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Krutyanskiy V, Galli M, Krcmarsky V, Baier S, Fioretto DA, Pu Y, Mazloom A, Sekatski P, Canteri M, Teller M, Schupp J, Bate J, Meraner M, Sangouard N, Lanyon BP, Northup TE. Entanglement of Trapped-Ion Qubits Separated by 230 Meters. Phys Rev Lett 2023; 130:050803. [PMID: 36800448 DOI: 10.1103/physrevlett.130.050803] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Accepted: 12/20/2022] [Indexed: 06/18/2023]
Abstract
We report on an elementary quantum network of two atomic ions separated by 230 m. The ions are trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion is entangled with the polarization state of a single cavity photon; subsequent to interference of the photons at a beam splitter, photon detection heralds entanglement between the two ions. Fidelities of up to (88.0+2.2-4.7)% are achieved with respect to a maximally entangled Bell state, with a success probability of 4×10^{-5}. We analyze the routes to improve these metrics, paving the way for long-distance networks of entangled quantum processors.
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Affiliation(s)
- V Krutyanskiy
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - M Galli
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - V Krcmarsky
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - S Baier
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - D A Fioretto
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Y Pu
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - A Mazloom
- Department of Physics, Georgetown University, 37th and O Streets NW, Washington, D.C. 20057, USA
| | - P Sekatski
- Department of Applied Physics, University of Geneva, 1211 Geneva, Switzerland
| | - M Canteri
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - M Teller
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - J Schupp
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - J Bate
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - M Meraner
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - N Sangouard
- Institut de Physique Théorique, Université Paris-Saclay, CEA, CNRS, 91191 Gif-sur-Yvette, France
| | - B P Lanyon
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, 6020 Innsbruck, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - T E Northup
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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2
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Nadlinger DP, Drmota P, Nichol BC, Araneda G, Main D, Srinivas R, Lucas DM, Ballance CJ, Ivanov K, Tan EYZ, Sekatski P, Urbanke RL, Renner R, Sangouard N, Bancal JD. Experimental quantum key distribution certified by Bell's theorem. Nature 2022; 607:682-686. [PMID: 35896644 DOI: 10.1038/s41586-022-04941-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 06/07/2022] [Indexed: 11/09/2022]
Abstract
Cryptographic key exchange protocols traditionally rely on computational conjectures such as the hardness of prime factorization1 to provide security against eavesdropping attacks. Remarkably, quantum key distribution protocols such as the Bennett-Brassard scheme2 provide information-theoretic security against such attacks, a much stronger form of security unreachable by classical means. However, quantum protocols realized so far are subject to a new class of attacks exploiting a mismatch between the quantum states or measurements implemented and their theoretical modelling, as demonstrated in numerous experiments3-6. Here we present the experimental realization of a complete quantum key distribution protocol immune to these vulnerabilities, following Ekert's pioneering proposal7 to use entanglement to bound an adversary's information from Bell's theorem8. By combining theoretical developments with an improved optical fibre link generating entanglement between two trapped-ion qubits, we obtain 95,628 key bits with device-independent security9-12 from 1.5 million Bell pairs created during eight hours of run time. We take steps to ensure that information on the measurement results is inaccessible to an eavesdropper. These measurements are performed without space-like separation. Our result shows that provably secure cryptography under general assumptions is possible with real-world devices, and paves the way for further quantum information applications based on the device-independence principle.
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Affiliation(s)
- D P Nadlinger
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.
| | - P Drmota
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - B C Nichol
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - G Araneda
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - D Main
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - R Srinivas
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - D M Lucas
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - C J Ballance
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.
| | - K Ivanov
- School of Computer and Communication Sciences, EPFL, Lausanne, Switzerland
| | - E Y-Z Tan
- Institute for Theoretical Physics, ETH Zürich, Zürich, Switzerland
| | - P Sekatski
- Department of Applied Physics, University of Geneva, Geneva, Switzerland
| | - R L Urbanke
- School of Computer and Communication Sciences, EPFL, Lausanne, Switzerland
| | - R Renner
- Institute for Theoretical Physics, ETH Zürich, Zürich, Switzerland
| | - N Sangouard
- Université Paris-Saclay, CEA, CNRS, Institut de Physique Théorique, Gif-sur-Yvette, France.
| | - J-D Bancal
- Université Paris-Saclay, CEA, CNRS, Institut de Physique Théorique, Gif-sur-Yvette, France.
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3
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Riera-Sàbat F, Sekatski P, Pirker A, Dür W. Entanglement-Assisted Entanglement Purification. Phys Rev Lett 2021; 127:040502. [PMID: 34355942 DOI: 10.1103/physrevlett.127.040502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 06/22/2021] [Indexed: 06/13/2023]
Abstract
The efficient generation of high-fidelity entangled states is the key element for long-distance quantum communication, quantum computation, and other quantum technologies, and at the same time the most resource-consuming part in many schemes. We present a class of entanglement-assisted entanglement purification protocols that can generate high-fidelity entanglement from noisy, finite-size ensembles with improved yield and fidelity as compared to previous approaches. The scheme utilizes high-dimensional auxiliary entanglement to perform entangling nonlocal measurements and determine the number and positions of errors in an ensemble in a controlled and efficient way, without disturbing the entanglement of good pairs. Our protocols can deal with arbitrary errors, but are best suited for few errors, and work particularly well for decay noise. Our methods are applicable to moderately sized ensembles, as will be important for near term quantum devices.
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Affiliation(s)
- F Riera-Sàbat
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, 6020 Innsbruck, Austria
| | - P Sekatski
- Departement Physik, Universität Basel, Klingelbergstraße 82, 4056 Basel, Switzerland
| | - A Pirker
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, 6020 Innsbruck, Austria
| | - W Dür
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, 6020 Innsbruck, Austria
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Caspar P, Verbanis E, Oudot E, Maring N, Samara F, Caloz M, Perrenoud M, Sekatski P, Martin A, Sangouard N, Zbinden H, Thew RT. Heralded Distribution of Single-Photon Path Entanglement. Phys Rev Lett 2020; 125:110506. [PMID: 32975988 DOI: 10.1103/physrevlett.125.110506] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/30/2020] [Indexed: 06/11/2023]
Abstract
We report the experimental realization of heralded distribution of single-photon path entanglement at telecommunication wavelengths in a repeater-like architecture. The entanglement is established upon detection of a single photon, originating from one of two spontaneous parametric down-conversion photon pair sources, after erasing the photon's which-path information. In order to certify the entanglement, we use an entanglement witness which does not rely on postselection. We herald entanglement between two locations, separated by a total distance of 2 km of optical fiber, at a rate of 1.6 kHz. This work paves the way towards high-rate and practical quantum repeater architectures.
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Affiliation(s)
- P Caspar
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - E Verbanis
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - E Oudot
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
- Quantum Optics Theory Group, University of Basel, CH-4056 Basel, Switzerland
| | - N Maring
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - F Samara
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - M Caloz
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - M Perrenoud
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - P Sekatski
- Quantum Optics Theory Group, University of Basel, CH-4056 Basel, Switzerland
| | - A Martin
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - N Sangouard
- Quantum Optics Theory Group, University of Basel, CH-4056 Basel, Switzerland
- Institut de physique théorique, Université Paris Saclay, CEA, CNRS, F-91191 Gif-sur-Yvette, France
| | - H Zbinden
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
| | - R T Thew
- Department of Applied Physics, University of Geneva, CH-1211 Genève, Switzerland
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5
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Ho M, Sekatski P, Tan EYZ, Renner R, Bancal JD, Sangouard N. Noisy Preprocessing Facilitates a Photonic Realization of Device-Independent Quantum Key Distribution. Phys Rev Lett 2020; 124:230502. [PMID: 32603141 DOI: 10.1103/physrevlett.124.230502] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 05/26/2020] [Indexed: 06/11/2023]
Abstract
Device-independent quantum key distribution provides security even when the equipment used to communicate over the quantum channel is largely uncharacterized. An experimental demonstration of device-independent quantum key distribution is however challenging. A central obstacle in photonic implementations is that the global detection efficiency, i.e., the probability that the signals sent over the quantum channel are successfully received, must be above a certain threshold. We here propose a method to significantly relax this threshold, while maintaining provable device-independent security. This is achieved with a protocol that adds artificial noise, which cannot be known or controlled by an adversary, to the initial measurement data (the raw key). Focusing on a realistic photonic setup using a source based on spontaneous parametric down conversion, we give explicit bounds on the minimal required global detection efficiency.
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Affiliation(s)
- M Ho
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
- Department of Applied Physics, University of Geneva, Chemin de Pinchat 22, 1211 Geneva, Switzerland
| | - P Sekatski
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - E Y-Z Tan
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - R Renner
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - J-D Bancal
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
- Department of Applied Physics, University of Geneva, Chemin de Pinchat 22, 1211 Geneva, Switzerland
| | - N Sangouard
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
- Université Paris-Saclay, CEA, CNRS, Institut de physique théorique, 91191 Gif-sur-Yvette, France
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6
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Zwerger M, Dür W, Bancal JD, Sekatski P. Device-Independent Detection of Genuine Multipartite Entanglement for All Pure States. Phys Rev Lett 2019; 122:060502. [PMID: 30822083 DOI: 10.1103/physrevlett.122.060502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Indexed: 06/09/2023]
Abstract
We show that genuine multipartite entanglement of all multipartite pure states in arbitrary finite dimension can be detected in a device-independent way by employing bipartite Bell inequalities on states that are deterministically generated from the initial state via local operations. This leads to an efficient scheme for large classes of multipartite states that are relevant in quantum computation or condensed-matter physics, including cluster states and the ground state of the Affleck-Kennedy-Lieb-Tasaki (AKLT) model. For cluster states the detection of genuine multipartite entanglement involves only measurements on a constant number of systems with an overhead that scales linearly with the system size, while for the AKLT model the overhead is polynomial. In all cases our approach shows some robustness against experimental imperfections.
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Affiliation(s)
- M Zwerger
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, 6020 Innsbruck, Austria
| | - W Dür
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, 6020 Innsbruck, Austria
| | - J-D Bancal
- Departement Physik, Universität Basel, Klingelbergstraße 82, 4056 Basel, Switzerland
| | - P Sekatski
- Departement Physik, Universität Basel, Klingelbergstraße 82, 4056 Basel, Switzerland
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7
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Sekatski P, Skotiniotis M, Dür W. Improved Sensing with a Single Qubit. Phys Rev Lett 2017; 118:170801. [PMID: 28498713 DOI: 10.1103/physrevlett.118.170801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Indexed: 06/07/2023]
Abstract
We consider quantum metrology with arbitrary prior knowledge of the parameter. We demonstrate that a single sensing two-level system can act as a virtual multilevel system that offers increased sensitivity in a Bayesian single-shot metrology scenario, and that allows one to estimate (arbitrary) large parameter values by avoiding phase wraps. This is achieved by making use of additional degrees of freedom or auxiliary systems not participating in the sensing process. The joint system is manipulated by intermediate control operations in such a way that an effective Hamiltonian, with an arbitrary spectrum, is generated that mimics the spectrum of a multisystem interacting with the field. We show how to use additional internal degrees of freedom of a single trapped ion to achieve a high-sensitivity magnetic field sensor for fields with arbitrary prior knowledge.
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Affiliation(s)
- P Sekatski
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstr. 21a, A-6020 Innsbruck, Austria
| | - M Skotiniotis
- Física Teòrica: Informació i Fenòmens Quàntics, Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - W Dür
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstr. 21a, A-6020 Innsbruck, Austria
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Dür W, Sekatski P, Skotiniotis M. Deterministic superreplication of one-parameter unitary transformations. Phys Rev Lett 2015; 114:120503. [PMID: 25860727 DOI: 10.1103/physrevlett.114.120503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Indexed: 06/04/2023]
Abstract
We show that one can deterministically generate, out of N copies of an unknown unitary operation, up to N^{2} almost perfect copies. The result holds for all operations generated by a Hamiltonian with an unknown interaction strength. This generalizes a similar result in the context of phase-covariant cloning where, however, superreplication comes at the price of an exponentially reduced probability of success. We also show that multiple copies of unitary operations can be emulated by operations acting on a much smaller space, e.g., a magnetic field acting on a single n-level system allows one to emulate the action of the field on n^{2} qubits.
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Affiliation(s)
- W Dür
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - P Sekatski
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - M Skotiniotis
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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