Following our earlier thread the initial release is live:
The two-layer architecture sketched in that discussion became the skeleton of what’s here; a thin ISO_C_BINDING FFI layer over the Qiskit C API with an idiomatic Fortran module on top. Verified on macOS arm64 with gfortran 11–15 and flang 22.1.4; Linux is untested but expected to work.
The point of the release is to put something real and functional and build from here together. With that in mind, we’ve tried to create entry points for everyone:
For researchers and domain enthusiasts, there’s an applications directory for self-contained Fortran programs built on the binding. Building and running any application is a single configured CLI instruction against two paths for ease of use.
A companion APPLICATIONS.md outlines domains we think are natural fits from an initial search, not domain expertise (edits to this markdown more than welcome).
If you work in any of these areas and see a demonstration worth building, the applications directory is exactly the right place for it, and the application issues have some starter ideas already scoped to the current API surface.
One constraint to note at the current stage: qiskit-fortran has no execution runtime. Circuit construction and transpilation are fully native to the binding. Running a circuit against hardware or a simulator requires wrapping runtime code with this binding, as raised here
For developer contributors, there are open issues across the binding layer: fpm migration, QkObs (SparseObservable) bindings, transpiler module, CI, Linux validation, an open PR exploring SWIG %fortranbindc for FFI auto-generation, etc. Architectural questions have been formulated as open issues, to invite discussion.
The design choices made so far are a starting point and are not settled. Thoughts on architecture, domain fit, or anything that looks wrong from a Fortran perspective are all welcome in the repo (as issues worth discussing/fixing).
Thanks especially to @hkvzjal, @gronki, @RonShepard, and @eelis ; the prior thread shaped a lot of what’s here.