Observation of $\mathcal{PT}$-symmetry and exceptional point in ion trap

Wei-Chen Wang, Pin-xing Chen

Published 2020-06-30Version 1

The theory of parity time $(\mathcal{PT})$ symmetry has been quite successful in classical system. And classical $\mathcal{PT}$-symmetric systems exhibited many interesting features. However, $\mathcal{PT}$-symmetric experiments of quantum systems are progressing more slowly than $\mathcal{PT}$-symmetric experiments of classical systems. Hence, we constructed a passive quantum $\mathcal{PT}$-symmetric system by using the internal states of $ ^{40}Ca^{+}$ ion. Comparing with other systems, the experimental setup of single ion trap is easy to implement, meanwhile our single ion trap is a real quantum system and has a long coherence time. In this paper, we show the phenomenon of $\mathcal{PT}$-symmetry-breaking transions by controlling the dissipation factor of states, which is achieved through adjusting the power of laser beam. Moreover, we also investigated the quantum phase transition near exceptional point (EP) of $\mathcal{PT}$-symmetric system. The experimental results enable ion trap to be a successful device for investigating quantum $\mathcal{PT}$-symmetry.