Angles

Guppy has a dedicated angle type. It allows exact representation of angles for gates in the Clifford hierarchy, which can be useful for optimization.

An angle represents a rotation by a number of half-turns, where a half-turn is equivalent to \(\pi\) radians. For example, angle(1/2) is equivalent to \(\pi/2\). The built-in constant pi equals angle(1), so it is useful for converting between angles and radians, as performing arithmetic on it also results in an angle.

from guppylang import guppy
from guppylang.std.angles import angle, pi
from guppylang.std.quantum import qubit, rz

@guppy
def rotate_twice(q: qubit, r: float) -> None:
    # Both angle constructions and therefore rotations are equivalent.
    a = pi * r
    rz(q, a)
    a = angle(r)
    rz(q, a)

rotate_twice.check()

Note that the angle values do not wrap or identify with themselves modulo any number of complete turns, so for example, angle(2) does not equal angle(0).