ABA decomposer
One of the most common single qubit decomposition techniques is the ZYZ decomposition.
This technique decomposes a quantum gate into an Rz, Ry and Rz gate in that order.
The decompositions are found in opensquirrel.passes.decomposer,
an example can be seen below where a H, Z, Y, and Rx gate are all decomposed on a single qubit circuit.
from opensquirrel.circuit_builder import CircuitBuilder
from opensquirrel.passes.decomposer import ZYZDecomposer
import math
builder = CircuitBuilder(qubit_register_size=1)
builder.H(0).Z(0).Y(0).Rx(0, math.pi / 3)
circuit = builder.to_circuit()
circuit.decompose(decomposer=ZYZDecomposer())
print(circuit)
version 3.0
qubit[1] q
Rz(3.1415927) q[0]
Ry(1.5707963) q[0]
Rz(3.1415927) q[0]
Ry(3.1415927) q[0]
Rz(1.5707963) q[0]
Ry(1.0471976) q[0]
Rz(-1.5707963) q[0]
Similarly, the decomposer can be used on individual gates.