Add ContractIdleWiresInControlFlow to default pipelines
#13891
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This transpiler pass removes data dependencies on idle qubits from
control-flow operations. For example, given a circuit such as::
from qiskit.circuit import QuantumCircuit
qc = QuantumCircuit(1, 1)
qc.x(0)
with qc.if_test((qc.clbits[0], True)):
qc.x(0)
qc.x(0)
qc.x(0)
the current optimisation passes will collapse the inner control-flow
block to the identity, but the qubit dependency will remain, preventing
the outer two X gates from being cancelled. This pass removes the
now-spurious dependency, making it possible to detect and remove the two
X gates in a follow-up loop iteration.
As an accidental side-effect of their algorithms, the control-flow-aware
routing passes currently do this when they run. This aims to move the
logic into a suitable place to run before routing (so the spurious
dependency never arises in routing in the first place) and in the
low-level optimisation stage.
The aim of this pass is also to centralise the logic, so when the
addition of the new `box` scope with different semantics around whether
a wire is truly idle in the box or not, the routers aren't accidentally
breaking them, and it's clearer when the modifications happen.
This is cheap, and can be done both in the `init` stage (where it may help routing) and the the general optimisation loop (where it may allow chains of optimisations to collapse).
|
One or more of the following people are relevant to this code:
|
Pull Request Test Coverage Report for Build 13419423905Details
💛 - Coveralls |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Summary
This is cheap, and can be done both in the
initstage (where it may help routing) and the the general optimisation loop (where it may allow chains of optimisations to collapse).Details and comments
Built on top of #13779.