Add an IR for quantum circuits

[ChenZhao44]

No description provided.

[codecov]

Codecov Report

Merging #53 into master will increase coverage by 1.41%.
The diff coverage is 93.03%.

@@            Coverage Diff             @@
##           master      #53      +/-   ##
==========================================
+ Coverage   90.65%   92.06%   +1.41%     
==========================================
  Files          13       14       +1     
  Lines        1337     1488     +151     
==========================================
+ Hits         1212     1370     +158     
+ Misses        125      118       -7     

Impacted Files	Coverage Δ
src/ZXCalculus.jl	100.00% <ø> (ø)
src/qcircuit.jl	92.51% <92.51%> (ø)
src/circuit_extraction.jl	86.62% <100.00%> (+10.34%)	⬆️
src/simplify.jl	100.00% <100.00%> (ø)
src/zx_diagram.jl	97.18% <100.00%> (+0.03%)	⬆️
src/zx_graph.jl	84.35% <100.00%> (+0.08%)	⬆️
src/rules.jl	96.17% <0.00%> (+0.40%)	⬆️

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[ChenZhao44]

The current implementation of the global phase doesn't support symbolic variables. And it will also make the ZXDiagram mutable.

[Roger-luo]

I think I'll merge this first. But there are still a few things we should think about. It's very likely that we prefer to move gate decomposition to YaoLang at some point, given it's not about ZXCalculus and we would want to support more gates. On the other hand, I think a primitive gate set that is allowed in ZX Calculus needs to be defined at some point, so we limit the functionality of this IR.