# qf-diamond-norm v1.0.0: QuantumFlow Diamond Norm

Gavin E. Crooks (2020)

Calculation of the diamond norm between two completely positive trace-preserving (CPTP) superoperators, using the QuantumFlow package

The calculation uses the simplified semidefinite program of Watrous arXiv:0901.4709 [J. Watrous, Theory of Computing 5, 11, pp. 217-238 (2009)]

Kudos: Based on MatLab code written by Marcus P. da Silva

## Installation

Note: Diamond norm requires that the “cvxpy” package (and dependencies) be fully installed. Installing cvxpy via pip does not correctly install all the necessary packages.

```
$ conda install -c conda-forge cvxpy
$ git clone https://github.com/gecrooks/qf_diamond_norm.git
$ cd qf_diamond_norm
$ pip install -e .
```

## Example

```
> import quantumflow as qf
> from qf_diamond_norm import diamond_norm
> chan0 = qf.random_channel([0, 1, 2]) # 3-qubit channel
> chan1 = qf.random_channel([0, 1, 2])
> dn = diamond_norm(chan0, chan1)
> print(dn)
```