Bug in cudaq.exp_pauli for quantum devices (Python)

[bmhowe23]

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Describe the bug

This is similar to #2222

There are still some exp_pauli use cases in Python that do not lower to quantum hardware correctly.

Steps to reproduce the bug

Use the python/tests/kernel/test_kernel_exp_pauli.py file in the repo ... add the following statements to the bottom of it.

cudaq.set_target('quantinuum', emulate=True)
# This works
test_exp_pauli()
print('test_exp_pauli works')
# This fails
test_exp_pauli_param()
print('never gets here')

When run like the following, it produces this error:

$ python3 python/tests/kernel/test_kernel_exp_pauli.py
test_exp_pauli works
error: 'quake.exp_pauli' op cannot determine pauli word string
error: failed to legalize operation 'quake.exp_pauli'
RuntimeError: Remote rest platform Quake lowering failed.

Expected behavior

Lowering to quantum hardware should work just like the simulation use case.

Is this a regression? If it is, put the last known working version (or commit) here.

Not a regression

Environment

• CUDA-Q version: latest (22ffd96 as of the time of this writing)
• Python version: 3.10
• C++ compiler: N/A
• Operating system:

Suggestions

No response

[schweitzpgi]

Does #2664 fix this?

[bmhowe23]

Does #2664 fix this?

No.

[annagrin]

@schweitzpgi I have fix in one of my branches, hopefully this helps (after

cuda-quantum/lib/Optimizer/Transforms/DecompositionPatterns.cpp

Line 398 in 6a19c28

}

):

This is trying to read what old argument synthesis produces for a pauli word argument:

} else if (auto global = dyn_cast<cudaq::cc::GlobalOp>(symbol)) {
      auto attr = global.getValue();
      auto elementsAttr = cast<mlir::ElementsAttr>(attr.value());
      auto eleTy = elementsAttr.getElementType();
      auto values = elementsAttr.getValues<mlir::Attribute>();

      std::vector<char> result{};
      for (auto it = values.begin(); it != values.end(); ++it) {
        assert(isa<IntegerType>(eleTy));
        char v = static_cast<char>(cast<IntegerAttr>(*it).getInt());
        result.push_back(v);
      }
      pauliWordString = std::string(result.begin(), result.end());
      optPauliWordStr = pauliWordString;
    }```