QAMP - Expose IQP circuit generator via C bindings

[Ameya28Bhave]

Title: Expose IQP circuit generator via C bindings

Summary

This PR exposes the IQP circuit generator from qiskit-circuit-library through the C API and adds C tests for the new entry points.

Changes

• crates/circuit_library/src/iqp.rs

  • Make the internal helper

    pub fn iqp(interactions: ArrayView2<'_, i64>) -> impl Iterator<...>
    

    public so it can be reused by other crates without duplicating the instruction construction logic.

• crates/cext/src/circuit_library/iqp.rs

  • Add

    QkCircuit *qk_circuit_library_iqp_(uint32_t num_qubits, const int64_t *interactions);
    

    • Interprets interactions as an n × n row-major int64_t matrix.
    • Checks for NULL pointer, num_qubits > 0, and enforces symmetry on the upper triangle.
    • Wraps the buffer in an ArrayView2 and builds CircuitData using the shared iqp helper.
    • Returns NULL for invalid input (null pointer, zero qubits, or non-symmetric matrix).
  • Add

    QkCircuit *qk_circuit_library_random_iqp_(uint32_t num_qubits, int64_t seed);
    

    • Wraps py_random_iqp(num_qubits, Option<u64>) to generate a random IQP circuit.
    • Uses a negative seed to indicate “draw from OS entropy”, mirroring existing C bindings.

• test/c/test_iqp.c

  • Add C-level tests for the new bindings:
    • Build an IQP circuit from a small symmetric interaction matrix and check:
      • total instruction count,
      • that all gates are 1- or 2-qubit,
      • that exactly one 2-qubit gate appears for the chosen matrix.
    • Verify that a non-symmetric interaction matrix causes qk_circuit_library_iqp_ to return NULL.
    • Generate a random IQP circuit and assert it is non-empty and contains only 1- and 2-qubit gates.

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[coveralls]

Pull Request Test Coverage Report for Build 20303461709

Details

• 30 of 36 (83.33%) changed or added relevant lines in 2 files are covered.
• 8 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.005%) to 88.302%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/cext/src/circuit_library/iqp.rs	28	34	82.35%
<!--	Total:	30	36

Files with Coverage Reduction	New Missed Lines	%
crates/circuit/src/parameter/parameter_expression.rs	1	82.3%
crates/qasm2/src/lex.rs	1	93.57%
crates/qasm2/src/parse.rs	6	97.56%
<!--	Total:	8

Totals
Change from base Build 20225348384:	0.005%
Covered Lines:	96666
Relevant Lines:	109472

---

💛 - Coveralls

[Cryoris]

Thanks for opening the PR, Ameya! Just FYI, you don't need to add a detailed changelog like that usually. It's nice to summarize the PR if it is a complicated change, but here it would've been fine without (or much shorter) 🙂

[Cryoris]

Great, thanks for the updates! This now only needs a release note and we're good to go 🙂