Prospective directions for the development of microwave frequency standards for satellite navigation systems

The state of essential various quantum standards of GNSS frequencies for today are collected and presented, the results of analysis in the direction of modernization of time synchronization systems in global navigation satellite systems are presented. The most perspective directions of modernization of global navigation satellite systems are mentioned – the development of new atomic clocks on the mercury ions -199. The data on experimental satellite gives encouraging results.

Modified quantum frequency standard on Hg-199 ions

The world around us depends on devices capable of producing or maintaining a signal with an extreme precision. Quantum frequency standards are the answer to this problem. This article presents a modified version of newly developed quantum frequency standard based on trapping Hg-199 ions by magnetic field. The new prototype was developed a while ago and now it was modified due to algorithm improvements and renewed digital hardware, analog and digital circuitry being reordered. Results for Allan deviation show 3 % improvement for long-term frequency stability and more than 5 % for short-term stability

Cascaded Microwave Frequency Transfer over 300-km Fiber Link with Instability at the 10−18 Level

Comparing and synchronizing atomic clocks between distant laboratories with ultra-stable frequency transfer are essential procedures in many fields of fundamental and applied science. Existing conventional methods for frequency transfer based on satellite links, however, are insufficient for the requirements of many applications. In order to achieve high-precision microwave frequency transfer over a thousand kilometers of fiber and to construct a fiber-based microwave transfer network, we propose a cascaded system for microwave frequency transfer consisting of three 100-km single-span spooled fiber links using an improved electronic phase compensation scheme. The transfer instability measured for the microwave signal reaches 1.1 × 10−14 at 1 s and 6.8 × 10−18 at 105 s, which agrees with the root-sum-square of each span contribution. It is feasible to extend the length of the fiber-based microwave frequency transfer up to 1200 km using 4 stages of our cascaded system, which is still sufficient to transfer modern cold atom microwave frequency standards. Moreover, the transfer instability of 9.0 × 10−15 at 1 s and 9.0 × 10−18 at 105 s for a 100-MHz signal is achieved. The residual phase noise power spectral density of the 300-km cascaded link measured at 100-MHz is also obtained. The rejection frequency bandwidth of the cascaded link is limited by the propagation delay of one single-span link.

SIMULATION OF INSTABILITIES OF QUANTUM FREQUENCY STANDARDS FOR PROBLEMS OF TIME SERVICES AND NAVIGATION

In the article, two models of instability of quantum frequency standards (QFS) are considered. This is a generally accepted stochastic model that describes the effect of noise with different frequencies on the stability of the clock and the simulation model proposed by the authors of this article, based on the Monte Carlo method and a software random number generator. Based on simulation results, a comparative analysis of advantages and disadvantages of the proposed QFS model in comparison with the classical model was carried out. The results of modeling, which showed good convergence with the accepted theoretical assumptions, are presented. The rationale for the feasibility of using the proposed model in the processing of navigation measurements is given. The possibilities of increasing the accuracy of synchronization of remote sets of reference time are shown.

Non-destructive State Detection and Spectroscopy of Single Molecules

We review our recent experimental results on the non-destructive quantum-state detection and spectroscopy of single trapped molecules. At the heart of our scheme, a single atomic ion is used to probe the state of a single molecular ion without destroying the molecule or even perturbing its quantum state. This method opens up perspectives for new research directions in precision spectroscopy, for the development of new frequency standards, for tests of fundamental physical concepts and for the precise study of chemical reactions and molecular collisions with full control over the molecular quantum state.