Unitair Documentation

Unitair is a lightweight Python package that brings quantum computing to PyTorch.

Unitair differs from other quantum computing software packages in important ways. Quantum states are PyTorch tensors (the PyTorch version of the NumPy ndarray). There is no special class for quantum states class nor is there an abstract QuantumCircuit class. Unitair doesn’t directly rely on any circuit model although it supports circuit-model computation.

Manipulations of quantum states naturally take advantage of PyTorch’s strengths. You can

  • Apply gates and other operations to a batch of states

  • Use gradients to track gate parameters or parameters used to build an initial state

  • Set device='cuda' to get GPU-acceleration

  • Mix unitair functions with torch.nn networks or any other PyTorch functionality

The design of Unitair encourages users to do things that, really, should never be done to quantum states. Their components can be directly read and manipulated in physically unrealistic ways. This freedom allows for great efficiency when emulating quantum state evolution. If you know that the effect of a series of operations is to manipulate a state in a certain way, why not just change the components by hand rather than applying gates in a computationally complicated way?

Intended users

Unitair was designed with the goal of helping to bridge the fields of quantum computing and machine learning. Anyone with experience in PyTorch (or another machine learning library like TensorFlow) and basic knowledge of quantum computing should find Unitair to be very simple. Users that are experts in machine learning or quantum computing but not both should find Unitair helpful to start making a connection with the other discipline.

What Unitair Is and Is Not

Unitair…

  • is a library of PyTorch linear algebra functions for quantum computing

  • is a quantum computing emulation tool

  • can substantially reduce circuit simulation time (when used well)

  • is lightweight and easy to use if you have PyTorch experience

  • batches quantum states and operations for performance on a CPU or GPU

  • can simulate any quantum circuit (within computational constraints)

  • tracks gradients (everything PyTorch under the hood)

but Unitair is not…

  • a replacement for Circ, Qiskit, Quasar, Q#, etc.

  • designed to simulate noise realistically

  • a quantum circuit editor

  • helpful for deploying quantum circuits on quantum hardware

  • a quantum algorithm library

Tutorial:

API

Indices and tables