Gate has an invalid number of parameters

[sirgeorgesawcon]

The Error

I have a circuit made using qiskit, I'm converting it to tket using

from pytket.extensions.qiskit import qiskit_to_tk
c = qiskit_to_tk(qc)

but I'm getting the following error:

RuntimeError: Gate has an invalid number of parameters

How to Reproduce the Error?

The circuit is a bit complex, it requires some inbuilt Qiskit functionalities and ansatsz, here is the code:

import numpy as np
from qiskit import QuantumCircuit
from qiskit.circuit.library import RealAmplitudes
from qiskit_finance.circuit.library import NormalDistribution

qc = QuantumCircuit(15)
mu = 5
sigma = 2
# loading the demand distribution
demand = NormalDistribution(num_qubits=3,mu=mu,sigma=sigma,  bounds=[0,7])
params = [np.pi/2]*18   
supply1 = RealAmplitudes(3, reps=2)
supply2 = RealAmplitudes(3, reps=2)
    # taking the parameters from the list
list1 = params[:9]
list2 = params[9:]

    
supply1 = supply1.assign_parameters(list1)
supply2 = supply2.assign_parameters(list2)


qc.compose(demand,qubits=[8,9,10], inplace=True)
qc.compose(supply1, qubits = [0,1,2], inplace=True)
qc.compose(supply2, qubits = [3,4,5], inplace=True)
qc.draw('mpl')

Here is how the circuit looks like :

then using pytket

from pytket.extensions.qiskit import qiskit_to_tk
c = qiskit_to_tk(qc)

I'm getting the following error:

RuntimeError: Gate has an invalid number of parameters

[CalMacCQ]

Hi,

Thanks for making an issue for this. Here is a smaller snippet that reproduces the RuntimeError.

import numpy as np
from qiskit import QuantumCircuit
from qiskit.circuit.library import RealAmplitudes
from pytket.extensions.qiskit import qiskit_to_tk

qc = QuantumCircuit(3)

params = [np.pi/2]*9
supply1 = RealAmplitudes(3, reps=2)
   
supply1 = supply1.assign_parameters(params)
qc.compose(supply1, qubits = [0, 1, 2], inplace=True)

tkc = qiskit_to_tk(qc)

The qiskit_to_tk function appears to be trying to convert the RealAmplitudes instruction to a CustomGate and failing.

Relevant source line -> here

I'll look into this some more.

[CalMacCQ]

In the next release, the RealAmplitudes instruction should be handled as a CircBox

If there are any further problems please make a new issue or reopen this one.

Thanks again

[CalMacCQ]

As a temporary workaround you could decompose the quantum circuit with QuantumCircuit.decompose() before using qiskit_to_tk.