---
title: Clbit (v1.0)
description: API reference for qiskit.circuit.Clbit in qiskit v1.0
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/1.0/qiskit.circuit.Clbit
---

# Clbit

*class* `qiskit.circuit.Clbit(register=None, index=None)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.0/qiskit/circuit/classicalregister.py#L26-L47)

Bases: [`Bit`](/docs/api/qiskit/1.0/qiskit.circuit.Bit "qiskit.circuit.bit.Bit")

Implement a classical bit.

Creates a classical bit.

**Parameters**

- **register** ([*ClassicalRegister*](/docs/api/qiskit/1.0/qiskit.circuit.ClassicalRegister "qiskit.circuit.ClassicalRegister")) – Optional. A classical register containing the bit.
- **index** ([*int*](https://docs.python.org/3/library/functions.html#int)) – Optional. The index of the bit in its containing register.

**Raises**

[**CircuitError**](/docs/api/qiskit/1.0/circuit#qiskit.circuit.CircuitError "qiskit.circuit.CircuitError") – if the provided register is not a valid [`ClassicalRegister`](/docs/api/qiskit/1.0/qiskit.circuit.ClassicalRegister "qiskit.circuit.ClassicalRegister")