Combinatorics

Physics

Quantum dynamics

Nonlinear system

Topology (electrical circuits)

Mathematics

Van der Pol oscillator

Statistical physics

Quantum limit

Coherence (philosophical gambling strategy)

Synchronization (alternating current)

Quantum mechanics

Quantum

Limit cycle

Physical review. A/Physical review, A

Recently, several studies have investigated synchronization in quantum-mechanical limit-cycle oscillators. However, the quantum nature of these systems remained partially hidden, since the dynamics of the oscillator's phase was overdamped and therefore incoherent. We show that there exist regimes of underdamped and even quantum-coherent phase motion, opening up new possibilities to study quantum synchronization dynamics. To this end, we investigate the Van der Pol oscillator (a paradigm for a self-oscillating system) synchronized to an external drive. We derive an effective quantum model which fully describes the regime of underdamped phase motion and additionally allows us to identify the quality of quantum coherence. Finally, we identify quantum limit cycles of the phase itself.

Quantum-coherent phase oscillations in synchronization