Weekly Papers on Quantum Foundations (40)

Non-Abelian symmetry can increase entanglement entropy. (arXiv:2209.14303v1 [quant-ph])

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Shayan Majidy, Aleksander Lasek, David A. Huse, Nicole Yunger Halpern

Fri Sep 30 2022 08:52:12 (9 minutes)

# 1.

The pillars of quantum theory include entanglement and operators’ failure to commute. The Page curve quantifies the bipartite entanglement of a many-body system in a random pure state. This entanglement is known to decrease if one constrains extensive observables that commute with each other (Abelian “charges”). Non-Abelian charges, which fail to commute with each other, are of current interest in quantum thermodynamics. For example, noncommuting charges were shown to reduce entropy-production rates and may enhance finite-size deviations from eigenstate thermalization. Bridging quantum thermodynamics to many-body physics, we quantify the effects of charges’ noncommutation — of a symmetry’s non-Abelian nature — on Page curves. First, we construct two models that are closely analogous but differ in whether their charges commute. We show analytically and numerically that the noncommuting-charge case has more entanglement. Hence charges’ noncommutation can promote entanglement.

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Experimental Implementation of an Efficient Test of Quantumness. (arXiv:2209.14316v1 [quant-ph])

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quant-ph updates on arXiv.org

Laura Lewis, Daiwei Zhu, Alexandru Gheorghiu, Crystal Noel, Or Katz, Bahaa Harraz, Qingfeng Wang, Andrew Risinger, Lei Feng, Debopriyo Biswas, Laird Egan, Thomas Vidick, Marko Cetina, Christopher Monroe

Fri Sep 30 2022 08:52:11 (9 minutes)

# 2.

A test of quantumness is a protocol where a classical user issues challenges to a quantum device to determine if it exhibits non-classical behavior, under certain cryptographic assumptions. Recent attempts to implement such tests on current quantum computers rely on either interactive challenges with efficient verification, or non-interactive challenges with inefficient (exponential time) verification. In this paper, we execute an efficient non-interactive test of quantumness on an ion-trap quantum computer. Our results significantly exceed the bound for a classical device’s success.

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Remarks on Rydberg atom constraints on the cosmological constant. (arXiv:2209.14484v1 [gr-qc])

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gr-qc updates on arXiv.org

Stephen L. Adler

Fri Sep 30 2022 08:52:04 (9 minutes)

# 3.

In an interesting paper, Kundu, Pradhan, and Rosenzweig have obtained a bound on the cosmological constant using high accuracy energy level measurements of Rydberg atoms. We show here that the effective potential they use can be derived from the geodesic equation for the atomic electron, and that this method shows that the energy shifts are computable from the leading cosmological constant contribution to the temporal component of the gravitational metric. To within a small factor, bounds of similar magnitude are obtained from the standard cosmological constant action, in which “dark energy” is taken as a vacuum energy, and from a novel cosmological constant action based on Weyl scaling invariance, in which dark energy is not a vacuum energy. So the Rydberg atom bound does not reveal whether or not the vacuum gravitates.

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Quantum Speed Limit for States with a Bounded Energy Spectrum

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PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Gal Ness, Andrea Alberti, and Yoav Sagi

Thu Sep 29 2022 18:00:00 (15 hours)

# 4.

Author(s): Gal Ness, Andrea Alberti, and Yoav Sagi

Quantum speed limits set the maximal pace of state evolution. Two well-known limits exist for a unitary time-independent Hamiltonian: the Mandelstam-Tamm and Margolus-Levitin bounds. The former restricts the rate according to the state energy uncertainty, while the latter depends on the mean energy …

[Phys. Rev. Lett. 129, 140403] Published Thu Sep 29, 2022

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Einstein’s Happiest Moment: The Equivalence Principle. (arXiv:2209.13781v1 [physics.hist-ph])

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physics.hist-ph updates on arXiv.org

Paul Worden, James Overduin

Thu Sep 29 2022 09:34:32 (23 hours)

# 5.

Einstein’s happiest thought was his leap from the observation that a falling person feels no gravity to the realization that gravity might be equivalent to acceleration. It affects all bodies in the same way because it is a property of spacetime — its curvature — not a force propagating through spacetime (like electromagnetic or nuclear forces). When expressed in a way that is manifestly independent of the choice of coordinates, this idea became General Relativity. But the ground for what is now known as the “equivalence principle” was laid long before Einstein, affording a fascinating example of the growth of a scientific idea through the continuous interplay between theory and experiment. That story continues through the present era, with improved techniques and measurements, and in the new environment of space. Theoretically, equivalence is now understood to rank with Lorentz invariance as one of nature’s most fundamental principles. Violations of equivalence are generically predicted by attempts to unify gravity with “non-geometrical” fundamental interactions, but there is no consensus on the form that these violations will take. Experimental tests of equivalence thus face the challenge of striving simultaneously for the highest possible sensitivity and diversity in test materials.

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Quantum mechanics requires “conspiracy”

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

Wed Sep 28 2022 00:25:50 (2 days)

# 6.

Stoica, Ovidiu Cristinel (2022) Quantum mechanics requires “conspiracy”. [Preprint]

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Revising scientific concepts with multiple meanings: beyond pluralism and eliminativism

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

Wed Sep 28 2022 00:24:10 (2 days)