Electromagnetically induced transparency in a mono-isotopic 167Er:7LiYF4 crystal below 1 Kelvin: microwave photonics approach.

Electromagnetically induced transparency allows for the controllable change of absorption properties, which can be exploited in a number of applications including optical quantum memory. In this paper, we present a study of the electromagnetically induced transparency in a 167Er:7LiYF4 crystal at low magnetic fields and ultra-low temperatures. The experimental measurement scheme employs an optical vector network analysis that provides high precision measurement of amplitude, phase and group delay and paves the way towards full on-chip integration of optical quantum memory setups. We found that sub-Kelvin temperatures are the necessary requirement for observing electromagnetically induced transparency in this crystal at low fields. A good agreement between theory and experiment is achieved by taking into account the phonon bottleneck effect.

Quantum interference in the presence of a resonant medium.

Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting. We insert a sample in the Hong-Ou-Mandel interferometer and observe the modification of the two-photon interference pattern, which is driven by the coherent response of the medium, determined by the dephasing time. The dephasing time is then inferred from the observed pattern. This effect is distinctively different from the basic effect of spectral filtering, which was studied in earlier works. In addition to its ease of use, our technique does not require compensation of group velocity dispersion and does not induce photo-damage of the samples. Our technique will be useful for characterization of ultrafast phase relaxation processes in material science, chemistry, and biology.

Biantennary oligoglycines and glyco-oligoglycines self-associating in aqueous medium.

Oligoglycines designed in a star-like fashion, so-called tri- and tetraantennary molecules, were found to form highly ordered supramers in aqueous medium. The formation of these supramers occurred either spontaneously or due to the assistance of a mica surface. The driving force of the supramer formation is hydrogen bonding, the polypeptide chain conformation is related to the folding of helical polyglycine II (PG II). Tri- and tetraantennary molecules are capable of association if the antenna length reach 7 glycine (Gly) residues. Properties of similar biantennary molecules have not been investigated yet, and we compared their self-aggregating potency with similar tri- and tetraantennary analogs. Here, we synthesized oligoglycines of the general formula R-Gly n -Х-Gly n -R (X = -HN-(СН2) m -NH-, m = 2, 4, 10; n = 1-7) without pendant ligands (R = H) and with two pendant sialoligands (R = sialic acid or sialooligosaccharide). Biantennary oligoglycines formed PG II aggregates, their properties, however, differ from those of the corresponding tri- and tetraantennary oligoglycines. In particular, the tendency to aggregate starts from Gly4 motifs instead of Gly7. The antiviral activity of end-glycosylated peptides was studied, and all capable of assembling glycopeptides demonstrated an antiviral potency which was up to 50 times higher than the activity of peptide-free glycans.