Realizing a Spin Chain

K. Hallberg

Oleksandr V. Marchukov, Artem G. Volosniev, Manuel Valiente +2 more

Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements.

Horaƫiu Năstase

Li Dai, Y P Feng, L. C. Kwek

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.

Jill C. Bonner, Henk W. J. Blöte, Hans Beck +1 more

X. X. Yi, H. T. Cui, L. C. Wang

A relation between entanglement and criticality of spin chains is established. The entanglement we exploit is shared between auxiliary particles, which are isolated from each other, but are coupled to the same critical spin-$1∕2$ chain. We analytically evaluate the reduced density matrix, and numerically show the entanglement of the auxiliary particles in the proximity of the critical points of the spin chain. We find that the entanglement induced by the spin chain may reach 1, and it can signal very well the critical points of the chain. A physical understanding and experimental realization with trapped ions are presented.