QUROPE Quantum Information Processing and Communication in Europe

Single-photon entanglement is one of the primary resources for quantum networks, including quantum repeater architectures. Such entanglement can be revealed with only local homodyne measurements through the entanglement witness presented in Morin et al (2013 Phys. Rev. Lett. 110 130401). Here, we provide an extended analysis of this witness by introducing analytical bounds and by reporting measurements confirming its great robustness with regard to losses.

What is the most efficient way to generate random numbers device-independently using a photon pair source based on spontaneous parametric down conversion? We consider this question by comparing two implementations of a detection-loophole-free Bell test. In particular, we study in detail a scenario where a source is used to herald path-entangled states, i.e.

We study the operation of linear optics schemes for entanglement distribution based on nonlocal photon subtraction when input states, produced by imperfect single-photon sources, exhibit both vacuum and multiphoton contributions. Two models for realistic photon statistics with radically different properties of the multiphoton “tail” are considered. The first model assumes occasional emission of double photons and linear attenuation, while the second one is motivated by heralded sources utilizing spontaneous parametric down-conversion.

How can one detect entanglement between multiple optical paths sharing a single photon? We address this question by proposing a scalable protocol, which only uses local measurements where single photon detection is combined with small displacement operations. The resulting entanglement witness does not require postselection, nor assumptions about the photon number in each path. Furthermore, it guarantees that entanglement lies in a subspace with at most one photon per optical path and reveals genuinely multipartite entanglement.

DK MataiChairman and Founder at Quantum Innovation Labs (QiLabs.net) take a look of what he believes are the 10 key facts for investing in the Quantum Technologies field.

Read the full Linkedin entry here.

Y-L. Tang, H-L. Yin, S-J.Chen, Y. Liu, W-J. Zhang, X. Jiang, L. Zhang, J. Wang, L-X. You, J-Y. Guan, D- X. Yang, Z. Wang, H. Liang, Z. Zhang, N. Zhou, X. Ma, T-Y. Chen, Q. Zhang, and J-W. Pan
Phys. Rev. Lett. 113, 190501 (2014)

Measurement-device–independent quantum key distribution (MDIQKD) represents a valid alternative for quantum cryptography. It requires fewer assumptions for security than standard prepare-and-measure schemes, while its implementation is less demanding than fully device-independent protocols.

R. W. Andrews, R. W. Peterson, T. P. Purdy, K. Cicak, R. W. Simmonds, C. A. Regal, and K. W. Lehnert Nature Physics 10, 321-326 (2014)

A quantum gate between a flying optical photon and a single trapped atom
A. Reiserer, N. Kalb, G. Rempe, S. Ritter
Nature 508, 237-240 (2014);
Nanophotonic quantum phase switch with a single atom
T. G. Tiecke, J. D. Thompson, N. P. de Leon, L. R. Liu, V. Vuletic, M. D. Lukin Nature 508, 241-244 (2014);
Nonlinear π phase shift for single fibre-guided photons interacting with a single resonator-enhanced atom
J. Volz, M. Scheucher, C. Junge, A. Rauschenbeutel
Nature Photonics 8, 965-970 (2014);

Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory
F. Bussières, C. Clausen, A. Tiranov, B. Korzh, V. B Verma, S.W. Nam, F. Marsili, A. Ferrier, P. Goldner, H. Herrmann, C. Silberhorn, W. Sohler, M. Afzelius, N. Gisin
Nature Photonics 8, 775-778 (2014);
Unconditional quantum teleportation between distant solid-state quantum bits
W. Pfaff, B.J. Hensen, H. Bernien, S.B. van Dam, M.S. Blok, T.H. Taminiau, M.J. Tiggelman, R.N. Schouten, M. Markham, D.J. Twitchen, R. Hanson

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