Weekly Papers on Quantum Foundations (18)

Authors: Yurii V. Brezhnev

We deduce the Born rule. No use is required of quantum postulates. One exploits only rudimentary quantum mathematics — a linear, not Hilbert’s, vector space — and empirical notion of the statistical length of a state. Its statistical nature comes from experimental micro-events: the abstract quantum clicks.

Author(s): Alexander R. H. Smith

We generalize a quantum communication protocol introduced by Bartlett et al. [New J. Phys. 11, 063013 (2009)], in which two parties communicating do not share a classical reference frame, to the case where changes of their reference frames form a one-dimensional noncompact Lie group. Alice sends to …

[Phys. Rev. A 99, 052315] Published Fri May 10, 2019

Henriksson, Andreas (2019) On the ergodic theorem and information loss in statistical mechanics. [Preprint]
Dardashti, Radin and Dawid, Richard and Gryb, Sean and Thebault, Karim P Y (2018) On the Empirical Consequences of the AdS/CFT Duality. In: UNSPECIFIED.
Christian, Joy (2019) On a Surprising Oversight by John S. Bell in the Proof of his Famous Theorem. [Preprint]

Authors: Morgan W. MitchellSilvana Palacios Alvarez

The energy resolution per bandwidth $E_R$ is a figure of merit that combines the field resolution, bandwidth or duration of the measurement, and size of the sensed region. Several very different dc magnetometer technologies approach $E_R = \hbar$, while to date none has surpassed this level. This suggests a technology-spanning quantum limit, a suggestion that is strengthened by model-based calculations for nitrogen-vacancy centres in diamond, for dc SQUID sensors, and for optically-pumped alkali-vapor magnetometers, all of which predict a quantum limit close to $E_R = \hbar$. Here we review what is known about energy resolution limits, with the aim to understand when and how $E_R$ is limited by quantum effects. We include a survey of reported sensitivity versus size of the sensed region for a dozen magnetometer technologies, review the known model-based quantum limits, and critically assess possible sources for a technology-spanning limit, including zero-point fluctuations, magnetic self-interaction, and quantum speed limits. Finally, we describe sensing approaches that appear to be unconstrained by any of the known limits, and thus are candidates to surpass $E_R = \hbar$.

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