Permutation Bloq #1110
Permutation Bloq #1110
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| if self.val == 0: | ||
| x = bb.add(XGate(), q=x) | ||
| x, target = bb.add(CNOT(), ctrl=x, target=target) | ||
| if self.val == 0: | ||
| x = bb.add(XGate(), q=x) |
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can you add a note that this is just a negative-control CNOT so that in the future, if and when we add a cv attribute to CNOT we can replace it
| bloq_counts[CNOT()] += 1 | ||
| return set(bloq_counts.items()) | ||
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| return super().build_call_graph(ssa) |
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nit: I generally prefer inverting this so the method isn't as indented
if not self.is_symbolic():
return super().build_call_graph
op = ...
return bloq_countsThat being said --- my original design for the call graph protocol was always to provide the counts you'd expect to find in e.g. a paper, which would use the is_symbolic path even for concrete numbers. Then you can reconcile them in e.g. the unit test by using the generalizer argument and built-in generalizer functions. Maybe I'll open an issue because I know this sort of thing has come up in other places
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Inverted the method.
use `x` instead of `q` invert code in `build_call_graph` add note for neg-ctrl CNOT
| bit_flip_bloq = MultiControlX(cvs=self.cvs) if len(self.cvs) > 0 else XGate() | ||
| num_flips = self.bitsize if self.is_symbolic() else sum(self.dtype.to_bits(self.k)) | ||
| return {(bit_flip_bloq, num_flips)} |
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We shouldn't do n MCX gates to do n bit flips when number of controls > 1
Instead, divide it into 3 cases:
- Num controls == 0 : Simply do an XGate()
- Num controls == 1 : Simply do CNOT() gates
- Num controls > 1 : Use a temporary ancilla and do a
MultiAnd(cvs=self.cvs)with the temporary ancilla as the target. Then reduce to Case(2) with the temporary ancilla as control.
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In fact, I'd suggest we only support Case (1) and (2) and reducing Case (3) to Case (1) is a general strategy used for all multi controlled bloq so we can add a separate Bloq that does this reduction (maybe at a later point)
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I simplified this to only support a single control_val, as #1131 will handle the CtrlSpec -> QBit part.
| dtype: QDType | ||
| k: SymbolicInt |
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If k is a SymbolicInt should we restrict dtype to be QUInt / QInt ? Looking at the implementation below, it seems like this would also work for other types when k is not necessarily an integer.
| @cached_property | ||
| def bitsize(self): | ||
| return bit_length(self.N - 1) |
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Will there ever be a case when the user wants to specify the bitsize instead of the default log2(N) ? We can make it an attribute and use this as a default value if the user doesn't specify anything; if you think that's relevant.
| Decomposes a permutation into cycles and applies them in order. | ||
| See :meth:`from_dense_permutation` to construct this bloq from a permutation. |
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Ditto: Please add a latex equation describing the action of the unitary on an input state.
| and for every $x \not\in C$. | ||
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LGTM! |
Implements a simple circuit that permutes basis states in
O(N logN), andO(d logN)for a d-prefix (used to prepare d-sparse states).