Addition call_graph inconsistent with decomposition for registers with unequal bitsizes

[kjm538]

The number of cnots in the call graph for the Add bloq doesn't account for when a_bitsize < b_bitsize. In the decomposition, there is a cnot yielded conditioned on a_bitsize=b_bitsize

Qualtran/qualtran/bloqs/arithmetic/addition.py

Lines 192 to 193 in 9b1bacf

	if len(input_bits) == len(output_bits):
	yield CNOT().on(input_bits[-1], output_bits[-1])

but the call graph always includes this gate in the count

Qualtran/qualtran/bloqs/arithmetic/addition.py

Line 204 in 9b1bacf

n_cnot = (n - 2) * 6 + 3

This results in different gate counts depending on what level of decomposition you count. For example

from qualtran.bloqs.arithmetic import Add
a_dtype = QUInt(2)
b_dtype = QUInt(3)
gate = Add(a_dtype=a_dtype,b_dtype=b_dtype)
gate.t_complexity() == gate.decompose_bloq().t_complexity()

returns False.

[kjm538]

These CNOTs also contribute to a mismatch in count when a_bitsize < b_bitsize

Qualtran/qualtran/bloqs/arithmetic/addition.py

Lines 171 to 172 in af8592b

	yield CNOT().on(anc[depth - 1], inp[depth])
	yield CNOT().on(inp[depth], out[depth])