Weekly Papers on Quantum Foundations (30)

How to Explain the Direction of Time

上午10:34|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Fernandes, Alison (2022) How to Explain the Direction of Time. [Preprint]

Homodyne measurement with a Schr\”odinger cat state as a local oscillator. (arXiv:2207.10210v1 [quant-ph])

上午8:55|Joshua Combes, Austin P. Lund|quant-ph updates on arXiv.org

Homodyne measurements are a widely used quantum measurement. Using a coherent state of large amplitude as the local oscillator, it can be shown that the quantum homodyne measurement limits to a field quadrature measurement. In this work, we give an example of a general idea: injecting non-classical states as a local oscillator can led to non-classical measurements. Specifically, we consider injecting a superposition of coherent states, a Schr\”odinger cat state, as a local oscillator. We derive the Kraus operators and the positive operator-valued measure (POVM) in this situation and show the POVM is a reflection symmetric quadrature measurement when the coherent state amplitudes are large.

Bell nonlocality in quantum-gravity induced minimal-length quantum mechanics. (arXiv:2207.10418v1 [quant-ph])

上午8:55|Pasquale Bosso, Luciano Petruzziello, Fabian Wagner, Fabrizio Illuminati|quant-ph updates on arXiv.org

Different approaches to quantum gravity converge in predicting the existence of a minimal scale of length. This raises the fundamental question as to whether and how an intrinsic limit to spatial resolution can affect quantum mechanical observables associated to internal degrees of freedom. We answer this question in general terms by showing that the spin operator acquires a momentum-dependent contribution in quantum mechanics equipped with a minimal length. Among other consequences, this modification induces a form of quantum nonlocality stronger than the one arising in ordinary quantum mechanics. In particular, we show that violations of the Bell inequality can exceed the maximum value allowed in ordinary quantum mechanics by a positive multiplicative function of the momentum operator.

Quantum States of Fields for Quantum Split Sources. (arXiv:2207.10592v1 [gr-qc])

上午8:55|Lin-Qing Chen, Flaminia Giacomini, Carlo Rovelli|quant-ph updates on arXiv.org

Field mediated entanglement experiments probe the quantum superposition of macroscopically distinct field configurations. We show that this phenomenon can be described by using a transparent quantum field theoretical formulation of electromagnetism and gravity in the field basis. The strength of such a description is that it explicitly displays the superposition of macroscopically distinct states of the field. In the case of (linearised) quantum general relativity, this formulation exhibits the quantum superposition of geometries giving rise to the effect.

Teaching Qubits to Sing: Mission Impossible?. (arXiv:2207.08225v2 [quant-ph] UPDATED)

上午8:55|Eduardo Reck Miranda, Brian N. Siegelwax|quant-ph updates on arXiv.org

This paper introduces a system that learns to sing new tunes by listening to examples. It extracts sequencing rules from input music and uses these rules to generate new tunes, which are sung by a vocal synthesiser. We developed a method to represent rules for musical composition as quantum circuits. We claim that such musical rules are quantum native: they are naturally encodable in the amplitudes of quantum states. To evaluate a rule to generate a subsequent event, the system builds the respective quantum circuit dynamically and measures it. After a brief discussion about the vocal synthesis methods that we have been experimenting with, the paper introduces our novel generative music method through a practical example. The paper shows some experiments and concludes with a discussion about harnessing the creative potential of the system.

On the maximum size of black holes in our accelerating universe. (arXiv:2207.10202v1 [gr-qc])

上午8:55|gr-qc updates on arXiv.org

Authors: Tetsuya ShiromizuKeisuke IzumiKangjae LeeDiego Soligon

In accordance with current models of the accelerating universe as a spacetime with a positive cosmological constant, new results about a cosmological upper bound for the area of stable marginally outer trapped surfaces are found taking into account angular momentum, gravitational waves and matter. Compared to previous results which take into account only some of the aforementioned variables, the bound is found to be tighter, giving a concrete limit to the size of black holes especially relevant in the early universe.

Another look on the connections of Hubble tension with the Heisenberg Uncertainty Principle. (arXiv:2207.10570v1 [gr-qc])

上午8:55|gr-qc updates on arXiv.org

Authors: Oem Trivedi

The Hubble tension is one of the most exciting problems that Cosmology faces today. A lot of possible solutions for it have already been proposed in the last few years, with a lot of them using a lot of new and exotic physics ideas to deal with the problem. But it was shown recently that the H0 tension might not require new physics but only a more accurate discussion of measurements and interestingly it was the Heisenberg uncertainty principle which was pivotal for that revelation. Accordingly, if one observed the photon mass beyond the indeterminacy through uncertainty then one could in principle reconcile the tension. We examine this in a greater detail in this work by taking into account modifications of the Compton wavelength, which was pivotal in the initial discussion on the interconnection between uncertainty and the H0 tension. We mainly discuss two types of modifications, one based on generalized uncertainty principles (GUP) and the other on higher dimensional physics considerations. We firstly show that both minimal length and maximal momentum GUP based modifications do not provide photon mass values on the required scales and hence we cannot address the tension in this sense at all in this case. We then show that one can get the photon mass to be on the required scales even after incorporating higher dimensional effects, one cannot reconcile the Hubble Tension in the same sense as in the (3+1) space-time case. In this way, we show that certain new physics considerations cannot address the H0 tension in the same sense as one can using the original Heisenberg uncertainty principle in a (3+1) space-time.

Frontiers of Quantum Gravity: shared challenges, converging directions. (arXiv:2207.10618v1 [hep-th])

上午8:55|gr-qc updates on arXiv.org

Authors: Jan de BoerBianca DittrichAstrid EichhornSteven B. GiddingsSteffen GielenStefano LiberatiEtera R. LivineDaniele OritiKyriakos PapadodimasAntonio D. PereiraMairi SakellariadouSumati SuryaHerman Verlinde

Understanding the quantum nature of spacetime and gravity remains one of the most ambitious goals of theoretical physics. It promises to provide key new insights into fundamental particle theory, astrophysics, cosmology and the foundations of physics. Despite this common goal, the community of quantum gravity researchers is sometimes seen as divided into sub-communities working on different, mutually exclusive approaches. In practice however, recent years have shown the emergence of common techniques, results and physical ideas arising from different sub-communities, suggesting exciting new prospects for collaboration and interaction between traditionally distinct approaches. In this White Paper we discuss some of the common themes which have seen a growing interest from various directions, and argue that focusing on them will help the quantum gravity community as a whole towards shared objectives.

Quantized mass-energy effects in an Unruh-DeWitt detector. (arXiv:2205.02394v2 [quant-ph] UPDATED)

上午8:55|gr-qc updates on arXiv.org

Authors: Carolyn E. WoodMagdalena Zych

A simple but powerful particle detector model consists of a two-level system coupled to a field, where the detected particles are the field excitations. This is known as the Unruh-DeWitt detector. Research using this model has often focused on either a completely classical description of the external degrees of freedom of the detector, or a full field-theoretic treatment, where the detector itself is described as a field. Recently there has been much interest in quantum aspects of the detector’s center of mass — either described as moving in superposition along semiclassical trajectories, or dynamically evolving under a non-relativistic Hamiltonian. However, the processes of interest — the absorption or emission of field particles — necessarily change the detector’s rest mass by the amount of energy of the absorbed or emitted field quanta. Neither of the above models can capture such effects. Here we incorporate the quantization of the detector’s mass-energy into the Unruh-DeWitt model. We show that internal energy changes due to emission or absorption are relevant even in the lowest energy limit. Specifically, corrections to transition rates due to the detector’s mass changing cannot be ignored unless the entire center of mass dynamics is also ignored. Our results imply that one cannot have a consistent model of the Unruh-DeWitt detector as a massive particle without including the mass-energy equivalence.

Determinism and Chance from a Humean Perspective

2022年7月20日 星期三 上午1:02|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Frigg, Roman and Hoefer, Carl (2010) Determinism and Chance from a Humean Perspective.

Properties and the Born Rule in GRW Theory

2022年7月20日 星期三 上午1:01|Philsci-Archive: No conditions. Results ordered -Date Deposited.

Frigg, Roman (2018) Properties and the Born Rule in GRW Theory. Collapse of the Wave Function: Models, Ontology, Origin, and Implications..

Exact Solution of the Macroscopic Fluctuation Theory for the Symmetric Exclusion Process

2022年7月19日 星期二 下午6:00|Kirone Mallick, Hiroki Moriya, and Tomohiro Sasamoto|PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Author(s): Kirone Mallick, Hiroki Moriya, and Tomohiro Sasamoto

We present the first exact solution for the time-dependent equations of the macroscopic fluctuation theory (MFT) for the symmetric simple exclusion process by combining a generalization of the canonical Cole-Hopf transformation with the inverse scattering method. For the step initial condition with …

[Phys. Rev. Lett. 129, 040601] Published Tue Jul 19, 2022

Gao, Shan (2022) Quantum suicide and many worlds. [Preprint]

Werndl, Charlotte and Frigg, Roman (2020) Taming Abundance: on the Relation between Boltzmannian and Gibbsian Statistical Mechanics. Statistical Mechanics and Scientific Explanation: Determinism, Indeterminism and Laws of Nature. pp. 617-646.

Frigg, Roman and Werndl, Charlotte (2019) Statistical Mechanics:A Tale of Two Theories. The Monist. pp. 424-438.

Frigg, Roman and Werndl, Charlotte (2020) Boltzmannian Non-Equilibrium and Local Variables. [Preprint]

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