For the first time a single trapped antiproton ( " p) is used to measure the " p magnetic moment " p . The moment " p ¼ " p S=ð@=2Þ is given in terms of its spin S and the nuclear magneton ( N ) by " p = N ¼ À2:792 845 AE 0:000 012. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives " p = p ¼ À1:000 000 AE 0:000 005 to 5 ppm, for a proton moment p ¼ p S=ð@=2Þ, consistent with the prediction of the CPT theorem.

We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the post-expansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Boseenhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases, reducing error in expansion thermometry from tens of percent to only a few percent. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.

The proton magnetic moment in nuclear magnetons is measured to be μ(p)/μ(N) ≡ g/2 = 2.792 846 ± 0.000 007, a 2.5 parts per million uncertainty. The direct determination, using a single proton in a Penning trap, demonstrates the first method that should work as well with an antiproton (p) as with a proton (p). This opens the way to measuring the p magnetic moment (whose uncertainty has essentially not been reduced for 20 years) at least 10(3) times more precisely.

Previous measurements with a single trapped proton (p) or antiproton (p) detected spin resonance from the increased scatter of frequency measurements caused by many spin flips. Here a measured correlation confirms that individual spin transitions and states are rapidly detected instead. The 96% fidelity and an efficiency expected to approach unity suggests that it may be possible to use quantum jump spectroscopy to measure the p and p magnetic moments much more precisely.

We demonstrate a novel atom chip trapping system that allows the placement and high-resolution imaging of ultracold atoms within microns from any 100 µm-thin, UHV-compatible material, while also allowing sample exchange with minimal experimental downtime. The sample is not connected to the atom chip, allowing rapid exchange without perturbing the atom chip or laser cooling apparatus. Exchange of the sample and retrapping of atoms has been performed within a week turnaround, limited only by chamber baking. Moreover, the decoupling of sample and atom chip provides the ability to independently tune the sample temperature and its position with respect to the trapped ultracold gas, which itself may remain in the focus of a high-resolution imaging system. As a first demonstration of this new system, we have confined a 700-nK cloud of 8 × 10 4 87 Rb atoms within 100 µm of a gold-mirrored 100-µm-thick silicon substrate. The substrate was cooled to 35 K without use of a heat shield, while the atom chip, 120 µm away, remained at room temperature. Atoms may be imaged and retrapped every 16 s, allowing rapid data collection.Ultracold gases trapped near cryogenic surfaces using atom chips 1 can serve as elements of hybrid quantum systems for quantum information processing, e.g., by coupling quantum gases to superconducting qubits 2 , or as sensitive, high-resolution, and wide-area probes of electronic current flow 3 , electric ac and patch fields 4 , and magnetic domain structure 5 and dynamics. Previous experiments have succeeded in trapping and imaging ultracold thermal and quantum gases of alkali atoms around carbon nanotubes 6 , near superconductors 7 at 4 K, microns from room-temperature gold wires 8 , and within a He dilution refrigerator 9 .