We describe a novel use for superconducting flux pumping, namely a method for magnetizing a planar magnetic field source. The method is useful for many applications, but we illustrate it with the planar Penning trap with applications in quantum technology. A flux pumping mechanism and associated mathematical model are described. The method allows for complete control of the induced persistent current in a double-loop superconducting structure, whereby the final current is a known function of the applied flux and the loop geometry. We have tested our flux pumping technique and found excellent agreement with the theory.

We theoretically investigate the coupling of a single electron in a planar Penning trap with a remote superconducting microwave (MW) cavity. Coupling frequencies around Ω=2π·1 MHz can be reached with resonators with a loaded quality factor of Q=105, allowing for the strong coupling regime. The electron and the cavity form a system of two coupled quantum harmonic oscillators. This is a hybrid and linear microwave quantum network. We show that the coherent interaction can be sustained over distances of a few mm up to several cm. Similar to classical linear MW circuits, the coherent quantum exchange of photons is ruled by the impedances of the electron and the cavity. As one concrete application, we discuss the entanglement of the cyclotron motions of two electrons located in two separate traps.

We present a low-noise (<10 µ$\mathrm{rad}/\sqrt{\mathrm{Hz}}$) broadband Faraday Rotation Spectroscopy method which is feasible for near-ultraviolet through near-infrared wavelengths. We demonstrate this in the context of a high-precision spectroscopy experiment using a heated Pb vapor cell and two different lasers, one in the UV (368 nm) and a second in the IR (1279 nm). A key element of the experimental technique is the use of a uniaxial single crystal CeF₃ Faraday modulator with excellent transmission and optical rotation properties across the aforementioned wavelength range. Polarimeter performance is assessed as a function of crystal orientation and alignment, AC modulation amplitude, laser power, and laser wavelength. Crystal-induced distortion of the ${\left(6p^2\right)}^3{P}_0\to {\left(6p^2\right)}^3{P}_1$ (1279 nm) and ${\left(6p^2\right)}^3{P}_1\to {\left(6p7s\right)}^3{P}_0$ (368 nm) spectral lines due to misalignment-induced birefringence is discussed and modeled using the Jones calculus.

We present a planar, scalable magnetic field source, originally conceived for a chip ion trap. It consists of two symmetric sections, each with several independent currents arranged in coplanar, concentric rectangular loops. The currents allow for tuning the strength of the field and its lowest-order derivatives at one discretional position along the source’s vertical symmetry axis, a few mm above its surface. We describe the construction and calibration of the device and the cryogenic setup. The two most important current configurations for a Penning ion trap, the homogeneous field and the magnetic bottle, are investigated experimentally. Homogeneous fields around 0.5 T are routinely reached. We discuss the maximum attainable field, and we briefly describe ongoing further developments aiming at homogeneous fields well above 1 T.

We discuss how flux pumping can be applied to multiple inductively coupled superconducting circuits, and describe its importance to the operation of a novel, planar magnetic field source for quantum technology applications. Specifically, we discuss how applying a transformer-rectifier flux pumping technique to several double-loop superconducting structures simultaneously allows for the effect of cross-talk — the inevitable coupling between neighbouring superconducting loops — to be accounted for. Using both a theoretical model and an experimental verification, we introduce a method of calibrating a flux-pumped magnetic field source such that any desired magnetic field distribution within the critical current limits of the used materials can be obtained.

A switchless HTS flux pump and circuit model for a centimeter scale double-loop superconducting circuit of 2G-tape are presented. The flux pump mechanism $-$ which does not use a traveling magnetic wave $-$ operates via the generation of finite resistivity in the different arms of the multiply-connected superconducting circuit, resulting in the build up of a nonzero dc voltage which drives a superconducting persistent current. Using the principle of flux conservation, flux flow, and dynamic resistance, a theoretical model is given which is in qualitative agreement with the preliminary data presented.