The tracer should not work on the presence of measurements.

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Describe the bug

When tracing the circuit, the execution manager gathers the quantum operations without executing them, i.e., the process does not do any sort of simulation. This behavior work well for all operations that do not return need to return values; however it gives misleading/wrong results in the case of measurements.

The current behavior is to always return 0 as the result of measurement:
https://github.com/NVIDIA/cuda-quantum/blob/99b58fda0007540fab23e6f80021ddba2d235fa3/runtime/cudaq/qis/managers/BasicExecutionManager.h#L251-L253

Steps to reproduce the bug

Using any functionality that relies on the tracer, e.g., cudaq::estimate_resources, might return misleading/wrong results if the target kernels relies on measurements---specifically those that further process those measurements results, e.g., using them on conditions.

Expected behavior

When running the tracer, an error (or at least a warning) should be emitted if the kernel contain measurements.

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

Not a regression

Environment

• CUDA Quantum version: main branch

Suggestions

No response

Start with runtime/cudaq/qis/managers/BasicExecutionManager.h at the cited measurement handling around lines 251-253, then trace how cudaq::estimate_resources uses the execution manager. Reproduce the behavior with a kernel whose measurement result controls a condition. Done means tracing emits an error or warning instead of silently returning 0 for measurements.