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Phase transitions in a programmable quantum spin glass simulator

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Science  13 Jul 2018:
Vol. 361, Issue 6398, pp. 162-165
DOI: 10.1126/science.aat2025

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Simulating correlated electron systems

Correlated electron systems are generally difficult to simulate because of limited capabilities of computational resources. Harris et al. used a D-Wave chip based on a large array of superconducting elements to simulate the phases of a complex magnetic system. They tuned the amount of frustration within the lattice and varied the effective transverse magnetic field, which revealed phase transitions between a paramagnetic, an ordered antiferromagnetic, and a spin-glass phase. The results compare well to theory for this spin-glass problem, validating the approach for simulating problems in materials physics.

Science, this issue p. 162

Abstract

Understanding magnetic phases in quantum mechanical systems is one of the essential goals in condensed matter physics, and the advent of prototype quantum simulation hardware has provided new tools for experimentally probing such systems. We report on the experimental realization of a quantum simulation of interacting Ising spins on three-dimensional cubic lattices up to dimensions 8 × 8 × 8 on a D-Wave processor (D-Wave Systems, Burnaby, Canada). The ability to control and read out the state of individual spins provides direct access to several order parameters, which we used to determine the lattice’s magnetic phases as well as critical disorder and one of its universal exponents. By tuning the degree of disorder and effective transverse magnetic field, we observed phase transitions between a paramagnetic, an antiferromagnetic, and a spin-glass phase.

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