# Quantum Tensors

It is a JavaScript / TypeScript package for sparse tensor operations on complex numbers. For example for quantum computing, quantum information, and well - the Quantum Game.

`(1.00 +0.00i) |1,2,>,V⟩`

-> `(-0.71 +0.00i) |1,2,>,H⟩ + (0.71 +0.00i) |1,2,>,V⟩`

Developed at the Centre of Quantum Technologies, National University of Singapore, by Piotr Migdał, Philippe Cochin et al. It is a part of the Quantum Game 2 project.

We base the philosophy of this package on:

- Sparse operations (both for vectors and matrices)
- Complex numbers
- Tensor structure
- Named tensor dimensions (vide Tensors considered harmful): there is a difference between a 2x2 operator on spin and polarization. It helps with catching errors.

Documentation: quantum-flytrap.github.io/quantum-tensors (generated by TypeDoc).

## Installation

The easiest way is to install from the NPM repository:

```
npm install quantum-tensors
```

Or, if you use yarn package manager,

```
yarn add quantum-tensors
```

If you want to install a development version, you can get this package directly from this GitHub repository. In this case, the commands are:

```
npm install Quantum-Flytrap/quantum-tensors#master
```

Or if you use yarn:

```
yarn add Quantum-Flytrap/quantum-tensors#master
```

## Usage

And then in your project write:

```
import * as qt from 'quantum-tensors'
```

There are a few examples in demos folder.

## Why

For "Quantum Game 2" we needed a fast and precise way to simulate quantum stuff, so after tinkering with mathjs and TensorFlow.js we decided to code what we need from scratch. At some point, we may want to use one of these libraries for backend, if we discover that it helps.

Also, https://github.com/stared/thinking-in-tensors-writing-in-pytorch by Piotr Migdał.

## Contributing

- Create TSDoc for each new function, class, and method
- Setup ESLint configured as in this
`.eslintrc.js`

- Try to adhere to Angular-like commit style

A few insights on contributing, and starting your projects, are in How I Learned to Stop Worrying and Love the Types & Tests: the Zen of Python for TypeScript by Piotr Migdał.

## Interesting ideas

- A better notation (e.g.
`⨂(op1, opt2, op3)`

) - An equation viewer