Using quantum fields to achieve ultra-low temperatures, while being an emerging area of research, faces theoretical and experimental challenges. The quantum analog of a conventional refrigerator might exploit a combination of coherent manipulation of energy states, quantum tunneling, and interactions between particles. However, such a device remains speculative and is far from practical realization. The lowest temperatures to date are obtained using traditional cryogenic techniques that use helium-3 and dilution refrigerators to reach millikelvin and nano-kelvin ranges.