We use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between 85Rb and 87Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an Eötvös parameter of [1.6 +/- 1.8 (stat) +/- 3.4 (syst)] x 10^-12, consistent with zero violation of the equivalence principle. With a resolution of up to 1.4 x 10^-11 g per shot, we demonstrate the highest sensitivity to the Eötvös parameter of any laboratory experiment.
We use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between 85Rb and 87Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an Eötvös parameter of [1.6 +/- 1.8 (stat) +/- 3.4 (syst)] x 10^-12, consistent with zero violation of the equivalence principle. With a resolution of up to 1.4 x 10^-11 g per shot, we demonstrate the highest sensitivity to the Eötvös parameter of any laboratory experiment.
We use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between 85Rb and 87Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an E\"otv\"os parameter of $\ensuremath{\eta}=[1.6\ifmmode\pm\else\textpm\fi{}1.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.4(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$, consistent with zero violation of the equivalence principle. With a resolution of up to $1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }\text{ }\mathrm{g}$ per shot, we demonstrate a sensitivity to $\ensuremath{\eta}$ of $5.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}/\sqrt{\mathrm{Hz}}$.
In an ideal test of the equivalence principle, the test masses fall in a common inertial frame. A real experiment is affected by gravity gradients, which introduce systematic errors by coupling to initial kinematic differences between the test masses. Here we demonstrate a method that reduces the sensitivity of a dual-species atom interferometer to initial kinematics by using a frequency shift of the mirror pulse to create an effective inertial frame for both atomic species. Using this method, we suppress the gravity-gradient-induced dependence of the differential phase on initial kinematic differences by 2 orders of magnitude and precisely measure these differences. We realize a relative precision of Δg/g≈6×10^{-11} per shot, which improves on the best previous result for a dual-species atom interferometer by more than 3 orders of magnitude. By reducing gravity gradient systematic errors to one part in 10^{13}, these results pave the way for an atomic test of the equivalence principle at an accuracy comparable with state-of-the-art classical tests.
This article develops an expanded critical–propositional analysis of Lin Zhou and collaborators’ 2015 experiment, “Test of Equivalence Principle at 10−8 Level by a Dual-Species Double-Diffraction Raman Atom Interferometer,” published in Physical Review Letters, in systematic dialogue with the Theory of Objectivity (TO) formulated by Vidamor Cabannas and Denivaldo Silva. Zhou et al. implemented a simultaneous 85Rb– 87Rb atom interferometer employ- ing a four-wave double-diffraction Raman transition scheme and obtained an Eötvös parameter η = (2.8 ± 3.0) × 10−8 , finding no violation of the Weak Equivalence Principle within the sensitivity of the experiment (Zhou et al. 2015). The experiment is especially significant for the Theory of Objectivity because it combines elemental differentiation, fields, frequencies, radiation, phase evolution, relational measurement, information generation, and gravity within a single controlled physical architecture. The analysis distinguishes four epistemological categories that must not be conflated: direct empirical confirmation, indirect empirical corroboration, structural compatibility, and merely analogical correspondence. Zhou et al. do not test the primordial Logical Nothingness proposed by the First Absolute Truth of TO, nor do they directly demonstrate the ontological existence of a unique field belonging to every element, as asserted by the Second Absolute Truth. Likewise, the experiment does not establish that logical existence itself requires the relational observation described by the Fifth Absolute Truth. Nevertheless, the experiment offers significant operational bridges. The two rubidium isotopes remain physically distinguishable while participating in a common gravitational regularity; their interferometric information is produced through relations involving atoms, radiation, frequencies, momentum transfer, phase, and detection; and the measured equality of free-fall acceleration imposes a quantitative constraint on any TO-derived gravitational model in which elemental individuality or proper fields could generate composition-dependent acceleration. Particular attention is given to the TO conception of the transcendent element as knowledge or information generated in atomic relations and associated with atomic radiation. The interferometer provides a concrete physical chain in which interactions are converted into relative phase, populations, radiation-mediated detection, and finally experimentally accessible information. This does not establish the full ontological interpretation proposed by TO, but it supplies an unusually clear operational analogue. The article further articulates Zhou et al. with the foundational TO literature, the 2025–2026 reformulation of its modal and empirical program, and supporting or dialogical literature including Einstein, Heisenberg, Bohm, Prigogine, Penrose, Kuhn, Aspect, Planck, and gravitational-wave observations. A formal bridge is proposed in which a TO-specific field contribution Φi generates a potential differential acceleration δg(Φi). The Zhou result then becomes an empirical restriction on the magnitude of such a contribution. The central conclusion is therefore deliberately limited but scientifically pro- ductive: Zhou et al. do not confirm the Theory of Objectivity as a whole, but their experiment constitutes an important empirical constraint and a viable platform for converting selected TO propositions into quantitatively testable predictions. Keywords: Theory of Objectivity; Weak Equivalence Principle; atom interferometry; rubidium isotopes; gravity; modal ontology; information; Raman transitions; Eötvös parameter; empirical testability.
Quantum technology based on cold-atom interferometers is showing great promise for fields such as inertial sensing and fundamental physics. However, the best precision achievable on Earth is limited by the free-fall time of the atoms, and their full potential can only be realized in Space where interrogation times of many seconds will lead to unprecedented sensitivity. Various mission scenarios are presently being pursued, which plan to implement matter-waves inertial sensors to detect gravitational waves, to measure the Earth gravity field or to test fundamental physics such as the Equivalence Principle.We developed a cold atom sensor experiment adapted to microgravity platforms, especially the ZERO-G plane. To achieve a test of the Universality of Free Fall, we realize the first onboard operation of simultaneous ^{87}Rb - ^{39}K interferometers in the weightlessness environment produced during parabolic flight. The large vibration levels (10 ^{-2} g/Hz ^{1/2}), acceleration range and rotation rates (5 deg/s) during flight present significant technical challenges for atom interferometers. By hybridizing each atomic sensor with a common mechanical accelerometer, we achieve a sensitivity of 3.4 10 ^{-5} g per shot-more than 1600 times below the ambient vibration level onboard the aircraft. We demonstrate the capability of our dual-quantum sensor by measuring the Eötvös parameter with systematic-limited uncertainties of 3.0 10 ^{-4} during micro-gravity. This constitutes the first quantum test of the equivalence principle in a free falling vehicle. Our results can be extended to the trajectory of a satellite for future Space missions. We also achieved a simultaneous ^{87}Rb- ^{39}K interferometer on ground with a long term stability on the differential acceleration measurement around 5 10 ^{-8}g, limited by the fall of the atom clouds. To increase the interrogation time and the sensitivity, a ZERO-G simulator has been installed in our laboratory and allows our experiment to be in free fall during 500 ms every 12 seconds, to achieve highly repeatable measurements in microgravity. We expect to increase our short-term sensitivity by two orders of magnitude, and consequently reach a long-term measurement of the Eötvös parameter at the level of 10 ^{-11}.To benefit from the free fall of the experiment completely, it is necessary to produce atoms clouds with a reduced velocity dispersion. To reach this goal, we put ^{87}Rb atoms in an optical dipole trap supplied by a compact fiber laser compliant with onboard applications and decrease the optical power on a very controlled way to obtain evaporative cooling. Preliminary results of ultra-fast evaporative cooling (less than a few seconds) onboard the ZERO-G plane allowed us to reach a regime of temperature compliant with an interrogation time of the order of one second. This method and technology will be tested on the ZERO-G simulator as well.
We describe a test of the equivalence principle with quantum probe particles based on atom interferometry. For the measurement, a light pulse atom interferometer based on the diffraction of atoms from effective absorption gratings of light has been developed. A differential measurement of the Earth’s gravitational acceleration g for the two rubidium isotopes 85 Rb and 87 Rb has been performed, yielding a difference Δ g / g =(1.2±1.7)×10 −7 . In addition, the dependence of the free fall on the relative orientation of the electron to the nuclear spin was studied by using atoms in two different hyperfine states. The determined difference in the gravitational acceleration is Δ g / g =(0.4±1.2)×10 −7 . Within their experimental accuracy, both measurements are consistent with a free atomic fall that is independent from internal composition and spin orientation.
We use rubidium atoms with specified mass and internal energy to carry out a joint mass-energy test of the equivalence principle (EP). We improve the four-wave double-diffraction Raman transition method (4WDR) we proposed before to select atoms with a certain mass and angular momentum state, and form a dual-species atom interferometer. By using the extended 4WDR to 85Rb and 87Rb atoms with different angular momenta, we measure their differential gravitational acceleration, and we determine the value of the E\"otv\"os parameter, $\ensuremath{\eta}$, which measures the strength of the violation of EP. The E\"otv\"os parameters of the four paired combinations $^{85}\mathrm{Rb}|F=2\ensuremath{\rangle}\text{\ensuremath{-}}^{87}\mathrm{Rb}|F=1\ensuremath{\rangle}$, $^{85}\mathrm{Rb}|F=2\ensuremath{\rangle}\text{\ensuremath{-}}^{87}\mathrm{Rb}|F=2\ensuremath{\rangle}$, $^{85}\mathrm{Rb}|F=3\ensuremath{\rangle}\text{\ensuremath{-}}^{87}\mathrm{Rb}|F=1\ensuremath{\rangle}$, and $^{85}\mathrm{Rb}|F=3\ensuremath{\rangle}\text{\ensuremath{-}}^{87}\mathrm{Rb}|F=2\ensuremath{\rangle}$ were measured to be ${\ensuremath{\eta}}_{1}=(1.5\ifmmode\pm\else\textpm\fi{}3.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, ${\ensuremath{\eta}}_{2}=(\ensuremath{-}0.6\ifmmode\pm\else\textpm\fi{}3.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, ${\ensuremath{\eta}}_{3}=(\ensuremath{-}2.5\ifmmode\pm\else\textpm\fi{}4.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, and ${\ensuremath{\eta}}_{4}=(\ensuremath{-}2.7\ifmmode\pm\else\textpm\fi{}3.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, respectively. The violation parameter of mass is constrained to ${\ensuremath{\eta}}_{0}=(\ensuremath{-}0.8\ifmmode\pm\else\textpm\fi{}1.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, and that of internal energy to ${\ensuremath{\eta}}_{E}=(0.0\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ per reduced energy ratio a ($a=h{\ensuremath{\nu}}_{0}/{m}_{i}^{85}{c}^{2}$, and ${\ensuremath{\nu}}_{0}=1$ GHz). This work opens a door for joint tests of two attributes beyond the traditional pure mass or energy tests of EP with quantum systems.