Quantum adiabatic cycles and their breakdown

The assumption that quasi-static transformations do not quantitatively alter the equilibrium expectation of observables is at the heart of thermodynamics and, in the quantum realm, its validity may be confirmed by the application of adiabatic perturbation theory. Yet, this scenario does not straightforwardly apply to Bosonic systems whose excitation energy is slowly driven through the zero. Here, we prove that the universal slow dynamics of such systems is always non-adiabatic and the quantum corrections to the equilibrium observables become rate independent for any dynamical protocol in the slow drive limit. These findings overturn the common expectation for quasi-static processes as they demonstrate that a system as simple and general as the quantum harmonic oscillator, does not allow for a slow-drive limit, but it always displays sudden quench dynamics. While the Landau-Zener problem is conventionally used to describe defects formation in quantum systems, it cannot be applied to non-interacting Bose excitations as the adiabatic perturbation theory assumptions are violated by Bose statistics. Here, the author investigates adiabatic cycles across quantum critical points with harmonic Bose quasi-particles and shows that adiabaticity breakdown is a universal feature of these systems