[Aspuru-Guzik Group List] ITAMP lunch seminar - Robert Fickler, University of Ottawa (Thu, 03/03)

*ITAMP Topical Lunch Discussion* Date: Thursday, March 3rd Time: 12:00-1:30 pm Pizza will be served. Location: B-106 @ Center for Astrophysics (60 Garden Street) Directions: after entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, and B-106 is there. *Speaker:* Robert Fickler(University of Ottawa) *Title:*Twisted Photon Entanglement with 10010 Quanta and over large Distances *Abstract: * Photons with twisted phase-fronts can carry an (theoretically) unbounded amount of orbital angular momentum (OAM), which corresponds to a large state space for encoding quantum information. They can be used as laboratory realization of high-dimensional quantum states, which are known to be advantageous in quantum information schemes, e.g. quantum cryptography. Additionally, twisted photons are of fundamental interest to test how much information a single quantum system can carry, how large the dimensionality of entanglement can be or to challenge possible limits of quantum mechanical predictions. In a first experiment, we investigate the latter one by exploring how many quanta of orbital angular momentum an entangled photon pair allows. We employ a novel technique that is able to generate photons with unprecedented high quanta of OAM by reflecting them from a mirror with a surface profile corresponding to the required helical phase. With this we are able to entangle up to ±10010 quanta of OAM of one photon with the polarization of its partner, thereby realizing a quantum experiment involving the largest quantum number so far (to our knowledge). In a second experiment, we investigate the possibility of distributing OAM entangled photons over long distances. Despite pessimistic theoretical predictions, we experimentally demonstrate the successful distribution of entanglement encoded in OAM through a turbulent intra-city link of 3 kilometers. Here, we are able to verify entanglement of photons carrying up to ±2 OAM quanta and show the capability of our setup to distribute at least 11 orthogonal quantum channels. -- Dr. Igor Pikovski Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP) Harvard-Smithsonian Center for Astrophysics 60 Garden St, MS-14; Cambridge, MA 02138, USA Tel.: +1 (617) 496-7613 e-mail: igor.pikovski(a)cfa.harvard.edu www.cfa.harvard.edu/~igor.pikovski/