Support commutation check between Pauli-based gates and standard gates (Qiskit#15488)

* Transpiler: implement exact Pauli generators for LightCone in Rust

This PR adds exact Pauli generator expansions for the following gates:
- single-qubit: H (X+Z)
- 2-qubit: CX, CY, CZ, ECR, Swap, iSwap, CSX, CS, CSdg
- parametric: CRX, CRY, CRZ, CPhase, RXX, RYY, RZZ, RZX, XXPlusYY, XXMinusYY
- 3-qubit: CCX, CSwap

This enables high-performance bitwise commutation checks in the LightCone
pass, avoiding slow matrix-multiplication fallbacks. Parametric gates are
scaled dynamically in Rust using the input parameters.

Co-authored-by: Shelly Garion <shelly.garion@ibm.com>
Co-authored-by: Alexander Ivrii <alexander.ivrii@ibm.com>

* Lint: apply cargo fmt and fix clippy::map_clone in split_2q_unitaries.rs

* Expose generator_observable to Python

Following feedback from Alexander Ivrii, this commit exposes the Rust
generator_observable function and the StandardGate enum to Python under
the qiskit._accelerate.standard_generators submodule.

This allows developers to verify the mathematical generators directly from
Python and reuse the logic for other purposes like PauliEvolutionGate
verification. The Rust-internal API is maintained via a dedicated
generator_observable function that accepts slices.

* Refactor generator logic to use qiskit_circuit::StandardGate

* Update generator_observable with expansions for CCX/CCZ/CSwap

* Fix generator fallback for unsupported gates and update docs

* Narrow PR scope: remove split_2q_unitaries and pyext python wrapper

* Add generator support for CS, CSdg, CSX, CCX, CCZ; add commutation tests

* style: run black on test_commutation_checker.py

* style: run rustfmt on standard_generators.rs

* lint: fix license headers and pylint warnings

* style: remove decorative unicode lines and add operator equivalence tests

* fix: ensure strict Operator equivalence for all supported generators

* style: fix pylint reimport and missing variables in test_commutation_checker.py

* Add generic generator equivalence test, fix matrix conversion, and optimize gate generators

* Format python tests

* Update copyright year in standard_generators.rs

* Clarify docstring for multi-qubit generators context

* Fix XXPlusYY and XXMinusYY generator validation and test cases

* Move test imports to top of file

* Use ddt data parameterization for gate generator testing tests

* Refactor test_clifford_gates_have_generators to use ddt

* Add CPhase, CRX, CRY, CRZ to generator tests

* Update test_all_gates_operator_equivalence_ddt docstring to be more accurate

* Move all inline imports to the top of the file

* Reorganize test data to group related gates logically

* Add tests for unsupported gates and parameters in generator logic

* Rename test helper to _commute to reflect that it uses either generator or matrix paths

* Clarify parameter handling in generator_observable docstring

* Comprehensive audit: Add Identity support and register all missing gates in SUPPORTED_OP

* Fix: Correct gate generator expansions and resolve UnsortedIndices layout panic

* pose generator engine, restore overflow logic, expand tests, and centralize constants

* Update crates/circuit/src/util.rs

Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com>

* Update releasenotes/notes/pauli-evolution-commutation-8f7caab8.yaml

Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com>

* Update releasenotes/notes/pauli-evolution-commutation-8f7caab8.yaml

Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com>

* added missing gate, added test, copyright year, doc explaining

* restore negative constants to util.rs for generator expansions

* fix lint errors in regression test and move imports to top

* Final PR fixes: address remaining lint issues and update copyright headers

* Remove accidental temporary files from PR

* Restore original copyright years for existing files (only PR-created files keep 2026)

* Permanently delete bicycle-architecture-compiler from branch

---------

Co-authored-by: Shelly Garion <shelly.garion@ibm.com>
Co-authored-by: Alexander Ivrii <alexander.ivrii@ibm.com>
Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com>

Author: 4 people

crates/circuit/src/util.rs

@@ -47,3 +47,12 @@ pub const C_ONE: Complex64 = c64(1., 0.);
 pub const C_M_ONE: Complex64 = c64(-1., 0.);
 pub const IM: Complex64 = c64(0., 1.);
 pub const M_IM: Complex64 = c64(0., -1.);
+
+use std::f64::consts::{FRAC_PI_2, FRAC_PI_4, FRAC_PI_8, SQRT_2};
+pub const C_FRAC_PI_2: Complex64 = c64(FRAC_PI_2, 0.0);
+pub const C_FRAC_PI_4: Complex64 = c64(FRAC_PI_4, 0.0);
+pub const C_FRAC_PI_8: Complex64 = c64(FRAC_PI_8, 0.0);
+pub const C_FRAC_PI_2_SQRT_2: Complex64 = c64(FRAC_PI_2 / SQRT_2, 0.0);
+pub const C_M_FRAC_PI_4: Complex64 = c64(-FRAC_PI_4, 0.0);
+pub const C_M_FRAC_PI_8: Complex64 = c64(-FRAC_PI_8, 0.0);
+pub const C_M_FRAC_PI_2_SQRT_2: Complex64 = c64(-FRAC_PI_2 / SQRT_2, 0.0);

crates/pyext/src/lib.rs

@@ -72,6 +72,7 @@ fn _accelerate(m: &Bound<PyModule>) -> PyResult<()> {
     add_submodule(m, ::qiskit_transpiler::passes::sabre::sabre, "sabre")?;
     add_submodule(m, ::qiskit_accelerate::sampled_exp_val::sampled_exp_val, "sampled_exp_val")?;
     add_submodule(m, ::qiskit_quantum_info::sparse_observable::sparse_observable, "sparse_observable")?;
+    add_submodule(m, ::qiskit_quantum_info::sparse_observable::standard_generators::standard_generators, "standard_generators")?;
     add_submodule(m, ::qiskit_quantum_info::sparse_pauli_op::sparse_pauli_op, "sparse_pauli_op")?;
     add_submodule(m, ::qiskit_transpiler::passes::scheduling_mod, "scheduling")?;
     add_submodule(m, ::qiskit_quantum_info::unitary_sim::unitary_sim, "unitary_sim")?;

crates/quantum_info/src/sparse_observable/mod.rs

@@ -10,6 +10,8 @@
 // copyright notice, and modified files need to carry a notice indicating
 // that they have been altered from the originals.
 
+pub mod standard_generators;
+
 mod lookup;
 
 use hashbrown::HashSet;
@@ -4484,8 +4486,19 @@ fn coerce_to_observable<'py>(
         }
     }
 }
+#[pyfunction(name = "_generator_observable")]
+#[pyo3(signature = (gate, params = None))]
+pub fn generator_observable_py(
+    gate: qiskit_circuit::operations::StandardGate,
+    params: Option<Vec<qiskit_circuit::operations::Param>>,
+) -> Option<SparseObservable> {
+    let params = params.unwrap_or_default();
+    standard_generators::generator_observable(gate, &params)
+}
+
 pub fn sparse_observable(m: &Bound<PyModule>) -> PyResult<()> {
     m.add_class::<PySparseObservable>()?;
+    m.add_function(wrap_pyfunction!(generator_observable_py, m)?)?;
     Ok(())
 }