Sagnac Tractor Atom Interferometer on Photonic Integrated Circuit

TL;DR

This paper presents a theory and concrete design for a Sagnac tractor atom interferometer implemented on photonic chip ring resonators. By formulating a rotating-frame quantum-dynamics framework and using an adiabatic basis, it achieves efficient radial and azimuthal dynamics calculations and quantifies non-adiabatic losses during ramping. The authors design a rubidium-based PIC with multiple color evanescent fields to create counter-rotating azimuthal lattices, and through simulations show that smooth sin$^2$ ramps can realize high-visibility interference and rotation sensitivity on the order of $\sim$ a few $\mathrm{nrad/s}$ for a 1 s interrogation, with potential scalability via parallel PIC-TAIs or spin squeezing. Overall, the work demonstrates a viable, compact SWaP-friendly approach to high-precision rotation sensing on a photonic platform and outlines practical considerations for real-world implementation.

Abstract

We study the theory of, and propose an experimental design for, a Sagnac tractor atom interferometer based on a photonic integrated circuit (PIC). The atoms are trapped in counter-rotating azimuthal optical lattices, formed by interfering evanescent fields of laser modes injected into circular PIC waveguides. We develop quantum models for the radial and azimuthal dynamics of the interfering atoms in adiabatic frames, which provide computational efficiency. The theory is applied to an exemplary PIC, for which we first compute field modes and atom trapping potentials for $^{87}$Rb. We then evaluate non-adiabaticity, fidelity, and sensitivity of the exemplary PIC.

Figures (9)

• Figure 1: Two micro-ring resonators side by side on a photonic chip. The loading beam is partially reflected by the top surface of the chip, forming pancake-shaped traps that coherently load the azimuthal lattices above the ring resonators with cold atoms. Details are described in the text.
• Figure 2: (a) Top-down view of the photonic chip (PIC). Two counterpropagating red-detuned (855nm) modes form a trapping lattice above the ring. Two blue-detuned modes (734nm and 731nm) repel the atoms from the waveguide. The red shaded area between two rings is the atom loading area. All wavelengths are vacuum wavelengths. (b) Cross-section through the optical waveguides. Parameters are $R_0 = 600\um$, $H = 0.09\um$, $W = 1.8\um$. The blue shading represents silicon dioxide (SiO$_2$), and the yellow is silicon nitride (Si$_3$N$_4$).
• Figure 3: Electric field magnitudes of the $855nm$ TE00, $731nm$ TE00, and $734nm$ TE10 modes, from top to bottom. The red rectangle outlines the Si$_3$N$_4$ core of the waveguide. All wavelengths are vacuum wavelengths.
• Figure 4: Trapping potential for Rb $5S_{1/2}$ atoms along the radial and axial directions of the PIC rings at an antinode of the azimuthal PIC-TAIL. The intra-cavity circulating powers of the $855nm$ TE00 azimuthal-lattice modes, the $731nm$ TE00 running-wave mode, and the $734nm$ TE10 running-wave mode are $75mW$ (each lattice mode), $400mW$, and $200mW$, respectively. The potential minimum has a value of $-8.3MHz$ and is located at $z = 0.310\um$, which is $0.265\um$ above the surface of the PIC.
• Figure 5: (a) Trapping potential transverse to the chip surface, at $x = 0$ of Fig. \ref{['fig:potential_cross_section']}. (b) Trapping potential parallel to the chip surface and transverse to the direction of the PIC waveguides at $z = 0.31\um$. The red, yellow, and purple dashed curves show the contributions to the trapping potential from the $855nm$ TE00, $731nm$ TE00, and $734nm$ TE10 modes, respectively, for powers as in Fig. \ref{['fig:potential_cross_section']}. The blue curve is the sum of all modes.