Robert A. Nyman

Quartz Tuning Fork Viscometers for Helium Liquids

Mechanical resonators, in the form of vibrating wires or torsional oscillators, have long been employed as sensors in liquid 3He and 3He–4He mixtures. The damping of resonators is due to the viscosity of the surrounding liquid which is a strong, well-known function of temperature for bulk Fermi liquids. It is therefore possible to use the viscous damping for thermometry in the millikelvin regime. An alternative sensor is the small quartz tuning fork which is driven by the piezoelectric effect and requires no external magnetic field. In this paper, we present measurements of the viscous damping of such a tuning fork when immersed in a 6.2% 3He–4He mixture, between 3 and 100 mK, and at zero and high (10 T) magnetic field. The measurements indicate that damping of the tuning fork resonance is dominated by the liquid helium properties and is insensitive to the applied magnetic field. The response of the tuning fork to the saturated helium mixture demonstrates that it could potentially be used for thermometry in any magnetic field. There is evidence of slip at the interface between the fork and the helium suggesting specular scattering from the smooth surface of the quartz. The fork is also able to detect the superfluid transition in pure liquid 3He.

All-optical runaway evaporation to Bose-Einstein condensation

We demonstrate runaway evaporative cooling directly with a tightly confining optical-dipole trap and achieve fast production of condensates of

An array of integrated atom|[ndash]|photon junctions

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How to estimate the differential acceleration in a two-species atom interferometer to test the equivalence principle

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Experimental evidence for inhomogeneous pumping and energy-dependent effects in photon Bose-Einstein condensation

atoms. Our scheme uses a misaligned crossed-beam far off-resonance optical-dipole trap (MACRO-FORT). It is characterized by independent control of the trap confinement and depth allowing forced all-optical evaporation in the runaway regime. Although our configuration is particularly well suited to the case of

Interactions in dye-microcavity photon condensates and the prospects for their observation

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Minimally destructive detection of magnetically trapped atoms using frequency-synthesized light

atoms in a 1565 nm optical trap, where an efficient initial loading is possible, our scheme is general and will allow all-optical evaporative cooling at constant stiffness for every optically trappable atomic or even molecular species.

Spatiotemporal coherence of non-equilibrium multimode photon condensates

Photonic chips that integrate guides, switches, gratings and other components, process vast amounts of information rapidly on a single device. A new branch of this technology becomes possible if the light is coupled to cold atoms in a junction of small enough cross section, so that small numbers of photons interact appreciably with the atoms. Cold atoms are among the most sensitive of metrological tools and their quantum nature also provides a basis for new information processing methods. Here we demonstrate a photonic chip which provides multiple microscopic junctions between atoms and photons. We use the absorption of light at a junction to reveal the presence of one atom on average. Conversely, we use the atoms to probe the intensity and polarisation of the light. Our device paves the way for a new type of chip with interconnected circuits of atoms and photons.

Light-shift tomography in an optical-dipole trap for neutral atoms

We present a system of room-temperature extended-cavity grating-diode lasers for production of light in the range of 760–790nm. The extension of the tuning range towards the blue is permitted by the weak feedback in the cavity: the diodes are antireflection coated, and the grating has just 10% reflectance. The light is then amplified using semiconductor tapered amplifiers to give more than 400mW of power. The outputs are shown to be suitable for atomic-physics experiments with potassium (767nm), rubidium (780nm), or both, of particular relevance to doubly degenerate boson-fermion mixtures.