Implement `SparseObservable.evolve` by aaryav-3 · Pull Request #15561 · Qiskit/qiskit

Aaryav (aaryav-3) · 2026-01-13T13:09:50Z

Summary

Fixes #13763
This PR adds support for efficient evolution of SparseObservable objects under conjugation by single-term operators via a new :meth:SparseObservable.evolve API.
The implementation introduces an efficient, deterministic conjugation based on a precomputed lookup table for single-qubit BitTerm conjugation. Support for partial and non-contiguous evolution through optional qargs has been added, and so has the edge-case to handle scalar (0-qubit) operators. (Identity)
Further work could be done to support evolution via Cliffords, and Pauli Lists (as these cannot be coerced to a :class:SparseObservable by default), and also support cross-term conjugations (for BitTerm Operators with num_terms > 1, i.e. a sum of terms) can be added in a later PR

I have added the tests to cover my changes.
I have updated the documentation accordingly.
I have read the CONTRIBUTING document.

AI tool used: Claude Sonnet 4.5 (on Browser) for Lookup table generator script, and automated testing of the same.

…parseobservable

qiskit-bot · 2026-01-13T13:09:55Z

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Coveralls (coveralls) · 2026-01-13T13:46:02Z

Pull Request Test Coverage Report for Build 21390225658

Details

135 of 148 (91.22%) changed or added relevant lines in 3 files are covered.
5 unchanged lines in 2 files lost coverage.
Overall coverage increased (+0.02%) to 87.991%

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/cext/src/exit_codes.rs	0	1	0.0%
crates/quantum_info/src/sparse_observable/mod.rs	120	132	90.91%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	93.82%
crates/qasm2/src/lex.rs	4	91.77%

Totals
Change from base Build 21389396184:	0.02%
Covered Lines:	100177
Relevant Lines:	113849

💛 - Coveralls

Julien Gacon (Cryoris)

Thanks for the modifications! I didn't have a look at how the evolve logic is implemented yet, but here's already comments on the interface and some tests.

Co-authored-by: Julien Gacon <gaconju@gmail.com>

… enhance tests. Also update evolve logic

…/qiskit into evolve_sparseobservable

…, and also enhance comments

…tity pauli to make more physical sense

Co-authored-by: Julien Gacon <gaconju@gmail.com>

…ke exception testing more explicit

…/qiskit into evolve_sparseobservable

…parseobservable

Gadi Aleksandrowicz (gadial)

I created a script to generate the table independently and compared it to the one in the PR - all seems good to me. I approve.

- docs were failing - remove some test dups and dangling comments - more efficient qargs duplicate check

Julien Gacon (Cryoris)

Thanks for the contribution Aaryav (@aaryav-3) and thanks for the review Gadi Aleksandrowicz (@gadial) 🙂 There's some minor improvements we can do on the error handling here but nothing to hold the feature off on.

Aaryav Mishra (aaryav3) added 3 commits January 13, 2026 11:06

add basic evolve API

7ffb8e7

finalize evolve logic, add qargs support and make robust test cases

0a193aa

Merge branch 'main' of https://github.com/Qiskit/qiskit into evolve_s…

be89b52

…parseobservable

Aaryav (aaryav-3) requested a review from a team as a code owner January 13, 2026 13:09

qiskit-bot added the Community PR PRs from contributors that are not 'members' of the Qiskit repo label Jan 13, 2026

Aaryav (aaryav-3) changed the title ~~Evolve sparseobservable~~ Evolve SparseObservable Jan 13, 2026

Luciano Bello (1ucian0) added this to Contributor Monitoring Jan 13, 2026

Julien Gacon (Cryoris) reviewed Jan 13, 2026

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Comment thread crates/quantum_info/src/sparse_observable/lookup.rs Resolved

Julien Gacon (Cryoris) reviewed Jan 13, 2026

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Comment thread crates/quantum_info/src/sparse_observable/lookup.rs Resolved

Aaryav Mishra (aaryav3) added 2 commits January 15, 2026 03:33

resolve logic and comments

a4228bf

Merge branch 'main' into evolve_sparseobservable

fd9801f

Julien Gacon (Cryoris) reviewed Jan 16, 2026

View reviewed changes

Aaryav Mishra (aaryav3) and others added 8 commits January 19, 2026 13:50

Update test/python/quantum_info/test_sparse_observable.py

0c91419

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Update crates/quantum_info/src/sparse_observable/mod.rs

78c2f32

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Merge branch 'main' into evolve_sparseobservable

575dd3a

resolve comments, update docstrings, and remove redundant tests, plus…

855d30d

… enhance tests. Also update evolve logic

Merge branch 'evolve_sparseobservable' of https://github.com/aaryav-3…

f74fe9f

…/qiskit into evolve_sparseobservable

use as_inner method instead of rewriting the full inner read statemet…

04e4119

…, and also enhance comments

rename test correctly, and change identity test to evolve via an Iden…

418bd16

…tity pauli to make more physical sense

re-add the failing test case as a sanity check

172d878

Julien Gacon (Cryoris) added Changelog: Added Add an "Added" entry in the GitHub Release changelog. mod: quantum info Related to the Quantum Info module (States & Operators) and removed Community PR PRs from contributors that are not 'members' of the Qiskit repo labels Jan 20, 2026

Julien Gacon (Cryoris) reviewed Jan 20, 2026

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Comment thread crates/quantum_info/src/sparse_observable/mod.rs Resolved

Julien Gacon (Cryoris) reviewed Jan 20, 2026

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Comment thread crates/quantum_info/src/sparse_observable/mod.rs Resolved

Aaryav Mishra (aaryav3) and others added 3 commits January 20, 2026 17:20

add support and test cases curated to just paulis

ed663bc

Update crates/quantum_info/src/sparse_observable/mod.rs

696e13e

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Update crates/quantum_info/src/sparse_observable/mod.rs

24959ed

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Julien Gacon (Cryoris) reviewed Mar 12, 2026

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Comment thread test/python/quantum_info/test_sparse_observable.py Resolved

Julien Gacon (Cryoris) reviewed Mar 12, 2026

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Comment thread test/python/quantum_info/test_sparse_observable.py Resolved

Julien Gacon (Cryoris) reviewed Mar 12, 2026

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Comment thread test/python/quantum_info/test_sparse_observable.py Resolved

Aaryav Mishra (aaryav3) and others added 6 commits March 12, 2026 21:49

Update crates/quantum_info/src/sparse_observable/mod.rs

1adb7cf

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Update test/python/quantum_info/test_sparse_observable.py

62c12f7

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Update test/python/quantum_info/test_sparse_observable.py

ec50ff4

Co-authored-by: Julien Gacon <gaconju@gmail.com>

resolve comments; add more exception types, assign exit codes, and ma…

5c036cf

…ke exception testing more explicit

Merge branch 'evolve_sparseobservable' of https://github.com/aaryav-3…

d1ed7f6

…/qiskit into evolve_sparseobservable

Merge branch 'main' of https://github.com/Qiskit/qiskit into evolve_s…

612464b

…parseobservable

Gadi Aleksandrowicz (gadial) previously approved these changes Mar 18, 2026

View reviewed changes

Julien Gacon (Cryoris) changed the title ~~Evolve SparseObservable~~ Implement SparseObservable.evolve Mar 18, 2026

Small fixes

e0bfa63

- docs were failing - remove some test dups and dangling comments - more efficient qargs duplicate check

Julien Gacon (Cryoris) dismissed Gadi Aleksandrowicz (gadial)’s stale review via e0bfa63 March 18, 2026 16:17

Don't multiply Pauli by 2j

6bb14b4

Julien Gacon (Cryoris) previously approved these changes Mar 18, 2026

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Julien Gacon (Cryoris) added this pull request to the merge queue Mar 18, 2026

Alexander Ivrii (alexanderivrii) reviewed Mar 18, 2026

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Comment thread test/python/quantum_info/test_sparse_observable.py Resolved

Alexander Ivrii (alexanderivrii) removed this pull request from the merge queue due to a manual request Mar 18, 2026

Fix typo in comment

9d9d4e4

Julien Gacon (Cryoris) dismissed their stale review via 9d9d4e4 March 18, 2026 20:25

Julien Gacon (Cryoris) approved these changes Mar 18, 2026

View reviewed changes

Alexander Ivrii (alexanderivrii) enabled auto-merge March 18, 2026 20:26

Alexander Ivrii (alexanderivrii) added this to the 2.4.0 milestone Mar 18, 2026

github-project-automation Bot moved this to Ready in Qiskit 2.4 Mar 18, 2026

github-project-automation Bot added this to Qiskit 2.4 Mar 18, 2026

Alexander Ivrii (alexanderivrii) added this pull request to the merge queue Mar 18, 2026

Merged via the queue into Qiskit:main with commit ff2ee35 Mar 18, 2026
25 checks passed

github-project-automation Bot moved this from Ready to Done in Qiskit 2.4 Mar 18, 2026

github-project-automation Bot moved this to Done in Contributor Monitoring Mar 18, 2026

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Aaryav (aaryav-3) commented Jan 13, 2026 •

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