Continuous Cold-Atom Inertial Sensor with $1\mathrm{nrad}/\sec$ Rotation Stability

We report the operation of a cold-atom inertial sensor which continuously captures the rotation signal. Using a joint interrogation scheme, where we simultaneously prepare a cold-atom source and operate an atom interferometer (AI), enables us to eliminate the dead times. We show that such continuous operation improves the short-term sensitivity of AIs, and demonstrate a rotation sensitivity of $100\mathrm{nrad}/\sec /\sqrt{\mathrm{Hz}}$ in a cold-atom gyroscope of $11{\mathrm{cm}}^2$ Sagnac area. We also demonstrate a rotation stability of $1\mathrm{nrad}/\sec$ at ${10}^4\sec$ of integration time, which represents the state of the art for atomic gyroscopes. The continuous operation of cold-atom inertial sensors will lead to large area AIs at their full sensitivity potential, determined by the quantum noise limit.

Figure 1

(a) Schematic and operation principle of the continuous cold-atom gyroscope. Continuous measurement is performed with a joint interrogation sequence where the bottom $\pi /2$ pulse is shared between the clouds entering and exiting the interrogation region. (b) Space-time diagram of the four-pulse AI. We introduce a time asymmetry of $\mathrm{\Delta }T$ to avoid the recombination of parasitic interferometers resulting from the imperfect $\pi$ pulses. The gyroscope measures rotation rate along the $y$ direction, i.e., perpendicular to the AI area.

Figure 2

Correlation between the AI signal and the vibration phase calculated from the signal of auxiliary accelerometers. The AI interrogation time is $2T=800\mathrm{ms}\mathrm{e}\mathrm{c}$.

Figure 3

(a) Temporal variation of the rotation rate around its mean value. Each point is obtained from the combination of the two phase measurements extracted from correlation fringes (as shown in Fig. 2) involving 20 data points for each of the two opposite Raman wave vectors $+k_{\mathrm{eff}}$ and $-k_{\mathrm{eff}}$. (b) Allan deviation of the gyroscope sensitivity. The dashed line is a guide to the eye illustrating the ${\tau }^{-1/2}$ scaling. The error bars represent the 68% confidence intervals.