Composite laser-pulses spectroscopy for high-accuracy optical clocks: a review of recent progress and perspectives

Abstract

Probing an atomic resonance without disturbing it is an ubiquitous issue in physics. This problem is critical in high-accuracy spectroscopy or for the next generation of atomic optical clocks. Ultra-high resolution frequency metrology requires sophisticated interrogation schemes and robust protocols handling pulse length errors and residual frequency detuning offsets. This review reports recent progress and perspective in such schemes, using sequences of composite laser-pulses tailored in pulse duration, frequency and phase, inspired by NMR techniques and quantum information processing. After a short presentation of Rabi technique and NMR-like composite pulses allowing efficient compensation of electromagnetic field perturbations to achieve robust population transfers, composite laser-pulses are investigated within Ramsey's method of separated oscillating fields in order to generate non-linear compensation of probe-induced frequency shifts. Laser-pulses protocols such as hyper-Ramsey, modified hyper-Ramsey, generalized hyper-Ramsey and hybrid schemes as auto-balanced Ramsey spectroscopy are reviewed. These techniques provide excellent protection against both probe induced light-shift perturbations and laser intensity variations. More sophisticated schemes generating synthetic frequency-shifts are presented. They allow to reduce or completely eliminate imperfect correction of probe-induced frequency-shifts even in presence of decoherence due to the laser line-width. Finally, two universal protocols are presented which provide complete elimination of probe-induced frequency shifts in the general case where both decoherence and relaxation dissipation effects are present by using exact analytic expressions for phase-shifts and the clock frequency detuning. These techniques might be applied to atomic, molecular and nuclear frequency metrology, Ramsey-type mass spectrometry as well as precision spectroscopy.

Two-Photon Vibrational Transitions in 16O2+ as Probes of Variation of the Proton-to-Electron Mass Ratio

“…For lower-precision experiments with stable laser intensity, the Stark shift could be calibrated. Better would be to use a composite-pulse scheme such as hyper-and autobalanced Ramsey spectroscopy [88][89][90][91]. Such schemes have suppressed AC Stark shifts by four orders of magnitude when used on the electric octupole (E3) clock transition in Yb + [90,92,93].…”

“…For a target accuracy of 6 × 10 −14 , this shift can be calibrated and the optical power kept stable to better than 2 %. Higher accuracy experiments should use a composite pulse sequence immune to the shift [88][89][90][91]. In ref.…”

Electromagnetically induced absorption scheme for vapor-cell atomic clock

“…To circumvent this issue, different optimized CPT pumping schemes, generally based on the alkali D 1 line [16], have been proposed [17][18][19][20][21][22][23][24]. Such polarization schemes, combined with pulsed Ramsey-like interrogation protocols [21,25], have led to the demonstration of high-stability CPT atomic clocks [26][27][28][29].…”

Light-Shift Suppression with Novel Variants of Adaptive Ramsey Spectroscopy

“…Sophisticated interrogation protocols based on Ramsey's method and tailored composite laser pulses have been proposed and demonstrated that can eliminate probe-induced frequency shifts (for a review, see [6]). Key to these techniques is that the light shift magnitude for standard Ramsey spectroscopy depends on the duration of the Ramsey dark period, scaling as 1 / .…”