Creating long-range entangled Majorana pairs: from spin-1/2 twisted Kitaev to generalized XY chains

Abstract: Entangling a pair of far-distant qubits in many-body systems has been a challenging task in quantum computing. A robust entanglement was predicted in the rainbow states and generating nonlocal Bell pairs protected by a mirror symmetry was recently proposed. We investigate a way to create entangled Majorana fermions in the spin-1/2 Kitaev chain with open boundary conditions. The spin-1/2 Kitaev chain, a one-dimensional version of the honeycomb lattice with bond-dependent Ising interactions, has a macroscopic degeneracy related to the zero modes containing non-local spin strings. We show that applying a pair pulse sequence on the central unit cell of the chain promotes long distance spin correlations and maximal bipartite entanglement entropy. We extend this method to the generalized bond-dependent spin-1/2 chain by introducing another set of Majorana fermions and make a comparison to the entangled Bell pairs. The time to reach maximal bipartite entanglement entropy is shorter in the Kitaev chain as the zero modes do not participate in the entangled pairs. An application of our results to a recently proposed twisted Kitaev chain, CoNb2O6, is presented and future directions are also discussed.