High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Q</mml:mi></mml:mrow></mml:math> Magnetic Levitation and Control of Superconducting Microspheres at Millikelvin Temperatures
Joachim Hofer, R. Gross, Gerard Higgins, Hans Huebl, Oliver Kieler, R. Kleiner, D. Koelle, Philip Schmidt, Joshua A. Slater, Michael Trupke, Kevin Uhl, Thomas Weimann, Witlef Wieczorek, Markus Aspelmeyer
Abstract
We report the levitation of a superconducting lead-tin sphere with 100 μm diameter (corresponding to a mass of 5.6 μg) in a static magnetic trap formed by two coils in an anti-Helmholtz configuration, with adjustable resonance frequencies up to 240 Hz. The center-of-mass motion of the sphere is monitored magnetically using a dc superconducting quantum interference device as well as optically and exhibits quality factors of up to 2.6×10^{7}. We also demonstrate 3D magnetic feedback control of the motion of the sphere. The setup is housed in a dilution refrigerator operating at 15 mK. By implementing a cryogenic vibration isolation system, we can attenuate environmental vibrations at 200 Hz by approximately 7 orders of magnitude. The combination of low temperature, large mass, and high quality factor provides a promising platform for testing quantum physics in previously unexplored regimes with high mass and long coherence times.