Clifford+T Simulator Qasm Simulator method

[chriseclectic]

What is the expected enhancement?

Adding a simulation method for the QasmSimulator based on the techinques in Bravyi & Gosset (2016) for simulating Clifford + T circuits with low T gate depth.

Note This issue is to track the work already underway by @padraic-padraic

[atilag]

For the record: @padraic-padraic has already started a PR to address this issue.

[chriseclectic]

@atilag I can't seem to assign @padriac-padriac to the issue, his username doesn't show up

[atilag]

Yeah, Github limitation, we can only add Qiskit organization members, that's why I put a comment instead.