State Transfer in Permanently Coupled Quantum Chains

Daniel Klaus Burgarth

The thesis covers various aspects of quantum state transfer in permanently coupled spin systems.

Daniel Klaus Burgarth

Man‐Hong Yung

Quantum state transfer is an important task in quantum information processing. It is known that one can engineer the couplings of a one-dimensional spin chain to achieve the goal of perfect state transfer. To leverage the value of these spin chains, a spin star is potentially useful for connecting different parts of a quantum network. In this work, we extend the spin-chain engineering problem to the problems with a topology of a star network. We show that a permanently coupled spin star can function as a network switch for transferring quantum states selectively from one node to another by varying the local potentials only. Together with one-dimensional chains, this result allows applications of quantum state transfer to be applied to more general quantum networks.

Lorena Ballesteros Ferraz

Daniel Klaus Burgarth, Vittorio Giovannetti, Sougato Bose

We present a communication protocol for chains of permanently coupled qubits which achieves perfect quantum state transfer and which is efficient with respect to the number of chains employed in the scheme. The system consists of M uncoupled identical quantum chains. Local control (gates, measurements) is only allowed at the sending/receiving end of the chains. Under a quite general hypothesis on the interaction Hamiltonian of the qubits, a theorem is proved which shows that the receiver is able to asymptotically recover the messages by repetitive monitoring of his qubits.

Olga V. Man’ko