Abstract We investigate Floquet modulation for measuring the probe-induced AC Stark shift coefficient in optical lattice clocks. Periodic frequency modulation allows a high probe intensity to enlarge the measured frequency difference between the settings at low and high probe power while Bessel function dressing maintains a narrow excitation spectrum. This combination improves sensitivity to the coefficient without sacrificing frequency discrimination. We identify modulation conditions that suppress additional frequency shifts while avoiding strong motional resonances. At the same probe intensities and total measurement time, numerical simulations including preparation time show a lower coefficient uncertainty than conventional Rabi inter-rogation with a single π pulse. At high probe intensities, the Floquet coefficient uncertainty approaches a plateau dominated by Rabi frequency calibration.
Abstract We investigate Floquet modulation for measuring the probe-induced AC Stark shift coefficient in optical lattice clocks. Periodic frequency modulation allows a high probe intensity to enlarge the measured frequency difference between the settings at low and high probe power while Bessel function dressing maintains a narrow excitation spectrum. This combination improves sensitivity to the coefficient without sacrificing frequency discrimination. We identify modulation conditions that suppress additional frequency shifts while avoiding strong motional resonances. At the same probe intensities and total measurement time, numerical simulations including preparation time show a lower coefficient uncertainty than conventional Rabi inter-rogation with a single π pulse. At high probe intensities, the Floquet coefficient uncertainty approaches a plateau dominated by Rabi frequency calibration.
With the uncertainty of the optical clocks improving to the order of 10-18, the probe light used to detect the clock transition has demonstrated nonnegligible Stark shift, provoking to precisely evaluate this shift. Here, we demonstrate a frequency modulation technique to realize a large measurement lever arm of the probe Stark shift with no cost of the measurement accuracy of the interleaved stabilization method. This frequency-modulated spectrum is theoretical described and experimental verified. The probe Stark shift coefficient of the 87Sr optical lattice clock is experimentally determined as -(45.97+/-3.51) Hz/(W/cm2) using this frequency modulation spectroscopy.
In this paper, we demonstrate a frequency modulation technique to accurately measure the probe Stark shift of optical clocks. The effective coupling strength of the probe laser to the clock transition is precisely controlled by this frequency modulation technique, which is different from the traditional method by controlling the effective coupling strength via changing the probe light power. In an 87Sr optical lattice clock, the probe Stark shifts are measured as a function of the square of the bare state coupling strength. The probe Stark shift coefficient of 87Sr is experimentally determined as −6.0(5)×10−7/Hz using this frequency modulation technique. With the help of frequency modulation, the probe light power can be as large as possible without decreasing the measurement precision and the achieved measurement lever arm is improved by more than one order of magnitude compared with previous results.
Beyond hardware improvements, Floquet Engineering (FE), as a widely used Hamiltonian engineering method, offers new levels of control and promising opportunities for enhancing optical lattice clock performance. However, while FE shapes novel Hamiltonians, its time-periodic nature introduces micromotion, leading to periodic disturbances in the system, such as frequency shifts. In this work, we introduce a dual-modulation (DM) FE method, simultaneously driving the lattice and probing lasers, allowing independent control of atomic motional and electronic degrees of freedom. Using this framework, we theoretically predict and experimentally observe the micromotion shifts. Additionally, by tuning the DM modulation parameters appropriately, we can fully eliminate the Doppler shift caused by the lattice laser modulation. Building on this Doppler-free synchronization modulation, we observe the dynamic localization of atoms in a shallow lattice while eliminating the periodic interference from Doppler shifts. This study proposes a dual-modulation method for optical lattice clocks that synchronously modulates the lattice laser and probing laser to control atomic motion and light-atom interactions independently. The authors derive theoretically and verify experimentally the laws of micromotion shift, and achieving its effective suppression by optimizing modulation parameters.
In this paper, the magic wavelength of the 87Sr optical lattice clock is determined by a method that bypasses the need for lattice trap depth modulation. Instead, it relies on an additional AC Stark shift generated by a dipole beam operating near the frequency of the lattice light and oriented perpendicular to the optical lattice. The magic wavelength is inferred by measuring the AC Stark shift induced by the dipole beam as a function of its power under various frequency detunings. The effect of the dipole beam on the external states of the cold ensemble is evaluated through comparative analysis of the radial and axial sideband spectra, both with and without the dipole beam. Variations in density shift resulting from changes in external states are evaluated using comprehensive numerical calculations. By avoiding trap depth modulation, this method effectively suppresses the influence of the density shift, thereby offering a promising avenue for accurately determining the magic wavelength.
Quantum metrology with ultrahigh precision usually requires atoms prepared in an ultrastable environment with well-defined quantum states. Thus, in optical lattice clock systems deep lattice potentials are used to trap ultracold 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. Counterintuitively, shaking the system can deform the wide broad spectral line into a sharp peak with 5.4 Hz linewidth. 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.
Optical clock interrogation protocols, based on laser-pulse spectroscopy, are suffering from probe-induced frequency shifts and their variations induced by laser power. Original Hyper-Ramsey probing scheme, which was proposed to alleviate those issues, does not fully eliminate the shift, especially when decoherence and relaxation by spontaneous emission or collisions are present. We propose to solve the fundamental problem of frequency shifts induced by laser probe by deriving the exact canonical form of a multi-pulse generalized Hyper-Ramsey (GHR) resonance, including decoherence and relaxation. We present a universal interrogation protocol based on composite laser-pulses spectroscopy with phase-modulation eliminating probe-induced frequency shifts at all orders in presence of various dissipative processes. Unlike frequency shifts extrapolation-based methods, a universal interrogation protocol based on ±π/4 and ±3π/4 phase-modulated resonances is proposed which does not compromise the stability of the optical clock while maintaining an ultra-robust error signal gradient in presence of substantial uncompensated ac Stark-shifts. Such a scheme can be implemented in two flavours: either by inverting clock state initialization or by pulse order reversal even without a perfect quantum state initialization. This universal interrogation protocol can be applied to atomic, molecular and nuclear frequency metrology, mass spectrometry and to the field of precision spectroscopy. It might be designed using magic-wave induced transitions, two-photon excitation and magnetically-induced spectroscopy or it might even be implemented with quantum logic gate circuit and qubit entanglement.