Quantum test of the equivalence principle and space-time aboard the International Space Station

Abstract

We describe the Quantum Test of the Equivalence principle and Space Time (QTEST), a concept for an atom interferometry mission on the International Space Station (ISS). The primary science objective of the mission is a test of Einstein's equivalence principle with two rubidium isotope gases at a precision of better than 10 −15 , a 100-fold improvement over the current limit on equivalence principle violations, and over 1,000,000 fold improvement over similar quantum experiments demonstrated in laboratories. Distinct from the classical tests is the use of quantum wave packets and their expected large spatial separation in the QTEST experiment. This dual species atom interferometer experiment will also be sensitive to time-dependent equivalence principle violations that would be signatures for ultralight dark-matter particles. In addition, QTEST will be able to perform photon recoil measurements to better than 10 −11 precision. This improves upon terrestrial experiments by a factor of 100, enabling an accurate test of the standard model of particle physics and contributing to mass measurement, in the proposed new international system of units (SI), with significantly improved precision. The predicted high measurement precision of QTEST comes from the microgravity environment on ISS, offering extended free fall times in a well-controlled environment. QTEST plans to use high-flux, dual-species atom sources, and advanced cooling schemes, for N>10 6 non-condensed atoms of each species at temperatures below 1 nK. Suppression of systematic errors by use of symmetric interferometer configurations and rejection of commonmode errors drives the QTEST design. It uses Bragg interferometry with a single laser beam at the 'magic' wavelength, where the two isotopes have the same polarizability, for mitigating sensitivities to vibrations and laser noise, imaging detection for correcting cloud initial conditions and maintaining contrast, modulation of the atomic hyperfine states for reduced sensitivity to magnetic field gradients, two source-regions for simultaneous time reversal measurements and redundancy, and modulation of the gravity vector using a rotating platform to reduce otherwise difficult systematics to below 10 −16 . dilatons or moduli [6]. Such tests may thus be one of the best chances to detect new physics beyond the standard model.Recent advances in ultra-cold atom physics and atom interferometry have provided new measurement capabilities [7][8][9][10][11][12][13][14], with which the EP can be tested to unprecedented precisions. Already, laboratory experimental investigations have been carried out with atomic matter waves for tests of the equivalence principle [14][15][16][17][18][19], for precise photon recoil measurements [20,21], and for tests of inverse square laws of gravity [22][23][24]. The Quantum Test of the Equivalence principle and Space Time (QTEST) will fundamentally be a set of lightpulse atom interferometer (AI) experiments. Its primary science objective is to measure the differential gravitational a...

How Does Interference Fall?

“…The short de Broglie wavelength of an atom makes atomic interferometers highly sensitive, whilst the macroscopic nature of the condensate allows for a high degree of control. Proposals for tests on board the international space station have been put forward which, if performed, are expected to surpass the best classical tests by a factor of 100 [11]. Finally, tests of the uniquely quantum mechanical equivalence principle for superpositions have also been proposed [12].…”

Species-selective confinement of atoms dressed with multiple radiofrequencies

“…More recently, this mixture has been used in atom interferometry experiments where a second species can be used to remove common mode noise or test the weak equivalence principle [49][50][51][52][53][54].…”

Two-dimensional grating magneto-optical trap

“…These successes have spurred interest in transitioning cold atom devices from the lab to more demanding environments [9][10][11][12][13][14][15][16][17]. Recently, a three dimensional grating magneto-optical trap (3D GMOT) was demonstrated that satisfies many needs of a deployable system [18][19][20].…”