Southwest Quantum Information and Technology

Fourteenth Annual Meeting, February 16-19, 2012
Albuquerque, New Mexico

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SESSION 8: Superconductors, Resonators, and Optomechanics - Alvarado "D"
Session Chair:
8:30am-9:15am	Robert Schoelkopf, Yale University (invited)
	Entanglement and Quantum Algorithms with Superconducting Circuits
	Abstract. By using the unique properties of quantum physics, such as entanglement and superposition, quantum computers are predicted to be vastly more powerful than their classical counterparts for certain tasks. While some technologies, such as NMR and trapped ions, have succeeded in making and manipulating a handful of quantum bits (qubits), they look quite different from a conventional computer, and there are many obstacles to building large-scale processors. At Yale, we use superconducting circuits to make macroscopic, solid-state qubits which are controlled and measured entirely by a sequence of electronic pulses on wires. These devices have advanced to the point where we can generate and detect highly-entangled states, and perform universal quantum gates. I will describe recent experiments showing two and three qubit entanglement, the operation of Grover’s search algorithm, and the successful realization of simple quantum error correction.
9:15am-9:45am	Frederick Strauch, Williams College
	Entangled State Synthesis for Superconducting Resonator Qudits
	Abstract. I will present a theoretical analysis of methods to synthesize entangled states of two superconducting resonators, and their extension to general unitary operations on resonators as qudits. These methods use experimentally demonstrated interactions of resonators with artificial atoms, and offer efficient routes to generate nonclassical states and processes for high-dimensional quantum systems.
9:45am-10:15am	Lin Tian, University of California, Merced
	Transient and Adiabatic Quantum State Transfer in Optomechanical Systems
	Abstract. Light-matter interaction in optomechanical systems can be explored for optical quantum information processing. Here, we present transient and adiabatic schemes for quantum state transfer between optical modes with distinct frequencies via the optomechanical forces. In the transient scheme, red-detuned laser pulses generate state-swappings between the optical and the mechanical modes to achieve the state transfer. In the adiabatic scheme, the cavity dark mode that is immune to the mechanical noise is explored to transfer quantum states. The transfer fidelity for gaussian states can be derived by solving the Langevin equation in the adiabatic limit.
10:45am-11:30am	Stephanie Wehner, Centre for Quantum Technologies, National University of Singapore (invited)
	Quantum to Classical Randomness Extractors
	Abstract. Even though randomness is an essential resource for many information processing tasks, it is not easily found in nature. The goal of randomness extraction is to distill (almost) perfect randomness from a weak source of randomness. When the source yields a classical string X, many extractor constructions are known. Yet, when considering a physical randomness source, X is itself ultimately the result of a measurement on an underlying quantum system. When characterizing the power of a source to supply randomness it is hence a natural question to ask, how much classical randomness we can extract from a quantum state. To tackle this question we here take on the study of quantum-to-classical randomness extractors (QC-extractors). We provide constructions of QC-extractors based on measurements in a full set of mutually unbiased bases (MUBs), and certain single qubit measurements. As the first application, we show that any QC-extractor gives rise to entropic uncertainty relations with respect to quantum side information. Such relations were previously only known for two measurements. As the second application, we resolve the central open question in the noisy-storage model [Wehner et al., PRL 100, 220502 (2008)] by linking security to the quantum capacity of the adversary's storage device.