chore: add Apache 2.0 license, CLA, and SPDX header tooling

.github/workflows/cla.yml

@@ -0,0 +1,30 @@
+name: CLA Assistant
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_target:
+    types: [opened, closed, synchronize]
+
+permissions:
+  actions: write
+  contents: write
+  pull-requests: write
+  statuses: write
+
+jobs:
+  CLAAssistant:
+    runs-on: ubuntu-latest
+    steps:
+      - name: CLA Assistant
+        if: (github.event.comment.body == 'recheck' || github.event.comment.body == 'I have read the CLA Document and I hereby sign the CLA') || github.event_name == 'pull_request_target'
+        uses: contributor-assistant/github-action@v2.6.1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          path-to-signatures: '.github/cla-signatures.json'
+          path-to-document: 'https://github.com/QuEraComputing/ppvm/blob/main/CLA.md'
+          branch: 'main'
+          allowlist: dependabot[bot],renovate[bot],pre-commit-ci[bot]
+          custom-pr-sign-comment: 'I have read the CLA Document and I hereby sign the CLA'
+          custom-allsigned-prcomment: 'All contributors have signed the CLA ✔'

.github/workflows/license-headers.yml

@@ -0,0 +1,16 @@
+name: License headers
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  check:
+    name: hawkeye check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check SPDX headers
+        uses: korandoru/hawkeye@v6

CLA.md

@@ -0,0 +1,128 @@
+# ppvm Individual Contributor License Agreement
+
+Thank you for your interest in contributing to **ppvm** (the "Project"),
+maintained by QuEra Computing Inc. ("We" or "Us"). This Contributor License
+Agreement ("Agreement") documents the rights granted by contributors to Us.
+It is adapted from the Apache Software Foundation Individual Contributor
+License Agreement v2.2 and complements the Project's Apache License,
+Version 2.0 (see `LICENSE`).
+
+To make this Agreement effective, please indicate your acceptance by signing
+your commits as described in the "How to accept this Agreement" section
+below, or by signing electronically when prompted on a pull request.
+
+You accept and agree to the following terms and conditions for Your present
+and future Contributions submitted to Us. Except for the license granted
+herein to Us and recipients of software distributed by Us, You reserve all
+right, title, and interest in and to Your Contributions.
+
+## 1. Definitions
+
+**"You"** (or **"Your"**) shall mean the copyright owner or legal entity
+authorized by the copyright owner that is making this Agreement with Us. For
+legal entities, the entity making a Contribution and all other entities that
+control, are controlled by, or are under common control with that entity are
+considered to be a single Contributor. For the purposes of this definition,
+"control" means (i) the power, direct or indirect, to cause the direction or
+management of such entity, whether by contract or otherwise, or (ii)
+ownership of fifty percent (50%) or more of the outstanding shares, or (iii)
+beneficial ownership of such entity.
+
+**"Contribution"** shall mean any original work of authorship, including any
+modifications or additions to an existing work, that is intentionally
+submitted by You to Us for inclusion in, or documentation of, the Project.
+For the purposes of this definition, "submitted" means any form of
+electronic, verbal, or written communication sent to Us or our
+representatives, including but not limited to communication on electronic
+mailing lists, source code control systems, and issue tracking systems that
+are managed by, or on behalf of, Us for the purpose of discussing and
+improving the Project, but excluding communication that is conspicuously
+marked or otherwise designated in writing by You as "Not a Contribution."
+
+## 2. Grant of Copyright License
+
+Subject to the terms and conditions of this Agreement, You hereby grant to
+Us and to recipients of software distributed by Us a perpetual, worldwide,
+non-exclusive, no-charge, royalty-free, irrevocable copyright license to
+reproduce, prepare derivative works of, publicly display, publicly perform,
+sublicense, and distribute Your Contributions and such derivative works.
+
+You agree that Your Contributions may be licensed to third parties under
+the Apache License, Version 2.0 under which the Project is distributed, and
+You agree that We may also license Your Contributions under any other
+OSI-approved open source license that the Project may adopt in the future,
+provided that such relicensing does not retroactively impair the rights You
+retain in Your Contributions outside the Project.
+
+## 3. Grant of Patent License
+
+Subject to the terms and conditions of this Agreement, You hereby grant to
+Us and to recipients of software distributed by Us a perpetual, worldwide,
+non-exclusive, no-charge, royalty-free, irrevocable (except as stated in
+this section) patent license to make, have made, use, offer to sell, sell,
+import, and otherwise transfer the Project, where such license applies only
+to those patent claims licensable by You that are necessarily infringed by
+Your Contribution(s) alone or by combination of Your Contribution(s) with
+the Project to which such Contribution(s) was submitted. If any entity
+institutes patent litigation against You or any other entity (including a
+cross-claim or counterclaim in a lawsuit) alleging that Your Contribution,
+or the Project to which You have contributed, constitutes direct or
+contributory patent infringement, then any patent licenses granted to that
+entity under this Agreement for that Contribution or the Project shall
+terminate as of the date such litigation is filed.
+
+## 4. Representations
+
+You represent that:
+
+1. You are legally entitled to grant the above licenses. If your employer(s)
+   has rights to intellectual property that You create that includes Your
+   Contributions, You represent that You have received permission to make
+   Contributions on behalf of that employer, that Your employer has waived
+   such rights for Your Contributions to Us, or that Your employer has
+   executed a separate Corporate CLA with Us.
+
+2. Each of Your Contributions is Your original creation (see Section 7 for
+   submissions on behalf of others).
+
+3. Your Contribution submissions include complete details of any third-party
+   license or other restriction (including, but not limited to, related
+   patents and trademarks) of which You are personally aware and which are
+   associated with any part of Your Contributions.
+
+## 5. Support
+
+You are not expected to provide support for Your Contributions, except to
+the extent You desire to provide support. You may provide support for free,
+for a fee, or not at all. Unless required by applicable law or agreed to in
+writing, You provide Your Contributions on an "AS IS" BASIS, WITHOUT
+WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including,
+without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT,
+MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE.
+
+## 6. Notification of Changes
+
+You agree to notify Us of any facts or circumstances of which You become
+aware that would make these representations inaccurate in any respect.
+
+## 7. Submissions on behalf of others
+
+Should You wish to submit work that is not Your original creation, You may
+submit it to Us separately from any Contribution, identifying the complete
+details of its source and of any license or other restriction (including,
+but not limited to, related patents, trademarks, and license agreements) of
+which You are personally aware, and conspicuously marking the work as
+"Submitted on behalf of a third-party: [named here]".
+
+## How to accept this Agreement
+
+By submitting a pull request to this repository, You indicate Your
+acceptance of this Agreement for all Contributions in that pull request and
+for all future Contributions You submit to the Project. For non-trivial
+contributions, We may additionally request that You sign this Agreement
+electronically via [CLA Assistant](https://cla-assistant.io/) or an
+equivalent tool linked from the pull request.
+
+Contributors who are submitting on behalf of an employer should arrange for
+a Corporate CLA to be executed separately; contact the maintainers if one
+is required for your contribution.

LICENSE

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for describing the origin of the Work and
+      reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright 2026 QuEra Computing Inc.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

NOTICE

@@ -0,0 +1,5 @@
+ppvm - Pauli Propagation and Virtual Machine
+Copyright 2026 QuEra Computing Inc.
+
+This product includes software developed at
+QuEra Computing Inc. (https://www.quera.com/).