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Braunschweig, Germany

The Physikalisch-Technische Bundesanstalt is based in Braunschweig and Berlin. It is the national institute for natural and engineering science and the highest technical authority for metrology and physical safety engineering in Germany.The PTB is entrusted by the Time Act to realise and disseminate legal time to the public. The most popular means is the transmission of standard frequency and time signals by the longwave time signal DCF77. It is responsible for four German caesium atomic clocks, CS1, CS2, CSF1 and CSF2 . These atomic clocks have an important role in maintaining accurate worldwide time of day as they provide the German UTC legal time standard which - combined with other official atomic time standards - is used by the Bureau International des Poids et Mesures to create a single, official Coordinated Universal Time . In addition, the PTB operates the "stratum 1" ptbtime1.ptb.de, ptbtime2.ptb.de and ptbtime3.ptb.de public Network Time Protocol time servers for the distribution of time on the internet.They are also responsible for the certification of voting machines for the German federal and European elections, and electroshock weapons. Wikipedia.

Wulf M.,Physikalisch - Technische Bundesanstalt
Physical Review B - Condensed Matter and Materials Physics

Electron counting experiments attempt to provide a current of a known number of electrons per unit time. We propose architectures utilizing a few readily available electron pumps or turnstiles with modest error rates of 1 part per 104 with common sensitive electrometers to achieve the desirable accuracy of 1 part in 108. This is achieved not by counting all transferred electrons, but by counting only the errors of individual devices; these are less frequent and therefore readily recognized and accounted for. Our proposal thereby eases the route towards quantum-based standards for current and capacitance. © 2013 American Physical Society. Source

Single-mode optical fiber is a highly efficient connecting medium used not only for optical telecommunications but also for the dissemination of ultrastable frequencies or timing signals. Ma et al. [Opt. Lett. 19, 1777 (1994)] described a measurement and control system to deliver the same optical frequency at two places, namely the two ends of a fiber, by eliminating the "fiber-induced phase-noise modulation, which corrupts high-precision frequency-based applications." I present a simple detection and control scheme to deliver the same optical frequency at many places anywhere along a transmission path, or in its vicinity, with a relative instability of 1 part in 1019. The same idea applies to radio frequency and timing signals. This considerably simplifies future efforts to make precise timing or frequency signals available to many users, as required in some large-scale science experiments. © 2014 Optical Society of America. Source

Fischer J.,Physikalisch - Technische Bundesanstalt
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

At its 25th meeting, the General Conference on Weights and Measures (CGPM) approved Resolution 1 'On the future revision of the International System of Units, the SI', which sets the path towards redefinition of four base units at the next CGPM in 2018. This constitutes a decisive advance towards the formal adoption of the new SI and its implementation. Kilogram, ampere, kelvin and mole will be defined in terms of fixed numerical values of the Planck constant, elementary charge, Boltzmann constant and Avogadro constant, respectively. The effect of the new definition of the kelvin referenced to the value of the Boltzmann constant k is that the kelvin is equal to the change of thermodynamic temperature T that results in a change of thermal energy kT by 1.380 65 × 10-23 J. A value of the Boltzmann constant suitable for defining the kelvin is determined by fundamentally different primary thermometers such as acoustic gas thermometers, dielectric constant gas thermometers, noise thermometers and the Doppler broadening technique. Progress to date of the measurements and further perspectives are reported. Necessary conditions to be met before proceeding with changing the definition are given. The consequences of the new definition of the kelvin on temperature measurement are briefly outlined. © 2016 The Author(s). Source

Kashcheyevs V.,University of Latvia | Kaestner B.,Physikalisch - Technische Bundesanstalt
Physical Review Letters

Dynamic quantum dots can be formed by time-dependent electrostatic potentials, such as in gate- or surface-acoustic-wave-driven electron pumps. In this work we propose and quantify a scheme to initialize quantum dots with a controllable number of electrons. It is based on a rapid increase of the electron potential energy and simultaneous decoupling from the source lead. The full probability distribution for the final number of captured electrons is obtained by solving a master equation for stochastic cascade of single electron escape events. We derive an explicit fitting formula to extract the sequence of decay rate ratios from the measurements of averaged current in a periodically driven device. This provides a device-specific fingerprint which allows us to compare different architectures, and predict the upper limits of initialization accuracy from low precision measurements. © 2010 The American Physical Society. Source

Rohde & Schwarz and Physikalisch - Technische Bundesanstalt | Date: 2010-06-14

A method for the error correction of a vectorial network analyzer, where a primary system calibration is initially implemented using a calibration kit. Following this, a first, secondary error correction is implemented on at least two one-port networks of the vectorial network analyzer. After this first, secondary error correction of the one-port networks of the vectorial network analyzer, a second, secondary error correction is implemented, where either two one-port networks are through-connected in an ideal manner or a measurement is implemented on a reciprocal two-port network. The corrected system-error values from the first, secondary error correction are used even in this further measurement, and overall, a high-precision, calibrated multi-port network analyzer is obtained.

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