Atom Interferometry in an Optical Cavity

Abstract

We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beamsplitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beamsplitters (< 100 µW), large momentum transfer beamsplitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with > 75% contrast and measure the acceleration due to gravity, g, to 60 µg/ √ Hz resolution in a Mach-Zehnder geometry. We use > 10 7 cesium atoms in the compact mode volume (600 µm 1/e 2 waist) of the cavity and show trapping of atoms in higher transverse modes. This work paves the way toward compact, high sensitivity, multi-axis interferometry.In a light-pulse atom interferometer, recoils from photon-atom interactions are used to split and interfere matter waves (see Fig. 1). These interferometers have been used to measure the gravitational acceleration g [1], rotation Ω [2], gravity gradients [3], the fine structure constant [4], Newton's gravitational constant [5,6], and absolute masses in a proposed revision of the SI [7,8]; to test Einstein's equivalence principle [9][10][11][12]; and have been proposed to measure the free fall of antimatter [13] and to detect gravitational waves [14][15][16]. The sensitivity of a conventional Mach-Zehnder interferometer increases with the measured phase difference(1) (where v 0 is the initial velocity of the atom), which scales with the pulse separation time T and the recoil momentum p =h k eff , where k eff is the effective wavenumber of the photons. State of the art atom interferometers are limited by several engineering boundaries. T is limited by the free-fall time in atomic fountains, which are now as high as 10 m [17,18]. Multiphoton interactions can increase the recoil momentum to a multiple nhk of the single photon recoil [19][20][21][22][23] but are limited by the available laser power (e.g. 6 W in [24], 43 W in [25]). Finally, wavefront distortions spread the local wavevector around its mean, lowering interference contrast and reducing both sensitivity and accuracy. An optical cavity can solve these problems by providing spatial filtering to clean the wavefronts and enhancing laser intensity. However, running an atom interferometer inside an optical cavity presents challenges in keeping the atoms in the relatively small cavity mode volume and having multiple laser frequencies (needed due to recoil frequency shifts, Doppler shifts, and atomic structure) simultaneously resonant with the cavity. Here, we present a cesium atom interferometer inside an in-vacuum optical cavity and demonstrate gravity measurements using less than 100µW of laser power incident on the cavity.The use of an optical cavity has many advantages. First, laser power limits interferometers using both large momentum transfer beamsplitters and optical lattices. is modulated at the hyperfine frequ...

Spatially homogeneous entanglement for matter-wave interferometry created with time-averaged measurements

“…The 11(1) dB of squeezing observed in this work would in principle fully translate to this type of interferometer. In addition to the possibility of using entangled states, performing the final readout via a cavity measurement may allow for reduced technical noise, higher bandwidth, cleaner optical modes, and power buildup for Raman transitions [25].…”

“…The 11(1) dB of squeezing observed in this work would in principle fully translate to this type of interferometer. In addition to the possibility of using entangled states, performing the final readout via a cavity measurement may allow for reduced technical noise, higher bandwidth, cleaner optical modes, and power buildup for Raman transitions [25].Similarly, higher order transverse modes, atom-chip technologies [26,27], or tailored potentials [28,29] might be combined with the cavity measurement technique presented here to create new varieties of matter-wave Sagnac interferometers and other inertial sensors. The real-time observation of mechanical motion also opens the path to stochastic cooling schemes based on measurement and feedback [30] with applications to more complex systems such as molecules, which can be challenging to laser cool using conventional Doppler cooling methods.…”

Atom interferometry using a shaken optical lattice

“…For example, a closed-loop system can correct deviations from optimal fitness due to the parasitic lattice reflections discussed in the previous section as long as the deleterious effects are constant from shot-to-shot. Uncertainties in lattice parameters such as the lattice depth or wavelength due to imperfect lattice alignment or the Gouy phase [34,35] may also be corrected for in a closed-loop system.…”

Experimental progress in positronium laser physics

“…Alternatively, atom interferometry [778,779] is a well-developed field that is routinely used to perform high precision measurements of the gravitational field of the Earth (e.g. [780][781][782][783][784][785][786]). Interferometry of antihydrogen using a Ramsey-Bordé approach [787] has been proposed [788].…”