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Deterministic correction of qubit loss
[article]
2020
arXiv
pre-print
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The loss of qubits - the elementary carriers of quantum information - poses one of the fundamental obstacles towards large-scale and fault-tolerant quantum information processors. In this work, we experimentally demonstrate a complete toolbox and the implementation of a full cycle of qubit loss detection and correction on a minimal instance of a topological surface code. This includes a quantum non-demolition measurement of a qubit loss event that conditionally triggers a restoration procedure,
arXiv:2002.09532v1
fatcat:xeiwp75gyva3dn2qd4vw6nwuoq
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... mapping the logical qubit onto a new encoding on the remaining qubits. The demonstrated methods, implemented here in a trapped-ion quantum processor, are applicable to other quantum computing architectures and codes, including leading 2D and 3D topological quantum error correcting codes. These tools complement previously demonstrated techniques to correct computational errors, and in combination constitute essential building blocks for complete and scalable quantum error correction.
Entangling logical qubits with lattice surgery
[article]
2020
arXiv
pre-print
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Future quantum computers will require quantum error correction for faithful operation. The correction capabilities come with an overhead for performing fault-tolerant logical operations on the encoded qubits. One of the most resource efficient ways to implement logical operations is lattice surgery, where groups of physical qubits, arranged on lattices, can be merged and split to realize entangling gates and teleport logical information. Here, we report on the experimental realization of
arXiv:2006.03071v1
fatcat:uqcjyjzkdzfxzog7oo47irusqq
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... surgery between two topologically encoded qubits in a 10-qubit ion trap quantum information processor. In particular, we demonstrate entanglement between two logical qubits and we implement logical state teleportation.
Perspectives on Socially Intelligent Conversational Agents
2022
Multimodal Technologies and Interaction
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The propagation of digital assistants is consistently progressing. Manifested by an uptake of ever more human-like conversational abilities, respective technologies are moving increasingly away from their role as voice-operated task enablers and becoming rather companion-like artifacts whose interaction style is rooted in anthropomorphic behavior. One of the required characteristics in this shift from a utilitarian tool to an emotional character is the adoption of social intelligence. Although
doi:10.3390/mti6080062
fatcat:deaen7722jc7lb5sl2kmacmg3y
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... ast research has recognized this need, more multi-disciplinary investigations should be devoted to the exploration of relevant traits and their potential embedding in future agent technology. Aiming to lay a foundation for further developments, we report on the results of a Delphi study highlighting the respective opinions of 21 multi-disciplinary domain experts. Results exhibit 14 distinctive characteristics of social intelligence, grouped into different levels of consensus, maturity, and abstraction, which may be considered a relevant basis, assisting the definition and consequent development of socially intelligent conversational agents.
Quantum Computers for High-Performance Computing
2021
IEEE Micro
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ALEXANDER MCCASKEY is a Research Scientist with the Beyond Moore Computing Group within the Computer Science and Mathematics Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN, USA. ...
THOMAS MONZ is the Co-Founder and CEO at Alpine Quantum Technologies (AQT), Innsbruck, Austria, a quantum computer company focusing on trapped ions, and a Senior Scientist at the University of Innsbruck ...
doi:10.1109/mm.2021.3099140
fatcat:ubpmef4h7fcvjcv7qjhod6qoj4
Characterizing large-scale quantum computers via cycle benchmarking
[article]
2019
arXiv
pre-print
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Quantum computers promise to solve certain problems more efficiently than their digital counterparts. A major challenge towards practically useful quantum computing is characterizing and reducing the various errors that accumulate during an algorithm running on large-scale processors. Current characterization techniques are unable to adequately account for the exponentially large set of potential errors, including cross-talk and other correlated noise sources. Here we develop cycle
arXiv:1902.08543v1
fatcat:2mcojchaa5eztdowhk5geq2p5e
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... a rigorous and practically scalable protocol for characterizing local and global errors across multi-qubit quantum processors. We experimentally demonstrate its practicality by quantifying such errors in non-entangling and entangling operations on an ion-trap quantum computer with up to 10 qubits, with total process fidelities for multi-qubit entangling gates ranging from 99.6(1)% for 2 qubits to 86(2)% for 10 qubits. Furthermore, cycle benchmarking data validates that the error rate per single-qubit gate and per two-qubit coupling does not increase with increasing system size.
Relaxation times do not capture logical qubit dynamics
2022
Quantum
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Quantum error correction procedures have the potential to enable faithful operation of large-scale quantum computers. They protect information from environmental decoherence by storing it in logical qubits, built from ensembles of entangled physical qubits according to suitably tailored quantum error correcting encodings. To date, no generally accepted framework to characterise the behaviour of logical qubits as quantum memories has been developed. In this work, we show that generalisations of
doi:10.22331/q-2022-01-24-632
fatcat:antllord3vgnjdkkwpdshkevae
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... ell-established figures of merit of physical qubits, such as relaxation times, to logical qubits fail and do not capture dynamics of logical qubits. We experimentally illustrate that, in particular, spatial noise correlations can give rise to rich and counter-intuitive dynamical behavior of logical qubits. We show that a suitable set of observables, formed by code space population and logical operators within the code space, allows one to track and characterize the dynamical behaviour of logical qubits. Awareness of these effects and the efficient characterisation tools used in this work will help to guide and benchmark experimental implementations of logical qubits.
Characterizing quantum instruments: from non-demolition measurements to quantum error correction
[article]
2021
arXiv
pre-print
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In quantum information processing quantum operations are often processed alongside measurements which result in classical data. Due to the information gain of classical measurement outputs non-unitary dynamical processes can take place on the system, for which common quantum channel descriptions fail to describe the time evolution. Quantum measurements are correctly treated by means of so-called quantum instruments capturing both classical outputs and post-measurement quantum states. Here we
arXiv:2110.06954v1
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... sent a general recipe to characterize quantum instruments alongside its experimental implementation and analysis. Thereby, the full dynamics of a quantum instrument can be captured, exhibiting details of the quantum dynamics that would be overlooked with common tomography techniques. For illustration, we apply our characterization technique to a quantum instrument used for the detection of qubit loss and leakage, which was recently implemented as a building block in a quantum error correction (QEC) experiment (Nature 585, 207-210 (2020)). Our analysis reveals unexpected and in-depth information about the failure modes of the implementation of the quantum instrument. We then numerically study the implications of these experimental failure modes on QEC performance, when the instrument is employed as a building block in QEC protocols on a logical qubit. Our results highlight the importance of careful characterization and modelling of failure modes in quantum instruments, as compared to simplistic hardware-agnostic phenomenological noise models, which fail to predict the undesired behavior of faulty quantum instruments. The presented methods and results are directly applicable to generic quantum instruments.
Multicriteria Optimization in Intensity Modulated Rediotherapy Planning
[chapter]
2008
Handbook of Optimization in Medicine
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Monz, F. Alonso, T. Bortfeld
MW Munter, CP Karger, SG Hoffner, H Hof, C Thilmann, V Rudat, S Nill, M Wannenmacher, and Debus J. ...
[20] KH Küfer, A Scherrer, MP Monz, FV Alonso, H Trinkaus, TR Bortfeld,
and C Thieke. Intensity-modulated radiotherapy -a large scale multi-
criteria programming problem. ...
doi:10.1007/978-0-387-09770-1_5
fatcat:yimhx7gxdfcptj7buqxnm7svlq
Intensity-modulated radiotherapy - a large scale multi-criteria programming problem
2003
OR spectrum
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Monz, A. Scherrer, C. Thieke, H. ...
doi:10.1007/s00291-003-0125-7
fatcat:hvplnpef3zevxkt5x5uruiexja
Relaxation times do not capture logical qubit dynamics
[article]
2021
arXiv
pre-print
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DOI: 10.1103/Phys- Alexander Erhard, Roman Stricker, Daniel Nigg,
RevA.63.022307. ...
Relaxation times do not capture logical qubit dynamics
Amit Kumar Pal1,2,3 , Philipp Schindler4 , Alexander Erhard4 ...
arXiv:2012.07911v2
fatcat:onarvedntjbmzlmhssmoxwszne
Characterizing large-scale quantum computers via cycle benchmarking
2019
Nature Communications
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Quantum computers promise to solve certain problems more efficiently than their digital counterparts. A major challenge towards practically useful quantum computing is characterizing and reducing the various errors that accumulate during an algorithm running on large-scale processors. Current characterization techniques are unable to adequately account for the exponentially large set of potential errors, including cross-talk and other correlated noise sources. Here we develop cycle
doi:10.1038/s41467-019-13068-7
pmid:31767840
pmcid:PMC6877623
fatcat:4ywc7lrbf5bn5a43mg7bbf6ziy
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... a rigorous and practically scalable protocol for characterizing local and global errors across multi-qubit quantum processors. We experimentally demonstrate its practicality by quantifying such errors in non-entangling and entangling operations on an ion-trap quantum computer with up to 10 qubits, and total process fidelities for multi-qubit entangling gates ranging from [Formula: see text] for 2 qubits to [Formula: see text] for 10 qubits. Furthermore, cycle benchmarking data validates that the error rate per single-qubit gate and per two-qubit coupling does not increase with increasing system size.
IMRT planning on adaptive volume structures—a decisive reduction in computational complexity
2005
Physics in Medicine and Biology
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Monz, A. Scherrer, C. Thieke, H. ...
Monz, F. Alonso, T. ...
doi:10.1088/0031-9155/50/9/008
pmid:15843735
fatcat:bpuaww5hyvc6pablvyf5mqa3ky
Investigating Perceptions of Social Intelligence in Simulated Human-Chatbot Interactions
[chapter]
2020
Smart Innovation, Systems and Technologies
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2021 pre-print arXiv:2104.13823v1 fatcat:kvzrj2gl35gmthv6x6bae5v7bi
With the ongoing penetration of conversational user interfaces, a better understanding of social and emotional characteristic inherent to dialogue is required. Chatbots in particular face the challenge of conveying human-like behaviour while being restricted to one channel of interaction, i.e., text. The goal of the presented work is thus to investigate whether characteristics of social intelligence embedded in human-chatbot interactions are perceivable by human interlocutors and if yes,
doi:10.1007/978-981-15-5093-5_44
fatcat:2kfwiy75abg4pekzgh7k2qwdzm
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... such influences the experienced interaction quality. Focusing on the social intelligence dimensions Authenticity, Clarity and Empathy, we first used a questionnaire survey evaluating the level of perception in text utterances, and then conducted a Wizard of Oz study to investigate the effects of these utterances in a more interactive setting. Results show that people have great difficulties perceiving elements of social intelligence in text. While on the one hand they find anthropomorphic behaviour pleasant and positive for the naturalness of a dialogue, they may also perceive it as frightening and unsuitable when expressed by an artificial agent in the wrong way or at the wrong time.
Characterizing Quantum Instruments: From Nondemolition Measurements to Quantum Error Correction
2022
PRX quantum 3(3)
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Experimental quantification of spatial correlations in quantum dynamics
2018
Quantum
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Correlations between different partitions of quantum systems play a central role in a variety of many-body quantum systems, and they have been studied exhaustively in experimental and theoretical research. Here, we investigate dynamical correlations in the time evolution of multiple parts of a composite quantum system. A rigorous measure to quantify correlations in quantum dynamics based on a full tomographic reconstruction of the quantum process has been introduced recently [Á. Rivas et al.,
doi:10.22331/q-2018-09-03-90
fatcat:7hkjpbjx3vgktmua33yv7uhpxe
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... w Journal of Physics, 17(6) 062001 (2015).]. In this work, we derive a lower bound for this correlation measure, which does not require full knowledge of the quantum dynamics. Furthermore we also extend the correlation measure to multipartite systems. We directly apply the developed methods to a trapped ion quantum information processor to experimentally characterize the correlations in quantum dynamics for two- and four-qubit systems. The method proposed and demonstrated in this work is scalable, platform-independent and applicable to other composite quantum systems and quantum information processing architectures. We apply the method to estimate spatial correlations in environmental noise processes, which are crucial for the performance of quantum error correction procedures.
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