QROM uses unnecessary gates if non work wires provided

[KetpuntoG]

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---

Context:

Fix this bug [https://github.com//issues/6968]
[sc-84591]
Description of the Change:

Check if work wires are used and choose the correct decomposition based on that.

Benefits:

More efficient decomposition

Possible Drawbacks:

Related GitHub Issues:

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (ed30bf4) to head (0e40702).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6967   +/-   ##
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  Coverage   99.59%   99.59%           
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  Files         481      481           
  Lines       45783    45784    +1     
=======================================
+ Hits        45598    45599    +1     
  Misses        185      185           

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[Jaybsoni]

Just some small comments

[Jaybsoni]

Would swap_ops be empty in this case?

[Jaybsoni]

Haha, I see what you are doing here, but I would say this is a "lazy"-test. Since it's only one test case, I would say compute the expected decomposition by hand, and then test that the compute decomposition matches it.

Something like:

Suggested change

	def test_none_work_wires_case():
	"""Test that clean version is not applied if work wires are not used"""
	gates = qml.QROM.compute_decomposition(["1", "0", "0", "1"], [0, 1], [2], [], clean=True)
	for gate in gates:
	assert gate.name != "Hadamard"
	def test_none_work_wires_case():
	"""Test that clean version is not applied if work wires are not used"""
	gates_clean = qml.QROM.compute_decomposition(["1", "0", "0", "1"], [0, 1], [2], [], clean=True)
	expected_gates = qml.QROM.compute_decomposition(["1", "0", "0", "1"], [0, 1], [2], [], clean=False)
	assert gates_clean == expected_gates