Southwest Quantum Information and Technology

Twelfth Annual Meeting, February 18-21, 2010
Santa Fe, New Mexico

Full Program | Thursday | Friday | Saturday | Sunday

SESSION 10: Breakout III - Quantum Communication
Session Chair:
3:30-4:00	Artur Scherer, Institute for Quantum Information Science at the University of Calgary
	Mathematical model for real-world entanglement swapping and applications to practical long-distance quantum key distribution
	Abstract. Entanglement swapping between photon pairs is a key building block in entanglement-based quantum communication schemes using quantum relays or quantum repeaters to overcome the range limits of long-distance quantum key distribution (QKD). We present a nonperturbative mathematical model for practical entanglement swapping, which accounts for real-world imperfections due to detector inefficiencies, detector dark counts and the unavoidable multipair events of current realistic sources of entangled photon pairs. Our closed-form solution for the actual quantum states prepared by realistic entanglement swapping is useful for planning long-distance QKD experiments. In particular, our analysis provides the optimal photon-pair production rate (brightness) of the sources that maximizes the secret key rate for a given distance between a sender (Alice) and a receiver (Bob).
4:00-4:30	Netanel Lindner, Caltech - Institute of Quantum Information
	A photonic cluster state machine gun
	Abstract. We present a method to convert certain single photon sources into devices capable of emitting large strings of photonic cluster state in a controlled and pulsed ‘‘on-demand’’ manner. Standard spin errors, such as dephasing, are shown to affect only 1 or 2 of the emitted photons at a time. This allows for the use of standard fault tolerance techniques, and shows that the photonic machine gun can be fired for arbitrarily long times. Using realistic parameters for current quantum dot sources, we conclude high entangled photon emission rates are achievable, with Pauli-error rates per photon of less than 0.2%. For quantum dot sources, the method has the added advantage of alleviating the problematic issues of obtaining identical photons from independent, nonidentical quantum dots, and of exciton dephasing.
4:30-5:00	Hayden McGuinness, University of Oregon
	Frequency Translation of Single-Photon States by Four-Wave Mixing in a Photonic Crystal Fiber
	Abstract. We study the effect of frequency translation of single-photon states in optical fiber through use of the Bragg scattering four-wave mixing process. Preliminary evidence shows that we have successfully translated single-photon wave-packets from wavelength 696 nm to 680 nm, while maintaining photon statistics in the nonclassical regime.
5:00-5:30	Ben Fortescue, Institute for Quantum Information Science, University of Calgary
	Quantum secret sharing with qudit graph states
	Abstract. We present a formalism for quantum secret sharing using graph states of systems with prime dimension. As we show, such states allow for a unified structure for the sharing of classical and quantum secrets over both classical and quantum channels. We give explicit protocols for three varieties of threshold secret sharing within this formalism. Joint work with Adrian Keet and Barry C. Sanders.