Transferring entangled states through spin chains by boundary-state multiplets

TL;DR

This paper extends a quantum spin chain state transfer scheme to enable perfect transfer of all four Bell states, demonstrating the potential for reliable entangled state transfer in large, disorder-free chains.

Contribution

It introduces a method for perfect transfer of all Bell states in spin chains, expanding previous single-qubit transfer schemes to entangled states.

Findings

Perfect transfer of all four Bell states achieved in chains with hundreds of spins

Transfer scheme works for linear combinations of Bell states

Method applicable to large, disorder-free spin chains

Abstract

Quantum spin chains may be used to transfer quantum states between elements of a quantum information processing device. A scheme discovered recently \cite{BFR+12} was shown to have favorable transfer properties for ingle-qubit states even in the presence of built-in static disorder caused by manufacturing errors. We extend that scheme in a way suggested already in \cite{BFR+12} and study the transfer of the four Bell states which form a maximally entangled basis in the two-qubit Hilbert space. We show that perfect transfer of all four Bell states separately and of arbitrary linear combinations may be achieved for chains with hundreds of spins. For simplicity we restrict ourselves to systems without disorder.