Quantum phonon lasing with mixed species trapped ions

Active control of the interaction between a quantum system and its environment, a.k.a quantum reservoir engineering (QRE) has been proved to be a rich resource for quantum state preparation and quantum computation. It also provides the possibility to study open quantum systems, in particular quantum phase transitions driven by dissipation. To explore this direction, we implement QRE on a mixed species ion crystal consisting of a calcium ion and a beryllium ion. This allows us to realize a phonon laser and study the lasing phase transition deep in the quantum regime. We also demonstrate phase locking of such a phonon laser, which can find applications in quantum sensing. The rich toolbox provided by QRE on a mixed species ion crystal enables us to further investigate a nonclassical lasing regime. Such states are of great interest for quantum-enhanced parameter estimation.