Removal of _index and _registers from Bit

[sbrandhsn]

Summary

Addresses and builds on top of #11407

Details and comments

With the removal of _index and _registers from Bit, Bits become opaque and can only be distinguished by their id. This breaks several test cases, requires a new de/serialization and a caching of ControlledGate.definition. These issues are addressed in this PR, leaving a potential refactoring of Layout for the future (see #11604).

[coveralls]

Pull Request Test Coverage Report for Build 7700646687

• -9 of 70 (87.14%) changed or added relevant lines in 8 files are covered.
• 25 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.03%) to 89.518%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/qpy/binary_io/circuits.py	11	15	73.33%
qiskit/passmanager/qiskit_dill.py	34	39	87.18%

Files with Coverage Reduction	New Missed Lines	%
qiskit/qpy/binary_io/circuits.py	3	91.82%
crates/qasm2/src/lex.rs	4	91.94%
crates/qasm2/src/parse.rs	18	96.69%

Totals
Change from base Build 7700276174:	-0.03%
Covered Lines:	59527
Relevant Lines:	66497

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💛 - Coveralls

[qiskit-bot]

One or more of the the following people are requested to review this:

• @enavarro51
• @Qiskit/terra-core
• @mtreinish
• @nkanazawa1989

[1ucian0]

@mtreinish The effects of this PR in QPY.. are breaking the QPY specification? If so, we could delay this to 2.0 or to increase the QPY version.

[mtreinish]

There shouldn't be an issue for qpy here. The one place this will come up is probably in how we query the index and register in the serialization side. But if we're doing that we should be able to move to circuit.find_bit(). Qpy needs to be able to reason about the indices for bits and whether they're members of any registers. On the deserialization side there shouldn't be any changes needed because we shouldn't ever be setting these attributes manually.

[raynelfss]

I'll be taking over these efforts from now on since this PR would be helpful for #13269.

[1ucian0]

Possible close this one as pointless now, since performance looks much better nowadays.

[raynelfss]

Due to recent discussions and a change of perspective, we have decided to no longer pursue this approach. The PR is now closed! 🔨

[sbrandhsn]

[sad] Sebastian Brandhofer reacted to your message:

…

________________________________ From: Raynel Sanchez ***@***.***> Sent: Thursday, February 13, 2025 5:58:33 PM To: Qiskit/qiskit ***@***.***> Cc: Sebastian Brandhofer ***@***.***>; Author ***@***.***> Subject: [EXTERNAL] Re: [Qiskit/qiskit] Removal of `_index` and `_registers` from `Bit` (PR #11596) Due to recent discussions and a change of perspective, we have decided to no longer pursue this approach. The PR is now closed! 🔨 — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored Due to recent discussions and a change of perspective, we have decided to no longer pursue this approach. The PR is now closed! 🔨 — Reply to this email directly, view it on GitHub<#11596 (comment) >, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BDMWA4FIYCEYW3G4NCTQNAD2PTMMTAVCNFSM6AAAAABCBC5DHOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNJXGM2TEMRSHE >. You are receiving this because you authored the thread.Message ID: ***@***.***> [raynelfss]raynelfss left a comment (Qiskit/qiskit#11596)<#11596 (comment) > Due to recent discussions and a change of perspective, we have decided to no longer pursue this approach. The PR is now closed! 🔨 — Reply to this email directly, view it on GitHub<#11596 (comment) >, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BDMWA4FIYCEYW3G4NCTQNAD2PTMMTAVCNFSM6AAAAABCBC5DHOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNJXGM2TEMRSHE >. You are receiving this because you authored the thread.Message ID: ***@***.***>