BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT DTSTART:20250309T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20241103T010000 TZOFFSETFROM:-0400 TZOFFSETTO:-0500 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:EST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20241116T134610Z UID:81655D5A-AE08-43C1-B33C-9D45AC923B49 DTSTART;TZID=America/New_York:20241115T110000 DTEND;TZID=America/New_York:20241115T120000 DESCRIPTION:Montréal Quantum Photonics Seminar Series\n\nAbstract: When a pulse of light traverses a material\, it incurs a time delay referred to a s the group delay. Should the group delay experienced by photons be attrib uted to the time they spend as atomic excitations? However reasonable this connection may seem\, it appears problematic when the frequency of the li ght is close to the atomic resonance\, as the group delay becomes negative in this regime. To address this question\, I used the cross-Kerr effect t o probe the degree of atomic excitation caused by a resonant transmitted p hoton by measuring the phase shift on a separate beam that is weak and off -resonant. These results\, over a range of pulse durations and optical dep ths\, are consistent with the recent theoretical prediction that the mean atomic excitation time caused by a transmitted photon (as measured via the time integral of the observed phase shift) equals the group delay experie nced by the light. Specifically\, I measured mean atomic excitation times ranging from (−0.82 ±0.31)τ0 for the most narrowband pulse to (0.54 ± 0.28)τ0 for the most broadband pulse.\n\nI report these times normalized to the non-post-selected excitation time τ0\, which is equal to the scatt ering (absorption) probability multiplied by the atomic lifetime τsp. The se results suggest that negative values taken by times such as the group d elay have more physical significance than has generally been appreciated.\ n\nBio: Daniela Angulo is a physicist from Colombia who recently completed her PhD at the University of Toronto\, focusing on experimental light-mat ter interaction. Under the supervision of Aephraim Steinberg\, her researc h explored the behavior of photons in atomic clouds using weak measurement s. She is passionate about teaching and science communication. Outside the lab\, she is an avid cyclist and musician.\n\nLocal J-1035 Pavillon J. A. Bombardier\, Polytechnique Montréal\, Montréal\, Quebec\, Canada LOCATION:Local J-1035 Pavillon J. A. Bombardier\, Polytechnique Montréal\, Montréal\, Quebec\, Canada ORGANIZER:Benjamin.crockett@ieee.org SEQUENCE:5 SUMMARY:Can a photon spend a negative amount of time inside an atom cloud? URL;VALUE=URI:https://events.vtools.ieee.org/m/445186 X-ALT-DESC:Description: <br /><p><img src="https://events.vtools.ieee.org/v tools_ui/media/display/cedfc096-b492-48b7-9548-5751ee76ec6d" width="896" h eight="503"></p>\n<p class="x_MsoNormal"><strong>Montr&eacute\;al Quantum Photonics Seminar Series</strong></p>\n<p class="x_MsoNormal"><strong>Abst ract:</strong>&nbsp\;When a pulse of light traverses a material\, it incur s a time delay referred to as the group delay. Should the group delay expe rienced by photons be attributed to the time they spend as atomic excitati ons? However reasonable this connection may seem\, it appears problematic when the frequency of the light is close to the atomic resonance\, as the group delay becomes negative in this regime. To address this question\, I used the cross-Kerr effect to probe the degree of atomic excitation caused by a resonant transmitted photon by measuring the phase shift on a separa te beam that is weak and off-resonant. These results\, over a range of pul se durations and optical depths\, are consistent with the recent theoretic al prediction that the mean atomic excitation time caused by a transmitted photon (as measured via the time integral of the observed phase shift) eq uals the group delay experienced by the light. Specifically\, I measured m ean atomic excitation times ranging from (&minus\;0.82 &plusmn\;0.31)&tau\ ;0 for the most narrowband pulse to (0.54 &plusmn\;0.28)&tau\;0 for the mo st broadband pulse.</p>\n<p class="x_MsoNormal">I report these times norma lized to the non-post-selected excitation time &tau\;0\, which is equal to the scattering (absorption) probability multiplied by the atomic lifetime &tau\;sp. These results suggest that negative values taken by times such as the group delay have more physical significance than has generally been appreciated.</p>\n<p class="x_MsoNormal">&nbsp\;</p>\n<p class="x_MsoNorm al"><strong>Bio:</strong> Daniela Angulo is a physicist from Colombia who recently completed her PhD at the University of Toronto\, focusing on expe rimental light-matter interaction. Under the supervision of Aephraim Stein berg\, her research explored the behavior of photons in atomic clouds usin g weak measurements. She is passionate about teaching and science communic ation. Outside the lab\, she is an avid cyclist and musician.</p> END:VEVENT END:VCALENDAR