Open CatalinaAlbornoz opened 4 days ago
The metric tensor converts to measuring probabilities, and adjoint is only compatible with measuring expectation values.
lightning does not support backprop at all, as expected.
As for the issue posted above, this is the same issue we encountered last release cycle in #5624. We added a lightning specific patch, but obviously this issue is still an issue and now causing problems with default.qubit
too.
Expected behavior
I expect the code below to work with both lightning.qubit and default.qubit for any differentiation method. However qml.metric_tensor is failing for the cases outlined in the table below.
Actual behavior
The table below shows Yes if the combination of diff_method and device works or No if it doesn't. The exact error that shows up depends on the combination of device and method.
Additional information
This was originally reported as part of this forum post.
This issue might be the cause for QNGO to fail in many of these cases.
Source code
Tracebacks
System information
Existing GitHub issues