---
title: LeftU2ParametricMultiplicationNode (latest version)
description: API reference for samplomatic.samplex.nodes.LeftU2ParametricMultiplicationNode in the latest version of samplomatic
source: https://quantum.cloud.ibm.com/docs/en/api/samplomatic/auto/samplex-nodes-left-u-2-parametric-multiplication-node
---

# LeftU2ParametricMultiplicationNode

*class* `samplomatic.samplex.nodes.LeftU2ParametricMultiplicationNode(operand: Literal['rz', 'rx'], register_name: str, param_idxs: list[int])`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/samplex/nodes/u2_param_multiplication_node.py#L96-L136)

Bases: [`U2ParametricMultiplicationNode`](/docs/api/samplomatic/auto/samplex-nodes-u-2-parametric-multiplication-node "samplomatic.samplex.nodes.u2_param_multiplication_node.U2ParametricMultiplicationNode")

Perform parametric left multiplication on a [`U2Register`](/docs/api/samplomatic/auto/virtual-registers-u-2-register "samplomatic.virtual_registers.U2Register").

The node stores a parametric representation $g$ of a one-qubit gate or gates from the original circuit and performs a $g*reg$ multiplication, where $reg$ is the existing `U2Register`.

$g$ is limited to the gates `rz` or `rx`, and all gates within the node are of the same type.

**Parameters**

- **operand** – The gate type, given as a string.
- **register\_name** – The name of the register the operation is applied to.
- **param\_idxs** – List of `ParamIndex` for the parameter expressions specifying the gate arguments. List order must match the order subsystems in the register.

**Raises**

[**SamplexConstructionError**](/docs/api/samplomatic/auto/exceptions-samplex-construction-error "samplomatic.exceptions.SamplexConstructionError") – if param\_idxs is empty.

**Methods Summary**

|                                                                                                                                                                                            |                     |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------- |
| [`evaluate`](#samplomatic.samplex.nodes.LeftU2ParametricMultiplicationNode.evaluate "samplomatic.samplex.nodes.LeftU2ParametricMultiplicationNode.evaluate")(registers, parameter\_values) | Evaluate this node. |

**Methods Documentation**

### evaluate

`evaluate(registers: dict[str, VirtualRegister], parameter_values: ndarray)`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/samplex/nodes/u2_param_multiplication_node.py#L116-L136)

Evaluate this node.

**Parameters**

- **registers** – At least those registers needed by this node to read from or write to.
- **parameter\_values** – The evaluated values of the parameter expressions in indices `self.parameter_idxs`, at the same order.

**Raises**

[**SamplexRuntimeError**](/docs/api/samplomatic/auto/exceptions-samplex-runtime-error "samplomatic.exceptions.SamplexRuntimeError") – If the number of parameter values doesn’t match the number of parameter expressions in `self.parameter_idxs`.