in the order that the registers were added.

weights
¶ The weights for the qubit states.
 Return type
List
[int
] Returns
The weight for the qubit states.