A new measurement resolves cyclotron and spin levels for a single-electron quantum cyclotron to obtain an electron magnetic moment, given by g/2=1.001 159 652 180 85 (76) [0.76 ppt]. The uncertainty is nearly 6 times lower than in the past, and g is shifted downward by 1.7 standard deviations. The new g, with a quantum electrodynamics (QED) calculation, determines the fine structure constant with a 0.7 ppb uncertainty--10 times smaller than for atom-recoil determinations. Remarkably, this 100 mK measurement probes for internal electron structure at 130 GeV.
Because of the atomic thinness of graphene, its integration into a device will always involve its interaction with at least one supporting substrate, making the surface energy of graphene critical to its real-life applications. In the current paper, the contact angle of graphene synthesized by chemical vapor deposition (CVD) was monitored temporally after synthesis using water, diiodomethane, ethylene glycol, and glycerol. The surface energy was then calculated based on the contact angle data by the Fowkes, Owens-Wendt (extended Fowkes), and Neumann models. The surface energy of fresh CVD graphene grown on a copper substrate (G/Cu) immediately after synthesis was determined to be 62.2 ± 3.1 mJ/m(2) (Fowkes), 53.0 ± 4.3 mJ/m(2) (Owens-Wendt) and 63.8 ± 2.0 mJ/m(2) (Neumann), which decreased to 45.6 ± 3.9, 37.5 ± 2.3, and 57.4 ± 2.1 mJ/m(2), respectively, after 24 h of air exposure. The ellipsometry characterization indicates that the surface energy of G/Cu is affected by airborne hydrocarbon contamination. G/Cu exhibits the highest surface energy immediately after synthesis, and the surface energy decreases after airborne contamination occurs. The root cause of intrinsically mild polarity of G/Cu surface is discussed.
Levitated optomechanical systems, and particularly particles trapped in vacuum, provide unique platforms for studying the mechanical behavior of objects well-isolated from their environment. Ultimately, such systems may enable the study of fundamental questions in quantum mechanics, gravity, and other weak forces. While the optical trapping of nanoparticles has emerged as the prototypical levitated optomechanical system, it is not without problems due to the heating from the high optical intensity required, particularly when combined with a high vacuum environment. Here we investigate a magneto-gravitational trap in ultra-high vacuum. In contrast to optical trapping, we create an entirely passive trap for diamagnetic particles by utilizing the magnetic field generated by permanent magnets and the gravitational interaction. We demonstrate cooling the center of mass motion of a trapped silica microsphere from ambient temperature to an effective temperature near or below one milliKelvin in two degrees of freedom by optical feedback damping.
Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.
A one-electron oscillator is cooled from 5.2 K to 850 mK using electronic feedback. Novel quantum jump thermometry reveals a Boltzmann distribution of oscillator energies and directly measures the corresponding temperature. The ratio of electron temperature and damping rate (also directly measured) is observed to be a fluctuation-dissipation invariant, independent of feedback gain, as predicted for noiseless feedback. The sharply reduced linewidth that results from feedback cooling illustrates the likely importance for improved fundamental measurements and symmetry tests.
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