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We report on the experimental implementation of a Bennett-Brassard 1984 (BB84) protocol type quantum key distribution over a 144 km free-space link using weak coherent laser pulses. Optimization of the link transmission was achieved with bidirectional active telescope tracking, and the security was ensured by employing decoy-state analysis. This enabled us… (More)

Superposition is one of the most distinctive features of quantum theory and has been demonstrated in numerous single-particle interference experiments. Quantum entanglement, the coherent superposition of states in multi-particle systems, yields more complex phenomena. One important type of multi-particle experiment uses path-entangled number states, which… (More)

Distribution of entangled states between distant locations is essential for quantum communication over large distances. But owing to unavoidable decoherence in the quantum communication channel, the quality of entangled states generally decreases exponentially with the channel length. Entanglement purification--a way to extract a subset of states of high… (More)

Efficient long-distance quantum teleportation is crucial for quantum communication and quantum networking schemes. Here we describe the high-fidelity teleportation of photons over a distance of 600 metres across the River Danube in Vienna, with the optimal efficiency that can be achieved using linear optics. Our result is a step towards the implementation… (More)

- Xiao-Song Ma, Thomas Herbst, Thomas Scheidl, Daqing Wang, Sebastian Kropatschek, William Naylor +8 others
- Nature
- 2012

The quantum internet is predicted to be the next-generation information processing platform, promising secure communication and an exponential speed-up in distributed computation. The distribution of single qubits over large distances via quantum teleportation is a key ingredient for realizing such a global platform. By using quantum teleportation, unknown… (More)

- M. Peev, O. Maurhardt, T. Lorünser, M. Suda, M. Nölle, A. Poppe +4 others
- 2004

Introduction Quantum Key Distribution (QKD) or "quantum cryptography" is a Quantum Mechanics based cryptographic primitive, which, in principle, holds the potential of absolutely secure communication, which can not be compromised by any eavesdropping technique. The strength of the QKD primitive is the simultaneous generation of two identical bit streams at… (More)

We demonstrate the distribution of quantum entanglement via optical free-space links to independent receivers separated by 600 m, with no line of sight between each other. A Bell inequality between those receivers is violated by more than four standard deviations, confirming the quality of the entanglement. This outdoor experiment represents a step toward… (More)

- G. Gabrielse, J. Estrada, J. N. Tan, P. Oxley, T. Roach, M. Wessels +11 others
- 2001

Positrons are used to cool antiprotons for the first time. The oppositely charged positrons and antiprotons are first simultaneously accumulated in separate Penning trap volumes, and then are spatially merged in a nested Penning trap. The antiprotons cool until they reach a low relative velocity with respect to the cold positrons, the situation expected to… (More)

- Marissa Giustina, Alexandra Mech, Sven Ramelow, Bernhard Wittmann, Johannes Kofler, Jörn Beyer +6 others
- Nature
- 2013

The violation of a Bell inequality is an experimental observation that forces the abandonment of a local realistic viewpoint--namely, one in which physical properties are (probabilistically) defined before and independently of measurement, and in which no physical influence can propagate faster than the speed of light. All such experimental violations… (More)