Release Notes¶

spec/v3.1.0-57¶

The types bool and (scalar) bit are now explicitly described as being completely interchangeable in expression (r-value) positions, and that bit and bit[1] are distinct types. The difference between the types bool and bit is only in their intended storage mechanisms; bit is the scalar of the register-type bit[n], which is explicitly a bit-packed type, so cannot be used as the base type of an array, while bool is a byte-aligned single-bit integer-like type. bit[1] is a register (sequence) type that happens to be of length one.

Adds a recommendation that pragmas and annotations start with a namespaced identifier to avoid naming collisions between pragmas and annotations specified by different implementations. To support namespaced annotations, the annotations keyword may now include a dotted (‘.’) list of identifiers.

Added an explicit no-operation statement nop <qubits>;, which can be used to mark qubits as “used” by a scope (such as a box) without implying any operations on them. See Explicit no-operation for full details.

Removed the pow function from the built-in arithmetic functions list in the specification. The pow function could not be parsed by the reference grammar because it conflicted with the pow gate modifier. It was also not mentioned in the OpenQASM 3 paper. Use the ** operator instead.

It has been clarified that arrays and registers of size zero are allowed; however, integers and angles must have size greater than zero.

The qubit type is no longer a valid base type for an array, and it is no longer stated that the register type qubit[n] is equivalent to an array; there is no need for these semantics, and they clashed with the classical considerations and alignment concerns of arrays in general.

Some minor mathematical errors in the descriptions of the explicit gate actions in sdg, rx, ry, rz, crx and cry were corrected. The gates have not changed their intended meanings.