Add ZXGraphState class #102
Description
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The ZX-calculus is a notation that allows quantum circuits to be described diagrammatically using wires and spiders (that is, edges and nodes). After converting a measurement pattern into an equivalent ZX-diagram together with a gflow, one can apply transformations based on the ZX-calculus rules to produce a simpler measurement pattern while preserving both the semantics and the existence of the gflow.
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Implement ZXGraphState class for the ZX-calculus.
Additional context
M. Backens et al., There and Back Again: A Circuit Extraction Tale, Quantum 5, 421 (2021)