Sagnac Interferometry with a Single Atomic Clock.

The Sagnac effect enables interferometric measurements of rotation with high precision. Using matter waves instead of light promises resolution enhancement by orders of magnitude that scales with particle mass. So far, the paradigm for matter wave Sagnac interferometry relies on de Broglie waves and thus on free propagation of atoms either in free fall or within waveguides. However, the Sagnac effect can be expressed as a proper time difference experienced by two observers moving in opposite directions along closed paths and has indeed been measured with atomic clocks flown around Earth. Inspired by this, we investigate an interferometer comprised of a single atomic clock. The Sagnac effect manifests as a phase shift between trapped atoms in different internal states after transportation along closed paths in opposite directions, without any free propagation. With analytic models, we quantify limitations of the scheme arising from atomic dynamics and finite temperature. Furthermore, we suggest an implementation with previously demonstrated technology.

High quality anti-relaxation coating material for alkali atom vapor cells.

We present an experimental investigation of alkali atom vapor cells coated with a high quality anti-relaxation coating material based on alkenes. The prepared cells with single compound alkene based coating showed the longest spin relaxation times which have been measured up to now with room temperature vapor cells. Suggestions are made that chemical binding of a cesium atom and an alkene molecule by attack to the C = C bond plays a crucial role in such improvement of anti-relaxation coating quality.

Generation of two-mode squeezed and entangled light in a single temporal and spatial mode.

We analyse a novel squeezing and entangling mechanism which is due to correlated Stokes and anti-Stokes photon forward scattering in a multi-level atom vapour. We develop a full quantum model for an alkali atomic vapour including quantized collective atomic states which predicts high degree of squeezing for attainable experimental conditions. Following the proposal we present an experimental demonstration of 3.5 dB pulsed frequency nondegenerate squeezed (quadrature entangled) state of light using room temperature caesium vapour. The source is very robust and requires only a few milliwatts of laser power. The squeezed state is generated in the same spatial mode as the local oscillator and in a single temporal mode. The two entangled modes are separated by twice the Zeeman frequency of the vapour which can be widely tuned. The narrow-band squeezed light generated near an atomic resonance can be directly used for atom-based quantum information protocols. Its single temporal mode characteristics make it a promising resource for quantum information processing.

In situ detection of potassium atoms in high-temperature coal-combustion systems using near-infrared-diode lasers.

Direct tunable diode laser absorption spectroscopy at 769.9 and 767.5 nm was used to measure potassium (K) atom concentrations in situ in the high temperature (up to 1650 K) flue gas of two different pulverized coal dust combustion systems (atmospheric or pressurized (12 bar)). Two laser types (Fabry-Pérot (FP) and vertical-cavity surface-emitting lasers (VCSEL)) were used for the spectrometer and characterized with respect to the magnitude and linearity of their static and dynamic wavelength tuning properties. The wide continuous current-induced tuning range of the VCSEL of 20 cm(-1) (compared to 1 cm(-1) for the FP) make this laser ideal for species monitoring in high pressure processes. Two VCSELs were time-multiplexed to realize the simultaneous detection of the potassium D1 and D2 lines. Several oxygen absorption lines in the A-band, which are in close spectral vicinity of the K lines, were detected simultaneously, showing the possibility of multi-species detection with one laser. Using the FP-DL for the atmospheric process and the VCSEL for the high pressure process, the pressure-dependent coefficients for spectral broadening as well as a shift of the K line in the flue gas were determined to be (0.18 +/- 0.01) and (-0.060 +/- 0.003) cm(-1) per atm (at 1540 K and 11.2 bar). The total width and shift of the D1 line (11.2 bar/1540 K) were 60 and -20 GHz, respectively. The K atom concentration was determined continuously for several days in both plants under various operation conditions. Typical concentrations in the atmospheric plant were around 2 microg m(-3) with a range of 50 ng m(-3)-30 microg m(-3). Averaging 100 scans for each concentration value, we achieved a time resolution of 1.7 s and a detection limit of 10 ng m(-3), which corresponds to a fractional absorption in the 10(-3)-10(-4) range. A strong anti-correlation with the oxygen concentration could be verified. At the 12 bar plant, the concentration was again typically around 2 microg m(-3) but K levels up to 60 microg m(-3) were observed. Here, a strong dependence of the K-signal on the type of fuel could be verified.

Spin squeezing of atomic ensembles via nuclear-electronic spin entanglement.

We demonstrate spin squeezing in a room temperature ensemble of approximately 10(12) cesium atoms using their internal structure, where the necessary entanglement is created between nuclear and electronic spins of each individual atom. This state provides improvement in measurement sensitivity beyond the standard quantum limit for quantum memory experiments and applications in quantum metrology and is thus a complementary alternative to spin squeezing obtained via interatom entanglement. Squeezing of the collective spin is verified by quantum state tomography.