Only override control when global phase is zero #3113
Merged
Conversation
This file contains hidden or 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
smitsanghavi
previously requested changes
Jun 26, 2020
| Note that this only transforms into a CZPowGate (or controlled version | ||
| of that gate) if the global shift of the ZPowGate is 0, otherwise | ||
| it produces a normal ControlledGate. | ||
There was a problem hiding this comment.
Looks like the above two paragraphs can actually be combined more concisely into a single paragraph listing the preconditions for the specialization to occur.
There was a problem hiding this comment.
Combined for this and all other gates.
There was a problem hiding this comment.
I was suggesting more along the lines of:
This method will specialize the control only if:
1. global shift is 0
2. the last of the controls is a default-type control qubit (followed by the clarifying what that means)
It would make the prerequisites clearer to the reader. But it's a minor documentation nit and not worth blocking the PR.
smitsanghavi
approved these changes
Jul 1, 2020
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Outdated suggestions cannot be applied.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.
Fixes #3111
Presently the control override on XPowGate results in copying over the global phase shift of the XPowGate to the CXPowGate (similar for other control constuctions). This is inconsistent with most people's notion of "control" where the identity component has no phase.
This makes this override occur only when the global phase is zero.