The proof of the long-standing conjecture is presented that Markovian quantum master equations are at odds with quantum thermodynamics under conventional assumptions of fluctuation-dissipation theorems (implying a translation invariant dissipation). Specifically, except for identified systems, persistent system-bath correlations of at least one kind, spatial or temporal, are obligatory for thermalization. A practical methodology to mitigate this constraint in modeling atomic and molecular dynamics with friction is proposed. The quantum optical scheme for its laboratory assessment is outlined.
Quantum Physics From Abstract to Laboratory Space I. Q-States Sustained by Partite Material Systems: Linking A+B and AxB domains via Entanglement. (arXiv:1706.00288v1 [quant-ph])
Authors: Orlando Tapia
The paper focuses on aspects of the measurement problem introducing quantum states (q-states) for measured and measuring systems. The link between non-interacting and interacting quantum systems is first look at. For two independent partite systems logical sums A+B stand for non-interacting q-systems; while a direct product space AxB gathers interacting states. However this latter should support physical q-states with base states that do not separately belong to either A nor B; the latter correspond to bridge states, namely entangled states that can perform as links (bridges) between A+B and AxB domains. Bridge states at laboratory space open possibilities to describe transport in quantized amounts of energy and angular momentum. These link bases sustain entanglements of different kinds. Interactions bring in quantized electromagnetic (em) fields. Matter sustained q-states entangled to em-sustained q-states open bridges to transport information between matter and radiation.
Author(s): Katja Ried, Jean-Philippe W. MacLean, Robert W. Spekkens, and Kevin J. Resch
The landscape of causal relations that can hold among a set of systems in quantum theory is richer than in classical physics. In particular, a pair of time-ordered systems can be related as cause and effect or as the effects of a common cause, and each of these causal mechanisms can be coherent or n…
[Phys. Rev. A 95, 062102] Published Fri Jun 02, 2017
Local hidden-variable model for a recent experimental test of quantum nonlocality and local contextuality
Source:Physics Letters A, Volume 381, Issue 28
Author(s): Brian R. La Cour
An experiment has recently been performed to demonstrate quantum nonlocality by establishing contextuality in one of a pair of photons encoding four qubits; however, low detection efficiencies and use of the fair-sampling hypothesis leave these results open to possible criticism due to the detection loophole. In this Letter, a physically motivated local hidden-variable model is considered as a possible mechanism for explaining the experimentally observed results. The model, though not intrinsically contextual, acquires this quality upon post-selection of coincident detections.
Nature Physics 13, 618 (2017). doi:10.1038/nphys4158
Author: Stephan Schlamminger
Stephan Schlamminger looks at the origins of the Planck constant and its current role in redefining the kilogram.
Nature Physics 13, 533 (2017). doi:10.1038/nphys4159
Author: Jean-Philippe Karr
Improved-accuracy measurements of the ground-state hyperfine splitting in highly charged bismuth ions reveal a surprising discrepancy with the predictions of quantum electrodynamics.
Author(s): Matteo Caiaffa, Andrea Smirne, and Angelo Bassi
Stochastic unravelings represent a useful tool to describe the dynamics of open quantum systems, and standard methods, such as quantum state diffusion (QSD), call for the complete positivity of the open-system dynamics. Here, we present a generalization of QSD, which also applies to positive, but no…
[Phys. Rev. A 95, 062101] Published Thu Jun 01, 2017
H. G. Wells’ Time Traveller inhabits uniform Newtonian time. Where relativistic/quantum travelers into the past follow spacetime curvatures, past-bound Wellsians must reverse their direction of travel relative to absolute time. William Grey and Robin Le Poidevin claim reversing Wellsians must overlap with themselves or fade away piecemeal like the Cheshire Cat. Self-overlap is physically impossible but ‘Cheshire Cat’ fades destroy Wellsians’ causal continuity and breed bizarre fusions of traveler-stages with opposed time-directions. However, Wellsians who rotate in higher-dimensional space can reverse temporal direction without self-overlap, Cheshire Cats or mereological monstrosities. Alas, hyper-rotation in Newtonian space poses dynamic and biological problems, (e.g. gravitational/electrostatic singularities and catastrophic blood-loss). Controllable and survivable Wellsian travel needs topologically-variable spaces. Newtonian space, not Newtonian time, is Wellsians’ real enemy.
Despite certain quantum concepts, such as superposition states, entanglement, ‘spooky action at a distance’ and tunnelling through insulating walls, being somewhat counterintuitive, they are no doubt extremely useful constructs in theoretical and experimental physics. More uncertain, however, is whether or not these concepts are fundamental to biology and living processes. Of course, at the fundamental level all things are quantum, because all things are built from the quantized states and rules that govern atoms. But when does the quantum mechanical toolkit become the best tool for the job? This review looks at four areas of ‘quantum effects in biology’. These are biosystems that are very diverse in detail but possess some commonality. They are all (i)effects in biology: rates of a signal (or information) that can be calculated from a form of the ‘golden rule’ and (ii) they are all protein–pigment (or ligand) complex systems. It is shown, beginning with the rate equation, that all these systems may contain some degree of quantumeffect, and where experimental evidence is available, it is explored to determine how the quantum analysis aids in understanding of the process.
Author(s): Martí Perarnau-Llobet and Theodorus Maria Nieuwenhuizen
The possibility of performing simultaneous measurements in quantum mechanics is investigated in the context of the Curie-Weiss model for a projective measurement. Concretely, we consider a spin–12 system simultaneously interacting with two magnets, which act as measuring apparatuses of two different…
[Phys. Rev. A 95, 052129] Published Tue May 30, 2017
- Yakir Aharonova,b,c,1,
- Eliahu Cohend,1,2,
- Fabrizio Colomboe,
- Tomer Landsbergerc,2,
- Irene Sabadinie,
- Daniele C. Struppaa,b, and
- Jeff Tollaksena,b
Feynman stated that the double-slit experiment “…has in it the heart of quantum mechanics. In reality, it contains the only mystery” and that “nobody can give you a deeper explanation of this phenomenon than I have given; that is, a description of it” [Feynman R, Leighton R, Sands M (1965) The Feynman Lectures on Physics]. We rise to the challenge with an alternative to the wave function-centered interpretations: instead of a quantum wave passing through both slits, we have a localized particle with nonlocal interactions with the other slit. Key to this explanation is dynamical nonlocality, which naturally appears in the Heisenberg picture as nonlocal equations of motion. This insight led us to develop an approach to quantum mechanics which relies on pre- and postselection, weak measurements, deterministic, and modular variables. We consider those properties of a single particle that are deterministic to be primal. The Heisenberg picture allows us to specify the most complete enumeration of such deterministic properties in contrast to the Schrödinger wave function, which remains an ensemble property. We exercise this approach by analyzing a version of the double-slit experiment augmented with postselection, showing that only it and not the wave function approach can be accommodated within a time-symmetric interpretation, where interference appears even when the particle is localized. Although the Heisenberg and Schrödinger pictures are equivalent formulations, nevertheless, the framework presented here has led to insights, intuitions, and experiments that were missed from the old perspective.
Contributed by Yakir Aharonov, March 20, 2017 (sent for review September 26, 2016; reviewed by Pawel Mazur and Neil Turok)