# Custom parameterised gates on default device
**URL:** https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886
**Category:** PennyLane Help
**Created:** [February 25, 2021, 5:48pm UTC](https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886 "2021-02-25T17:48:45Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@DanielPolatajko](https://discuss.pennylane.ai/u/DanielPolatajko)
#### Post date: [February 25, 2021, 5:48pm UTC](https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886/1 "2021-02-25T17:48:45Z")
Is there a good way to declare a custom unitary gate (ideally from a matrix representation) with learnable parameters? I tried to subclass pennylane.operations.Operation in a similar fashion to pennylane.ops.qubit.QubitUnitary, but couldn’t get past the following error “DeviceError: Gate MyCustomGate not supported on device default.qubit.autograd”. I couldn’t see how but perhaps it is possible to use QubitUnitary directly to create a trainable gate? Any help much appreciated!
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### Author:  [@Tom\_Bromley](https://discuss.pennylane.ai/u/Tom_Bromley)
#### Post date: [February 25, 2021, 7:08pm UTC](https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886/2 "2021-02-25T19:08:29Z")
Hi @DanielPolatajko!
Check out [ArbitraryUnitary](https://pennylane.readthedocs.io/en/stable/code/api/pennylane.templates.subroutines.ArbitraryUnitary.html), which provides a parametrization of an arbitrary `n` qubit unitary into `4 ** n - 1` real parameters.
Thanks!
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### Author:  [@DanielPolatajko](https://discuss.pennylane.ai/u/DanielPolatajko)
#### Post date: [February 26, 2021, 12:39pm UTC](https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886/3 "2021-02-26T12:39:07Z")
Sweet, thanks very much!
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### Author:  [@Tom\_Bromley](https://discuss.pennylane.ai/u/Tom_Bromley)
#### Post date: [February 26, 2021, 8:16pm UTC](https://discuss.pennylane.ai/t/custom-parameterised-gates-on-default-device/886/4 "2021-02-26T20:16:13Z")
No problem @DanielPolatajko! Let us know if you have any further questions.