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Briegel H.J.,University of Innsbruck | Briegel H.J.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | Muller T.,University of Konstanz
Minds and Machines | Year: 2015

Can we sensibly attribute some of the happenings in our world to the agency of some of the things around us? We do this all the time, but there are conceptual challenges purporting to show that attributable agency, and specifically one of its most important subspecies, human free agency, is incoherent. We address these challenges in a novel way: rather than merely rebutting specific arguments, we discuss a concrete model that we claim positively illustrates attributable agency in an indeterministic setting. The model, recently introduced by one of the authors in the context of artificial intelligence, shows that an agent with a sufficiently complex memory organization can employ indeterministic happenings in a meaningful way. We claim that these considerations successfully counter arguments against the coherence of libertarian (indeterminism-based) free will. © 2015, The Author(s). Source

Slodicka L.,University of Innsbruck | Hetet G.,University of Innsbruck | Rock N.,University of Innsbruck | Schindler P.,University of Innsbruck | And 3 more authors.
Physical Review Letters | Year: 2013

A scheme for entangling distant atoms is realized, as proposed in the seminal paper by. The protocol is based on quantum interference and detection of a single photon scattered from two effectively one meter distant laser cooled and trapped atomic ions. The detection of a single photon heralds entanglement of two internal states of the trapped ions with high rate and with a fidelity limited mostly by atomic motion. Control of the entangled state phase is demonstrated by changing the path length of the single-photon interferometer. © 2013 American Physical Society. Source

Brandl M.F.,University of Innsbruck | Schindler P.,University of Innsbruck | Monz T.,University of Innsbruck | Blatt R.,University of Innsbruck | Blatt R.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften
Applied Physics B: Lasers and Optics | Year: 2016

Trapping ions in Paul traps require high radio frequency voltages, which are generated using resonators. When operating traps in a cryogenic environment, an in-vacuum resonator showing low loss is crucial to limit the thermal load to the cryostat. In this study, we present a guide for the design and production of compact, shielded cryogenic resonators. We produced and characterized three different types of resonators and furthermore demonstrate efficient impedance matching of these resonators at cryogenic temperatures. © 2016, The Author(s). Source

Schindler P.,University of Innsbruck | Monz T.,University of Innsbruck | Nigg D.,University of Innsbruck | Barreiro J.T.,University of Innsbruck | And 7 more authors.
Physical Review Letters | Year: 2013

In general, a quantum measurement yields an undetermined answer and alters the system to be consistent with the measurement result. This process maps multiple initial states into a single state and thus cannot be reversed. This has important implications in quantum information processing, where errors can be interpreted as measurements. Therefore, it seems that it is impossible to correct errors in a quantum information processor, but protocols exist that are capable of eliminating them if they affect only part of the system. In this work we present the deterministic reversal of a fully projective measurement on a single particle, enabled by a quantum error-correction protocol in a trapped ion quantum information processor. We further introduce an in-sequence, single-species recooling procedure to counteract the motional heating of the ion string due to the measurement. © 2013 American Physical Society. Source

Barz S.,University of Vienna | Vasconcelos R.,University of Vienna | Greganti C.,University of Vienna | Zwerger M.,University of Innsbruck | And 5 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

In measurement-based quantum computing an algorithm is performed by measurements on highly entangled resource states. To date, several implementations were demonstrated, most of them assuming perfect noise-free environments. Here we consider measurement-based information processing in the presence of noise and demonstrate quantum error detection. We implement the protocol using a four-qubit photonic cluster state where we first encode a general qubit nonlocally such that phase errors can be detected. We then read out the error syndrome and analyze the output states after decoding. Our demonstration shows a building block for measurement-based quantum computing which is crucial for realistic scenarios. © 2014 American Physical Society. Source

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