Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften

Innsbruck, Austria

Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften

Innsbruck, Austria
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Mautner J.,University of Innsbruck | Mautner J.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | Makmal A.,University of Innsbruck | Makmal A.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | And 7 more authors.
New Generation Computing | Year: 2015

We study the model of projective simulation (PS), a novel approach to artificial intelligence based on stochastic processing of episodic memory which was recently introduced. 2) Here we provide a detailed analysis of the model and examine its performance, including its achievable efficiency, its learning times and the way both properties scale with the problems’ dimension. In addition, we situate the PS agent in different learning scenarios, and study its learning abilities. A variety of new scenarios are being considered, thereby demonstrating the model’s flexibility. Furthermore, to put the PS scheme in context, we compare its performance with those of Q-learning and learning classifier systems, two popular models in the field of reinforcement learning. It is shown that PS is a competitive artificial intelligence model of unique properties and strengths. © 2015, Ohmsha and Springer Japan.


Guerreschi G.G.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | Guerreschi G.G.,University of Innsbruck | Tiersch M.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | Tiersch M.,University of Innsbruck | And 3 more authors.
Chemical Physics Letters | Year: 2013

The yield of radical pair reactions is influenced by magnetic fields well beyond the levels expected from energy considerations. This dependence can be traced back to the microscopic dynamics of electron spins and constitutes the basis of chemical compasses. Here we propose a new experimental approach based on molecular photoswitches to achieve additional control on the chemical reaction and allow short-time resolution of the spin dynamics. Our proposal enables experiments to test some of the standard assumptions of the radical pair model and improves the sensitivity of a paradigmatic model of chemical magnetometer by up to two orders of magnitude. © 2013 Elsevier B.V. All rights reserved.


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).


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.


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.


Nigg D.,University of Innsbruck | Barreiro J.T.,University of Innsbruck | Schindler P.,University of Innsbruck | Mohseni M.,Massachusetts Institute of Technology | And 6 more authors.
Physical Review Letters | Year: 2013

We report on the implementation of a quantum process tomography technique known as direct characterization of quantum dynamics applied on coherent and incoherent single-qubit processes in a system of trapped Ca+40 ions. Using quantum correlations with an ancilla qubit, direct characterization of quantum dynamics reduces substantially the number of experimental configurations required for a full quantum process tomography and all diagonal elements of the process matrix can be estimated with a single setting. With this technique, the system's relaxation times T1 and T2 were measured with a single experimental configuration. We further show the first, complete characterization of single-qubit processes using a single generalized measurement realized through multibody correlations with three ancilla qubits. © 2013 American Physical Society.


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.


Makmal A.,University of Innsbruck | Melnikov A.A.,University of Innsbruck | Melnikov A.A.,Institute For Quantenoptik Und Quanteninformation Der Osterreichischen Akademie Der Wissenschaften | Dunjko V.,University of Innsbruck | Briegel H.J.,University of Innsbruck
IEEE Access | Year: 2016

Learning models of artificial intelligence can nowadays perform very well on a large variety of tasks. However, in practice, different task environments are best handled by different learning models, rather than a single universal approach. Most non-trivial models thus require the adjustment of several to many learning parameters, which is often done on a case-by-case basis by an external party. Meta-learning refers to the ability of an agent to autonomously and dynamically adjust its own learning parameters or meta-parameters. In this paper, we show how projective simulation, a recently developed model of artificial intelligence, can naturally be extended to account for meta-learning in reinforcement learning settings. The projective simulation approach is based on a random walk process over a network of clips. The suggested meta-learning scheme builds upon the same design and employs clip networks to monitor the agent's performance and to adjust its meta-parameters on the fly. We distinguish between reflex-type adaptation and adaptation through learning, and show the utility of both approaches. In addition, a trade-off between flexibility and learning-time is addressed. The extended model is examined on three different kinds of reinforcement learning tasks, in which the agent has different optimal values of the meta-parameters, and is shown to perform well, reaching near-optimal to optimal success rates in all of them, without ever needing to manually adjust any meta-parameter. © 2016 IEEE.


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).


Schindler P.,University of Innsbruck | Nigg D.,University of Innsbruck | Monz T.,University of Innsbruck | Barreiro J.T.,University of Innsbruck | And 11 more authors.
New Journal of Physics | Year: 2013

Quantum computers hold the promise to solve certain problems exponentially faster than their classical counterparts. Trapped atomic ions are among the physical systems in which building such a computing device seems viable. In this work we present a small-scale quantum information processor based on a string of 40Ca+ ions confined in a macroscopic linear Paul trap. We review our set of operations which includes non-coherent operations allowing us to realize arbitrary Markovian processes. In order to build a larger quantum information processor it is mandatory to reduce the error rate of the available operations which is only possible if the physics of the noise processes is well understood. We identify the dominant noise sources in our system and discuss their effects on different algorithms. Finally we demonstrate how our entire set of operations can be used to facilitate the implementation of algorithms by examples of the quantum Fourier transform and the quantum order finding algorithm. © IOP Publishing and Deutsche Physikalische Gesellschaft.

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