Southwest Quantum Information and Technology

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

Full Program | Thursday | Friday | Saturday | All Sessions

SESSION 12: Quantum Information Theory II
1:45am - 2:30pm	Emanuel Knill, University of Colorado at Boulder (invited)
	Certifying violations of local realism
	Abstract. Many applications of quantum systems require measurements that verify the presence of sufficiently strong quantum correlations. The probability of the following unwanted event must be extremely small: The event where the correlations are not sufficiently strong but one is nevertheless convinced that they are strong enough. Important examples of quantum correlation occur in experiments showing violations of Bell's inequalities, which are thought to invalidate local realism. This is a review of how such violations are quantified and robustly certified, with or without predetermined Bell's inequalities.
2:30pm - 3:15pm	Ben Reichardt, University of Southern California (invited)
	Classical command of quantum systems
	Abstract. Can a classical experimentalist command an untrusted quantum system to realize arbitrary quantum dynamics, aborting if it misbehaves? We give a way for a classical system to certify the joint, entangled state of a bipartite quantum system, as well as command the application of specific operators on each subsystem. This is accomplished by showing a strong converse to Tsirelson's optimality result for the CHSH game: the only way to win many games is if the bipartite state is close to the tensor product of EPR states, and the measurements are the optimal CHSH measurements on successive qubits. This leads directly to a scheme for device-independent quantum key distribution. Control over the state and operators can also be leveraged to create more elaborate protocols for reliably realizing general quantum circuits. Joint work with Falk Unger and Umesh Vazirani.
3:15pm - 3:45pm	Jason Twamley, Macquarie University
	All-Optical Switching and Router via the Direct Quantum Control of Coupling between Cavity Modes
	Abstract. We describe a scheme to execute all-optical routing of photonic information by optically controlling the internal quantum state of a individual scatterer coupled to two independent cavity modes. We show that through this quantum control one can dynamically and rapidly modulate the cavity coupling. This allows all-optical modulation of intercavity couplings via ac Stark or shuffle (stimulated Raman adiabatic passage) control of the scatterer’s internal states, and from this modulation, we show that we can perform all-optical switching and all-optical routing with near-unit switching contrast and with high bandwidth. [1] K. Xia and J. Twamley, Phys Rev X 3, 031013 (2013)