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We have realized an atom interferometer that probes gravitational potentials by holding, rather than dropping, atoms. Up to one minute of coherence times are realized by suspending the spatially separated atomic wave packets in an optical…
Optical lattice clocks have the potential for extremely high frequency stability owing to the simultaneous interrogation of many atoms, but this precision may come at the cost of systematic inaccuracy due to atomic interactions.…
We report a frequency measurement of the 1S0-3P0 transition of 87Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879 (5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical…
In this paper we present a novel method of atomic clock synchronisation combining digital error correction and phase tracking. Microwave broadcasts are used to measure the difference in frequency between a pair of atomic clocks. We use the…
We describe a transportable optical lattice clock based on the $^1\mathrm{S}_0 \rightarrow {^3\mathrm{P}_0}$ transition of lattice-trapped $^{87}$Sr atoms with a total systematic uncertainty of $2.1 \times 10^{-18}$. The blackbody radiation…
Optical clocks are not only powerful tools for prime fundamental research, but are also deemed for the re-definition of the SI base unit second as they now surpass the performance of caesium atomic clocks in both accuracy and stability by…
The gravity field maps of the satellite gravimetry missions GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On are derived by means of precise orbit determination. The key observation is the biased inter-satellite range,…
We report on the isotope shift between ${}^{88}$Sr and ${}^{87}$Sr on the ${}^1S_0 - {}^3P_0$ clock transitions. The interleaved operation of an optical lattice clock with two isotopes allows the canceling out of common perturbations, such…
The gedanken experiment of the clock paradox is solved exactly using the general relativistic equations for a static homogeneous gravitational field. We demonstrate that the general and special relativistic clock paradox solutions are…
Considering the OPERA neutrino-velocity measurement from the point of view of a GPS satellite we find that the detector at Gran Sasso has a velocity component in the order of $10^{-5}c$ towards the neutrino emission location at CERN. On…
An alternative to the current accepted model of expanding universe is presented. The proposal is anchored in the objective realist, stochastic formulation of quantum mechanics wherein the Planck constant plays the role of a diffusion…
Recent advances in optical atomic clocks and optical time transfer have enabled new possibilities in precision metrology for both tests of fundamental physics and timing applications. Here we describe a space mission concept that would…
Several space missions that will use atomic clocks on board of an Earth-orbiting satellite are planned for the near future, such as the Atomic Clock Ensemble in Space (ACES) or the Space Optical Clock on the ISS (I-SOC). The increasing…
Assuming a model of aether non-entrained by the motion of celestial bodies, one can provide a rational explanation of the experimental processes affecting the measurement of time when clocks are in motion. Contrary to special relativity,…
We have measured the absolute frequency of the optical lattice clock based on $^{87}$Sr at PTB with an uncertainty of $3.9\times 10^{-16}$ using two caesium fountain clocks. This is close to the accuracy of today's best realizations of the…
A fundamental description of time can be consistent not only with the usual monotonic behavior but also with a periodic physical clock variable, coupled to the degrees of freedom of a system evolving in time. Generically, one would in fact…
Recently invented and demonstrated, optical lattice clocks hold great promise for improving the precision of modern timekeeping. These clocks aim at the 10^-18 fractional accuracy, which translates into a clock that would neither lose or…
The general relativistic gravitomagnetic clock effect consists in the fact that two point particles orbiting a central spinning object along identical, circular equatorial geodesic paths, but in opposite directions, exhibit a time…
The new technique of measuring frequency by optical lattice clocks now approaches to the relative precision of $(\Delta f/f)=O(10^{-18})$. We propose to place such precise clocks in space and to use Doppler tracking method for detecting…
We report on a new test of the gravitational redshift and thus of local position invariance, an integral part of the Einstein equivalence principle, which is the foundation of general relativity and all metric theories of gravitation. We…