[Bug] Horqrux GPSR for 2nd order derivatives

[dominikandreasseitz]

cc @atiyo

[rajaiitp]

Random question/thought. In GPSR we compute the coefficients that scale the eigenvalue spectrum differences using a set of random shifts. It seems like these are the same coefficients used for higher order derivatives, with higher powers of shifts. Does it mean that we get all the higher order derivatives for free once we compute these coefficients. Am I missing out something

[atiyo]

This should come relatively easily with the correct jacobinan-vector product implementation, which I think is already in qadence. We can bring it over.

Random question/thought. In GPSR we compute the coefficients that scale the eigenvalue spectrum differences using a set of random shifts. It seems like these are the same coefficients used for higher order derivatives, with higher powers of shifts. Does it mean that we get all the higher order derivatives for free once we compute these coefficients. Am I missing out something

We should chat about this! Probably internally so we can back and forth about it a bit easier.

[Roland-djee]

Hiya @atiyo would you be able to take that on ? (Also tagging @gvelikova)

[atiyo]

Happy to take this on. Not sure what the bug is, though 🤷.

The plan is to take the GPSR implementation out of qadence and put it directly in horqrux---qadence doesn't feel like the right place to implement horqrux functionality. AFAICT, moving it horqrux will also be seamless from the perspective of an end user since it hooks directly into jax's AD either way.

Are we happy to close this issue and raise a corresponding one in horqrux?

[Roland-djee]

Happy to take this on. Not sure what the bug is, though 🤷.

The plan is to take the GPSR implementation out of qadence and put it directly in horqrux---qadence doesn't feel like the right place to implement horqrux functionality. AFAICT, moving it horqrux will also be seamless from the perspective of an end user since it hooks directly into jax's AD either way.

Are we happy to close this issue and raise a corresponding one in horqrux?

Indeed. I don't think this is a bug rather than a feature (but aren't they the same ? 😬 ) and agreed it can move to Horqrux board. Thanks @atiyo.

[atiyo]

Nice. In that case I'm closing this issue since it's covered by this one: pasqal-io/horqrux#22