André

Improve mappers, add ModeBasedMapper

4

### Summary Adds a new class `ModeBasedMapper` which implements the basic functionality of the mode based mappers (JW, BK, parity, direct mapper) through a Pauli table. Reverts `pauli_table` to instance...

Add Ternary Tree Mapper

1

### Summary Adds a new mapper class `TernaryTreeMapper` to implement the Ternary Tree based mapping algorithm (cf. [arXiv:1910.10746](https://arxiv.org/abs/1910.10746)). Fixes #582 Depends on the two previous pull requests #1270 and #1301...

Add MajoranaOp class

7

### Summary Adds a new class `.second_q.operators.MajoranaOp` implementing a Majorana fermion operator, along with a `M̀ajoranaOp.from_fermionic_op` constructor method to convert a `FermionicOp` into a `MajoranaOp`. Fixes #1257 `M̀ajoranaOp` is implemented...

Inconsistent handling of class attributes in docs and missing attribute descriptions

1

I noticed that class attributes are not documented very well, take e.g. [`FermionicOp`](https://qiskit.org/ecosystem/nature/stubs/qiskit_nature.second_q.operators.FermionicOp.html#qiskit_nature.second_q.operators.FermionicOp): - `num_spin_orbitals` is listed in the class docstring under an `Attributes:` header. In the html docs this...

### What should we add? Implement a standalone MajoranaOp (incl. a MajoranaOp.from_fermionic_op constructor). As discussed in #582 the MajoranaOp could be the basis for the implementation of Majorana mappers such...

What is the point of the register_length() method?

1

### (More a feature removal request, actually) Both `second_q.hamiltonians.hamiltonian.Hamiltonian` and `second_q.operators.SparseLabelOp` (and accordingly all their children) require a `.register_length()` method. However, this method does not seem to be used anywhere...