Exporter for Binary Quadratic Models

[dakk]

Thanks to the fact that qlasskit uses boolean expression as intermediate representation, we can easily write an exporter able to translate a qlassf to a binary quadratic model, exporting a QUBO or an Ising model.

This integration will enable qlasskit to be used on quantum annealers like the DWave, or similar types of machine (like the Fujitsu Digital Annealer).

We can use the pyqubo library for this process, as an optional dependency.