Are classical and quantum machines fundamentally different?

The Holy Grail of quantum thermodynamics is finding a concrete quantum machine that performs better than classical ones. Some early suggestions indicate that quantum resources such as quantum coherences¹ or quantum reservoir engineering² provide heat machines with unique features compared  to their classical counterparts.  Nevertheless, once all the preparation costs³ and non-equilibrium sources⁴ have been properly accounted for, quantum and classical heat machines are essentially the same. But physicists don’t give up easily, so the quest for a quantum heat machine that is fundamentally different from its classical counterpart still goes on.  

In this talk, I will show that a basic quantum property - energy quantization - allows quantum heat machines to operate even with incompressible working fluids, which would forbid work extraction for classical heat machines^5,6.

I will discuss how to experimentally measure this effect by realizing the same heat machine operating in the classical and in the quantum limit. This research opens up the possibility for experimentally studying the difference between classical and quantum systems well beyond the realm of heat machines.

[1] Scully, Marlan O., et al. "Extracting work from a single heat bath via vanishing quantum coherence." Science 299.5608 (2003): 862-864.

[2] Roßnagel, Johannes, et al. "Nanoscale heat engine beyond the Carnot limit." Physical review letters 112.3 (2014): 030602.

[3] Zubairy, M. Suhail. "The Photo‐Carnot Cycle: The Preparation Energy for Atomic Coherence." AIP Conference Proceedings. Vol. 643. No. 1. American Institute of Physics, 2002.

[4] Alicki, Robert, and David Gelbwaser-Klimovsky. "Non-equilibrium quantum heat machines." New Journal of Physics 17.11 (2015): 115012.

[5] Gelbwaser-Klimovsky, David, et al. "Single-atom heat machines enabled by energy quantization." Physical review letters 120.17 (2018): 170601.

[6] Levy, Amikam, and David Gelbwaser-Klimovsky. "Quantum features and signatures of quantum thermal machines." Thermodynamics in the Quantum Regime. Springer, Cham, 2018. 87-126.