1. What is Landauer's Principle?
Landauer's Principle (LP) was originally presented by Landauer in terms of computation. It proposes that 'computing machines' engaging in logically irreversible steps incur a cost of the order of kT per each step. While LP has been largely accepted, there is a dissenting minority. The present authors dispute the identification of physical irreversibility with logical/computational irreversibility inherent in Landauer's original proposal. However, they adduce a physical basis for a restricted form of LP, which is not identified with computation but with a narrower class of genuinely irreversible physical processes. This restricted form of LP is not dependent on epistemic uncertainty but supervenes on specific physics involving the ontology of the system, independently of human knowledge or lack thereof. Essentially, LP is a form of the Second Law, but only insofar as both are independent of epistemic considerations. If LP is defined as applying to epistemic uncertainty, it can be refuted based on an analysis of the actual physics involved in epistemic 'erasure' or 'reset' operations.
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2. What is the Received View in the context of Landauer's Principle?
The Received View is a consensus in the literature that Bennett refuted Brillouin's identification of measurement as the source of entropy cost in Maxwell's Demon. It portrays erasure of memory devices as the relevant irreversible process, rather than measurement. However, this view has been criticized for neglecting the fundamental level and the impact of the uncertainty principle on the irreversible process of measuring a system's position or momentum.
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3. What is the implication of a restricted form of Landauer's Principle?
The restricted form of Landauer's Principle, corresponding to ontological information, implies that for a thermal system, the joint entropy related to the quantum uncertainty principle is independent of the Second Law. This form of Landauer's Principle serves as a remedy for situations where it is used as a surrogate for the Second Law when the latter is being challenged. It provides the true physical basis for the Second Law and reinforces the understanding that there can be no Maxwell's Demon. This restricted form of Landauer's Principle highlights the importance of considering relevant physics and the role of quantum uncertainty in thermodynamic systems.
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4. What is the relationship between erasure of memory devices and phase space compression?
Erasure of a classically-modeled memory device does not correspond to a true phase space compression. This is because erasure reduces logical space but not physical phase space. Norton (2013, 3.6) explains that erasure reduces logical space but not physical phase space. The differential form can in principle yield negative values, but may be viewed as an idealization. In addition, there is no true position observable at the fully relativistic level, so that localization is likely limited to a Planck volume (cf. Schlatter and Kastner, 2023). Thus, (2) may be viewed as an excellent approximation for the macroscopic level. Quantum measurement and its relation to entropy increase is discussed in detail in Kastner (2017). Approaches assuming that quantum theory has only unitary evolution are subject to the same lack of true state space compression as the classical theory, which may be why the results offered herein have thus far been overlooked.
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