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Quantum metrology with ultra-high precision usually requires atoms prepared in an ultra-stable environment with well-defined quantum states. Thus, in optical lattice clock systems deep lattice potentials are used to trap ultra-cold atoms. However, decoherence, induced by Raman scattering and higher order light shifts, can significantly be reduced if atomic clocks are realized in shallow optical lattices. On the other hand, in such lattices, tunneling among different sites can cause additional dephasing and strongly broadening of the Rabi spectrum. Here, in our experiment, we periodically drive a shallow $^{87}$Sr optical lattice clock. Counter intuitively, shaking the system can deform the wide broad spectral line into a sharp peak with 5.4Hz line-width. With careful comparison between the theory and experiment, we demonstrate that the Rabi frequency and the Bloch bands can be tuned, simultaneously and independently. Our work not only provides a different idea for quantum metrology, such as building shallow optical lattice clock in outer space, but also paves the way for quantum simulation of new phases of matter by engineering exotic spin orbit couplings., Comment: 6 pages, 5 figures, comments are welcome and more information at http://cqutp.org/users/xfzhang/

The quantum system under periodical modulation is the simplest path to understand the quantum non-equilibrium system, because it can be well described by the effective static Floquet Hamiltonian. Under the stroboscopic measurement, the initial phase is usually irrelevant. However, if two uncorrelated parameters are modulated, their relative phase can not be gauged out, so that the physics can be dramatically changed. Here, we simultaneously modulate the frequency of the lattice laser and the Rabi frequency in an optical lattice clock (OLC) system. Thanks to ultra-high precision and ultra-stability of OLC, the relative phase could be fine-tuned. As a smoking gun, we observed the interference between two Floquet channels. Finally, by experimentally detecting the eigen-energies, we demonstrate the relation between effective Floquet Hamiltonian and 1-D topological insulator with high winding number. Our experiment not only provides a direction for detecting the phase effect, but also paves a way in simulating quantum topological phase in OLC platform., 7 pages, 4 figures, almost published version, comments are welcome and more information at http://cqutp.org/users/xfzhang/

We periodically modulate the lattice trapping potential of a $^{87}$Sr optical clock to Floquet engineer the clock transition. In the context of atomic gases in lattices, Floquet engineering has been used to shape the dispersion and topology of Bloch quasi-energy bands. Differently from these previous works manipulating the external (spatial) quasi-energies, we target the internal atomic degrees of freedom. We shape Floquet spin quasi-energies and measure their resonance profiles with Rabi spectroscopy. We provide the spectroscopic sensitivity of each band by measuring the Fisher information and show that this is not depleted by the Floquet dynamical modulation. The demonstration that the internal degrees of freedom can be selectively engineered by manipulating the external degrees of freedom inaugurates a novel device with potential applications in metrology, sensing and quantum simulations., 6 pages, 4 figures, including supplementary material, comments are welcome and more information at http://cqutp.org/users/xfzhang/

The work presented in this paper is based on an optical frequency comb injection-locking, active filtering and amplification method to build a narrow linewidth laser for second cooling of the strontium atoms in an optical lattice clock. An optical femtosecond laser comb with mode spacing of 250 MHz as master laser is applied to directly inject into an external cavity semiconductor laser at 689 nm called slave laser, a single mode is selected and amplified from the optical femtosecond laser comb.

With the rapid development of science and technology, the demand for time and time signal is getting higher and higher by users in various fields. Most of the world's time laboratories use high performance cesium clocks and hydrogen masers for timekeeping in order to ensure the accuracy and stability of their atomic time scale. The hydrogen maser has excellent stability. However, the hydrogen maser has frequency drift, and the inaccurate deduction of the frequency drift of the maser will affect the accuracy of the atomic time calculation directly. Therefore, in this paper, a method based on the minimum error theory is used to estimate the frequency drift parameter of masers in a certain time interval. Three hydrogen masers operated in NTSC (National Time Service Center) are used to determine the frequency drift parameter. After removing hydrogen maser frequency drift, we use exponential filtering method to calculate the time scale based on hydrogen masers. At the same time, according to the frequency drift parameters of the hydrogen masers published in BIPM Circular T, the frequency drift is deducted and the time scale is calculated. The former is a dynamic estimation of the drift and the initial values is set to the values which come from Circular T. Then the comparative analysis is made at the end. The results show that the method based on minimum error theory can accurately estimate the drift of hydrogen maser, and the accuracy of this time scale is significantly higher than another atomic time scale, and the absolute value of maximum deviation with TA(NTSC) is 3.51ns.

We present an experimental determination on the Lande g-factors for the 5s2 1S0 and 5s5p 3 P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the 87Sr optical lattice clock. The Zeeman shift of the 5s5p 3P0–5s2 1S0 forbidden transition is measured with the π-polarized and σ±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5s2 1S0 g-factor for the 87Sr atom is −1.306(52)×10−4, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factor δg between the 5s5p 3P0 state and the 5s2 1S0 state of the 87Sr atoms is measured in the experiment as well, which are −7.67(36) × 10−5 with π-transition spectra and −7.72(43) × 10−5 with σ±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76 (2007) 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.

By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4nm intervals range from 1063.3 to 1065.7nm with the temperature change of the fiber Bragg grating. The maximum output power could reach 32mW while the pump power increases to 120mW. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.

A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were