Engineering quantum cloning through maximal entanglement between boundary qubits in an open spin chain

In this paper, we show how maximal entanglement between boundary qubits in the open spin chain of an XX model is realized. This creation of maximal entanglement could be used for phase covariant quantum cloning in a spin chain. The maximal entanglement is achieved with specially engineered couplings. We compare our realization with alternative methods and find that the method of pre-engineered couplings is straightforward and the decrease of cloning fidelity due to time errors is smaller.