I was going to post the same. Robert Smith, a known lisper, is Director of Software Engineering at Rigetti.

Kind regards, Another Smug Lisp Weenie.

We're also big users of Julia.

Not just R&D, but it runs in production as well. Their downloadable SDK as well as some of the software backing their QMI’s are written in Lisp.

Which CL implementation do they use in production?

Scanning their GitHub repositories shows that they are written for SBCL.

[0] https://github.com/rigetti/rpcq

[1] https://github.com/rigetti/magicl