A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime

Abstract

We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the dispersive properties of latticetrapped atoms enhanced by a high finesse cavity. By design, this scheme offers a 1st order rejection of the technical noise sources, an enhanced signal-to-noise ratio, and an homogeneous atom-cavity coupling. We theoretically show that this scheme is optimal with respect to the photon shot noise limit. We experimentally realize this detection scheme in an operational strontium optical lattice clock. The resolution is on the order of a few atoms with a photon scattering rate low enough to keep the atoms trapped after detection. This scheme opens the door to various different interrogations protocols, which reduce the frequency instability, including atom recycling, zero-dead time clocks with a fast repetition rate, and sub quantum projection noise frequency stability.

Cavity-enhanced non-destructive detection of atoms for an optical lattice clock

“…Compared with the similar cavity-based detection technique presented in Ref. [16], we make several important advances toward realizing a quantum-enhanced clock: a short lock capture time, the recycling of atoms after non-destructive probe, compatibility with large atom number in the 10 4 range, and compensation of inhomogeneous ac Stark shifts from the probe.…”

“…Cavity-enhanced detection methods have previously been applied to microwave atomic clocks, in which weak cavity-based measurements were used to prepare spin-squeezed states [11,12] or to implement an atom phase lock [13]. However, efforts to employ such techniques on optical lattice clocks, a highly accurate and stable configuration of atomic clock [3,14], have so far been much too destructive to realize correlated quantum states [15,16].…”

Seconds-scale coherence on an optical clock transition in a tweezer array

“…Sinc and Gaussian fits shown in gray and black respectively. In this case a 1.5 s probe yields an approximately Fourier-limited Gaussian linewidth of 450 (20) mHz. (c) Ramsey spectroscopy in 200 photon recoil energy (ER) deep tweezers, showing a coherence time of 3.4(4) seconds.…”

A low-noise resonant input transimpedance amplified photodetector

“…The input current noise of 1.2 pA/ √ Hz at 90 MHz is near the theoretical limit imposed by the Johnson noise set by the transimpedance and corresponds to shot noise limited performance for incident optical powers above 14 µW. The intended use of this photodetector is for cavity-based non-destructive detection of trapped strontium atoms 15 , but it can be easily modified to operate at a different resonant frequency or wavelength, making it well suited to a range of applications.…”