Add Xor bloq
#1149
Add Xor bloq
#1149
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| for i in range(len(xs)): | ||
| xs[i], ys[i] = bb.add_t(CNOT(), ctrl=xs[i], target=ys[i]) | ||
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| return {'x': bb.join(xs), 'y': bb.join(ys)} | ||
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| def build_call_graph(self, ssa: 'SympySymbolAllocator') -> Set['BloqCountT']: | ||
| return {(CNOT(), self.dtype.num_qubits)} | ||
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You need to use a Toffoli() instead of a CNOT whenever self.control_val is not None. So this decomposition would be incorrect.
I think I take my suggestion back -- for a simple bloq like this, it's probably best to just let the Controlled() bloq handle the controlled version and it's cost instead of explicitly defining the controlled bloq. The advantages of having a custom controlled Bloq, as I see it, is mainly
a) More control over diagrams
b) Explicit control over decomposition and costings, though in this case that shouldn't matter.
@anurudhp Do you remember why you explicitly defined the controlled version for XorK in https://github.com/quantumlib/Qualtran/pull/1110/files?
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Falling back to Controlled().
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Actually not sure, I think I had it initially to match AddK, but forgot to remove it later.
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I think it's best to avoid specialized controls unless we want to explicitly specify the diagrams for Xor and XorK. I'll cleanup the XorK bloq.
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Add a bloq to copy a register in computational basis via CNOTs that can be used to simplify diagrams.