Hardware Abstraction Layer (HAL)

Scope and Purpose

This document sets out a Hardware Abstraction Layer (HAL) for quantum computers based on four leading qubit technologies: superconducting qubits, trapped-ion qubits, photonic systems and silicon-based qubits. The aim is to define a multi-level HAL that makes software portable across platforms but not at the cost of performance. The HAL allows high-level quantum computer users, such as application developers, platform and system software engineers, cross-platform software architects, to abstract away the hardware implementation details while keeping the performance.

This document defines the HAL levels, categorised by the types of applications that they enable. The definition includes the general HAL architecture, HAL features (e.g. which commands need to be implemented) and the HAL specification format. The document does not define the HAL implementation or how to compile/transpile between the different levels. This document is a part of the NISQ.OS ISCF project as a collaborative effort of ARM, Duality Quantum Photonics, Hitachi Europe Limited, the National Physical Laboratory, Oxford Ionics, Oxford Quantum Circuits, Riverlane, Seeqc, and Universal Quantum.

This joint project’s commitment is to implement applications that require the fastest classical/quantum interaction, such as measurement and control-based applications and error correction. Deltaflow.OS, the operating system for quantum computers which will be developed within the ISCF NISQ.OS project, builds on this open HAL specification.

The HAL is to be an open standard on which other parties can also build. One aim of the ISCF project is to engage in international standardisation efforts with this HAL.

Table 1 Contributors



Duality Quantum Photonics (DQP)

Hitachi Europe Ltd (HEU)

National Physical Laboratory (NPL)

Oxford Ionics (OI)

Oxford Quantum Circuits (OQC)

Riverlane (RL)


Universal Quantum (UQ)


This specification must be considered a work in progress. The document is currently used to guide discovery, initiate discussion and enable future improvements. Even though all the parties involved are putting their best efforts on verifying the validity and correctness of what is stated, extensive reviews are still to be conducted. This disclaimer will be removed once the document reaches sufficient maturity.