1,330 research outputs found
Estimation of Output Channel Noise for Continuous Variable Quantum Key Distribution
Estimation of channel parameters is important for extending the range and
increasing the key rate of continuous variable quantum key distribution
protocols. We propose a new estimator for the channel noise parameter based on
the method of moments. The method of moments finds an estimator from the
moments of the output distribution of the protocol. This estimator has the
advantage of being able to use all of the states shared between Alice and Bob.
Other estimators are limited to a smaller publicly revealed subset of the
states. The proposed estimator has a lower variance for high loss channel than
what has previously been proposed. We show that the method of moments estimator
increases the key rate by up to an order of magnitude at the maximum
transmission of the protocol.Comment: 5 pages, 3 figure
Real time demonstration of high bitrate quantum random number generation with coherent laser light
We present a random number generation scheme that uses broadband measurements
of the vacuum field contained in the radio-frequency sidebands of a single-mode
laser. Even though the measurements may contain technical noise, we show that
suitable algorithms can transform the digitized photocurrents into a string of
random numbers that can be made arbitrarily correlated with a subset of the
quantum fluctuations (high quantum correlation regime) or arbitrarily immune to
environmental fluctuations (high environmental immunity). We demonstrate up to
2 Gbps of real time random number generation that were verified using standard
randomness tests
Raw-data attacks in quantum cryptography with partial tomography
We consider a variant of the BB84 protocol for quantum cryptography, the
prototype of tomographically incomplete protocols, where the key is generated
by one-way communication rather than the usual two-way communication. Our
analysis, backed by numerical evidence, establishes thresholds for
eavesdropping attacks on the raw data and on the generated key at quantum bit
error rates of 10% and 6.15%, respectively. Both thresholds are lower than the
threshold for unconditional security in the standard BB84 protocol.Comment: 11 pages, 2 figure
Crop production efficiency of sugarcane in the state of São Paulo: I. Climate and soil aspects.
Neste artigo, utilizou-se o método das zonas agroecológicas da FAO como energia de entrada e o rendimento real da cultura, observado em condições de campo ou tabulado em escala municipal pelos institutos de estatística, foi considerado como a energia resultante do processo de bioconversão. Este trabalho teve por objetivo gerar mapas de eficiência para o Estado de São Paulo e analisar qual a importância relativa do clima e do solo na variabilidade espacial da eficiência no Estado de São Paulo
Joint measurement of multiple noncommuting parameters
Although quantum metrology allows us to make precision measurements beyond the standard quantum limit, it mostly works on the measurement of only one observable due to the Heisenberg uncertainty relation on the measurement precision of noncommuting observables for one system. In this paper, we study the schemes of joint measurement of multiple observables which do not commute with each other using the quantum entanglement between two systems. We focus on analyzing the performance of a SU(1,1) nonlinear interferometer on fulfilling the task of joint measurement. The results show that the information encoded in multiple noncommuting observables on an optical field can be simultaneously measured with a signal-to-noise ratio higher than the standard quantum limit, and the ultimate limit of each observable is still the Heisenberg limit. Moreover, we find a resource conservation rule for the joint measurement
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