421 research outputs found
Measuring confidence and uncertainty during the financial crisis : evidence from the CFS survey
The CFS survey covers individual situations of banks and other companies of the financial sector during the financial crisis. This provides a rare possibility to analyze appraisals, expectations and forecast errors of the core sector of the recent turmoil. Following standard ways of aggregating individual survey data, we first present and introduce the CFS survey by comparing CFS indicators of confidence and predicted confidence to ifo and ZEW indicators. The major contribution is the analysis of several indicators of uncertainty. In addition to well established concepts, we introduce innovative measures based on the skewness of forecast errors and on the share of ‘no response’ replies. Results show that uncertainty indicators fit quite well with pattern of real and financial time series of the time period 2007 to 2010. Business Sentiment , Financial Crisis , Survey Indicator , Uncertaint
Remote state preparation of a photonic quantum state via quantum teleportation
We demonstrate an experimental realization of remote state preparation via
the quantum teleportation algorithm, using an entangled photon pair in the
polarization degree of freedom as the quantum resource. The input state is
encoded on the path of one of the photons from the pair. The improved
experimental scheme allows us to control the preparation and teleportation of a
state over the entire Bloch sphere with a resolution of the degree of mixture
given by the coherence length of the photon pair. Both the preparation of the
input state and the implementation of the quantum gates are performed in a pair
of chained displaced Sagnac interferometers, which contribute to the overall
robustness of the setup. An average fidelity above 0.9 is obtained for the
remote state preparation process. This scheme allows for a prepared state to be
transmitted on every repetition of the experiment, thus giving an intrinsic
success probability of 1.Comment: 6 pages, 4 figures, accepted for publication in Applied Physics
B:Lasers and Optic
Noisy quantum teleportation: An experimental study on the influence of local environments
We report experimental results on the action of selected local environments
on the fidelity of the quantum teleportation protocol, taking into account
non-ideal, realistic entangled resources. Different working conditions are
theoretically identified, where a noisy protocol can be made almost insensitive
to further addition of noise. We put to test these conditions on a photonic
implementation of the quantum teleportation algorithm, where two polarization
entangled qubits act as the entangled resource and a path qubit on Alice
encodes the state to be teleported. Bob's path qubit is used to implement a
local environment, while the environment on Alice's qubit is simulated as a
weighed average of different pure states. We obtain a good agreement with the
theoretical predictions, we experimentally recreate the conditions to obtain a
noise-induced enhancement of the protocol fidelity, and we identify parameter
regions of increased insensibility to interactions with specific noisy
environments.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.
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