82 research outputs found
NOON states from cavity-enhanced down-conversion: High quality and super-resolution
Indistinguishable photons play a key role in quantum optical information
technologies. We characterize the output of an ultra-bright photon-pair source
using multi-particle tomography [R. B. A. Adamson et al., Phys. Rev. Lett. 98,
043601 (2007)] and separately identify coherent errors, decoherence, and
distinguishability. We demonstrate generation of high-quality indistinguishable
pairs and polarization NOON states with 99% fidelity to an ideal NOON state.
Using a NOON state we perform a super-resolving angular measurement with 90%
visibility.Comment: 4 Pages, 5 figure
Symmetrical clock synchronization with time-correlated photon pairs
We demonstrate a point-to-point clock synchronization protocol based on
bidirectionally exchanging photons produced in spontaneous parametric down
conversion (SPDC). The technique exploits tight timing correlations between
photon pairs to achieve a precision of 51ps in 100s with count rates of order
200s. The protocol is distance independent, secure against symmetric
delay attacks and provides a natural complement to techniques based on Global
Navigation Satellite Systems (GNSS). The protocol works with mobile parties and
can be augmented to provide authentication of the timing signal via a Bell
inequality check.Comment: 5 pages, 5 figure
Probing quantum-classical boundary with compression software
We experimentally demonstrate that it is impossible to simulate quantum
bipartite correlations with a deterministic universal Turing machine. Our
approach is based on the Normalized Information Distance (NID) that allows the
comparison of two pieces of data without detailed knowledge about their origin.
Using NID, we derive an inequality for output of two local deterministic
universal Turing machines with correlated inputs. This inequality is violated
by correlations generated by a maximally entangled polarization state of two
photons. The violation is shown using a freely available lossless compression
program. The presented technique may allow to complement the common statistical
interpretation of quantum physics by an algorithmic one.Comment: 7 pages, 6 figure
Urban-scale framework for assessing the resilience of buildings informed by a delphi expert consultation
The integration of resilience in disaster management is an emerging field as evidenced by an abundant literature. While resilience has been widely explored in several domains, its application demands the consideration of the entire ecosystem and its lifecycle, including disaster stressors and consequences, recovery process, and ultimately the prevention phase. In this paper, a qualitative characterization of resilience for buildings on an urban scale of analysis is achieved throughout the conduct of a Delphi-based expert consultation. The aim is to elicit and validate relevant criteria to characterize the resilience of our built-environment in face of geo-environmental hazards through two phases of consultation involving 23 and 21 respondents, respectively. The initial set of criteria consisted of 40 indicators, increasing to 48 at the end of the survey. The different criteria are clustered into seven categories, ranging from environmental to socio-organizational and technical. The results from both rounds of consultation were then analysed by means of statistical analysis with MATLAB and discussed for each category. The preliminary version of the framework for buildings’ resilience assessment on an urban scale is presented with a final set of 43 validated criteria
Experimental Test of Two-way Quantum Key Distribution in Presence of Controlled Noise
We describe the experimental test of a quantum key distribution performed
with a two-way protocol without using entanglement. An individual incoherent
eavesdropping is simulated and induces a variable amount of noise on the
communication channel. This allows a direct verification of the agreement
between theory and practice.Comment: 4 pages, 3 figure
Football history: a German perspective on current research fields
In the last 25 years, German football has experienced several turning points. First, the collapse of communism in 1989 rendered necessary a complete reorganisation of the sport and football landscape in eastern Germany. Second, in parallel with the award in the year 2000 of the right to host the 2006 FIFA World Cup in the Federal Republic of Germany, a significant upturn took place in academic research on football. The reappraisal of the National Socialist era, in particular, has experienced a noticeable upswing since the year 2000. The present article focuses on several key thematic areas that shape current research and will shape research in the future. They include, first, the question of the character of the Vereine (here: football clubs) under the conditions of a communist dictatorship, and second, an increased interest in the biographical component of the history of the development of football. At the same time, it is clear that by now the question of a memory culture in football is no longer limited to national perspectives such as the reappraisal of the "Miracle of Bern". Rather, the dynamic development of European football renders possible the emergence of European realms of shared memory. At the same time, a boom in public engagement with football history can be observed in Germany and elsewhere. This holds true for both the social commemoration of footballers who were victims of war and tyranny and for popular cultural publications. In recent years, therefore, there has not only been an increase in the “museumisation” but also in the media marketing of football history. Thus, football history itself has become a market that is served by various stakeholders, such as clubs, companies, and the media
Narrowband tunable filter based on velocity-selective optical pumping in an atomic vapor
We demonstrate a tunable, narrow-band filter based on optical-pumping-induced
circular dichroism in rubidium vapor. The filter achieves a peak transmission
of 14.6%, a linewidth of 80 MHz, and an out-of-band extinction >35 dB. The
transmission peak can be tuned within the range of the Doppler linewidth of the
D1 line of atomic rubidium at 795 nm. While other atomic filters work at
frequencies far from absorption, the presented technique provides light
resonant with atomic media, useful for atom-photon interaction experiments. The
technique could readily be extended to other alkali atoms.Comment: 3 Pages, 4 figure
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