München, Germany
München, Germany

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Furst M.,Ludwig Maximilians University of Munich | Furst M.,Qutools GmbH | Weier H.,Ludwig Maximilians University of Munich | Weier H.,Qutools GmbH | And 5 more authors.
Optics Express | Year: 2010

We present a fully integrated, ready-for-use quantum random number generator (QRNG) whose stochastic model is based on the randomness of detecting single photons in attenuated light. We show that often annoying deadtime effects associated with photomultiplier tubes (PMT) can be utilized to avoid postprocessing for bias or correlations. The random numbers directly delivered to a PC, generated at a rate of up to 50 Mbit/s, clearly pass all tests relevant for (physical) random number generators. © 2010 Optical Society of America.

Steinlechner F.,ICFO - Institute of Photonic Sciences | Trojek P.,Qutools GmbH | Trojek P.,Ludwig Maximilians University of Munich | Trojek P.,Max Planck Institute of Quantum Optics | And 15 more authors.
Optics Express | Year: 2012

We present a simple but highly efficient source of polarizationentangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phasematching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW. © 2012 Optical Society of America.

Agency: Cordis | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-2011-ITN | Award Amount: 2.87M | Year: 2012

Rare-earth ions (lanthanides) play an increasingly important role in modern optical technologies. Lanthanides are extensively used in solid-state laser physics, e.g. as key components in telecommunication networks. Rare-earths are also employed as luminescent materials in lamps or as radiation detectors in X-ray imaging. Rare-earths are already commercially omnipresent. However, the full potential of rare-earth ions is not yet explored in particular with regard to the rapidly evolving field of future information technology. Future data storage and processing will require novel types of memories (e.g. based on interactions between light and quantized matter), algorithms (e.g. based on quantum computations) and materials (e.g. appropriate quantum systems). Rare-earth ion doped solids are very promising candidates to permit implementation of future quantum technology. The media combine the advantages of solids (i.e. large density and scalability) and atomic gases (i.e. long coherence times). CIPRIS will build on the advantages of rare-earth doped media and drive applications towards future information technology. CIPRIS follows two scientific approaches : Classical processing and quantum processing. Both are meant as pronounced inter-disciplinary research efforts, combining physics, material science and information technology. To exploit the results, the public and private sector partners will closely cooperate to develop commercial demonstration devices. In terms of training, CIPRIS aims at the development of the next generation of young researchers with appropriate skills in rare-earth-based information technology pushing it towards commercial applications. CIPRIS offers a large variety of training actions, e.g. mini schools, laboratory courses, secondments to the private sector, or training sessions to strengthen complementary skills and contacts to the private sector. This will contribute to a European knowledge base for future information technology.

Vest G.,Ludwig Maximilians University of Munich | Vest G.,Qutools GmbH | Rau M.,Ludwig Maximilians University of Munich | Fuchs L.,Ludwig Maximilians University of Munich | And 10 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2015

Currently most quantum key distribution (QKD) experiments are focusing on efficient long-distance implementations. Yet the recent development of miniaturized photonic modules and integrated quantum optics circuits could open new perspectives toward secure short-distance communication for daily-life applications. Here, we present the design of a new integrated optics architecture with an effective size of 25 mm\, {\times } \,2 mm\, {\times } \, 1\,mm. Our objective is to obtain an ultraflat microoptics QKD add-on suitable for integration into handheld platforms such as smartphones. In this context, we evaluated the suitability of various optical subsystems. We tested an array of four vertical cavity surface emitting lasers (VCSEL) with highly similar emission properties capable of producing subnanosecond near-infrared pulses at 100-MHz repetition rate. As short pulses exhibit a low polarization degree, their polarization can be externally controlled by a micropolarizer array. The fabrication of such elements is quite straightforward using standard lithographic techniques and extinction ratios up to 29 \,dB have been measured. To guarantee spatial indistinguishability of the qubits, we investigate the option of using low-birefringence, single-mode waveguide array manufactured via femtosecond laser micromachining. © 1995-2012 IEEE.

Moll F.,German Aerospace Center | Weinfurter H.,Ludwig Maximilians University of Munich | Rau M.,Ludwig Maximilians University of Munich | Schmidt C.,German Aerospace Center | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

A worldwide growing interest in fast and secure data communications pushes technology development along two lines. While fast communications can be realized using laser communications in fiber and free-space, inherently secure communications can be achieved using quantum key distribution (QKD). By combining both technologies in a single device, many synergies can be exploited, therefore reducing size, weight and power of future systems. In recent experiments we demonstrated quantum communications over large distances as well as between an aircraft and a ground station which proved the feasibility of QKD between moving partners. Satellites thus may be used as trusted nodes in combination with QKD receiver stations on ground, thereby enabling fast and secure communications on a global scale. We discuss the previous experiment with emphasis on necessary developments to be done and corresponding ongoing research work of German Aerospace Center (DLR) and Ludwig Maximilians University Munich (LMU). DLR is performing research on satellite and ground terminals for the high-rate laser communication component, which are enabling technologies for the QKD link. We describe the concept and hardware of three generations of OSIRIS (Optical High Speed Infrared Link System) laser communication terminals for low Earth orbiting satellites. The first type applies laser beam pointing solely based on classical satellite control, the second uses an optical feedback to the satellite bus and the third, currently being in design phase, comprises of a special coarse pointing assembly to control beam direction independent of satellite orientation. Ongoing work also targets optical terminals for CubeSats. A further increase of beam pointing accuracy can be achieved with a fine pointing assembly. Two ground stations will be available for future testing, an advanced stationary ground station and a transportable ground station. In parallel the LMU QKD source size will be reduced by more than an order of magnitude thereby simplifying its integration into future free-space optical communication links with CubeSats. © 2016 COPYRIGHT SPIE.

Weier H.,Ludwig Maximilians University of Munich | Weier H.,Qutools GmbH | Krauss H.,Ludwig Maximilians University of Munich | Rau M.,Ludwig Maximilians University of Munich | And 6 more authors.
New Journal of Physics | Year: 2011

The security of quantum key distribution (QKD) can easily be obscured if the eavesdropper can utilize technical imperfections in the actual implementation. Here, we describe and experimentally demonstrate a very simple but highly effective attack that does not need to intercept the quantum channel at all. Only by exploiting the dead time effect of single-photon detectors is the eavesdropper able to gain (asymptotically) full information about the generated keys without being detected by state-of-the-art QKD protocols. In our experiment, the eavesdropper inferred up to 98.8% of the key correctly, without increasing the bit error rate between Alice and Bob significantly. However, we find an even simpler and more effective countermeasure to inhibit this and similar attacks. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Heindel T.,University of Würzburg | Kessler C.A.,Institute For Halbleiteroptik Und Funktionelle Grenzflachen | Rau M.,Ludwig Maximilians University of Munich | Schneider C.,University of Würzburg | And 19 more authors.
New Journal of Physics | Year: 2012

We report on in-lab free space quantum key distribution (QKD) experiments over 40 cm distance using highly efficient electrically driven quantum dot single-photon sources emitting in the red as well as near-infrared spectral range. In the case of infrared emitting devices, we achieve sifted key rates of 27.2 kbit s -1(35.4 kbit s -1) at a quantum bit error rate (QBER) of 3.9% (3.8%) and a g (2)(0) value of 0.35 (0.49) at moderate (high) excitation. The red emitting diodes generate sifted keys at a rate of 95.0 kbit s -1 at a QBER of 4.1% and a g (2)(0) value of 0.49. This first successful proof of principle QKD experiment based on electrically operated semiconductor single-photon sources can be considered as a major step toward practical and efficient quantum cryptography scenarios. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Rau M.,Ludwig Maximilians University of Munich | Vogl T.,Ludwig Maximilians University of Munich | Corrielli G.,CNR Institute for Photonics and Nanotechnologies | Vest G.,Ludwig Maximilians University of Munich | And 5 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2014

The quantum key distribution protocol uses one degree of freedom of a single quantum system to encode information. If this information has correlations with the system's other degrees of freedom, or if the measurement efficiencies on the receiver side depend on them, a security loophole called side channel is created. An eavesdropper can exploit it to gain information without disturbing the system, and thus, without revealing the attack. Here, we analyze side channels in a free-space QKD sender and receiver implementation and focus especially on the dependencies and side channels for the spatial degree of freedom. © 2014 IEEE.

Steinlechner F.,ICFO - Institute of Photonic Sciences | Trojek P.,Qutools GmbH | Trojek P.,Ludwig Maximilians University of Munich | Trojek P.,Max Planck Institute of Quantum Optics | And 6 more authors.
Optics InfoBase Conference Papers | Year: 2011

We present a simple but highly efficient source of polarization entangled photons based on SPDC in bulk PPKTP. Utilizing the highest available nonlinear coefficient in a type 0 collinear configuration, as well as an optimized geometry of the setup, we expect to exceed the brightness achieved in current schemes by at least an order of magnitude.

Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2011.9.9 | Award Amount: 2.16M | Year: 2013

Quantum technologies promise to revolutionise our digital world providing security in communications and solutions for what have been thought of as unsolvable computational problems. The project QWAD introduces the technology of laser-written integrated optics, a powerful new tool for next generation quantum communications and computing, solving critical problems in terms of scalability and reliability. This disruptive photonic technology will speed up the evolution from lab systems to real world applications.\n\nOur consortium will target three main outcomes:\n1) Fabricate laser-written waveguides in highly integrated three dimensional structures to generate and to manipulate both path- and polarization entangled photonic qubits.\n2) Implement large integrated circuits to perform scalable quantum logic operations and quantum simulation of many-body dynamics.\n3) Design dedicated waveguide structures for fully integrated quantum key exchange and for quantum enhanced sensing in application ready prototypes.\n\nThe project benefits from the outstanding expertise of consortium members who have pioneered photonic and quantum information technologies over the past decades. The development of laser-written waveguide structures will allow extraordinary progress in terms of miniaturization and scalability while maintaining incomparable stability and durability. Key advances in quantum ICT will exploit the 3D waveguide geometries and other innovations to produce tailored quantum simulators and photonic quantum computer nodes. The development of novel ready-made quantum devices within QWAD will open new doors for innovative chip based quantum key exchange components and unrivalled efficiency and sensitivity Lab-on-a-chip devices.

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