We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Deltaa(N),(Be-Ti)=(0.6+/-3.1)x10(-15) m/s2 improves limits on equivalence-principle violations with ranges from 1 m to infinity by an order of magnitude. The Eötvös parameter is eta(Earth,Be-Ti)=(0.3+/-1.8)x10(-13). By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding eta(DM,Be-Ti)=(-4+/-7)x10(-5). Space-fixed differential accelerations in any direction are limited to less than 8.8x10(-15) m/s2 with 95% confidence.

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Abstract. We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium-aluminum and beryllium-titanium test body pairs with precisions at the part in 10 13 level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects for further improvements in experimental sensitivity.

Around the globe several observatories are seeking the first direct detection of gravitational waves (GWs). These waves are predicted by Einstein's general theory of relativity and are generated, for example, by black-hole binary systems. Present GW detectors are Michelson-type kilometre-scale laser interferometers measuring the distance changes between mirrors suspended in vacuum. The sensitivity of these detectors at frequencies above several hundred hertz is limited by the vacuum (zero-point) fluctuations of the electromagnetic field. A quantum technology--the injection of squeezed light--offers a solution to this problem. Here we demonstrate the squeezed-light enhancement of GEO600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for GWs for the next 3-4 years. GEO600 now operates with its best ever sensitivity, which proves the usefulness of quantum entanglement and the qualification of squeezed light as a key technology for future GW astronomy

We used a torsion pendulum containing ≈ 10 23 polarized electrons to search new interactions that couple to electron spin. We limit CP-violating interactions between the pendulum's electrons and unpolarized matter in the earth or the sun, test for rotation and boost-dependent preferred-frame effects using the earth's rotation and velocity with respect to the entire cosmos, and search for exotic velocity-dependent potentials between polarized electrons and unpolarized matter in the sun and moon. We find CP -violating parameters |g e P g N S |/(hc) < 9.4 × 10 −37 and |g efor λ > 1AU. We test for preferred-frame interactions of the form V = −σ e ·A, V = −Bσ e ·v/c, on A in terms of non-commutative geometry, we obtain an upper bound of (355 l GUT ) 2 on the minimum observable area, where l GUT =hc/(10 16 GeV) is the grand unification length. We find that |B| ≤ 1.2 × 10 −19 eV. All 9 components of C are constrained at the 10 −17 to 10 −18 eV level.We determine 9 linear combinations of parameters of the Standard Model Extension; rotationalnoninvariant and boost-noninvariant terms are limited at roughly the 10 −31 GeV and 10 −27 GeV levels, respectively. Finally, we find that the gravitational mass of an electron spinning toward the galactic center differs by less than about 1 part in 10 21 from an electron spinning in the opposite direction. As a byproduct of this work, the density of polarized electrons in Sm Co 5 was measured to be (4.19 ± 0.19) × 10 22 cm −3 at a field of 9.6 kG.

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We used a torsion pendulum containing ∼ 9 × 10 22 polarized electrons to search for CP-violating interactions between the pendulum's electrons and unpolarized matter in the laboratory's surroundings or the sun, and to test for preferred-frame effects that would precess the electrons about a direction fixed in inertial space. We find |g e P g N S |/(hc) < 1.7 × 10 −36 and |g e A g N V |/(hc) < 4.8 × 10 −56 for λ > 1AU. Our preferred-frame constraints, interpreted in the Kostelecký framework, set an upper limit on the parameter |b e | ≤ 5.0 × 10 −21 eV that should be compared to the benchmark value m 2 e /M Planck = 2 × 10 −17 eV.PACS numbers: 11.30. Cp,12.20.Fv This Letter reports constraints on proposed new spincoupled interactions using a torsion pendulum containing ∼ 9 × 10 22 polarized electrons. Several lines of speculation motivated our work. We were motivated to consider preferred-frame effects because the cosmic microwave background does establish a such a frame. Kostelecký and coworkers [1] have discussed an unusual cosmic preferred-frame effect where vector and axial-vector fields could have been spontaneously generated in the early universe and then been inflated to enormous extents. They emphasize that these fields would provide a mechanism for CPT and Lorentz violation. Because the fields invalidate the Pauli-Luders theorem, one can construct a field theory with CPT-and Lorentz-violating effects (the Standard-Model Extension) and quantify the sensitivity of various CPT and preferred-frame tests. One manifestion of such fields would be an anomalous torque on a spinning electron[2] arising from a potentialwhereb e is the product of the presumed cosmic axialvector field and its coupling to electrons.Spin-dependent forces are also generically produced by the exchange of pseudoscalar particles. Moody and Wilczek[3] discussed the forces produced by the exchange of low-mass, spin-0 particles and pointed out that particles containing CP-violating J π = 0 + and J π = 0 − admixtures would produce a macroscopic, CP-violating "monopole-dipole" interaction between a polarized electron and an unpolarized atom with mass and charge numbers A and Zwhere m φ =h/(λc) is the mass of the hypothetical spin-0 particle, g P and g S are its pseudoscalar and scalar couplings, and gFor simplicity, we assume below that g Recently Dobrescu and Mocioiu[4] classified the kinds of potentials that might arise from exchange of low-mass bosons, constrained only by rotational and translational invariance. We are sensitive to 3 of their potentials; in addition to a potential equivalent to Eq. 2, we probe two potentials that we write as V eN (r) = σ e · A ⊥h c (ṽ ×r) m e

The redefinition of the SI unit of mass in terms of a fixed value of the Planck constant has been made possible by the Kibble balance, previously known as the watt balance. Once the new definition has been adopted, the Kibble balance technique will permit the realisation of the mass unit over a range from milligrams to kilograms. We describe the theory underlying the Kibble balance and practical techniques required to construct such an instrument to relate a macroscopic physical mass to the Planck constant with an uncertainty, which is achievable at present, in the region of 2 parts in 10 8 . A number of Kibble balances have either been built or are under construction and we compare the principal features of these balances.