The IndexError key-not-found issue from updateCache in LQ

[maliasadi]

Using the C++ modules of LQ in Catalyst along with the Python interface may raise IndexError: unordered_map::at: key not found from updateCache in ./gates/KernelMap.hpp when multiple versions of LQ for accessing the Python and C++ modules are loaded.

The issue is related to the fact that Catalyst Runtime builds the C++ modules of LQ from source and Catalyst Frontend imports the Python interface shipped with the PyPI package. With the current setup, the LQ dynamic dispatcher will be triggered twice in the Catalyst pipeline,

1. with the PL device initialization: qml.device('lighnting.qubit', wires=n)
2. when the compiled program is linked against the LQ shared library

The cached kernels in the dynamic dispatcher is not well-scoped and thread-local and as such using multiple versions of LQ in one process (or from both Python and C++ in Catalyst) will lead to some error messages about missing kernels or operations.