The Role of Singular Control in Frictionless Atom Cooling in a Harmonic   Trapping Potential
  In this article we study the frictionless cooling of atoms trapped in a harmonic potential, while minimizing the transient energy of the system. We show that in the case of unbounded control, this goal is achieved by a singular control, which is also the time-minimal solution for a "dual" problem, where the energy is held fixed. In addition, we examine briefly how the solution is modified when there are bounds on the control. The results presented here have a broad range of applications, from the cooling of a Bose-Einstein condensate confined in a harmonic trap to adiabatic quantum computing and finite time thermodynamic processes. 
Dionisis Stefanatos and Jr-Shin Li
math.OC cond-mat.quant-gas cs.SY quant-ph