Add test for the add_dd_and_align_right in 2D GHZ state generation

[shashwatk1998]

Fix #7784

[shashwatk1998]

@NoureldinYosri

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.57%. Comparing base (4d75b4b) to head (d6fcdcf).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7793   +/-   ##
=======================================
  Coverage   99.57%   99.57%           
=======================================
  Files        1102     1102           
  Lines       98434    98449   +15     
=======================================
+ Hits        98014    98029   +15     
  Misses        420      420           

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[NoureldinYosri]

LGTM % @pavoljuhas 's review

[pavoljuhas]

Can you please rewrite this test without mocking?

For example, you could compare the circuits produced with and without the dynamical decoupling and check that the extra operations added by the dd have expected gate kinds.

[pavoljuhas]

Let us avoid mocking in the new test. Applying some rudimentary check for what is added by the DD would be fine.

On another page - can you please apply the patch below?
The code does the same, but I found it confusing as to how is the lambda and list comprehension expanded.

diff --git a/cirq-core/cirq/experiments/ghz_2d.py b/cirq-core/cirq/experiments/ghz_2d.py
index 48394af6..2d884c3f 100644
--- a/cirq-core/cirq/experiments/ghz_2d.py
+++ b/cirq-core/cirq/experiments/ghz_2d.py
@@ -52,3 +52,7 @@ def _transform_circuit(circuit: circuits.Circuit) -> circuits.Circuit:
     circuit = transformers.stratified_circuit(
-        circuit[::-1], categories=[lambda op: protocols.num_qubits(op) == k for k in (1, 2)]
+        circuit[::-1],
+        categories=[
+            lambda op: protocols.num_qubits(op) == 1,
+            lambda op: protocols.num_qubits(op) == 2,
+        ],
     )[::-1]