  We present a study on preparing and manipulating path-like temporal-mode (TM)
qubits based on third-order nonlinear interactions. Specifically, we consider
the process of frequency conversion via difference frequency generation. To
prepare a qubit, we aim to use Gaussian input states to a nonlinear waveguide.
The coupling between the input state and a specific TM is maximized, obtaining
qubits prepared with fidelities close to one. TMs evolve linearly within the
medium; therefore, it is possible to define rotations around any axis contained
in the $xy$ plane, allowing spanning the full Bloch sphere in two steps.
Particularly, we present a method to obtain any of the Pauli quantum gates by
varying geometric or user-accessible parameters in a given experimental
configuration. Our study allows for experimentally feasible proposals capable
of controllable arbitrary qubit transformations.
