Demonstration of Einstein-Podolsky-Rosen Steering Using Single-Photon Path Entanglement and Displacement-Based Detection.

We demonstrate the violation of an Einstein-Podolsky-Rosen steering inequality developed for single-photon path entanglement with displacement-based detection. We use a high-rate source of heralded single-photon path-entangled states, combined with high-efficiency superconducting-based detectors, in a scheme that is free of any postselection and thus immune to the detection loophole. This result conclusively demonstrates single-photon entanglement in a one-sided device-independent scenario, and opens the way towards implementations of device-independent quantum technologies within the paradigm of path entanglement.

Practical Relativistic Bit Commitment.

Bit commitment is a fundamental cryptographic primitive in which Alice wishes to commit a secret bit to Bob. Perfectly secure bit commitment between two mistrustful parties is impossible through an asynchronous exchange of quantum information. Perfect security is, however, possible when Alice and Bob each split into several agents exchanging classical information at times and locations suitably chosen to satisfy specific relativistic constraints. In this Letter we first revisit a previously proposed scheme [C. Crépeau et al., Lect. Notes Comput. Sci. 7073, 407 (2011)] that realizes bit commitment using only classical communication. We prove that the protocol is secure against quantum adversaries for a duration limited by the light-speed communication time between the locations of the agents. We then propose a novel multiround scheme based on finite-field arithmetic that extends the commitment time beyond this limit, and we prove its security against classical attacks. Finally, we present an implementation of these protocols using dedicated hardware and we demonstrate a 2 ms-long bit commitment over a distance of 131 km. By positioning the agents on antipodal points on the surface of Earth, the commitment time could possibly be extended to 212 ms.

High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films.

We report on MoSi SNSPDs which achieved high system detection efficiency (87.1 ± 0.5% at 1542 nm) at 0.7 K and we demonstrate that these detectors can also be operated with saturated internal efficiency at a temperature of 2.3 K in a Gifford-McMahon cryocooler. We measured a minimum system jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.3 ± 0.1%. The performance of MoSi SNSPDs at 2.3 K is similar to the performance of WSi SNSPDs at < 1 K. The higher operating temperature of MoSi SNSPDs makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation.

Experimental bit commitment based on quantum communication and special relativity.

Bit commitment is a fundamental cryptographic primitive in which Bob wishes to commit a secret bit to Alice. Perfectly secure bit commitment between two mistrustful parties is impossible through asynchronous exchange of quantum information. Perfect security is however possible when Alice and Bob split into several agents exchanging classical and quantum information at times and locations suitably chosen to satisfy specific relativistic constraints. Here we report on an implementation of a bit commitment protocol using quantum communication and special relativity. Our protocol is based on [A. Kent, Phys. Rev. Lett. 109, 130501 (2012)] and has the advantage that it is practically feasible with arbitrary large separations between the agents in order to maximize the commitment time. By positioning agents in Geneva and Singapore, we obtain a commitment time of 15 ms. A security analysis considering experimental imperfections and finite statistics is presented.

Fast and simple characterization of a photon pair source.

We present an exact model of the detection statistics of a probabilistic source of photon pairs from which a fast, simple and precise method to measure the source's brightness and photon channel transmissions is demonstrated. We measure such properties for a source based on spontaneous parametric downconversion in a periodically poled LiNbO(3) crystal producing pairs at 810 and 1550 nm wavelengths. We further validate the model by comparing the predicted and measured values for the g((2))(0) of a heralded single photon source over a wide range of the brightness. Our model is of particular use for monitoring and tuning the brightness on demand as required for various quantum communication applications. We comment on its applicability to sources involving spectral and/or spatial filtering.

[Role of Cahuzac's operation in clubfoot varus equina revision surgery]. / Place de l'opération de Cahuzac dans la chirurgie itérative du pied bot varus équin.

PURPOSE OF THE STUDY: The authors report 24 cases of revision in recurrent club foot deformity. They assessed Cahuzac's procedure for treatment of the residual forefoot adduction. This procedure (opening of the first cuneo-metatarsal joint and proximal abduction osteotomy of the second, third, and fourth metatarsals) was generally associated with postero-medial, plantar release, and split tibialis anterior tendon transfer. MATERIAL: Twenty four procedures for 20 children at mean age of five years have been performed. The revision chart comprised 12 clinical and radiological items as proposed by Seringe. RESULTS: Seven feet were considered as excellent, 14 as good, 2 as fair, and 1 as poor. The mean follow-up was four years. DISCUSSION: Treatment of the adduction component with Cahuzac procedure is focused on the fore part of the foot, and on the calcaneo-pedal block by postero medial release, but never on the midfoot, as no Evans or Lichtblau's procedure has been performed. This series was compared to others procedures, and morphological results were equivalent. Cahuzac's operation is riskless for foot growth, and needs two approaches which can be useful for simultaneous procedures as split lateral transfer of tibialis anterior tendon. CONCLUSION: Metatarsal osteotomies (Cahuzac's procedure), associated with soft tissues release and split anterior tibial transfer, seems to be effective in surgical treatment of relapsed clubfeet, but the debate concerning the location of the adduction component of the deformity remains still open.