No abstract

Atom interferometers are powerful tools for both measurements in fundamental physics and inertial sensing applications. Their performance, however, has been limited by the available interrogation time of freely falling atoms in a gravitational field. We realize an unprecedented interrogation time of 20 seconds by suspending the spatially-separated atomic wavepackets in a lattice formed by the mode of an optical cavity. Unlike traditional atom interferometers, this approach allows potentials to be measured by holding, rather than dropping, atoms. After seconds of hold time, gravitational potential energy differences from as little as microns of vertical separation generate megaradians of interferometer phase. This trapped geometry suppresses the phase sensitivity to vibrations by 3-4 orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. Finally, we study the wavefunction dynamics driven by gravitational potential gradients across neighboring lattice sites.Matter-wave interferometers with freely falling atoms have demonstrated the ability to precisely measure e.g., gravity [1] and fundamental constants [2,3], to test general relativity [4][5][6], and to search for new forces [7,8].A major obstacle to increasing their sensitivity, however, has been the limited time during which coherent, spatially-separated superpositions of atomic wave packets can be interrogated. Up to 2.3 seconds of interrogation time has been realized in a 10-meter atomic fountain [9], and several seconds of interrogation time are the target of experiments in fountains measuring hundreds of meters [10,11], zero-gravity planes [12], drop towers [13], sounding rockets [14], and the International Space Station [15][16][17]. Geometries that trap the interferometer in an optical lattice [18,19] have been explored, but attempts to date have suffered from dephasing in the trap.Here, we demonstrate 20 seconds of coherence in an atom interferometer held in an optical lattice, overcoming trap dephasing by using an optical cavity as a spatial mode-filter. After 20 seconds, sensitivity to vibrations is suppressed by 10 3 − 10 4 relative to traditional atomic gravimeters at the same sensitivity, due to the continuous accumulation of free evolution phase in the trapped wave packets. Trapping the interferometer allows for the sensitivity to be increased by extending interrogation times rather than wavepacket separations or free fall distances, reducing experimental complexity and potentially minimizing systematics.Our matter-wave interferometer builds upon the setup described previously in [7,20]. Cesium atoms are laser-cooled to ∼300 nK, prepared in the magneticallyinsensitive m F =0 state, and launched millimeters upwards into free fall (see Methods for details). In free fall, counter-propagating laser beams in the cavity manipulate the atomic trajectories. We stimulate two-photon Raman transitions between the hyperfine ground states of cesium, F = 3 and F = 4, imparting two photons' momenta to the atom with each lase...

Objects at finite temperature emit thermal radiation with an outward energy-momentum flow, which exerts an outward radiation pressure. At room temperature, a caesium atom scatters on average less than one of these blackbody radiation photons every 10 8 years. Thus, it is generally assumed that any scattering force exerted on atoms by such radiation is negligible. However, atoms also interact coherently with the thermal electromagnetic field. In this work, we measure an attractive force induced by blackbody radiation between a caesium atom and a heated, centimetre-sized cylinder, which is orders of magnitude stronger than the outward-directed radiation pressure. Using atom interferometry, we find that this force scales with the fourth power of the cylinder's temperature. The force is in good agreement with that predicted from an a.c. Stark shift gradient of the atomic ground state in the thermal radiation field 1 . This observed force dominates over both gravity and radiation pressure, and does so for a large temperature range. Quantum technology continues to turn formerly unmeasurable effects into technologically important physics. For example, minuscule shifts of atomic energy levels due to room-temperature blackbody radiation have become leading influences in atomic clocks at or beyond the 10 −14 level of accuracy 2 . They have thus become important to precision timekeeping 3 , and for applications such as improving time standards, relativistic geodesy and searches for variations of fundamental constants. Thermal radiation from a heated source should also result in a repulsive radiation pressure on atoms through absorption of photons [4][5][6][7] . However, the scattering rate for room-temperature blackbody radiation is small, leading to only mm s −1 velocity changes in hundreds of thousands of years for the caesium D line, for example. Here, we show that spatially inhomogeneous blackbody radiation produces a much higher acceleration at the μ m s −2 level pointing towards the source, even near room temperature. It is well described by the intensity gradient of blackbody radiation that gives rise to a spatially dependent a.c. . We expect it to be the dominant force on polarizable objects over a large temperature range 1 and thus important in atom interferometry, nanomechanics or optomechanics 12 . Controlling this force will enable higher precision in atom interferometers, including tests of fundamental physics such as of the equivalence principle [13][14][15] , planned searches for dark matter and dark energy 16 , gravity gradiometry 17,18 , inertial navigation and perhaps even Casimir force measurements and gravitational wave detection 19,20 .As shown in Fig. 1, we perform atom interferometry with caesium atoms 21 in an optical cavity to measure the force induced by blackbody radiation. Our setup is similar to the one we used previously 22,23 . Caesium atoms act as matter waves in our experiment. They are laser-cooled to a temperature of about 300 nK and launched upwards into free fall, reaching 3.7 mm into t...

We present an atom interferometry technique in which the beam splitter is split into two separate operations. A microwave pulse first creates a spin-state superposition, before optical adiabatic passage spatially separates the arms of that superposition. Despite using a thermal atom sample in a small (600  μm) interferometry beam, this procedure delivers an efficiency of 99% per ℏk of momentum separation. Utilizing this efficiency, we first demonstrate interferometry with up to 16ℏk momentum splitting and free-fall limited interrogation times. We then realize a single-source gradiometer, in which two interferometers measuring a relative phase originate from the same atomic wave function. Finally, we demonstrate a resonant interferometer with over 100 adiabatic passages, and thus over 400ℏk total momentum transferred.

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages.