Problem with qml.load()

PennyLane Help Code Together
1

Hello! I am facing the following error while using the qml.load(), below is an example code that I have used form here
https://discuss.pennylane.ai/t/how-to-train-a-circuit-imported-from-qiskit/1832/2

# Put code here
import pennylane as qml
from pennylane import numpy as np
from qiskit.circuit import QuantumCircuit, Parameter

qc = QuantumCircuit(2)
theta = Parameter('θ')

state = [1/2,1/2,1/2,1/2]

qc.initialize(state, qc.qubits)
qc.rx(theta, [0])
qc.cx(0, 1)

my_circuit = qml.load(qc, format='qiskit')

#dev = qml.device('default.qubit', wires=2)
dev = qml.device(
        "qiskit.aer",
        wires=2,
        shots=1000,
        noise_model=noise_model,
        backend="aer_simulator_statevector",
        seed_simulator=1,
        seed_transpiler=1,
    )

@qml.qnode(dev)
def circuit(x):
    my_circuit(params={theta: x},wires=(1, 0))
    return qml.expval(qml.PauliZ(0))

theta_train = np.array(0.4, requires_grad=True)

opt = qml.GradientDescentOptimizer()

for i in range(100):
    theta_train = opt.step(circuit, theta_train)
    if i % 10 == 0:
        print('Cost', circuit(theta_train))

This is the error that I am getting. Please help me.

# Put full error message here
Traceback (most recent call last):
  Cell In[2], line 14
    my_circuit = qml.load(qc, format='qiskit')
  File /opt/conda/lib/python3.10/site-packages/pennylane/io.py:74 in load
    raise ValueError(
ValueError: Converter does not exist. Make sure the required plugin is installed and supports conversion.

Use %tb to get the full traceback.

And, finally, make sure to include the versions of your packages. Specifically, show us the output of qml.about().

Name: PennyLane
Version: 0.34.0
Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc.
Home-page: https://github.com/PennyLaneAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: /opt/conda/lib/python3.10/site-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml, typing-extensions
Required-by: PennyLane-Lightning

Platform info:           Linux-5.4.0-156-generic-x86_64-with-glibc2.35
Python version:          3.10.8
Numpy version:           1.23.5
Scipy version:           1.9.3
Installed devices:
- default.gaussian (PennyLane-0.34.0)
- default.mixed (PennyLane-0.34.0)
- default.qubit (PennyLane-0.34.0)
- default.qubit.autograd (PennyLane-0.34.0)
- default.qubit.jax (PennyLane-0.34.0)
- default.qubit.legacy (PennyLane-0.34.0)
- default.qubit.tf (PennyLane-0.34.0)
- default.qubit.torch (PennyLane-0.34.0)
- default.qutrit (PennyLane-0.34.0)
- null.qubit (PennyLane-0.34.0)
- lightning.qubit (PennyLane-Lightning-0.34.0)
2

Hey @Priyansh, welcome to the forum!

I think the function you want to use is qml.from_qiskit: qml.from_qiskit — PennyLane 0.34.0 documentation. It’s made specifically for what you’re trying to do! Let me know if that helps :slight_smile:

3

Thank you very much @isaacdevlugt for the reply, but I am again getting the error

Code

qc = QuantumCircuit(2)
theta = Parameter('θ')

state = [1/2,1/2,1/2,1/2]

qc.initialize(state, qc.qubits)
qc.rx(theta, [0])
qc.cx(0, 1)

my_circuit = qml.from_qiskit(qc)

Error

Traceback (most recent call last):
  Cell In[8], line 10
    my_circuit = qml.from_qiskit(qc)
  File /opt/conda/lib/python3.10/site-packages/pennylane/io.py:107 in from_qiskit
    return load(quantum_circuit, format="qiskit")
  File /opt/conda/lib/python3.10/site-packages/pennylane/io.py:74 in load
    raise ValueError(
ValueError: Converter does not exist. Make sure the required plugin is installed and supports conversion.

Use %tb to get the full traceback.
4

Hi @Priyansh!

It looks like you need the pennylane-qiskit plugin. You can install this with:

pip install pennylane-qiskit

Let us know if you are still seeing an error after installing the above.

2 Likes