PyQASM 1.0.4

Release 1.0.4 (July 15, 2026)

Summary

Added

• Added support for the c3x (3-controlled X) and rc3x/rcccx (relative-phase 3-controlled X) gates, decomposed into basis gates following qiskit's C3XGate/RC3XGate definitions. Also extended the ctrl @ modifier chain so that 3- and 4-control stacks on x (e.g. ctrl @ ctrl @ ctrl @ x, ctrl(4) @ x) resolve to c3x/c4x. (#320)

Improved / Modified

• Consolidated the hardcoded "__PYQASM_QUBITS__" string literals scattered across visitor.py, transformer.py and pulse/utils.py into a single INTERNAL_QUBIT_REGISTER constant in elements.py, alongside an is_internal_qubit_register() helper that is now the one place the internal register is recognised. (#325)

Fixed

• Fixed reset on a physical qubit rewriting the operand to the internal pulse register, e.g. reset $2; unrolled to reset __PYQASM_QUBITS__[2];. That names a register the program never declares, so the unrolled output did not round-trip through dumps()/loads(), and the qubit was never registered (a program whose only operation was reset $3; reported num_qubits == 0). Physical qubits are now kept as-is in plain QASM programs, matching how gate and measurement operands already treat them; the rename is still applied for OpenPulse programs, where the pulse visitor expects it. (#325)
• Fixed measure and reset on a user register whose name merely starts with the reserved internal register name (e.g. __PYQASM_QUBITS__foo) being mistaken for the internal register itself. Such statements were short-circuited out of unrolling and emitted verbatim, so c = measure __PYQASM_QUBITS__foo; was never expanded per qubit and reset __PYQASM_QUBITS__foo; silently reset nothing. The register is now matched on its exact name, or on the name followed by an index or slice. (#325)
• Fixed the c4x (4-controlled X) gate, which previously raised TypeError: c4x_gate() takes 4 positional arguments but 5 were given because it was declared with four parameters for a five-qubit gate. It is now implemented via qiskit's structured rc3x/c3sx/cphaseshift decomposition. (#320)
• Added inv @ (inverse modifier) support for the multi-controlled-X family: inv @ c3x / inv @ c4x resolve to the (self-inverse) gate, and inv @ rc3x / inv @ rcccx resolve to the correct relative-phase dagger. These previously raised Unsupported / undeclared QASM operation. (#320)
• Fixed the ctrl @ modifier not resolving gate aliases: ctrl @ toffoli / ctrl @ ccnot (aliases of ccx) and ctrl @ cnot / ctrl @ CX (aliases of cx) now escalate controls identically to their canonical gate instead of raising Unsupported controlled QASM operation. (#320)
• Fixed the backend-dependent dt duration unit being incorrectly relabeled as ns when unrolling delay and box statements without a device_cycle_time. Since dt cannot be converted to SI units without a sample rate, it is now preserved as dt. (#317)

Dependencies

• Migrated the Linux wheel build container from manylinux2014 to manylinux_2_28. NumPy stopped publishing manylinux2014 (glibc 2.17) wheels for CPython 3.12+, so pip fell back to building NumPy from source inside the build container, whose GCC is older than NumPy requires — failing every Linux wheel job for cp312/cp313/cp314. The published wheels are unaffected: auditwheel tags them from the extension's actual symbol requirements, so they remain manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64 and still install on glibc 2.17 systems.

Full Changelog: v1.0.3...v1.0.4