Generalize exp_pauli()

[poojarao8]

Required prerequisites

• [X] Search the issue tracker to check if your feature has already been mentioned or rejected in other issues.

Describe the feature

It will be great to have the exp_paul function take the spin_op as the input or the string form of it. I believe the issue with H.to_string() is that it dumps coefficients and exp_pauli takes pauli words only, but I haven't fully investigated it yet.

import cudaq
from cudaq import spin

kernel = cudaq.make_kernel()
qreg = kernel.qalloc(1)

H = spin.z(0)
    
kernel.exp_pauli(0.3, qreg, H)
#kernel.exp_pauli(0.3, qreg, H.to_string()) ###This would work great too.

cudaq.sample(kernel)

[amccaskey]

In C++, we have H.to_string(/*printCoeffs*/ false);. This just needs to be exposed in py_spin_operator.cpp, although just taking the spin_op as input (with an exception thrown if its more than one term) is cleaner / better.

[ikkoham]

import cudaq
from cudaq import spin

kernel = cudaq.make_kernel()
qreg = kernel.qalloc(1)

H = spin.z(0)
    
kernel.exp_pauli(0.3, qreg, H.to_string(False))

print(cudaq.sample(kernel))

works well. Is it enough? Do you need more enhencement?

[bettinaheim]

Closing due to no response and options provided.