English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

As known, the degree of entanglement of biphoton states with respect to thetransverse components of photon wave vectors (momenta) or coordinates can becharacterized either by the parameter K associated with the Schmidtdecompositions, or by the parameter R, defined as the ratio of the widths ofthe unconditional and conditional single-particle distributions of biphotonstates. As entanglement is a fundamental characteristics of a state, it must beindependent of a choice of its different representations, i.e. its entanglementparameters must be identical in the coordinate and momentum representations.Likewise, entanglement itself and its characterization parameters must remainconstant along the photon propagation length. It's known, however, that onlythe parameter K obeys these requirements, whereas the parameter R in thecoordinate representation deviates from K beyond the near zone and, thus,becomes inapplicable as a measure of the degree of entablement. But, as shownbelow, there is a way of saving the parameter R by means of modifying itsdefinition in such a way that the modified parameter R turns out to be as goodas the parameter K both in the momentum and coordinate representations, as wellas in the near and far zones and everywhere between them. We will discuss alsopossible ways of measuring this newly defined parameter R experimentally.

SPDC: once again on the parameters of transverse entanglement outside the near zone