---
title: Qiskit SDK API documentation (latest version)
description: Re-exports in the root namespace in the latest version of qiskit.
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/root
---

# Root namespace ([`qiskit`](/docs/api/qiskit/index#module-qiskit "qiskit"))

Most Qiskit functionality is accessed through specific submodules. You can consult the top-level documentation of [`qiskit`](/docs/api/qiskit/index#module-qiskit "qiskit") to find the list of modules, such as [`qiskit.circuit`](/docs/api/qiskit/circuit#module-qiskit.circuit "qiskit.circuit") or [`qiskit.transpiler.passes`](/docs/api/qiskit/transpiler_passes#module-qiskit.transpiler.passes "qiskit.transpiler.passes").

Several names are re-exported from the repository root, whose canonical public locations are in submodules. The re-exports in the root namespace are part of Qiskit’s public API.

Names re-exported from [`qiskit.circuit`](/docs/api/qiskit/circuit#module-qiskit.circuit "qiskit.circuit"):

|                                                                                                                                          |                                                  |
| ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------ |
| [`AncillaRegister`](/docs/api/qiskit/circuit#qiskit.circuit.AncillaRegister "qiskit.circuit.AncillaRegister")(\[size, name, bits])       | Implement an ancilla register.                   |
| [`ClassicalRegister`](/docs/api/qiskit/circuit#qiskit.circuit.ClassicalRegister "qiskit.circuit.ClassicalRegister")(\[size, name, bits]) | Implement a register.                            |
| [`QuantumCircuit`](/docs/api/qiskit/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")(\*regs\[, name, global\_phase, ...])  | Core Qiskit representation of a quantum circuit. |
| [`QuantumRegister`](/docs/api/qiskit/circuit#qiskit.circuit.QuantumRegister "qiskit.circuit.QuantumRegister")(\[size, name, bits])       | Implement a register.                            |

Names re-exported from [`qiskit.compiler`](/docs/api/qiskit/compiler#module-qiskit.compiler "qiskit.compiler"):

|                                                                                                                                         |                                                                                  |
| --------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- |
| [`transpile`](/docs/api/qiskit/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile")(circuits\[, backend, basis\_gates, ...]) | Transpile one or more circuits, according to some desired transpilation targets. |

Names re-exported from [`qiskit.exceptions`](/docs/api/qiskit/exceptions#module-qiskit.exceptions "qiskit.exceptions"):

|                                                                                                                                                                                   |                                             |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------- |
| [`MissingOptionalLibraryError`](/docs/api/qiskit/exceptions#qiskit.exceptions.MissingOptionalLibraryError "qiskit.exceptions.MissingOptionalLibraryError")(libname, name\[, ...]) | Raised when an optional library is missing. |
| [`QiskitError`](/docs/api/qiskit/exceptions#qiskit.exceptions.QiskitError "qiskit.exceptions.QiskitError")(\*message)                                                             | Base class for errors raised by Qiskit.     |

Names re-exported from [`qiskit.transpiler`](/docs/api/qiskit/transpiler#module-qiskit.transpiler "qiskit.transpiler"):

|                                                                                                                                                            |                                                                                                                   |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
| [`generate_preset_pass_manager`](/docs/api/qiskit/qiskit.transpiler.generate_preset_pass_manager "qiskit.transpiler.generate_preset_pass_manager")(\[...]) | Generate a preset [`PassManager`](/docs/api/qiskit/qiskit.transpiler.PassManager "qiskit.transpiler.PassManager") |