fix: add barrier adjoint

[sesmart]

Issue #, if available:

Closes #1259 by adding a counterpart.

Description of changes:

Testing done:

Merge Checklist

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Tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e4274ea) to head (514489b).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1260   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          169       169           
  Lines        10961     10963    +2     
  Branches      1412      1412           
=========================================
+ Hits         10961     10963    +2     

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