Port core pyzx features

[ABorgna]

QuiZX is not intended to have all the features of PyZX, but certainly the core stuff. Here's where it's at:

• ZX-diagrams
  • [X] building ZX-diagrams and doing basic graph manipulations
  • [X] converting ZX-diagrams to Z + hadamard form
  • [X] switchable underlying graph model (fast vector-based model for sparse graphs, slower hash-based model for dense graphs)
• ZX-calculus rules
  • [X] spider fusion
  • [X] local complementation
  • [X] pivoting
  • [X] remove identity spiders
  • [X] colour-change
  • [X] pivoting variations (boundary-pivot and gadget-pivot)
• simplifiers
  • [X] clifford simplifier (from this paper)
  • [X] phase gadget simplifier (from this paper)
  • [X] simplification-based equality checker
• tensor evaluation based on ndarray
  • [X] exact scalars with cyclotomic rational numbers
  • [X] floating point scalars based on num_complex
  • [X] tensor contraction for arbitrary ZX-diagrams
  • [X] equality of tensors with exact scalars
  • [ ] approximate equality of tensors with floating point scalars
  • [ ] space optimisations
  • [ ] choose good contraction ordering (currently uses reverse-insertion-order)
  • [ ] more human-readable tensor output (e.g. converting to normal matrices, pretty printing)
• circuits
  • [X] circuit data type
  • [X] read and write QASM
  • [X] conversion from circuits to ZX-diagrams
  • [X] circuit extraction

[ABorgna]

This TODO list was extracted from the repo README

[akissinger]

Thanks for moving this here from the README. I think it makes more sense as an issue.

"simplification-based equality checker" is done now: 789cd97 thanks to @alexandru-duca !