Issue while transpiling CCZ for the IQM20 backend

[geexie]

I constructed circuit with controlled Z in it and run with.

$ python ccz-transpile.py &> error.txt

Transpiler fails with an error

  File "/Users/geexie/code/chip/.venv/lib/python3.12/site-packages/qibo/transpiler/decompositions.py", line 31, in _check_instance
    decomposition = self.decompositions[gate.__class__]
                    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
KeyError: <class 'qibo.gates.gates.Z'>

full log

This is a minimal reproducer for an issue.

import matplotlib.pyplot as plt
from qibo import Circuit, gates
from qibo.ui import plot_circuit
from qibo.transpiler import (
    NativeGates,
    Passes,
    Unroller
)

sat_solver = Circuit(5)
sat_solver.add(gates.Z(4).controlled_by(*(2, 3)))
# sat_solver.add(gates.X(4).controlled_by(*(2, 3)))

plot_circuit(sat_solver)
plt.title("Original Circuit")
plt.savefig("ccz_orig.png")

glist = [gates.GPI2, gates.RZ, gates.Z, gates.CZ]
natives = NativeGates(0).from_gatelist(glist)

custom_passes = [Unroller(native_gates=natives)]
custom_pipeline = Passes(custom_passes)
transpiled_circuit, _ = custom_pipeline(sat_solver)
plot_circuit(transpiled_circuit)
plt.title("Transpiled Circuit")
plt.savefig("ccz_simple.png")

I used both simple transpiler and transpiler which employs connectivity. I tried to debug it's the case that transformation pass for CCZ is not registered in the dictionary but I don't know why since it's present in the code

for custom pipeline what I have:

dec <class 'qibo.gates.gates.CNOT'>
dec <class 'qibo.gates.gates.CZ'>
dec <class 'qibo.gates.gates.SWAP'>
dec <class 'qibo.gates.gates.iSWAP'>
dec <class 'qibo.gates.gates.CRX'>
dec <class 'qibo.gates.gates.CRY'>
dec <class 'qibo.gates.gates.CRZ'>
dec <class 'qibo.gates.gates.CU1'>
dec <class 'qibo.gates.gates.CU2'>
dec <class 'qibo.gates.gates.CU3'>
dec <class 'qibo.gates.gates.FSWAP'>
dec <class 'qibo.gates.gates.RXX'>
dec <class 'qibo.gates.gates.RYY'>
dec <class 'qibo.gates.gates.RZZ'>
dec <class 'qibo.gates.gates.TOFFOLI'>
dec <class 'qibo.gates.gates.Unitary'>
dec <class 'qibo.gates.gates.fSim'>
dec <class 'qibo.gates.gates.GeneralizedfSim'>

what I search in decompositions

<class 'qibo.gates.gates.CCZ'>

Please help me to make it work? I'm quite new in qibo🙏🏻

[renatomello]

@geexie Could you provide a minimal code block that reproduces your issue? Also this may be better as a Issue than a Discussion here on Github.

[geexie]

@renatomello I attached the code reproducer as a txt. Just rename it to py. It seems GitHub don't also attaching something executable.

[renatomello]

In any case, I pushed a solution to the branch in the PR #1670. The Toffoli decomposition, even though present in the transpiler, was not activated in the decompose method of the gates.TOFFOLI class.

In [5]: from qibo import Circuit, gates
   ...: 
   ...: circuit = Circuit(3)
   ...: circuit.add(gates.CCZ(0, 1, 2))
   ...: circuit.draw()
   ...: print()
   ...: 
   ...: circuit = circuit.decompose()
   ...: circuit.draw()
   ...: print()
   ...: 
   ...: circuit = circuit.decompose()
   ...: circuit.draw()
   ...: print()
   ...: 
   ...: #equivalent to
   ...: circuit = Circuit(3)
   ...: circuit.add(gates.CCZ(0, 1, 2).decompose())
   ...: circuit = circuit.decompose()
   ...: circuit.draw()
0: ─o─
1: ─o─
2: ─Z─

0: ───o───
1: ───o───
2: ─H─X─H─

0: ───────────o─────────o─o─T─────o───
1: ─────o─────|───o─T───|─X─TDG───X───
2: ─H─H─X─TDG─X─T─X─TDG─X───T───H───H─

0: ───────────o─────────o─o─T─────o───
1: ─────o─────|───o─T───|─X─TDG───X───
2: ─H─H─X─TDG─X─T─X─TDG─X───T───H───H─

[geexie]

@renatomello, thanks for the quick fix! Your example works if I apply the patch locally, however I'm still getting the same error if I use the transpiler instead of decompose method. Did I miss something?

import matplotlib.pyplot as plt
from qibo import Circuit, gates
from qibo.ui import plot_circuit
from qibo.transpiler import (
    NativeGates,
    Passes,
    Unroller
)

circuit = Circuit(3)
circuit.add(gates.CCZ(0, 1, 2))
circuit.draw()
print()

glist = [gates.GPI2, gates.RZ, gates.Z, gates.CZ]
natives = NativeGates(0).from_gatelist(glist)

custom_passes = [Unroller(native_gates=natives)]
custom_pipeline = Passes(custom_passes)
transpiled_circuit, _ = custom_pipeline(circuit)
plot_circuit(transpiled_circuit)
plt.title("Transpiled Circuit")
plt.savefig("ccz_simple.png")

[renatomello]

Now I added what was missing to make it work with the transpiler. Your code snippet is working for me locally. Can you confirm it is also working for you when you install qibo from that branch?

[geexie]

@renatomello, yeah, it works! Thank you🙏🏻

[renatomello]

OK. Then, I'm closing the discussion and we wait for the PR to be reviewed and merged. Thanks for finding this bug.