# Simulating quantum circuits parallel

**URL:** <https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293>\
**Category:** PennyLane Help\
**Created:** [August 9, 2023, 5:26am UTC](https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293 "2023-08-09T05:26:11Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![maar\_hybrid](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/maar_hybrid/32/1860_2.png) [@maar\_hybrid](https://discuss.pennylane.ai/u/maar_hybrid)\
**Post date:** [August 9, 2023, 5:26am UTC](https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293/1 "2023-08-09T05:26:11Z")

</div>

Hello i want to simulate quantum circuit simultaneously.  
I searched google and saw there are two kind of method, one is using qnode’s parameter broadcasting and one is use QNodeCollection.

When i tried to see QNodeCollection document, 404 error happens for website. How to use this? Is this discarded?

Also qnode does not seems to work. My test code was below

```auto
import pennylane as qml
import numpy as np

n_qubits=3
dev=qml.device("default.qubit",wires=n_qubits)
N_test=1000
def qc(theta0,theta1,theta2):
    qml.RX(theta0,wires=0)
    qml.RX(theta1,wires=1)
    qml.RX(theta2,wires=2)
    return qml.state()
qn=qml.QNode(qc,dev)
th=np.random.randn(3,N_test)
res=qn(th[0],th[1],th[2])

```

Then such error happens :

```auto
ValueError: all input arrays must have the same shape

```

Also when i printed device’s capabilities, there was no “supports\_broadcasting”

```auto
print(dev.capabilities())
>>>{'model': 'qubit', 
'supports_finite_shots': True,
'supports_tensor_observables': True,
'returns_probs': True,
'supports_reversible_diff': True,
'supports_inverse_operations': True,
'supports_analytic_computation': True,
'returns_state': True, 
'passthru_devices': {'tf': 'default.qubit.tf', 'torch': 'default.qubit.torch', 'autograd': 'default.qubit.autograd', 'jax': 'default.qubit.jax'}}

```

Here’s my pennylane information

```auto
Name: PennyLane
Version: 0.23.1
Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc.
Home-page: https://github.com/XanaduAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: c:\users\user\anaconda3\lib\site-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, retworkx, scipy, semantic-version, toml
Required-by: PennyLane-Lightning, PennyLane-qiskit, PennyLane-SF

Platform info: Windows-10-10.0.19041-SP0
Python version: 3.8.5
Numpy version: 1.20.2
Scipy version: 1.6.2
Installed devices:
- default.gaussian (PennyLane-0.23.1)
- default.mixed (PennyLane-0.23.1)
- default.qubit (PennyLane-0.23.1)
- default.qubit.autograd (PennyLane-0.23.1)
- default.qubit.jax (PennyLane-0.23.1)
- default.qubit.tf (PennyLane-0.23.1)
- default.qubit.torch (PennyLane-0.23.1)
- strawberryfields.fock (PennyLane-SF-0.20.1)
- strawberryfields.gaussian (PennyLane-SF-0.20.1)
- strawberryfields.gbs (PennyLane-SF-0.20.1)
- strawberryfields.remote (PennyLane-SF-0.20.1)
- strawberryfields.tf (PennyLane-SF-0.20.1)
- qiskit.aer (PennyLane-qiskit-0.24.0)
- qiskit.basicaer (PennyLane-qiskit-0.24.0)
- qiskit.ibmq (PennyLane-qiskit-0.24.0)
- qiskit.ibmq.circuit_runner (PennyLane-qiskit-0.24.0)
- qiskit.ibmq.sampler (PennyLane-qiskit-0.24.0)
- lightning.qubit (PennyLane-Lightning-0.23.0)

```

---

<div class="post-metadata">

**Author:** ![Ivana\_at\_Xanadu](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/ivana_at_xanadu/32/1852_2.png) [@Ivana\_at\_Xanadu](https://discuss.pennylane.ai/u/Ivana_at_Xanadu)\
**Post date:** [August 9, 2023, 9:32am UTC](https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293/2 "2023-08-09T09:32:18Z")

</div>

Hi @maar_hybrid , thanks for checking in! 🙂

You’re spot on, `QNodeCollection` was deprecated in [PennyLane v0.31](https://pennylane.ai/blog/2023/06/pennylane-release-0.31/#deprecations-and-breaking-changes-), just a month and a half ago. This might be a great time for you to upgrade to the latest version of PennyLane! 😃

In PennyLane v0.31 your device reports as `'supports_broadcasting'` and parameter broadcasting should work as expected. ☺

---

<div class="post-metadata">

**Author:** ![maar\_hybrid](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/maar_hybrid/32/1860_2.png) [@maar\_hybrid](https://discuss.pennylane.ai/u/maar_hybrid)\
**Post date:** [August 10, 2023, 5:30am UTC](https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293/3 "2023-08-10T05:30:45Z")

</div>

Thank you! It works well after update pennylane

---

<div class="post-metadata">

**Author:** ![Ivana\_at\_Xanadu](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/ivana_at_xanadu/32/1852_2.png) [@Ivana\_at\_Xanadu](https://discuss.pennylane.ai/u/Ivana_at_Xanadu)\
**Post date:** [August 10, 2023, 6:46am UTC](https://discuss.pennylane.ai/t/simulating-quantum-circuits-parallel/3293/4 "2023-08-10T06:46:48Z")

</div>

Awesome, really glad to hear that. Hope you enjoy playing with parameter broadcasting! 🙂