BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69f27c1c73bdb DTSTART:20211216T090000Z SEQUENCE:0 TRANSP:OPAQUE DTEND:20211216T120000Z LOCATION:ICFO Auditorium and Online (Teams) SUMMARY:ICFO | VINDHIYA PRAKASH CLASS:PUBLIC DESCRIPTION:This thesis describes experimental work to generate and charact erise single photons and photon pairs\, with frequency content suitable fo r controlled interaction with cold rubidium atoms. We describe a photon-pa ir source\, consisting of a cavity-enhanced spontaneous parametric down-co nversion (CE-SPDC) system\, followed by Fabry-Perot interferometer (FPI) f ilters\, that produces narrowband photon pairs that have a bandwidth of &a symp\; 5 MHz. Both photons from the photon-pair source are matched to the D1 line in atomic rubidium. Type-II phase matching\, a tuneable-birefringe nce resonator and MHz-resolution pump tuning are used to achieve independe nt frequency control over each photon in the pair with MHz precision\, ena bling them to excite different hyperfine transitions in rubidium. We have designed and implemented tuneable FPI\, also with ~ MHz control over their resonance frequencies\, to isolate a single frequency mode-pair from the CE-SPDC source. The filters have ~ 90 % on-resonance transmission and exti nguish unwanted frequency components by over 20 dB. The thesis includes pr edictions of the two-photon spectra at the output of the CE-SPDC source\, and also after the filters\, based on existing theoretical models of CE-SP DC. We measure the two-photon linewidth\, the number of modes in an emissi on cluster and the spacing between clusters\, the second-order cross-corre lation and heralded autocorrelation functions\, and find good agreement wi th predictions. We demonstrate independent tuneability of the signal and i dler frequencies by atomic absorption spectroscopy with the filtered CE-SP DC output as the light source. We also report a technique to resolve narro w frequency differences between photons with a high frequency resolution. The technique\, which we call autoheterodyne characterisation\, can measur e the photon-pair joint spectra by detecting the time-correlation beat-not e when nondegenerate photon-pairs interfere at a beamsplitter. It implemen ts a temporal analog of the Ghosh-Mandel effect with one photon counter an d a time-resolved Hong-Ou-Mandel interference with two. We provide a compl ete theoretical description of the process and show how the distribution o f sum and difference frequencies in the photon-pair spectrum can be obtain ed from measured correlation functions. Through a power spectral analysis of the correlation measurements\, the strengths\, linewidths and relative frequencies of the spectral content in the two-photon state is obtained. W ith this\, it is possible to quantify the contribution of undesired freque ncy modes when a single mode output is required. We analyse the applicatio n of this technique to photon-pairs that are produced by narrowband pumpin g and are strongly anti-correlated in frequency\, and to pairs with reduce d frequency correlations produced by broadband pumping. Experimentally\, w e demonstrate this technique using photon-pairs from the filtered CE-SPDC source described in the previous paragraph\, that have a frequency separat ion of ~ 200 MHz. From the results\, we quantify the performance of the fi lters and verify the accuracy of our model for the two-photon joint spectr a from this source. Thursday\, December 16\, 2021\, 10:00. ICFO Auditorium and Online (Teams) Thesis Director: \;Prof Dr. Morgan Mitchell DTSTAMP:20260429T214604Z END:VEVENT END:VCALENDAR