Southwest Quantum Information and Technology

Sixteenth Annual Meeting, February 20-22, 2014
Santa Fe, New Mexico

Full Program | Thursday | Friday | Saturday | All Sessions

2:15pm - 2:45pm	Francisco Elohim Becerra, University of New Mexico
	Robust and high-sensitivity nonorthogonal coherent state discrimination
	Abstract. Measurements for accessing the information contained in quantum states are limited by the inherent noise of these states. Strategies for nonorthogonal state discrimination for optimally extracting information from these states have fundamental interest in quantum mechanics and can allow for communications approaching the quantum limits. Conventional measurements for nonorthogonal state discrimination of coherent states with different phases implement a direct phase-sensitive detection, and can ideally reach the standard quantum limit (SQL). However, measurement strategies based on the quantum properties of these states can allow for better measurements which surpass the SQL and approach the ultimate measurement limits allowed by quantum mechanics. We present the demonstration of a receiver based on adaptive measurements and single-photon counting that unconditionally discriminates multiple nonorthogonal coherent states below the SQL. We also discuss the potential of photon-number-resolving detection to provide robustness under realistic conditions for an adaptive coherent receiver with detectors with finite photon-number resolution.
SESSION 3: Quantum Optics
1:30pm - 2:15pm	Vladan Vuletic, MIT (invited)
	Strongly interacting photons
	Abstract. I discuss two experimental systems where individual photons interact strongly with one another. One is a cavity QED system with an atomic ensemble inside an optical resonator where one photon stored in the ensemble in the form of a collective excitation can switch the transmission of more than one photon through the cavity. The other is a free-space system where photons traveling slowly in an atomic ensemble interact with one another via the coupling to strongly mutually interacting Rydberg states. We observe attractive forces between individual photons leading to the formation of a two-photon bound state, and measure a conditional two-photon phase shift exceeding pi/4.
2:45pm - 3:15pm	Michael Raymer, University of Oregon
	Spectrally Entangled Photon Pairs for Ultrafast Probing of Molecules
	Abstract. We introduce a new method, called entangled photon-pair two-dimensional fluorescence spectroscopy (EPP-2DFS), to sensitively probe the nonlinear electronic response of complex molecular systems. The method incorporates a separated two-photon (Franson) interferometer, which generates time-frequency-entangled photon pairs, into the framework of a fluorescence-detected 2D optical spectroscopic experiment. The EPR-like correlations in time and frequency allow circumventing the usual restrictions imposed by the time-frequency uncertainty principle.