73 research outputs found
Reply to Gao’s ”Comment on ”How to protect the interpretation of the wave function against protective measurements”
No full textShan Gao (Gao 2011) recently presented a critical reconsideration of a paper I wote (Uffink 1999) on the subject of protective measurement. Here, I take the occasion to reply to his objections
Afanassjewa and the Foundations of Thermodynamics
No full textWe review aspects of Afanassjewa’s work on the foundations of thermodynamics from her 1925 paper on the Second Law and her 1956 book Grundlagen der Thermodynamik. We argue that her work contained several valuable original insights in these foundations, often much ahead of her times. In particular, we discuss how her 1956 book anticipated and showed the way to solve an alleged paradox about reversible processes raised by Norton (2014, 2016) and discuss the remarkable comments in her 1925 paper on the asymmetry between work and heat exchange —which still awaits more common recognition—, and on the conceptual possibility of negative absolute temperatures, long before Ramsey (1956) made this an accepted physical possibility
Uses of a Quantum Master Inequality
No full textAn inequality in quantum mechanics, which does not appear to be well known, is derived by elementary means and shown to be quite useful. The inequality applies to 'all' operators and 'all' pairs of quantum states, including mixed states. It generalizes the rule of the orthogonality of eigenvectors for distinct eigenvalues and is shown to imply all the Robertson generalized uncertainty relations. It severely constrains the difference between probabilities obtained from 'close' quantum states and the different responses they can have to unitary transformations. Thus, it is dubbed a master inequality. With appropriate definitions the inequality also holds throughout general probability theory and appears not to be well known there either. That classical inequality is obtained here in an appendix. The quantum inequality can be obtained from the classical version but a more direct quantum approach is employed here. A similar but weaker classical inequality has been reported by Uffink and van Lith
The Origins of Time-asymmetry in Thermodynamics: The Minus First Law
No full textThis paper investigates what the source of time-asymmetry is in thermodynamics, and comments on the question whether a time-symmetric formulation of the Second Law is possible
Bluff your Way in the Second Law of Thermodynamics
No full textThe aim of this article is to analyse the relation between the second law of thermodynamics and the so-called arrow of time. For this purpose, a number of different aspects in this arrow of time are distinguished, in particular those of time-(a)symmetry and of (ir)reversibility. Next I review versions of the second law in the work of Carnot, Clausius, Kelvin, Planck, Gibbs, Carath\'eodory and Lieb and Yngvason, and investigate their connection with these aspects of the arrow of time. It is shown that this connection varies a great deal along with these formulations of the second law. According to the famous formulation by Planck, the second law expresses the irreversibility of natural processes. But in many other formulations irreversibility or even time-asymmetry plays no role. I therefore argue for the view that the second law has nothing to do with the arrow of tim
On Uffink's alternative interpretation of protective measurements
No full textProtective measurement is a new measuring method introduced by Aharonov, Anandan and Vaidman (1993). By a protective measurement, one can measure the expectation value of an observable on a single quantum system, even if the system is initially not in an eigenstate of the measured observable. This remarkable feature of protective measurements was challenged by Uffink (1999, 2012). He argued that only observables that commute with the system's Hamiltonian can be protectively measured, and a protective measurement of an observable that does not commute with the system's Hamiltonian does not actually measure the observable, but measure another related observable that commutes with the system's Hamiltonian. In this paper, we show that there are several errors in Uffink's arguments, and his alternative interpretation of protective measurements is untenable
Response to Pashby: Time operators and POVM observables in quantum mechanics
No full textI argue against a general time observable in quantum mechanics except for quantum gravity theory. Then I argue in support of case specific arrival time and dwell time observables with a cautionary note concerning the broad approach to POVM observables because of the wild proliferation available
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