— Using cold atoms, a very sensitive and high resolution magnetic and electric field sensor can be realised. Ultra-close trapping of atoms would improve the resolution of cold-atom based surface probes. The limitation on the trapping dis-tance arises from strongly distance-dependent effects such as Casimir force, Johnson noise etc. We are constructing an experimental system to trap atoms at surface sep-arations of less than a micron. We will demonstrate the possibility of using special surfaces such as silicon nitride membranes and graphene for sub-micron trapping. We have designed a 10-layer printed circuit board, which can magnetically trap the cold atom cloud and transport it precisely to a desired location. This gives us the ability to study multiple samples within the same vacuum environment. In order to achieve higher atom number in the initial trapping stages, we use a dual-color MOT technique for Rb-87 atoms. Using this technique we achieve a significant increase in atom number and decrease in temperature. In this talk, I will present the results of the dual color MOT. I will also report on results related to magnetic transport and sub-micron trapping of atoms.

We study experimentally and theoretically a dense ensemble of negatively charged nitrogen-vacancy centers in diamond coupled to a high $Q$ superconducting coplanar waveguide cavity mode at low temperature. The nitrogen-vacancy centers are modeled as effective spin one defects with inhomogeneous frequency distribution. For a large enough ensemble the effective magnetic coupling of the collective spin dominates the mode losses and inhomogeneous broadening of the ensemble and the system exhibits well resolved normal mode splitting in probe transmission spectra. We use several theoretical approaches to model the probe spectra and the number and frequency distribution of the spins. This analysis reveals an only slowly temperature dependent q-Gaussian energy distribution of the defects with a yet unexplained decrease of effectively coupled spins at very low temperatures below $\unit{100}{\milli\kelvin}$. Based on the system parameters we predict the possibility to implement an extremely stable maser by adding an external pump to the system.

We report strong coupling between an ensemble of nitrogen-vacancy center electron spins in diamond and a superconducting microwave coplanar waveguide resonator. The characteristic scaling of the collective coupling strength with the square root of the number of emitters is observed directly. Additionally, we measure hyperfine coupling to (13)C nuclear spins, which is a first step towards a nuclear ensemble quantum memory. Using the dispersive shift of the cavity resonance frequency, we measure the relaxation time of the NV center at millikelvin temperatures in a nondestructive way.

We realize a one-dimensional Josephson junction using quantum degenerate Bose gases in a tunable double well potential on an atom chip. Matter wave interferometry gives direct access to the relative phase field, which reflects the interplay of thermally driven fluctuations and phase locking due to tunneling. The thermal equilibrium state is characterized by probing the full statistical distribution function of the two-point phase correlation. Comparison to a stochastic model allows us to measure the coupling strength and temperature and hence a full characterization of the system.

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous correlations play an important role. Comparison with a recent theoretical approach described by Imambekov et al. yields good agreement with our experimental results and shows that density correlations can be used for thermometry of quasicondensates.

We present a novel imaging system for ultracold quantum gases in expansion. After release from a confining potential, atoms fall through a sheet of resonant excitation laser light and the emitted fluorescence photons are imaged onto an amplified CCD camera using a high numerical aperture optical system. The imaging system reaches an extraordinary dynamic range, not attainable with conventional absorption imaging. We demonstrate single-atom detection for dilute atomic clouds with high efficiency where at the same time dense BoseEinstein condensates can be imaged without saturation or distortion. The spatial resolution can reach the sampling limit as given by the 8 μm pixel size in object space. Pulsed operation of the detector allows for slice images and hence a 3D tomography of the measured object. The scheme can easily be implemented for any atomic species and all optical components are situated outside the vacuum system. As a first application we perform thermometry on rubidium Bose-Einstein condensates created on an atom chip. PACS numbers: 1315, 9440T Submitted to: New J. Phys.

Placing an ensemble of 10;{6} ultracold atoms in the near field of a superconducting coplanar waveguide resonator with a quality factor Q approximately 10;{6}, one can achieve strong coupling between a single microwave photon in the coplanar waveguide resonator and a collective hyperfine qubit state in the ensemble with g_{eff}/2pi approximately 40 kHz larger than the cavity linewidth of kappa/2pi approximately 7 kHz. Integrated on an atomchip, such a system constitutes a hybrid quantum device, which also can be used to interconnect solid-state and atomic qubits, study and control atomic motion via the microwave field, observe microwave superradiance, build an integrated micromaser, or even cool the resonator field via the atoms.

We present a novel imaging system for ultracold quantum gases in expansion. After release from a confining potential, atoms fall through a sheet of resonant excitation laser light and the emitted fluorescence photons are imaged onto an amplified CCD camera using a high numerical aperture optical system. The imaging system reaches an extraordinary dynamic range, not attainable with conventional absorption imaging. We demonstrate single-atom detection for dilute atomic clouds with high efficiency where at the same time dense Bose–Einstein condensates can be imaged without saturation or distortion. The spatial resolution can reach the sampling limit as given by the 8 μm pixel size in object space. Pulsed operation of the detector allows for slice images, a first step toward a three-dimensional (3D) tomography of the measured object. The scheme can easily be implemented for any atomic species and all optical components are situated outside the vacuum system. As a first application we perform thermometry on rubidium Bose–Einstein condensates created on an atom chip.

We employ an evolutionary algorithm to automatically optimize different stages of a cold atom experiment without human intervention. This approach closes the loop between computer based experimental control systems and automatic real time analysis and can be applied to a wide range of experimental situations. The genetic algorithm quickly and reliably converges to the most performing parameter set independent of the starting population. Especially in many-dimensional or connected parameter spaces, the automatic optimization outperforms a manual search.

Epidemiologic studies have shown that trace concentrations of inhalation anaesthetics polluting the air of operating theatres could have deleterious effects on the personnel's health. Nitrous oxide (N2O) oxidises vitamin B-12 and thus decreases DNA production by inactivation of methionine synthase. Therefore, the United States and most European health authorities recommend threshold values to protect against potential health risks. These values range from 25 to 100 ppm, expressed as time-weighted averages (TWA). There is a lack of data concerning measurements of trace concentrations under defined conditions. The aim of this study was to quantify levels of N2O in a recovery room (RR) with an air conditioning system.Methods. Trace concentrations of N2O were determined in the main RR of the University Hospital of Regensburg (Germany). Measurements were taken for 5 days from 8:00 a.m. to 8:00 p.m. Trace concentrations of N-2,O were measured directly by means of a highly sensitive photoacoustic infrared spectrometry analyser. The lower detection limit was 0.03 ppm. Samples of room air were taken continuously from six different places in the recovery room, five of which had a distance of 50 cm to the patients' heads. One point represented the nurses' desk 5 m away from the patients. TWAs were calculated for each day and location.Results. All values were below 5 ppm TWA at each location. Typical TWA (range) values recorded at day 2 were for point 1:3.5 ppm (0.4-8.9), point 2:3.2 (0.5-7.3), point 3:3.0 (0.5-5.4), point 4:3.7 (0.5-21.2), point 5:3.2 (0.6-6.6), and at the nurses' desk 3.3 (0.5-6.3). Peak concentrations of nearly 25 ppm were reached for at least 10 min. Significant differences between the days and locations could not be found (P<0.05, Wilcoxon test).Conclusion. Exposure to N2O in a climatised RR is determined by several factors: (1) efficacy of air conditioning, with 10.7 changes per hour without recirculation; (2) recovery room size; (3) transport of the patients takes about 15 min, during which some quantities of N2O leave the patient; and (4) high numbers of patients staying 2 and more hours in the recovery room and exhaling smaller concentrations of N2O into the room air. Because of these factors, all measured values are significantly below the standard international threshold values. Under other conditions of room design, such as ventilation and size, measured values may be higher.

Isoflurane is a suitable agent to produce sedation in the intensive care unit (ICU). However, data concerning occupational exposure to isoflurane during long-term sedation are not yet available. The purpose of this study was to evaluate occupational exposure to isoflurane in the ICU.Trace concentrations of isoflurane were measured directly by means of photoacustic infrared spectrometry during isoflurane sedation in ten cases over a period of 24 hours. Values were obtained at four personnel-related and two leakage-related locations in an ICU chamber.All measured values were low, the majority under 3 ppm isoflurane at the personnel-related points. Peak concentrations up to 40 ppm were recorded for several minutes during nursing interventions. At measurement point "nearby patient's mouth" values up to 5 ppm were recorded, at location "anaesthesia machine" values ranged from 2 to 69 ppm isoflurane.We conclude that an effective high flow scavenging system, a low-leakage anaesthesia machine and an airconditioning equipment without recirculation could keep occupational exposure low. The majority of the measured values was below the NIOSH recommendation (2 ppm). All values was lower than a national state recommendation (10 ppm). Under other circumstances (e.g. without scavenging system) air pollution will be higher and therefore measurements at the working place are needed.