Physics Department Colloquia |
Events During the Week of April 6th through April 13th, 2008
Monday, April 7th, 2008
- No events scheduled
Tuesday, April 8th, 2008
- No events scheduled
Wednesday, April 9th, 2008
- No events scheduled
Thursday, April 10th, 2008
- No events scheduled
Friday, April 11th, 2008
- Trapping and Counting Photons without Destroying Them: A New Way to Look at Light
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Serge Haroche, Ecole Normale Superieure
- Abstract: An experiment realizing a quantum non-demolition measurement of a microwave field trapped in a cavity will be described. While usual photo-detection destroys light quanta, we have developed a new way to count photons without absorbing them, making it possible to measure the same field repeatedly. We use as detectors atoms prepared in a superposition of Rydberg states which cross the cavity one at a time and behave as microscopic clocks whose ticking rate is affected by light. By measuring the clocks' delay, information is extracted without energy absorption and the field progressively collapses into a well-defined photon number state. Quantum jumps between decreasing photon numbers are recorded as the cavity field subsequently relaxes towards vacuum. This new way to "look" at light also generates coherent superpositions of photonic states with different phases called "Schroedinger cats". By monitoring the evolution of these states, we directly observe the process of decohere once in experiments opening new avenues for the exploration of the boundary between the quantum and classical worlds.
- Host: Yavuz