Can thermodynamics and quantum mechanics be bridged in heat machines?

In recent years we have examined a variety of quantum mechanical mechanisms that may boost the performance of heat machines (HM) based on simple designs: working-media (WM) of qubits coupled to thermal or squeezed baths and a quantized harmonic-oscillator piston ^[1-4].  Cooperative (superradiant) effects in multi-qubit WM have been found to boost the HM power^[4] but they may have a classical counterpart.  We have found uniquely quantum boost (advantage) only when quantum electrodynamics affects the system-bath coupling^[5,6]. Yet all existing HM, including the ones examined by us, are essentially dissipative open systems, so that their thermodynamic description disqualifies them from being genuinely quantum mechanical devices. We have now broken away from this established thermodynamic paradigm by putting forth a fundamentally novel HM: Few-mode nonlinear interferometers wherein cold field modes passively “measure” hot modes and thereby enable autonomous HM operation^[7], unlike HM based on active measurements and feedforward of this information^[8].  Our novel nonlinear-dynamic mechanism replaces dissipative thermal- bath effects by purely coherent evolution and thus constitutes a stepping stone towards   bridging quantum mechanics and thermodynamics.

 

[1] Nat. Commun. 9, 165 (2018). [2] PNAS 115, 9941 (2018). [3] PNAS 114, 12156 (2017). [4] NJP [5] Commun. Phys. 2, 1 (2019). [6] Phys. Rev. Res. 2, 033285 92020.

[7] Arxiv2108.10157 (2021). [8] PRL 127, 040602 (2021).