Release/v0.6.0

[PabloAndresCQ]

Changelog

• New feature: Tree Tensor Network (TTN) simulator, supporting both fixed chi and truncation_fidelity. Calculation of single amplitudes is supported by get_amplitude and inner products by vdot. Measurement and postselection are not yet supported.

• New API: both MPS and TTN share a common interface: StructuredState. Import paths have changed, multiple classes have been renamed: ConfigMPS is now Config, ContractionAlg is now SimulationAlgorithm. Documentation has been updated accordingly.

• Canonicalisation of MPS is now always applied before a two-qubit gate. We found that this tends to reduce runtime due to canonicalisation decreasing virtual bond dimension.

• Two-qubit gates are now decomposed (SVD) before applying them to remove null singular values (e.g. in XXPhase gates).

• Fixed a bug on copying an MPS if truncation_fidelity was set.

• Fixed a bug on CuTensorNetHandle that would prevent it from working when the device set was different from the default one (dev=0) and when using cuTensorNet>=2.3.0.

• Fixed a bug on TensorNetwork due to unsupported Create operation.

• Updated pytket version requirement to 1.26.

Checklist

• [x] I have run the tests on a device with GPUs.
• [x] I have performed a self-review of my code.
• [ ] I have commented hard-to-understand parts of my code.
• [x] I have made corresponding changes to the public API documentation.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [x] I have updated the changelog with any user-facing changes.

[cqc-melf]

Do you want to do the release now, or should we wait for the pytket release next week?

[PabloAndresCQ]

I'd rather make a release now, then we can go back to releasing with each new pytket version. The reason why I wanted to stagger this release was that there were some PRs on TTN already merged in develop that didn't really make sense to release until others were merged.

[PabloAndresCQ]

In particular, the reason why I'd like to get 0.6.0 out with pytket 1.26 is that I've been writing some docs for reproducibility of the paper with HSBC and I've been assuming these versions. It wouldn't be too much work to update them, but since the deadline is next Tuesday I'd rather just get it through, then get a new 0.6.1 release whenever pytket 1.27 is released.