An article titled “Efficient quantum information probes of nonequilibrium quantum criticality” by researchers Miguel M. Oliveira, Pedro Ribeiro and Stefan Kirchner was published in npj-quantum information. It resulted from a collaboration of researchers at the Center of Physics and Engineering of Advanced Materials (CeFEMA) and the Department of Physics at Técnico, and the Department of Electrophysics at the National Yang Ming Chiao Tung University in Hsinchu, Republic of China.

In their research, the authors address the problem of quantum criticality out-of-equilibrium. Quantum criticality refers to phase transitions that occur at vanishing temperatures which are driven by quantum fluctuations that become more and more prevalent as the transition point is approached. While there is a well-established theory for conventional quantum criticality in thermal equilibrium a complete description far away from equilibrium is lacking. In particular, it is unclear to which extent new forms of quantum criticality may emerge in out-of-equilibrium settings. Progress in these areas has been hampered by the lack of numerical techniques that avoid the fast scaling computational complexity.

Motivated the usefulness of quantum information-based approaches, the authors propose a class of quantities, defining a notion of distance between quantum states, which can serve as a generally applicable tool to determine the location of critical points in out-of-equilibrium systems. Being efficiently accessible by state-of-the-art numerical techniques of condensed matter physics, these quantities are expected to be of multidisciplinary interest.

Miguel Oliveira, the lead author on the study explains “We demonstrate that our proposed measure not only is able to signal previously identified nonequilibrium phase transitions. It also has predictive power as it can detect unknown phases in models of quantum matter far from equilibrium.”