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---
title: HRSCumulativeMultiplier (latest version)
description: API reference for qiskit.circuit.library.HRSCumulativeMultiplier in the latest version of qiskit
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit.circuit.library.HRSCumulativeMultiplier
---
# HRSCumulativeMultiplier
<Class id="qiskit.circuit.library.HRSCumulativeMultiplier" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/arithmetic/multipliers/hrs_cumulative_multiplier.py#L21-L138" signature="qiskit.circuit.library.HRSCumulativeMultiplier(num_state_qubits, num_result_qubits=None, adder=None, name='HRSCumulativeMultiplier')" modifiers="class">
Bases: `Multiplier`
A multiplication circuit to store product of two input registers out-of-place.
Circuit uses the approach from \[1]. As an example, a multiplier circuit that performs a non-modular multiplication on two 3-qubit sized registers with the default adder is as follows (where `Adder` denotes the `CDKMRippleCarryAdder`):
```python
a_0: ────■─────────────────────────
a_1: ────┼─────────■───────────────
│ │
a_2: ────┼─────────┼─────────■─────
┌───┴────┐┌───┴────┐┌───┴────┐
b_0: ┤0 ├┤0 ├┤0 ├
│ ││ ││ │
b_1: ┤1 ├┤1 ├┤1 ├
│ ││ ││ │
b_2: ┤2 ├┤2 ├┤2 ├
│ ││ ││ │
out_0: ┤3 ├┤ ├┤ ├
│ ││ ││ │
out_1: ┤4 ├┤3 ├┤ ├
│ Adder ││ Adder ││ Adder │
out_2: ┤5 ├┤4 ├┤3 ├
│ ││ ││ │
out_3: ┤6 ├┤5 ├┤4 ├
│ ││ ││ │
out_4: ┤ ├┤6 ├┤5 ├
│ ││ ││ │
out_5: ┤ ├┤ ├┤6 ├
│ ││ ││ │
aux_0: ┤7 ├┤7 ├┤7 ├
└────────┘└────────┘└────────┘
```
Multiplication in this circuit is implemented in a classical approach by performing a series of shifted additions using one of the input registers while the qubits from the other input register act as control qubits for the adders.
**References:**
\[1] Häner et al., Optimizing Quantum Circuits for Arithmetic, 2018. [arXiv:1805.12445](https://arxiv.org/pdf/1805.12445.pdf)
**Parameters**
* **num\_state\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")) The number of qubits in either input register for state $|a\rangle$ or $|b\rangle$. The two input registers must have the same number of qubits.
* **num\_result\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)") *| None*) The number of result qubits to limit the output to. If number of result qubits is $n$, multiplication modulo $2^n$ is performed to limit the output to the specified number of qubits. Default value is `2 * num_state_qubits` to represent any possible result from the multiplication of the two inputs.
* **adder** ([*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.quantumcircuit.QuantumCircuit") *| None*) Half adder circuit to be used for performing multiplication. The CDKMRippleCarryAdder is used as default if no adder is provided.
* **name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) The name of the circuit object.
**Raises**
[**NotImplementedError**](https://docs.python.org/3/library/exceptions.html#NotImplementedError "(in Python v3.13)") If `num_result_qubits` is not default and a custom adder is provided.
## Attributes
### ancillas
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.ancillas">
A list of `AncillaQubit`s in the order that they were added. You should not mutate this.
</Attribute>
### calibrations
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.calibrations">
Return calibration dictionary.
The custom pulse definition of a given gate is of the form `{'gate_name': {(qubits, params): schedule}}`
</Attribute>
### clbits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.clbits">
A list of `Clbit`s in the order that they were added. You should not mutate this.
</Attribute>
### data
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.data">
The circuit data (instructions and context).
**Returns**
a list-like object containing the [`CircuitInstruction`](qiskit.circuit.CircuitInstruction "qiskit.circuit.CircuitInstruction")s for each instruction.
**Return type**
QuantumCircuitData
</Attribute>
### global\_phase
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.global_phase">
The global phase of the current circuit scope in radians.
</Attribute>
### instances
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.instances" attributeValue="198" />
### layout
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.layout">
Return any associated layout information about the circuit
This attribute contains an optional [`TranspileLayout`](qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") object. This is typically set on the output from [`transpile()`](compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") or [`PassManager.run()`](qiskit.transpiler.PassManager#run "qiskit.transpiler.PassManager.run") to retain information about the permutations caused on the input circuit by transpilation.
There are two types of permutations caused by the [`transpile()`](compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") function, an initial layout which permutes the qubits based on the selected physical qubits on the [`Target`](qiskit.transpiler.Target "qiskit.transpiler.Target"), and a final layout which is an output permutation caused by [`SwapGate`](qiskit.circuit.library.SwapGate "qiskit.circuit.library.SwapGate")s inserted during routing.
</Attribute>
### metadata
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.metadata">
Arbitrary user-defined metadata for the circuit.
Qiskit will not examine the content of this mapping, but it will pass it through the transpiler and reattach it to the output, so you can track your own metadata.
</Attribute>
### num\_ancillas
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_ancillas">
Return the number of ancilla qubits.
</Attribute>
### num\_captured\_vars
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_captured_vars">
The number of real-time classical variables in the circuit marked as captured from an enclosing scope.
This is the length of the `iter_captured_vars()` iterable. If this is non-zero, [`num_input_vars`](#qiskit.circuit.library.HRSCumulativeMultiplier.num_input_vars "qiskit.circuit.library.HRSCumulativeMultiplier.num_input_vars") must be zero.
</Attribute>
### num\_clbits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_clbits">
Return number of classical bits.
</Attribute>
### num\_declared\_vars
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_declared_vars">
The number of real-time classical variables in the circuit that are declared by this circuit scope, excluding inputs or captures.
This is the length of the `iter_declared_vars()` iterable.
</Attribute>
### num\_input\_vars
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_input_vars">
The number of real-time classical variables in the circuit marked as circuit inputs.
This is the length of the `iter_input_vars()` iterable. If this is non-zero, [`num_captured_vars`](#qiskit.circuit.library.HRSCumulativeMultiplier.num_captured_vars "qiskit.circuit.library.HRSCumulativeMultiplier.num_captured_vars") must be zero.
</Attribute>
### num\_parameters
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_parameters">
The number of parameter objects in the circuit.
</Attribute>
### num\_qubits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_qubits">
Return number of qubits.
</Attribute>
### num\_result\_qubits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_result_qubits">
The number of result qubits to limit the output to.
**Returns**
The number of result qubits.
</Attribute>
### num\_state\_qubits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_state_qubits">
The number of state qubits, i.e. the number of bits in each input register.
**Returns**
The number of state qubits.
</Attribute>
### num\_vars
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.num_vars">
The number of real-time classical variables in the circuit.
This is the length of the `iter_vars()` iterable.
</Attribute>
### op\_start\_times
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.op_start_times">
Return a list of operation start times.
This attribute is enabled once one of scheduling analysis passes runs on the quantum circuit.
**Returns**
List of integers representing instruction start times. The index corresponds to the index of instruction in `QuantumCircuit.data`.
**Raises**
[**AttributeError**](https://docs.python.org/3/library/exceptions.html#AttributeError "(in Python v3.13)") When circuit is not scheduled.
</Attribute>
### parameters
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.parameters">
The parameters defined in the circuit.
This attribute returns the [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit sorted alphabetically. Note that parameters instantiated with a [`ParameterVector`](qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") are still sorted numerically.
**Examples**
The snippet below shows that insertion order of parameters does not matter.
```python
>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> a, b, elephant = Parameter("a"), Parameter("b"), Parameter("elephant")
>>> circuit = QuantumCircuit(1)
>>> circuit.rx(b, 0)
>>> circuit.rz(elephant, 0)
>>> circuit.ry(a, 0)
>>> circuit.parameters # sorted alphabetically!
ParameterView([Parameter(a), Parameter(b), Parameter(elephant)])
```
Bear in mind that alphabetical sorting might be unintuitive when it comes to numbers. The literal “10” comes before “2” in strict alphabetical sorting.
```python
>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> angles = [Parameter("angle_1"), Parameter("angle_2"), Parameter("angle_10")]
>>> circuit = QuantumCircuit(1)
>>> circuit.u(*angles, 0)
>>> circuit.draw()
┌─────────────────────────────┐
q: ┤ U(angle_1,angle_2,angle_10) ├
└─────────────────────────────┘
>>> circuit.parameters
ParameterView([Parameter(angle_1), Parameter(angle_10), Parameter(angle_2)])
```
To respect numerical sorting, a [`ParameterVector`](qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") can be used.
```python
>>> from qiskit.circuit import QuantumCircuit, Parameter, ParameterVector
>>> x = ParameterVector("x", 12)
>>> circuit = QuantumCircuit(1)
>>> for x_i in x:
... circuit.rx(x_i, 0)
>>> circuit.parameters
ParameterView([
ParameterVectorElement(x[0]), ParameterVectorElement(x[1]),
ParameterVectorElement(x[2]), ParameterVectorElement(x[3]),
..., ParameterVectorElement(x[11])
])
```
**Returns**
The sorted [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit.
</Attribute>
### prefix
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.prefix" attributeValue="'circuit'" />
### qubits
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.qubits">
A list of `Qubit`s in the order that they were added. You should not mutate this.
</Attribute>
### name
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.name" attributeTypeHint="str">
A human-readable name for the circuit.
</Attribute>
### qregs
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.qregs" attributeTypeHint="list[QuantumRegister]">
A list of the `QuantumRegister`s in this circuit. You should not mutate this.
</Attribute>
### cregs
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.cregs" attributeTypeHint="list[ClassicalRegister]">
A list of the `ClassicalRegister`s in this circuit. You should not mutate this.
</Attribute>
### duration
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.duration" attributeTypeHint="int | float | None">
The total duration of the circuit, set by a scheduling transpiler pass. Its unit is specified by [`unit`](#qiskit.circuit.library.HRSCumulativeMultiplier.unit "qiskit.circuit.library.HRSCumulativeMultiplier.unit").
</Attribute>
### unit
<Attribute id="qiskit.circuit.library.HRSCumulativeMultiplier.unit">
The unit that [`duration`](#qiskit.circuit.library.HRSCumulativeMultiplier.duration "qiskit.circuit.library.HRSCumulativeMultiplier.duration") is specified in.
</Attribute>
</Class>