The thermodynamics of clocks

Abstract

All clocks, classical or quantum, are open non equilibrium irreversible systems subject to the constraints of thermodynamics. Using examples I show that these constraints necessarily limit the performance of clocks and that good clocks require large energy dissipation. For periodic clocks, operating on a limit cycle, this is a consequence of phase diffusion. It is also true for non periodic clocks (for example, radio carbon dating) but due to telegraph noise not to phase diffusion. In this case a key role is played by accurate measurements that decrease entropy, thereby raising the free energy of the clock, and requires access to a low entropy reservoir. In the quantum case, for which thermal noise is replaced by quantum noise (spontaneous emission or tunnelling), measurement plays an essential role for both periodic and non periodic clocks. The paper concludes with a discussion of the Tolman relations and Rovelli's thermal time hypothesis in terms of clock thermodynamics.

34 pages, 20 figures

References in corpus (5)

• Charge insensitive qubit design derived from the Cooper pair box
• Observation of quantum jumps in a superconducting artificial atom
• Quantum Non-demolition Detection of Single Microwave Photons in a Circuit
• Thermal time and the Tolman-Ehrenfest effect: temperature as the "speed of time"
• Dynamics and performance of clock pendulums

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