Bath-assisted cooling of spins.

  title={Bath-assisted cooling of spins.},
  author={Armen E. Allahverdyan and Rub{\`e}n Serral Graci{\`a} and Theo M. Nieuwenhuizen},
  journal={Physical review letters},
  volume={93 26 Pt 1},
A suitable sequence of sharp pulses applied to a spin coupled to a bosonic bath can cool its state, i.e., increase its polarization or ground state occupation probability. Starting from an unpolarized state of the spin in equilibrium with the bath, one can reach very low temperatures or sizable polarizations within a time shorter than the decoherence time. Both the bath and external fields are necessary for the effect, which comes from the backreaction of the spin on the bath. This method can… 
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