Austrian Academy of Sciences
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Principal Investigators: Professor Caslav Brukner / Dr Rupert Ursin

The Project 

Quantum Repeaters: Terrestrial and satellite free-space quantum communication 

The subproject Quantum Repeaters focuses on a number of tools that are common and central for quantum communication over long distances.

Several key ingredients for future quantum technology are to be developed in this subproject, such as sources of entanglement, quantum channels, quantum networks and quantum memories. 

Quantum communication protocols require the distribution of entanglement between separate locations with high fidelity. Transmission of quantum information is limited by decoherence and the absorption on the link. Reshaping and amplification of a quantum state is forbidden by the no-cloning theorem and so other methods must be used to ensure high fidelity transmission of quantum information. Quantum repeaters will resolve this problem by breaking quantum channels into shorter links. Entanglement distribution and purification at separate links will be used to ensure transmission of quantum information over the full channel with the required fidelity. 

An independent approach to overcome the limitation in the distance for distribution of entanglement is using free-space links, involving satellites in space for bridging distances on a global scale and eventually establishing a world wide quantum communication network. A typical free space channel consists of two telescopes with a free line of sight between them. In a close collaboration between OEAW, LMU and UBRISTOL together with the European Space agency (ESA), we demonstrated the distribution of entanglement over distances of 144 km between the Canary island La Palma and Tenerife [1], which is already 30% of the distance to the international space station ISS. Free space channels are an exciting prospect because of the potential for use in conjunction with satellite technologies. In the project we will investigate the feasibility of satellite quantum communication links, including potential satellite based components and space-compatible sources of entangled photons. Potential timing, pointing and tracking problems associated with satellites will be addressed via simulations and experimental demonstrations. Objectives include measurement of single photons reflected from a low orbiting laser ranging satellite [2]. 

Among our goals in other subprojects (SP2.3 “Multiphoton Networks”) are the production and characterization of various multi-photon entangled states, such as GHZ, W, or Cluster states, experimental demonstration of their counter-intuitive features, and exploitation of these features for quantum information technology. Major goal is realization of one-way quantum computer based on processing of single qubits in a highly-entangled cluster state. Using this cluster state we aim to implement various quantum algorithms. 

In the SP2.5 “Multi-particle and qubit entanglement purification and algorithms” we investigate entanglement between orbital angular momentum of photons, which are states of the electromagnetic field with phase singularities (doughnut modes). This opens up a practical approach to multi-dimensional entanglement where the entangled states do not only consist of two orthogonal states but of many of them. These states are expected to be of importance for the current efforts in the quantum computation and communication scheme based on higher-dimensional systems. 

Figure: The setup for free-space entanglement distribution between La Palma and Tenerife. Polarisation entangled photon pairs are produced in a type-II parametric down conversion (DC) source by pumping a beta-barium-borate crystal (BBO) with a high power UV laser. One photon is measured locally on La Palma, the other one is sent through a 15 cm transceiver lens over the 144 km free-space optical link to the 1 m mirror telescope of the Optical Ground Station (OGS) on the island of Tenerife.


Other QAP Activities 

  • Multi-photon Networks with LMU
  • Multi-particle and qudit entanglement and purification algorithms with IMPERIAL
  • Quantum Channels with UG
  • Advanced sources of entangled photon pairs with CNRSGRE
  • Long distance fibre-optic quantum relays and purification with UNIGE  


List of Publications


M. Aspelmeyer, H. R. Boehm, A. Fedrizzi et al, Advanced Quantum Communication Experiments with Entangled Photons in "Quantum Communication and Cryptography", Quantum Communications and Cryptography , A. Sergienko (Ed.), CRC Press LLC (2005)

C. Brukner and A. Zeilinger, Quantum Physics as a Science of Information, Springer (2005) ISBN: 3-540-22188-3

C. Lunkes, C. Brukner and V. Vedral, Natural Multiparticle Entanglement in a Fermi Gas, Phys. Rev. Lett. 95 030503 (2005) quant-ph/0502122

C. Lunkes, C. Brukner and V. Vedral, Equation of State for Entanglement in a Fermi Gas, Phys. Rev. A 71 034309 (2005) quant-ph/0410166

K. Maruyama, C. Brukner and V. Vedral, Thermodynamical Cost of Accessing Quantum Information, J. Phys. A 38 7175-7181 (2005) quant-ph/0407151

A. Sen De, U. Sen, C. Brukner et al, Entanglement Swapping of Noisy States: A Kind of Superadditivity in Nonclassicality, Phys. Rev. A 72 042310 (2005) quant-ph/0311194

P. Trojek, C. Schmid, M. Bourennane et al, Experimental Quantum Communication Complexity, Phys. Rev. A 72 00305(R) (2005) quant-ph/0502066

P. Walther, M. Aspelmeyer, K. J. Resch et al, Experimental violation of a cluster state Bell inequality, Phys. Rev. Lett. 95 042325 (2005) quant-ph/0507086

P. Walther, K. J. Resch, C. Brukner et al, Quantum Nonlocality Obtained from Local States by Entanglement Purification, Phys. Rev. Lett. 94 040504 (2005) quant-ph/0502026

P. Walther, K. Resch, T. Rudolph et al, Experimental one-way quantum computing, Nature 434 169 (2005) quant-ph/0503126

M. Wiesniak, V. Vedral and C. Brukner, Magnetic Susceptibility as Macroscopic Entanglement Witness, New J. Phys. 7 258 (2005) quant-ph/0503037

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Oemer, M. Fuerst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter and A. Zeilinger, Free-Space distribution of entanglement and single photons over 144 km, submitted to Nature Physics quant-ph/0607182 

M. F. Andersen, C. Ryu, P. Clade et al, Quantized Rotation of Atoms From Photons with Orbital Angular Momentum, Phys. Rev. Lett. (2006) quant-ph/0607171

H. R. Böhm, S. Gigan, G. Langer et al, A high-reflective high-Q micromechanical Bragg-mirror, Appl. Phys. Lett. 89, 223101 (2006) (2006) cond-mat/0607771

C. Bonato, M. Aspelmeyer, T. Jennewein et al, Influence of satellite motion on the qubit transmission in a space-earth quantum communication link, Optics Express 14 10050 (2006) opticsexpress/116342

C. Bonato, M. Aspelmeyer, T. Jennewein, C. Pernechele, P. Villoresi and A. Zeilinger, Influence of satellite motion on the qubit transmission in a space-earth quantum communication link, Optics Express, Vol. 14, 10050 (2006)

C. Brukner, N. Paunkovic, T. Rudolph and V. Vedral, Entanglement-assisted Orientation in Space, Int. J. of Quant. Inf 4 365 (2006) quant-ph/0509123

C. Brukner, V. Vedral and A. Zeilinger, Crucial Role of Quantum Entanglement in Bulk Properties of Solids, Phys. Rev. A 73 012110 (2006) quant-ph/0410138

G. De Chiara, C. Brukner, R. Fazio, G. M. Palma and V. Vedral, A Scheme for Entanglement Extraction From a Solid, New J. Phys 8 95 (2006) quant-ph/0505107

M. Fürst, H. Weier, T. Schmitt-Manderbach et al, Free-space quantum key distribution over 144 km, Proceedings SPIE 6399 (2006)

S. Gröblacher, T. Jennewein, A. Vaziri, G. Weihs, A. Zeilinger, Experimental Quantum Cryptography With Qutrits, New J. Phys. 8 75 (2006) quant-ph/0511163

H. Huebel and A. Zeilinger, From Entanglement to Quantum Key Distribution, Vol. 199, IOS Press (2006) ISBN: 1-58603-611-4

R. Kaltenbaek, B. Blauensteiner, M. Zukowski, M. Aspelmeyer, A. Zeilinger, Experimental interference of independent photons, Phys. Rev. Lett. 96 240502 (2006) quant-ph/0603048

J. Kofler, C. Brukner, Entanglement Distribution Revealed by macroscopic Observations, Phys. Rev. A 74 050304 (2006) quant-ph/0603208

J. Kofler, V. Vedral, M. S. Kim, C. Brukner, Entanglement between Collective Operators in a Linear Harmonic Chain, Phys. Rev. A 73 052107 (2006) quant-ph/0506236

J. Kofler, T. Paterek and C. Brukner, Experimenter's Freedom in Bell's Theorem and Quantum Cryptography, Phys. Rev. A 73 022104 (2006)

K. J. Resch, M. Lindenthal, B. Blauensteiner et al, Distributing entanglement and single photons through an intra-city, free-space quantum channel, Opt. Express 13 202 (2006) quant-ph/0501008

K. Sanaka, K. J. Resch, A. Zeilinger, Filtering Out Photonic Fock States, Phys. Rev. Lett. 96 083601 (2006)

W. Son, C. Brukner, and M. S. Kim, Test of Nonlocality for a Continuous-Variable State Based on an Arbitrary Number of Measurement Outcomes, Phys. Rev. Lett. 97 110401 (2006) quant-ph/0602119

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach et al, Free-Space distribution of entanglement and single photons over 144 km, submitted to Nature Physics quant-ph/0607182

P. Walther, K. J. Resch, C. Brukner et al, Experimental Entangled Entanglement, Phys. Rev. Lett. 97 020501 (2006) quant-ph/0508183

A. Zeilinger, Einsteins Spuk , Bertelsmann (2006) ISBN: 3570006913

M. Aspelmeyer, Quantum Optics: Enlightened Chips, Nature 1 94 (2007)

P. Böhi, R. Prevedel, T. Jennewein et al, Implementation and characterization of active feed-forward for deterministic linear optics quantum computing, Appl. Phys. B 89 499 (2007)

A. Fedrizzi, T. Herbst, A. Poppe et al, A wavelength-tunable fiber-coupled source of narrowband entangled photons, Optics Express 15 15377 (2007)

A. Fedrizzi, T. Herbst, T. Jennewein et al, A fiber-coupled wavelength tunable source of narrowband entangled photons (2007)

C. Genes, D. Vitali, P. Tombesi et al, Ground-state cooling of a micromechanical oscillator: comparing cold damping and cavity-assisted cooling schemes (2007)

S. Gröblacher, S. Gigan, H. R. Boehm et al, Radiation-pressure self-cooling of a micromirror in a cryogenic environment (2007)

S. Gröblacher, T. Paterek, R. Kaltenbaek et al, An experimental test of non-local realism, Nature 446 871 (2007)

H. Hübel, M. R. Vanner, T. Lederer et al, High-fidelity transmission of polarization encoded qubits from an entangled source over 100 km of fiber, Optics express 15 7853 (2007)

N. Kiesel, Ch. Schmid, U. Weber et al, Experimental analysis of a simple linear optics phase gate, International J. Quantum Informa 5 235 (2007)

J. Kofler and C. Brukner, Classical world arising out of quantum physics under the restriction of coarse-grained measurements, Phys. Rev. Lett. 99 180403 (2007)

M. Marhöfer, I. Wimberger, and A. Poppe, Applicability of quantum cryptography for securing mobile communication networks, Nova Science Publishers (2007) ISBN: 1-60021-912-8

T. Paterek, A. Fedrizzi, S. Gröblacher et al, Experimental test of non-local realistic theories without the rotational symmetry assumption, Phys. Rev. Lett. 99 210406 (2007)

M. Paternostro, D. Vitali, S. Gigan et al, Creating and probing macroscoping entanglement, Phys. Rev. Lett. 99 250401 (2007) quant-ph/0609210

A. Poppe, 'Quantenkryptographie: von einzelnen Photonen zum sicheren Schlüssel, Elektrotechnik & Informationstechnik 124/ 121 (2007)

A. Poppe, H. Hübel, B. Schrenk et al, Der Einsatz verschränkter Photonen für die Quantenkryptographie, Elektrotechnik & Informationstechnik 124 142 (2007)

R. Prevedel, A. Stefanov, P. Walther et al, Experimental realization of a quantum game on a one-way quantum computer, New J. Phys 9 205 (2007)

R. Prevedel, P. Walther, F. Tiefenbacheret et al, High-speed linear optics quantum computing via active feed-forward, Nature 445 65-69 (2007) quant-ph/0701017

R. Prevedel, M. Aspelmeyer, C. Brukner et al, Photonic Entanglement as a Resource in Quantum Information Processing, J. Opt. B 24 241 (2007)

K. J. Resch, K. L. Pregnell, R. Prevedel et al, Time-Reversal and Super-Resolving Phase Measurements, Phys. Rev. Lett. 98 223601 (2007) quant-ph/0511214

T. Schmitt-Manderbach, H, Weier, M. Fürst et al, Experimental Demonstration of Free-Space Decoy-State Quantum Key Distribution over 144 km, Phys. Rev. Lett. 98 010504 (2007)

M. Stütz, S. Gröblacher, T. Jennewein et al, How to create and detect N-dimensional entangled photons with an active phase hologram, Appl. Phys. Lett. 90 261114 (2007)

M. S. Tame, R. Prevedel, M. Paternostro et al, Experimental Realization of Deutsch's Algorithm in a One-way Quantum Computer, Phys. Rev. Lett. 98 140501 (2007) quant-ph/0611186

R. Ursin, F. Tiefenbacher, T. Jennewein et al, Applications of quantum communication protocols in real world scenarios towards space, E&I. Electronics 5 149 (2007)

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach et al, Entanglement based quantum communication over 144 km, Nature Phys. 3 481 (2007)

D. Vitali, S. Gigan, A. Ferreira et al, Optomechanical entanglement between a movable mirror and a cavity field, Phys. Rev. Lett. 98 030405 (2007) quant-ph/0609197

P. Walther, M. Aspelmeyer and A. Zeilinger, Heralded generation of multiphoton entanglement, Phys. Rev. A 75 12313 (2007)

J. Armengol, B. Furch, C. J. D. Matos et al, Quantum communications at ESA: Towards a space experiment on the ISS , Acta Astronautica 63 165 (2008)

P. Badziag, C. Brukner, W. Laskowski et al, Experimentally Friendly Geometrical Criteria for Entanglement, Phys. Rev. Lett. 100 140403 (2008) arXiv:0711.4282

G. D. Cole, S. Gröblacher, K. Gugler et al, Monocrystalline AlGaAs heterostructures for high-reflectivity high-Q micromechanical resonators in the MHz regime, Appl. Phys. Lett. 92 261108 (2008) arXiv:0802.0465

B. Dakic, M. Suvakov, T. Paterek et al, Hidden-variable simulation of quantum measurements, Phys. Rev. Lett. 101 190402 (2008) arXiv:0805.1728

C. Genes, D. Vitali, P. Tombesi et al, Ground-state cooling of a micromechanical oscillator: comparing cold damping and cavity-assisted cooling schemes, Phys. Rev. A 77 033804 (2008)

I. M. Herbauts, S. Bettelli, H. Hübel et al, On the optimality of individual entangling-probe attacks against BB84 quantum key distribution, Eur. Phys. J. D 46 395 (2008)

J. Kofler and C. Brukner, Conditions for Quantum Violation of Macroscopic Realism, Phys. Rev. Lett. 101 090403 (2008)

M. Wiesniak, V. Vedral and C. Brukner, Heat Capacity as A Witness of Entanglement, Phys. Rev. A 78 064108 (2008) quant-ph/0508193

P. Villoresi, T. Jennewein, F. Tamburini et al, Experimental verification of the feasibility of a quantum channel between Space and Earth (2008)

S. Ashhab, K. Maruyama, C. Brukner, and F. Nori, Bell's experiment with intra- and inter-pair entanglement: Single-particle mode entanglement as a case study Phys. Rev. A 80 062106 

M. Aspelmeyer, Quantum Tomography: Measured Measurement, Nature 5 11 (2009)

M. Aspelmeyer, J. Eisert, Quantum Mechanics: Entangled Families , Nature 455 180 (2009)

G. D. Cole, S. Gröblacher, K. Gugler, S. Gigan, M. Aspelmeyer, Monocrystalline AlGaAs heterostructures for high-reflectivity high-Q micromechanical resonators in the MHz regime, APL 92 261108 (2009)

F. Costa, N. Harrigan, T. Rudolph, and C. Brukner, Entanglement detection with bounded reference frames , NJP 11 123007 (2009)

A. Fedrizzi, T. Herbst, M. Aspelmeyer, M. Barbieri, T. D. Jennewein, A. Zeilinger, Anti-symmetrization reveals hidden entanglement , NJP 11 103052 (2009)

A. Fedrizzi, R. Ursin, T. Herbst, M. Nespoli, R. Prevedel, T. Scheidl, F. Tiefenbacher, T. Jennewein, A. Zeilinger, High-fidelity transmission of entanglement over a high-loss free-space channel , Nature 5 389 (2009)

C. Genes, D. Vitali, P. Tombesi, S. Gigan, M. Aspelmeyer, Ground-state cooling of a micromechanical oscillator: comparing cold damping and cavity-assisted cooling schemes , Phys. Rev. A 77 033804 (2009)

S. Gröblacher, K. Hammerer, M. R. Vanner, M. Aspelmeyer, Observation of strong coupling between a micromechanical resonator and an optical cavity field , Nature 460 724 (2009)

S. Gröblacher, J. B. Hertzberg, M. R. Vanner, G. D. Cole, S. Gigan, K. C. Schwab, M. Aspelmeyer, Demonstration of an ultracold micro-optomechanical oscillator in a cryogenic cavity , Nature 5 485 (2009)

K. Hammerer, M. Aspelmeyer, E. S. Polzik, P. Zoller, Establishing Einstein-Podolsky-Rosen channels between Nanomechanics and Atomic Ensembles , Phys. Rev. Lett. 102 020501 (2009)

R. Kaltenbaek, R. Prevedel, M. Aspelmeyer, A. Zeilinger, High-fidelity entanglement swapping with fully independent sources , Phys. Rev. A 79 040302 (2009)

M. Pawlowski and C. Brukner, Monogamy of Bell's inequality violations in nonsignaling theories , Phys. Rev. Lett. 102 030403 (2009)

R. Prevedel, G. Cronenberg, M. S. Tame, M. Paternostro, P. Walther, M. S. Kim, A. Zeilinger, Experimental Realization of Dicke States of up to Six Qubits for Multiparty Quantum Networking , Phys. Rev. Lett. 103 020503 (2009)

P. Rabl, C. Genes, K. Hammerer, M. Aspelmeyer, Phase-noise induced limitations on resolved-sideband cavity cooling of mechanical resonators , Phys. Rev. A 80 063819 (2009)

S. Ramelow, L. Ratschbacher, A. Fedrizzi, N. K. Langford, A. Zeilinger, Discrete, Tunable Color Entanglement , Phys. Rev. Lett. 103 253601 (2009)

T. Scheidl, R. Ursin, A. Fedrizzi, S. Ramelow, X. S. Ma, T. Herbst, R. Prevedel, L. Ratschbacher, J. Kofler, T. Jennewein, A. Zeilinger, Feasibility of 300km quantum key distribution with entangled states , njp 11 085002 (2009)

W. Son, J. Kofler, M. S. Kim, V. Vedral, and C. Brukner, Positive Phase Space Transformation Incompatible with Classical Physics , Phys. Rev. Lett. 102 110404 (2009)

P. Villoresi, T. Jennewein, F. Tamburini, M. Aspelmeyer, C. Bonato, R. Ursin, C. Pernechele, V. Luceri, G. Bianco, A. Zeilinger, C. Barbieri, Experimental verification of the feasibility of a quantum channel between Space and Earth , NJP 10 033038 (2009)


Related work

R. Prevedel, M. S. Tame, A. Stefanov et al, Experimental demonstration of decoherence-free one-way quantum processing, accepted for publication in Phys. Rev. Lett.

P. Villoresi, T. Jennewein, F. Tamburini et al, Experimental demonstration of a quantum communication channel from a LEO satellite to Earth, submitted to Science


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