Experimental Study of Universal Scaling in Super-radiant Quantum Phase Transitions with a Single Trapped Ion

Abstract:

Phase transitions typically manifest under thermodynamic conditions, where the emergence of a universal scaling function near a critical point serves as a pivotal sign of phase transition. Recently, the quantum Rabi model (QRM) has been highlighted for its ability to undergo quantum phase transitions from normal to super-radiant phases, with a simple system of a qubit and a harmonic oscillator mode [1,2]. QRM's order parameters can reveal universal scaling functions when approaching to the critical point, which, however, it has not been observed in experiment. Here we employ a single trapped ion to realize the QRM, and measure the order parameters of squeezing parameters and excitation of super-radiance and their corresponding universal scaling function. We speed up the process by optimizing the adiabatic evolution trajectories to overcome the limitation of coherence time of vibrational mode. This methodology offers a quantitative study of quantum phase transition and an avenue for exploring quantum sensing using QRM.



Reference:

[1] Myung-Joong Hwang, et al., Phys. Rev. Lett. 115, 180404 (2015).

[2] Ricardo Puebla, et al., Phys. Rev. Lett. 118, 073001 (2017).