Continuous longitudinal Rabi spectroscopy on clock atoms transported in a moving optical lattice

Optical lattice clocks have achieved unprecedented accuracy and stability, yet their operation remains fundamentally constrained by dead time associated with sequential cooling, state preparation, and interrogation. Eliminating this dead time is essential for realizing continuous optical clocks with improved stability scaling. Here we present a new spectroscopy paradigm in which Rabi interrogation is performed on clock atoms transported in a moving optical lattice under continuous atomic flux. By exploiting longitudinal excitation of the magnetically induced ¹S₀-³P₀ clock transition of ⁸⁸Sr, spectroscopy is defined in space rather than in time while maintaining Lamb–Dicke confinement. A uniform bias magnetic field enables the clock transition and confines excitation to a selected region of the lattice, allowing precise control of the effective interrogation time. We demonstrate Rabi oscillations over a centimeter-scale interaction length with Fourier-limited linewidths at the hertz level. This method removes the conventional distinction between preparation and interrogation and establishes a direct route toward continuous optical clock operation with 1/τ stability scaling, while opening new opportunities for high-resolution spectroscopy of moving quantum systems and continuous precision measurements. We will also discuss ongoing efforts in our group toward zero-dead-time optical clock operation and its implications for long-baseline clock comparisons.