We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of the Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate, that Newton's inverse square law of Gravity is understood at micron distances on an energy scale of 10 −14 eV. At this level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β > 5.8 × 10 8 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axion-like spin-mass coupling is excluded for the coupling strength gsgp > 3.7 × 10 −16 (5.3 × 10 −16 ) at a Yukawa length of λ = 20 µm (95% (C.L.).PACS numbers: 12.15. Ji,13.30.Ce,14.20.Dh,23.40.Bw Experiments that rely on frequency measurements can be performed with incredibly high precision. One example is Rabi spectroscopy, a resonance spectroscopy technique to measure the energy eigenstates of quantum systems. It was originally developed by I. Rabi to measure the magnetic moment of molecules [1]. Today, resonance spectroscopy techniques are applied in various fields of science and medicine including nuclear magnetic resonance, masers, and atomic clocks. These methods have opened up the field of low-energy particle physics with studies of particle properties and their fundamental interactions and symmetries. In an attempt to investigate gravity at short distances, we applied the concept of resonance spectroscopy to quantum states of very slow neutrons in the Earth's gravity potential [2]. Here, we present the first precision measurements of gravitational quantum states with this method that we refer to as gravity resonance spectroscopy (GRS). The strength of GRS is that it does not rely on electromagnetic interactions. The use of neutrons as test particles bypasses the electromagnetic background induced by van der Waals and Casimir forces and other polarizability effects.Within this work, we link these new measurements to dark matter and dark energy searches. Observational cosmology has determined the dark matter and dark energy density parameters to an accuracy of two significant figures [3]. While dark energy explains the accelerated expansion of the universe, dark matter is needed in order to describe the rotation curves of galaxies and the largescale structure of the universe. The true nature of dark energy and the content of dark matter remain a mystery, however. The two most obvious candidates for dark energy are either Einstein's cosmological constant [4] or quintessence theories [5,6], where the dynamic vacuum energy changes over time. The resonant frequencies of our quantum states are intimately related to these models. If some as yet undiscovered dark matter or dark energy particles interact with neutrons, this should result in a measurable energy shift of the observed quantum states. One prom...

A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.

An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.Comment: 5 pages, 4 figure

We present a magnetically shielded environment with a damping factor larger than one million at the mHz frequency regime and an extremely low field and gradient over an extended volume. This extraordinary shielding performance represents an improvement of the state-of-the-art in the difficult regime of damping very low-frequency distortions by more than an order of magnitude. This technology enables a new generation of high-precision measurements in fundamental physics and metrology, including searches for new physics far beyond the reach of accelerator-based experiments. We discuss the technical realization of the shield with its improvements in design.

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