# Weekly Papers on Quantum Foundations (14)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

Quantum Galileo’s experiments and mass estimation in a gravitational field. (arXiv:1603.09559v1 [gr-qc])

on 2016-4-02 8:26am GMT

We address the problem of estimating the mass of a (quantum) particle interacting with a classical gravitational field. In particular, we analyze in details the ultimate bounds to precision imposed by quantum mechanics and study the effects of gravity in a variety of settings. Our results show that the presence of a gravitational field generally leads to a precision gain, which can be significant in a regime half-way between the quantum and classical domains. We also address quantum enhancement to precision, i.e. the advantages coming from taking into account the quantum nature of the probe particle, and show that non-classicality is indeed a relevant resource for mass estimation. In particular, we suggest schemes for mass-sensing measurements using quantum probes and show that upon employing non-classical states like quantum coherent superpositions one may improve precisions by orders of magnitude. In addition, we discuss the compatibility of the weak equivalence principle (WEP) within the quantum regime using as a guide the notion of Fisher Information. We find that the information on the probe’s mass that can be extracted through position measurements is unchanged by turning on a uniform gravitational field. This conclusion is somehow at variance with certain views expressed in the literature that the WEP cannot hold in the quantum regime. In fact, our results show that in an information-theoretic framework, no clash occurs between quantum mechanics and the WEP.

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A “Garden of Forking Paths” – the Quantum Mechanics of Histories of Events. (arXiv:1603.09664v1 [quant-ph])

on 2016-4-02 8:26am GMT

We present a short survey of a novel approach, called “ETH approach”, to the quantum theory of events happening in isolated physical systems and to the effective time evolution of states of systems featuring events. In particular, we attempt to present a clear explanation of what is meant by an “event” in quantum mechanics and of the significance of this notion. We then outline a theory of direct (projective) and indirect observations or recordings of physical quantities and events. Some key ideas underlying our general theory are illustrated by studying a simple quantum-mechanical model of a mesoscopic system.

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On Modern Approaches to the Einsteinian View of Quantum States. (arXiv:1603.09463v1 [quant-ph])

on 2016-4-02 8:26am GMT

Authors: Florian Boge

Quantum mechanics notoriously faces the measurement problem, the problem that if read thoroughly, it implies the nonexistence of definite outcomes in measurement procedures. A plausible reaction to this and to related problems is to regard a system’s quantum state $|\psi\rangle$ merely as an indication of our lack of knowledge about the system, i.e., to interpret it epistemically. However, there are radically different ways to spell out such an epistemic view of the quantum state. We here investigate new developments in the branch that introduces hidden variables $\lambda$ in addition to the quantum state $|\psi\rangle$ and has its roots in Einstein’s views. In particular, we confront purported achievements of the view in the light of recent no-go results. It will be demonstrated that, despite the debatability of the premises of such results, they force the hidden variable theorist to make ad hoc moves which undermine the very conceptual basis of his own approach.

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Reconsidering Local Hidden Variables: When One is Enough. (arXiv:1603.09430v1 [quant-ph])

on 2016-4-02 8:26am GMT

In this Letter, we explore the possibility of developing Bell inequalities predicated on models using a single Local Hidden Variable (s-LHV), a strict subset of general LHV models. Because of the less strenuous constraints imposed by s-LHV models, we were able to derive a contingent Bell inequality in analogy to the CHSH inequality, but which does not require bounding of measurement statistics. Following this, we show by explicit example that there are cases of states that rule out s-LHV models by violating our inequality, but which nonetheless have a multivariate LHV model. Even so, we show how merely ruling out s-LHV models is still sufficient to allow for fully device independent quantum key distribution (QKD) and entanglement witnessing. This being the case, our inequality illustrates two things. First, it makes fully device-independent QKD on continuous variables substantially more straightforward. Second, it shows how the degree of correlation needed to demonstrate device-independent QKD is distinct from both Bell-nonlocality and EPR-steering. Although nonlocality in general requires ruling out all LHV models, s-LHV models are sufficiently useful to warrant further exploration.

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Comparing Dualities and Gauge Symmetries

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-3-28 7:53pm GMT

De Haro, Sebastian and Teh, Nicholas and Butterfield, Jeremy (2016) Comparing Dualities and Gauge Symmetries. [Preprint]

Testing typicality in multiverse cosmology

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-3-28 1:34am GMT

Azhar, Feraz (2015) Testing typicality in multiverse cosmology. [Published Article]