Are Givens rotations (i.e excitations) the only way to do quantum chemistry VQE?

Hello everyone!

I’m currently simulating a molecule on PennyLane and to perform VQE I’ve been following the scheme described in the tutorial here : A brief overview of VQE — PennyLane.
I was wondering whether if using Givens rotation was the only way to do VQE with PennyLane.

Thank you!!

Hi @Mohamed_SO,

Givens rotations are useful for helping you make sure that you’re conserving the particles in your system. Another function you can use, which takes into account single and double excitations in a different way, is qml.UCCSD. In the usage details in the documentation you will see an example of how to use this ansatz.

Was there any particular reason why you preferred not to use Givens rotations? And is using UCCSD better for your use case?

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Thank you for your response!

OK I’m taking note of what you’ve said.
I asked because I’m doing a VQE project using PennyLane and I wanted to know whether using Givens rotation was the only accessible way of doing it.

It’s cool that you’re doing a VQE project @Mohamed_SO!

And it’s great that you’re trying out different alternatives :raised_hands:

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