From 3642d67eb8d926a16504b6950e6b8b68aed77777 Mon Sep 17 00:00:00 2001 From: Luciano Bello Date: Mon, 8 Jul 2024 16:54:43 +0200 Subject: [PATCH] Explain QPY support in install#release-schedule (#1563) Qiskit contract with respect of QPY is kind of strong and deserves an explanation. Adding it to https://docs.quantum.ibm.com/start/install#release-schedule --- docs/guides/install-qiskit.mdx | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/docs/guides/install-qiskit.mdx b/docs/guides/install-qiskit.mdx index 5839c65e04c..0d02e9a5af7 100644 --- a/docs/guides/install-qiskit.mdx +++ b/docs/guides/install-qiskit.mdx @@ -327,6 +327,12 @@ ensures that you see any deprecation warnings before a major version release. Without the cap, `pip` installs the newest version available by default. + +The QPY serialization format is backwards-compatible so that a new Qiskit release can always load a QPY +file generated with an earlier release of Qiskit. However, the format isn't forward-compatible so, in principle, it's not possible +to load QPY files generated with a newer version of Qiskit using an older release. To facilitate user migration across major version releases, the (`qiskit.qpy.dump()`](/api/qiskit/qpy#dump) function will always support at least one overlapping version between the `X.0.0` and the `X-1.Y.0` release (where `Y` is the last minor version of +that series). The parameter `qiskit.qpy.dump(..., version=...)` will enable saving QPY format files that can be loaded by both major versions from the newer +release. See more details in [RFC 0020](https://github.com/Qiskit/RFCs/blob/master/0020-release_cycle.md#qpy-support).