Quantum information storage in the localized state of a spin chain

Francesco Plastina, Tony J. G. Apollaro, Alexander I. Lvovsky

Tony J. G. Apollaro, Francesco Plastina

We describe a chain of qubits with always on exchange interaction in the presence of a spatial inhomogeneity in the qubit level spacing. Similarly to the phenomenon of Anderson localization, this system has a localized eigenstate which can be used to store or trap quantum information. We discuss both the fidelity of storage and the leakage of information from this localized state and show that even a very small defect can be useful.

Davide Rossini

Marta P. Estarellas, Irene D’Amico, Timothy P. Spiller

Reliable quantum communication and/or processing links between modules are a necessary building block for various quantum processing architectures. Here we consider a spin-chain system with alternating strength couplings and containing three defects, which impose three domain walls between topologically distinct regions of the chain. We show that---in addition to its useful, high-fidelity, quantum state transfer properties---an entangling protocol can be implemented in this system, with optional localization and storage of the entangled states. We demonstrate both numerically and analytically that, given a suitable initial product-state injection, the natural dynamics of the system produces a maximally entangled state at a given time. We present detailed investigations of the effects of fabrication errors, analyzing random static disorder both in the diagonal and off-diagonal terms of the system Hamiltonian. Our results show that the entangled state formation is very robust against perturbations of up to $\ensuremath{\sim}10%$ the weaker chain coupling, and also robust against timing injection errors. We propose a further protocol, which manipulates the chain in order to localize and store each of the entangled qubits. The engineering of a system with such characteristics would thus provide a useful device for quantum information processing tasks involving the creation and storage of entangled resources.

E. V. Orlenko, Fedor E. Orlenko

Our work generally focuses on the problems of quantum information physics and more specifically on the problem of secret key distribution using the spin1 chain. Spin-1 antiferromagnetic chain allows noiseless information transfer from photonic to spin subsystem and the information storage with 100% fidelity due to features of spin-1 antiferromagnetic chain like as a gap spectrum excitation and a coherent ground state of whole chain with total spin equals to1.

J. L. Maddox