Iterative quantum-state transfer along a chain of nuclear spin qubits

Transferring quantum information between two qubits is a basic requirement for many applications in quantum communication and quantum-information processing. In the iterative quantum-state transfer proposed by Burgarth [Phys. Rev. A 75, 062327 (2007)], this is achieved by a static spin chain and a sequence of gate operations applied only to the receiving end of the chain. The only requirement on the spin chain is that it transfers a finite part of the input amplitude to the end of the chain, where the gate operations accumulate the information. For an appropriate sequence of evolutions and gate operations, the fidelity of the transfer can asymptotically approach unity. We demonstrate the principle of operation of this transfer scheme by implementing it in a nuclear magnetic resonance quantum-information processor.