Spectrally pure microwave sources are highly desired for several<br> applications, ranging from wireless communication to next generation<br> radar technology and metrology. Additionally, to generate very pure<br> signals at even higher frequencies, these advanced microwave sources<br> have to be compact, low in weight, and low energy consumption to comply<br> with in-field applications. A hybrid optical and electronic cavity,<br> known as an optoelectronic oscillator (OEO), has the potential to<br> leverage the high bandwidth of optics to generate ultrapure<br> high-frequency microwave signals. Here we present a widely tunable, low<br> phase noise microwave source based on a photonic chip. Using on-chip<br> stimulated Brillouin scattering as a narrow-band active filter allows<br> single-mode OEO operation and ultrawide frequency tunability with no<br> signal degeneration. Furthermore, we show very low close-to-carrier<br> phase noise. This Letter paves the way to a compact, fully integrated<br> pure microwave source. (C) 2016 Optical Society of America
Attacks on practical quantum key distribution systems (and how to
prevent them)
Nitin Jain,
Birgit Stiller,
Imran Khan,
Dominique Elser,
Christoph Marquardt,
Gerd Leuchs
With the emergence of an information society, the idea of protecting sensitive data is steadily gaining importance. Conventional encryption methods may not be sufficient to guarantee data protection in the future. Quantum key distribution (QKD) is an emerging technology that exploits fundamental physical properties to guarantee perfect security in theory. However, it is not easy to ensure in practice that the implementations of QKD systems are exactly in line with the theoretical specifications. Such theory-practice deviations can open loopholes and compromise security. Several such loopholes have been discovered and investigated in the last decade. These activities have motivated the proposal and implementation of appropriate countermeasures, thereby preventing future attacks and enhancing the practical security of QKD. This article introduces the so-called field of quantum hacking by summarising a variety of attacks and their prevention mechanisms.
Efficient microwave to optical photon conversion: an electro-optical
realization
Alfredo Rueda,
Florian Sedlmeir,
Michele C. Collodo,
Ulrich Vogl,
Birgit Stiller,
Gerhard Schunk,
Dmitry V. Strekalov,
Christoph Marquardt,
Johannes M. Fink, et al.
Linking classical microwave electrical circuits to the optical telecommunication band is at the core of modern communication. Future quantum information networks will require coherent microwave-to-optical conversion to link electronic quantum processors and memories via low-loss optical telecommunication networks. Efficient conversion can be achieved with electro-optical modulators operating at the single microwave photon level. In the standard electro-optic modulation scheme, this is impossible because both up-and down-converted sidebands are necessarily present. Here, we demonstrate true single-sideband up-or down-conversion in a triply resonant whispering gallery mode resonator by explicitly addressing modes with asymmetric free spectral range. Compared to previous experiments, we show a 3 orders of magnitude improvement of the electro-optical conversion efficiency, reaching 0.1% photon number conversion for a 10 GHz microwave tone at 0.42 mW of optical pump power. The presented scheme is fully compatible with existing superconducting 3D circuit quantum electrodynamics technology and can be used for nonclassical state conversion and communication. Our conversion bandwidth is larger than 1 MHz and is not fundamentally limited. (C) 2016 Optical Society of America
Contact
Research Group Birgit Stiller
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
