David Raventós
Quantum optics theory group, ICFO
Spin models with disorder, and spin glasses in particular, are paradigms of multidisciplinary science. They are most relevant for various fields of physics, reaching from condensed matter to high energy physics, but they also find several applications beyond the physical sciences. D-Wave computers, recently introduced on the market, are in fact quantum simulators that solve classical spin glass models using quantum annealing. It remains an open question whether the machine provides a speed-up advantage over the best classical algorithms. This triggers interest in alternative quantum systems designed to solve general spin models via quantum simulation. Indeed, exploiting quantum properties to outperform classical ways of information-processing is an outstanding goal of modern physics. A promising route is quantum simulation which aims at implementing relevant and computationally hard problems in controllable quantum systems. A noteworthy physical system for this goal are trapped ions. Here we consider trapped ions and demonstrate concretely that, with present day technology, a spin model of the Mattis type can be obtained that exhibits spin glass phases. Remarkably, our method produces the glassy behavior without the need of any disorder potential, just by controlling the detuning of the spin-phonon coupling. Applying a transverse field, the system can be used to benchmark quantum annealing strategies which aim at reaching the ground state of the spin glass starting from the paramagnetic phase. In the vicinity of a phonon resonance, the problem maps onto number partitioning, and instances which are difficult to address classically can be implemented.