Add method to get a Clifford gate and phase global phase from unitary #5568
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
viathor
approved these changes
Jun 22, 2022
| # decomposition. | ||
| self._state.apply_global_phase(u[k] / final_unitary[k]) | ||
| # Apply global phase. | ||
| self._state.apply_global_phase(global_phase) |
| cirq.SingleQubitCliffordGate.X_nsqrt, | ||
| cirq.SingleQubitCliffordGate.Y_nsqrt, | ||
| cirq.SingleQubitCliffordGate.Z_nsqrt, | ||
| ), |
There was a problem hiding this comment.
No action needed: It just occurred to me how weird this selection of test inputs is (it's all over this file, not just in this PR). Single-qubit Clifford group has five conjugacy classes:
- identity,
- three Paulis,
- six square roots of Paulis,
- six "Hadamards",
- eight order-3 elements like (I+iX+iY+iZ)/2.
We're testing on all elements from the first three and a single element from the "Hadamards" and none of the order-3 elements. I'll do something about this later.
There was a problem hiding this comment.
Yes, I thought this as well. We should really have a member cirq.SingleQubitCliffordGate.ALL which contains all 24 clifford gates. Then tests can be parametrized on that.
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Outdated suggestions cannot be applied.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 #2847
Various options were proposed in the linked issue to handle global phase in
SingleQubitCliffordGate, but I think the cleanest is the one proposed by @viathor in the description, namely to return a tuple (Clifford, phase) rather than trying to add global phase to the gates themselves. I've added a new helper methodfrom_unitary_with_global_phasewhich does this, and modified the stabilizer simulator to use this rather than doing its own global phase correction.