Extremal quantum states

[Lawrence Crowell]

This has been making the pop-sci pubs of late. This does look interesting and appears to be some version of stable large quantization state, similar to an einselected state. 

LC

Extremal quantum states

Aaron Z. Goldberg, Andrei B. Klimov, Markus Grassl, Gerd Leuchs, Luis L. Sánchez-Soto

The striking differences between quantum and classical systems predicate disruptive quantum technologies. We peruse quantumness from a variety of viewpoints, concentrating on phase-space formulations because they can be applied beyond particular symmetry groups. The symmetry-transcending properties of the Husimi Q function make it our basic tool. In terms of the latter, we examine quantities such as the Wehrl entropy, inverse participation ratio, cumulative multipolar distribution, and metrological power, which are linked to intrinsic properties of any quantum state. We use these quantities to formulate extremal principles and determine in this way which states are the most and least "quantum;" the corresponding properties and potential usefulness of each extremal principle are explored in detail. While the extrema largely coincide for continuous-variable systems, our analysis of spin systems shows that care must be taken when applying an extremal principle to new contexts.  

https://arxiv.org/abs/2010.04732

[scerir]

https://link.springer.com/article/10.1007/s10701-020-00398-6?fbclid=IwAR1_T-xMzYavf_FyyMdIb4iPyKrpzdqh2s3xYDK4w3hi8lvUDzC4uXznlMY

[Lawrence Crowell]

This is a somewhat different topic. The issue I think is resolved when we realize there is a difference between the generator of a group, which is a Lie algebraic structure, and the observables of a system which are Jordan algebraic. In this setting there is a correspondence between time or with i = √-1 for it = τ a correspondence between the unitary factor e^{-iHt/ħ} ↔ e^{-Eβ} and time with temperature τ = ħβ. 

Thanks for the paper, I will try to read it soon.

LC

On Wednesday, November 25, 2020 at 9:44:19 AM UTC-6 sce...@libero.it wrote:

https://link.springer.com/article/10.1007/s10701-020-00398-6?fbclid=IwAR1_T-xMzYavf_FyyMdIb4iPyKrpzdqh2s3xYDK4w3hi8lvUDzC4uXznlMY