Wolfgang Dür

Universität Innsbruck

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Hans J. Briegel

Universität Innsbruck

J. I. Cirac

Munich Center for Quantum Science and Technology

Pavel Sekatski

University of Geneva

Jorge Miguel-Ramiro

Universität Innsbruck

Michael Zwerger

Universität Innsbruck

Michael Skotiniotis

Universitat Autònoma de Barcelona

A. Pirker

Universität Innsbruck

M. Van den Nest

Max Planck Society

Ferran Riera-Sàbat

Universität Innsbruck

H. J. Briegel

Universität Innsbruck

Cooperative Institutions

Universität Innsbruck

Institute for Quantum Optics and Quantum Information Innsbruck

Austrian Academy of Sciences

University of Vienna

Max Planck Institute of Quantum Optics

Ludwig Boltzmann Institut Health Promotion Research

University of Oxford

Max Planck Society

University of Waterloo

Ludwig Boltzmann Gesellschaft

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Entanglement generation secure against general attacks

New Journal of Physics (2017)

A. Pirker Vedran Dunjko Wolfgang Dür Hans J. Briegel

We present a security proof for establishing private entanglement by means of recurrence-type entanglement distillation protocols over noisy quantum channels. We consider protocols where the local devices are imperfect, and show that nonetheless a confidential quantum channel can be established, and used to e.g. perform distributed quantum computation in a secure manner. While our results are not fully device independent (which we argue to be unachievable in settings with quantum outputs), our proof holds for arbitrary channel noise and noisy local operations, and even in the case where the eavesdropper learns the noise. Our approach relies on non-trivial properties of distillation protocols which are used in conjunction with de-Finetti and post-selection-type techniques to reduce a general quantum attack in a non-asymptotic scenario to an i.i.d. setting. As a side result, we also provide entanglement distillation protocols for non-i.i.d. input states.

10.1088/1367-2630/aa8086

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Citations (7)

Multipartite entanglement outperforming bipartite entanglement under limited quantum system sizes

Physical review. A/Physical review, A (2018)

Hayata Yamasaki A. Pirker Mio Murao Wolfgang Dür Barbara Kraus

The nuances between entangled resource states that can or cannot be prepared from the distribution of bipartite entanglement are analyzed. Concrete examples are given to prove that multipartite entanglement outperforms bipartite entanglement when limitations on the local system sizes exist.

Multipartite entanglement

Multipartite

10.1103/physreva.98.052313

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Citations (23)

Quantum computing and quantum communication with atoms

Luming Duan Wolfgang Dür J. I. Cirac Dieter Jaksch Guifré Vidal

10.1142/9789812705099_0028

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Citations (0)

Exponentially improved classical and quantum algorithms for three-body Ising models

Physical Review A (2014)

M. Van den Nest Wolfgang Dür

We present an algorithm to approximate partition functions of three-body classical Ising models on two-dimensional lattices of arbitrary genus, in the real-temperature regime. Even though our algorithm is purely classical, it is designed by exploiting a connection to topological quantum systems, namely, the color codes. The algorithm performance (in achievable accuracy) is exponentially better than other approaches that employ mappings between partition functions and quantum state overlaps. In addition, our approach gives rise to a protocol for quantum simulation of such Ising models by simply measuring local observables on color codes.

10.1103/physreva.89.012334

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Citations (2)

Two-dimensional quantum repeaters

Physical review. A/Physical review, A (2016)

Julius Wallnöfer Michael Zwerger Christine A. Muschik Nicolas Sangouard Wolfgang Dür

The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

Repeater (horology)

Realization (probability)

Quantum teleportation

10.1103/physreva.94.052307

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Citations (56)

Implementing quantum control for unknown subroutines

Physical Review A (2014)

Nicolai Friis Vedran Dunjko Wolfgang Dür Hans J. Briegel

We present setups for the practical realization of adding control to unknown subroutines, supplementing the existing quantum optical scheme for black-box control with a counterpart for the quantum control of the ordering of sequences of operations. We also provide schemes to realize either task using trapped ions. These practical circumventions of recent no-go theorems are based on existing technologies. We argue that the possibility to add control to unknown operations in practice is a common feature of many physical systems. Based on the proposed implementations we discuss the apparent contradictions between theory and practice.

Subroutine

Realization (probability)

Implementation

Feature (linguistics)

10.1103/physreva.89.030303

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Citations (95)

Multiparty teleportation

Journal of Modern Optics (2000)

Wolfgang Dür J. I. Cirac

Abstract We consider the problem of multiparty teleportation, where N copies of a qubit are teleported to N different locations. We show how to achieve this by measuring an appropriate POVM and using the multiparticle entangled state introduced in the context of telecloning. Our procedure also gives the optimal N ← M telecloning.

Teleportation

Quantum teleportation

POVM

Superdense coding

10.1080/09500340008244039

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Citations (42)

Tensor operators: Constructions and applications for long-range interaction systems

Physical Review A (2010)

Florian Fröwis Volckmar Nebendahl Wolfgang Dür

We consider the representation of operators in terms of tensor networks and their application to the ground-state approximation and time evolution of systems with long-range interactions. We provide an explicit construction to represent an arbitrary many-body Hamilton operator in terms of a one-dimensional tensor network (i.e., as a matrix product operator). For pairwise interactions, we show that such a representation is always efficient and requires a tensor dimension growing only linearly with the number of particles. For systems obeying certain symmetries or restrictions we find optimal representations with minimal tensor dimension. We discuss the analytic and numerical approximation of operators in terms of low-dimensional tensor operators. We demonstrate applications for time evolution and the ground-state approximation, in particular for long-range interaction with inhomogeneous couplings. The operator representations are also generalized to other geometries such as trees and two-dimensional lattices, where we show how to obtain and use efficient tensor network representations respecting a given geometry.

Operator (biology)

Representation

Matrix product state

Tensor operator

Cartesian tensor

10.1103/physreva.81.062337

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Citations (75)

Activating bound entanglement in multiparticle systems

Physical Review A (2000)

Wolfgang Dür J. I. Cirac

We analyze the existence of activable bound entangled states in multi-particle systems. We first give a series of examples which illustrate some different ways in which bound entangled states can be activated by letting some of the parties to share maximally entangled states. Then, we derive necessary conditions for a state to be distillable as well as to be activable. These conditions turn out to be also sufficient for a certain family of multi-qubit states. We use these results to explicitely to construct states displaying novel properties related to bound entanglement and its activation.

10.1103/physreva.62.022302

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Citations (74)

Was man vom einzelnen Qubit über Quantenphysik lernen kann

PhyDid A - Physik und Didaktik in Schule und Hochschule (2012)

Wolfgang Dür Stefan Heusler

In diesem Artikel wird ein Zugang zur Quantenphysik vorgestellt, der auf dem einfachsten moglichen Quantensystem basiert – dem Qubit. Dabei wird demonstriert, wie viele der zentralen Prinzipien der Quantenphysik – insbesondere das Uberlagerungsprinzip, das stochastische Verhalten, die Zustandsanderung bei Messungen, sowie die Heisenberg’sche Unscharferelation, mit Hilfe von Bildern und einfacher Mathematik den Schulern zuganglich gemacht werden konnen. Groser Wert wird dabei auf die Entwicklung von Visualisierungen gelegt, wobei neben den abstrakten Eigenschaften eines Qubits auch verschiedene physikalische Realisierungen des Qubits im Detail vorgestellt werden. Abschliesend werden noch Anwendungen der vorgestellten Prinzipien, insbesondere im Bereich der Quantenkryptographie, diskutiert.

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Citations (3)