Tunable Rydberg-Rydberg transitions in helium with reduced sensitivity to dc electric fields by two-colour microwave dressing

The difference in the static electric dipole polarizabilities of the 1\mathrm{s}55\mathrm{s}\,^3\mathrm{S}_1 and 1\mathrm{s}56\mathrm{s}\,^3\mathrm{S}_1 Rydberg levels in helium has been eliminated by dressing the atom with a microwave field near resonant with the single-photon 1\mathrm{s}55\mathrm{s}\,^3\mathrm{S}_1 \rightarrow 1\mathrm{s}55\mathrm{p}\,^3\mathrm{P}_J transition. For an $2.82\,\mathrm{mV}\,\mathrm{cm}^{-1}$ amplitude dressing field, detuned by $2\pi\times10\,\mathrm{MHz}$ from the zero-field 1\mathrm{s}55\mathrm{s}\,^3\mathrm{S}_1 \rightarrow 1\mathrm{s}55\mathrm{p}\,^3\mathrm{P}_2 transition frequency, the dc Stark shift of the two-photon 1\mathrm{s}55\mathrm{s}\,^3\mathrm{S}_1 \rightarrow 1\mathrm{s}56\mathrm{s}\,^3\mathrm{S}_1 transition between these states remained within $\pm 15\,\mathrm{kHz}$ for electric fields up to ${\sim}60\,\mathrm{mV}\,\mathrm{cm}^{-1}$. This transition was probed by single-color two-photon microwave spectroscopy, and by two-color two-photon spectroscopy with one strong additional dressing field and a weak probe field. For all measurements, the transition frequencies and Stark shifts were compared, and found to be in excellent quantitative agreement with the results of Floquet calculations of the energy-level structure of the Rydberg states in the presence of the dressing fields and applied dc electric fields. The two-color microwave dressing scheme demonstrated, with one field applied to null the differential polarizability of the Rydberg–Rydberg transition, and the second exploited to allow the two-photon transition to be employed to achieve tunable absorption of single-photons from a weak probe field, will facilitate improved coherence times and tunable single-photon absorption in hybrid cavity QED experiments with Rydberg atoms and superconducting microwave circuits

Electrometry of a single resonator mode at a Rydberg-atom–superconducting-circuit interface

The electric-field distribution in a single mode of a λ/4 superconducting coplanar waveguide (CPW) microwave resonator has been probed using beams of helium Rydberg atoms. In the experiments the atoms were prepared in the 1s55s3S1 Rydberg level by laser photoexcitation. They then traveled over the CPW resonator that was fabricated on a NbN superconducting chip operated at 3.8 K. The resonator was driven at its third-harmonic frequency, near resonant with the two-photon 1s55s3S1→1s56s3S1 transition at ω55s,56s/2=2π×19.556499 GHz. The coherence times of the atom–resonator-field interaction were determined at selected locations above the resonator by time-domain measurements of Rabi oscillations and found to be up to 0.8μs for Rabi frequencies of ∼2π×3 MHz. The coherence times of the atomic superposition states, generated following the interaction of the atoms with the microwave field in the resonator, were inferred from high-resolution cavity-enhanced Ramsey spectra to be ∼2.5μs. These Ramsey spectra also allowed the measurement of residual uncanceled dc electric fields of 26.6±0.6 mV/cm at the position of the atoms ∼300μm above the surface of the superconducting chip. These results represent an essential step toward applications of hybrid systems, comprising Rydberg atoms coherently coupled to superconducting microwave circuits, in quantum optics and quantum information processing

The functions of the embassy in the world-making experiments of China Miéville

What happens when social scientific theorising seeks to take instruction from Science Fiction and Fantasy writing rather than using it as a source of convenient examples? This paper discusses the ways in which the figure of the ‘embassy’ and ambassadorial functions operate within the work of China Miéville. Focusing in particular on three key novels – The City and The City, Kraken and Embassytown – the paper reads the secondary worlds constructed by Miéville as offering their own self-contained problematics of relevance to social science. These concerns the mechanisms of territorial distinction, the nature of communication and the organization of spatio-temporal relations. The embassy emerges as an embodied site for the mediation of specialized communicative relations that are fundamentally irreconcilable, but which nevertheless offer the hope of reaching outside of human temporality. The relevance of these considerations for a social science of the Anthropocene and the Chthulucene are outlined