Controlled multi-photon subtraction with cascaded Rydberg superatoms as single-photon absorbers.

The preparation of light pulses with well-defined quantum properties requires precise control at the individual photon level. Here, we demonstrate exact and controlled multi-photon subtraction from incoming light pulses. We employ a cascaded system of tightly confined cold atom ensembles with strong, collectively enhanced coupling of photons to Rydberg states.

Storage and control of optical photons using Rydberg polaritons.

We use a microwave field to control the quantum state of optical photons stored in a cold atomic cloud. The photons are stored in highly excited collective states (Rydberg polaritons) enabling both fast qubit rotations and control of photon-photon interactions. Through the collective read-out of these pseudospin rotations it is shown that the microwave field modifies the long-range interactions between polaritons.

Sources of unwanted variability in measurement and description of skin surface topography.

Background/aims: Quantitative measurement of skin roughness has proved to be a valuable tool in the efficacy-control of external applications, but it suffers from not yielding easily comparable results. The most important sources of inter-observer variability are high-pass filters used to separate roughness and waviness, and low-pass filters which result from the finite resolution of the instrument or from the finite sampling interval of digital measurement. In the present study, the effects of high-pass filters and sampling intervals on the roughness measured were investigated.

Quantitative surface topography as a tool in the differential diagnosis between melanoma and naevus.

Background/aims: The mainstays of the clinical diagnosis of melanoma are asymmetry, border irregularity, color variegation, and a diameter >6 mm, and any major progress in diagnostic accuracy will probably be related to the development of additional criteria. Such independent criteria might arise from the study of the geometry of the tumour surface, because this quality has been substantially disregarded until now. Our work is aimed at utilizing the surface topography for the differential diagnosis between malignant melanoma and naevocytic naevus.