We measure the AC Zeeman force on an ultracold gas of 87 Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near-field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple 2-level theory for the AC Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin-selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

We demonstrate the ability to receive live color analog television and video game signals with the use of the Rydberg atom receiver. The typical signal expected for traditional 480i National Television Standards Committee format video signals requires a bandwidth of over 3 MHz. We determine the beam sizes, powers, and detection method required for the Rydberg atoms to receive this type of signal. The beam size affects the average time the atoms remain in the interaction volume, which is inversely proportional to the bandwidth of the receiver. We find that small beam diameters (less than 100  μm) lead to much faster responses and allow for color reception. We demonstrate the effect of the beam size on bandwidth by receiving a live 480i video stream with the Rydberg atom receiver. The best video reception was achieved with a beam width of [Formula: see text]m full-width at half-max.

We present a simple demonstration of the skin effect by observing the current distribution in a wide rectangular strip conductor driven at frequencies in the 0.25–5 kHz range. We measure the amplitude and phase of the current distribution as a function of the transverse position and find that they agree well with numerical simulations: The current hugs the edges of the strip conductor with a significant variation in phase across the width. The experimental setup is simple, uses standard undergraduate physics instructional laboratory equipment, and is easy to implement as a short in-class demonstration. Our study is motivated by modeling ac magnetic near fields in the vicinity of a rectangular trace on an atom chip.