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
  • building ZX-diagrams and doing basic graph manipulations
  • converting ZX-diagrams to Z + hadamard form
  • switchable underlying graph model (fast vector-based model for sparse graphs, slower hash-based model for dense graphs)
• ZX-calculus rules
  • spider fusion
  • local complementation
  • pivoting
  • remove identity spiders
  • colour-change
  • pivoting variations (boundary-pivot and gadget-pivot)
• simplifiers
  • clifford simplifier (from this paper)
  • phase gadget simplifier (from this paper)
  • simplification-based equality checker
• tensor evaluation based on ndarray
  • exact scalars with cyclotomic
    rational numbers
  • floating point scalars based on num_complex
  • tensor contraction for arbitrary ZX-diagrams
  • 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
  • circuit data type
  • read and write QASM
  • conversion from circuits to ZX-diagrams
  • 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 !