The thermodynamics of readout devices and semiclassical gravity

Abstract

We analyse the common claim that nonlinear modifications of quantum theory necessarily violate the second law of thermodynamics. We focus on hypothetical extensions of quantum theory that contain readout devices. These black boxes provide a classical description of quantum states without perturbing them. They allow quantum state cloning, though in a way consistent with the relativistic no-signalling principle. We review the existence of such devices in the context of Moller-Rosenfeld semiclassical gravity, which postulates that the gravitational field remains classical and is sourced by the expectation value of a quantum energy-momentum tensor. We show that the definition of information in the models examined in this paper deviates from that given by von Neumann entropy, and that claims of second law violations based on the distinguishability of non-orthogonal states or on violations of uncertainty principles fail to hold in such theories.

arXiv comment14 pages, 3 figures, Expanded discussion

References in corpus (22)

• The Stretched Horizon and Black Hole Complementarity
• A Spin Entanglement Witness for Quantum Gravity
• Gravitationally-induced entanglement between two massive particles is sufficient evidence of quantum effects in gravity
• The uncertainty principle determines the non-locality of quantum mechanics
• A generalized no-broadcasting theorem
• Semiclassical Gravity Theory and Quantum Fluctuations
• Sourcing semiclassical gravity from spontaneously localized quantum matter
• Non-Gaussianity as a signature of a quantum theory of gravity
• Entropy in general physical theories
• Newtonian Quantum Gravity
• Nonlinearity without Superluminality
• A violation of the uncertainty principle implies a violation of the second law of thermodynamics
• Thermodynamics and the structure of quantum theory
• Any consistent coupling between classical gravity and quantum matter is fundamentally irreversible
• Testing the nonclassicality of spacetime: what can we learn from Bell-Bose et al.-Marletto-Vedral experiments?
• Binding quantum matter and space-time, without romanticism
• Tests of Quantum Gravity near Measurement Events
• Quantum State Readout, Collapses, Probes and Signals
• Propagators in the Correlated Worldline Theory of Quantum Gravity
• Response to "The measurement postulates of quantum mechanics are not redundant"
• The measurement postulates of quantum mechanics are not redundant
• Mixture equivalence principles and post-quantum theories of gravity