Unable to access register_length attribute in FermionicOp class.

[kvvedavyasa]

Environment

• Qiskit Nature version:0.7.2
• Python version: 3.12
• Operating system: windows

What is happening?

In the below code, I am getting an error like TypeError: FermionicOp.init() got an unexpected keyword argument 'register_length'.

Why is not taking in register_length?What corrections should I make to the code?

How can we reproduce the issue?

''' N_sites = 5
hopping_terms = []

for ii in range (N_sites - 1):
hopping_terms.append(sum(FermionicOp(label,register_length = N_sites)
for label in ["+%i -%i" % (ii, ii+1),
"+%i -%i" % (ii+1, ii)])) '''

What should happen?

The code should create the fermionic operators for a given system of linear lattice with 5 sites. But, it is showing error in accepting the register_length keyword.

Any suggestions?

No response

[woodsp-ibm]

There was an earlier FermionicOp in qiskit_nature.operators that took a register length. These were all deprecated and removed - the version that now exists takes num_spin_orbitals https://qiskit-community.github.io/qiskit-nature/stubs/qiskit_nature.second_q.operators.FermionicOp.html You can see an instance created in this tutorial https://qiskit-community.github.io/qiskit-nature/tutorials/12_deuteron_binding_energy.html