Neutrons test Gravity, Dark Matter and Dark Energy: Snapshots of a Quantum Bouncing Ball & Gravity Resonance Spectroscopy

Abstract

We report a measurement of the local acceleration with ultracold neutrons based on quantum states in the gravity potential of the Earth. The new method uses resonant transitions between the states |1 ↔ |3 and for the first time between |1 ↔ |4 . The measurements demonstrate that Newton's Inverse Square Law of Gravity is understood at micron distances at an energy level of 10 −14 eV with ∆g g = 4 × 10 −3 . The results provide constraints on any possible gravitylike interaction at a micrometer interaction range. In particular, a dark energy candidate, the chameleon field is restricted to β < 6.9 × 10 6 for n = 2 (95% C.L.).

Chirped-frequency excitation of gravitationally bound ultracold neutrons

“…The transition between two quantum states is triggered by a sinusoidal oscillation of the plates. These experiments pave the way to the purely mechanical control and manipulation of quantum gravitational states, with potential applications to fundamental physics, such as the testing of dark matter scenarios and nonstandard theories of gravity [6,7]. Here, we show that a chirped oscillation with slowly varying frequency (classically known as autoresonance) can be used to bring the neutrons to higher excited states by climbing the energy levels one by one.…”

“…(7), we obtain t à ¼ 87 ms. The typical horizontal velocity of the neutrons [5] being of the order of 6 ms −1 , this would require the mirror plate to be 50 cm long, while in the most recent published experiment it is 20 cm [7]. This gap could be bridged with relative ease by increasing the length of the mirror and slightly reducing the transit speed of the neutrons.…”

“…However, in the last decade, several experiments and theoretical developments have helped clarify how a quantum object responds to gravity, in particular, the gravitational field of the Earth. These include the measurement of gravitationally induced quantum phases by neutron interferometry [2], interference experiments on free-falling Bose-Einstein condensates (BECs) [3], the observation of the quantized energy levels of ultracold neutrons (UCNs) [4], and the realization of gravity-resonance spectroscopy [5], which was recently exploited to search for extra short-range interactions [6,7]. Tests of the equivalence principle in the quantum regime were also proposed [8,9].…”

“…More recent studies were pursued independently by three groups: (i) The GRANIT experiment aims at realizing transitions between gravitational quantum states using inhomogeneous magnetic fields [14]; (ii) Ichikawa et al [15] reported on measurements of the spatial distribution of these states using a dedicated high-resolution detector; (iii) finally, in a series of experiments conducted at the PF2 source of the Institut Laue-Langevin (qBounce project), mechanical oscillations of the neutron mirrors were used to induce transitions between several gravitational quantum states [5][6][7].…”

What laboratory experiments can teach us about cosmology: A chameleon example

“…Tests of gravity can be performed by allowing a beam of ultra cold neutrons to bounce above a mirror, and measuring the quantized energy levels of the neutrons. An additional chameleon force would perturb these energy levels, and as neutrons are sufficiently small that they are un-screened, they would feel the chameleon effects without any additional suppression [28][29][30][31]. Alternatively interferometry experiments with neutrons can also be used to test gravity.…”