Abstract
The efficient conversion of thermal energy to mechanical work by a heat engine is an ongoing technological challenge. Since the pioneering work of Carnot, it is known that the efficiency of heat engines is bounded by a fundamental upper limit, the Carnot limit. Theoretical studies suggest that heat engines may be operated beyond the Carnot limit by exploiting stationary, non-equilibrium reservoirs that are characterized by a temperature as well as further parameters. In a proof-of-principle experiment, we demonstrate that the efficiency of a nano-beam heat engine coupled to squeezed thermal noise is not bounded by the standard Carnot limit. Remarkably, we also show that it is possible to design a cyclic process that allows for extraction of mechanical work from a single squeezed thermal reservoir. Our results demonstrate a qualitatively new regime of non-equilibrium thermodynamics at small scales and provide a new perspective on the design of efficient, highly miniaturized engines.
Highlights
Advances in microtechnology and nanotechnology allow for testing concepts derived from classical thermodynamics in regimes where the underlying assumptions, such as the thermodynamic limit and thermal equilibrium, no longer hold [1,2,3,4,5,6]
Miniaturized forms of heat engines, in which the working medium is represented by a single particle, have revealed a fluctuation-dominated regime in the conversion of heat to work far away from the thermodynamic limit [7,8,9,10,11]
It is expected that the efficiency of work generation can surpass standard thermodynamic bounds, as has been theoretically suggested for quantum coherent [12], quantum correlated [13,14], quantum-measurement-induced [15,16,17], and squeezed thermal reservoirs [18,19,20,21,22,23]
Summary
Advances in microtechnology and nanotechnology allow for testing concepts derived from classical thermodynamics in regimes where the underlying assumptions, such as the thermodynamic limit and thermal equilibrium, no longer hold [1,2,3,4,5,6]. It is expected that the efficiency of work generation can surpass standard thermodynamic bounds, as has been theoretically suggested for quantum coherent [12], quantum correlated [13,14], quantum-measurement-induced [15,16,17], and squeezed thermal reservoirs [18,19,20,21,22,23]. The realization of such engines extends our knowledge of finite-size, nonequilibrium, and quantum effects in thermodynamics, but could lead to important applications in nanotechnology and in the life sciences [24]. We demonstrate that by a phase-selective coupling to the squeezed or antisqueezed quadrature, work can be extracted even from a single squeezed reservoir, which is not possible with a standard thermal reservoir [12,21,32]
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