Entangled photons from single atoms and molecules
Artikel i vetenskaplig tidskrift, 2018

The first two-photon entanglement experiment performed 50 years ago by Kocher and Commins (KC) provided isolated pairs of entangled photons from an atomic three-state fluorescence cascade. In view of questioning of Bell's theorem, data from these experiments are re-analyzed and shown sufficiently precise to confirm quantum mechanical and dismiss semi-classical theory without need for Bell's inequalities. Polarization photon correlation anisotropy (A) is useful: A is near unity as predicted quantum mechanically and well above the semi-classic range, 0⩽A⩽1/2. Although yet to be found, one may envisage a three-state molecule emitting entangled photon pairs, in analogy with the KC atomic system. Antibunching in fluorescence from single molecules in matrix and entangled photons from quantum dots promise it be possible. Molecules can have advantages to parametric down-conversion as the latter photon distribution is Poissonian and unsuitable for producing isolated pairs of entangled photons. Analytical molecular applications of entangled light are also envisaged.

Bell's inequality

Non-Poissonian entangled photons

Isolated entangled photons

Non-local hidden-variable theories

Quantum entanglement

Bell-free quantum criteria


Bengt Nordén

Chalmers, Kemi och kemiteknik, Kemi och biokemi

Chemical Physics

0301-0104 (ISSN)

Vol. 507 28-33


Atom- och molekylfysik och optik

Annan fysik

Teoretisk kemi



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