[CQT-467] Add three-qubit gates CCX and CSWAP - #711
Merged
Merged
Conversation
SoufiTNO
changed the title
SoufiTNO
marked this pull request as ready for review
September 8, 2026 08:38
elenbaasc
reviewed
Sep 11, 2026
elenbaasc
left a comment
elenbaasc
left a comment
Collaborator
There was a problem hiding this comment.
Very nice work here, great implementation!
I have no comments on the changes made 🙂!
What is still missing though, is the additions to the User documentation, i.e., a page on the ThreeQubitGateDecomposer, adding the three qubit gates to the list of gates that the CircuitBuilder accepts, and it would be good to add the toffoli gate to (some of) the examples of the cQASM v1 exporter.
elenbaasc
approved these changes
Sep 14, 2026
elenbaasc
left a comment
elenbaasc
left a comment
Collaborator
There was a problem hiding this comment.
Looks good to me! Nice addition of the documentation (and also thanks for spotting the missing tow-qubit gates and mistakes in the docs of the cQASM v1 exporter).
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
I added ThreeQubitGate with CCX (alias CCNOT) and CSWAP, a ThreeQubitGateDecomposer into CZ and single-qubit gates, and cQASM v1 export of the Toffoli gate.
The CCX decomposition uses 6 CZ gates, which Shende and Markov (2008) prove is minimal. CSWAP uses 8, but that's an upper bound only: the Fredkin CNOT-cost is still open. Both preserve global phase exactly.