Implement Graph State

[masa10-f]

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• Make sure you have tests for the new code and that test passes (run pytest)
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Description of the change:

Implement GraphState, which provides an interface to design graph state and measurement in MBQC.

Close #33

[Copilot]

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Comments suppressed due to low confidence (1)

tests/test_graphstate.py:44

• Consider using a more specific exception type (e.g., ValueError) when testing for duplicate nodes to maintain consistency with similar error cases in the file.

with pytest.raises(Exception, match="Node already exists"):

[masa10-f]

@nabe98 I have slightly modified the API from the mf branch, so please comment on this PR if any. I will implement visualizer and improve append method later.

[masa10-f]

memo: I'll add some examples of graph operation (graph edit and graph composition)

memo: I'll add this when the visualizer is implemented

[masa10-f]

memo: Local Cliffords can be removed from pattern layer if I properly design canonical form of graphstate.

[nabe98]

@masa10-f
There's one point I'm concerned about. Can you take a look and make any necessary adjustments?

[masa10-f]

I also replaced MappingProxyType with .copy() method.

[EarlMilktea]

Excellent!