Probing Mean Values and Correlations of High-Spin Systems on a Quantum Computer

Andrij Romanovych Kuzmak, V. M. Tkachuk

Abstract We consider simulation of the high spins on a quantum computer. The protocols which allow one to measure the mean value of spin and correlations between spins are proposed. As a result, we determine the time dependence of the mean values of spin-1 in the magnetic field prepared on the ibmq-santiago quantum computer. In addition, we study the evolution of two interacting spins on the ibmq-lima quantum computer. The time-dependencies of the mean value of spin-1 and correlations between these spins are detected. Finally, we generalize these protocols for the spins of arbitrary values.

Guo-Feng Zhang, Heng Fan, Ai-Ling Ji +3 more

LvZhou Ye, Dong Hou, Xiao Hong Zheng +2 more

Probes that measure the local thermal properties of systems out of equilibrium are emerging as new tools in the study of nanoscale systems. One can then measure the temperature of a probe that is weakly coupled to a bias-driven system. By tuning the probe temperature so that the expectation value of some observable of the system is minimally perturbed, one obtains a parameter that measures its degree of local statistical excitation, and hence its local heating. However, one anticipates that different observables may lead to different temperatures and thus different local heating expectations. We propose an experimentally realizable protocol to measure such local temperatures and apply it to bias-driven quantum dots. By means of a highly accurate open quantum system approach, we show theoretically that the measured temperature is quite insensitive both to the choice of observable and to the probe-system coupling. In particular, even with observables that are distinct both physically and in their degree of locality, such as the local magnetic susceptibility of the quantum dot and the global spin-polarized current measured at the leads, the resulting local temperatures are quantitatively similar for quantum dots ranging from noninteracting to Kondo-correlated regimes, and are close to those obtained with the traditional ``local equilibrium'' definition.

Marric Stephens

Kim G. L. Pedersen, Brian M. Andersen, Georg M. Bruun +1 more

We previously proposed [K. G. L. Pedersen, B. M. Andersen, G. M. Bruun, O. F. Sylju\aa{}sen, and A. S. S\o{}rensen, Phys. Rev. A 84, 041603 (2011)] a method to utilize a temporally dependent superlattice potential to mediate spin-selective transport and thereby probe long- and short-range magnetic correlations in optical lattices. Specifically, this can be used for detecting antiferromagnetic ordering in repulsive fermionic optical lattice systems, but more generally it can serve as a means of directly probing correlations among the atoms by measuring the mean value of an observable, the number of double occupied sites. Here we provide a detailed investigation of the physical processes that limit the effectiveness of this ``conveyer belt method.'' Furthermore, we propose a simple way to improve the procedure, resulting in an essentially perfect (error-free) probing of the magnetic correlations. These results shows that suitably constructed superlattices constitute a promising way of manipulating atoms of different spin species as well as probing their interactions.

Daniel Manzano