Fortran interface

[m-meller]

Introduced CQ Fortran interface:

• new modules (under include/fortran) and implementation (under device/fortran and host/fortran)
• new examples
• new tests

[otbrown]

I have updated the call to the time evolution function to reflect the new API in QuEST. A boolean to determine whether the Pauli string should be permuted was added -- for now I've just set it to false, but we should explore the benefits of setting it to true. See QuEST#708.

[otbrown]

...test failure above is just a timing issue, probably not a 'real' failure

[otbrown]

Commenting here as a note to myself: it looks like the fortran qkern subroutine takes a classical reg which is fixed at size NQUBITS. This is probably not correct. We could try to pass it in as a c_ptr but the more "fortranic" way might be to make it an assumed shape integer(c_short) :: arr(:).

A problem for next week anyway!

[otbrown]

As we discussed on the train, cr should be of arbitrary length in the quantum kernel -- when I attempted this it segfaulted in the registration step (which was a bit odd...).

Hopefully you have more luck getting it working!

[otbrown]

Thanks Mateusz, LGTM! I should update CQ-spec soon-ish.