We propose to develop a new generation of compact high sensitivity gyroscopes using guided matter-waves on atom chips, able to fulfill the requirements of metrological applications. They will be designed to overcome the main limitations of free falling atoms interferometers: interrogation time and quantum projection noise. A cloud of cold 87Rb atoms will be coherently split and constrained to propagate along a circular guide of a few millimeters radius. At the output of the guide an interference signal sensitive to rotation via the Sagnac effect will be measured.
We propose to develop a new generation of compact high sensitivity gyroscopes using guided matter-waves on atom chips, able to fulfill the requirements of metrological applications. They will be designed to overcome the main limitations of free falling atoms interferometers: interrogation time and quantum projection noise. A cloud of cold 87Rb atoms will be coherently split and constrained to propagate along a circular guide of a few millimeters radius. At the output of the guide an interference signal sensitive to rotation via the Sagnac effect will be measured.
This work reviews the topic of rotation sensing with compact cold atom interferometers. A representative set of compact free-falling cold atom gyroscopes is considered because, in different respects, they establish a rotation-measurement reference for cold guided-atom technologies. This review first discusses enabling technologies relevant to a set of key functional building blocks of an atom chip-based compact inertial sensor with cold guided atoms. These functionalities concern the accurate and reproducible positioning of atoms to initiate a measurement cycle, the coherent momentum transfer to the atom wave packets, the suppression of propagation-induced decoherence due to potential roughness, on-chip detection, and vacuum dynamics because of its impact on sensor stability, which is due to the measurement dead time. Based on the existing enabling technologies, the design of an atom chip gyroscope with guided atoms is formalized using a design case that treats design elements such as guiding, fabrication, scale factor, rotation-rate sensitivity, spectral response, important noise sources, and sensor stability.
Matter-wave interferometry with atoms propagating in a guiding potential is expected to provide compact, scalable and precise inertial sensing. However, a rotation sensing device based on the Sagnac effect with atoms guided in a ring has not yet been implemented despite continuous efforts during the last two decades. Here we discuss some intrinsic effects that limit the coherence in such a device and propose a scheme that overcomes these limitations and enables a multi-pass guiding Sagnac interferometer with a Bose-Einstein condensate (BEC) on a chip in a ring potential. We analyze crucial dephasing effects: potential roughness, phase diffusion due to atom-atom interactions and number uncertainty, and phase fluctuations. Owing to the recent progress in achieving high momentum beam splitting, creating smooth guides, and manipulating the matter-wavepacket propagation, guided interferometry can be implemented within the coherence time allowed by phase diffusion. Despite the lower particle flux in a guided Sagnac ring and the miniaturization of the interferometer, the estimated sensitivity, for reasonable and practical realizations of an atom chip-based gyroscope, is comparable to that of free-space interferometers, reaching 45 nrads^{-1}Hz^{-1/2}. A significant improvement over state-of-the-art free-space gyrocope sensitivities can be envisioned by using thermal atoms instead of a BEC, whereby the interferometer can be operated in a continuous fashion with the coherence limited by the scattering rate of the atoms with the background gas. Taking into account the sensitivity times length of the interferometer as the figure of merit which takes into account compactness, our configuration is expected to deliver a potential improvement of 2-4 orders of magnitude over state-of-the-art free-space gyroscopes for a BEC, and 4-6 orders of magnitude for thermal atoms.
Summary form only given. Matter wave interferometers have become very promising tools in fundamental physics and metrology. The sensitivities obtained with such atomic quantum sensors compete with classical state-of-the-art devices for acceleration and rotation measurements. Currently, we are setting up a new cold atom Sagnac interferometer (CASI) to realize high precision measurements of rotations with a compact and flexible setup. Using cold atoms the experiment aims to achieve sensitivities down to 2/spl times/10/sup -9/ rad/s/Hz for a compact interferometer as short as 15 cm. Rotations and accelerations will be discriminated by synchronous operation of two counterpropagating ensembles of ultra-cold atoms. We will give an overview about the concept and the parameters of our future interferometer. The results of the characterization of our 2D-MOT, which serves as a brilliant source for our cold atom interferometer, will be presented. The compact design of the sensor will be transportable. Thus, it will permit the comparison with other gyroscopes. CASI will be a first step towards a cold atom space experiment of the second generation.
This thesis presents the experimental scheme for a guided cold atom Sagnac interferometer. Although atom interferometers have become an established method for precision measurements, a feasible clock-scheme based on fully guided atoms has yet to be realised. Radio frequency potentials, generated by a chip, provide a means to create a compact, fully controllable guided atom interferometer. The experimental infrastructure for a rubidium cold atom system is built and characterised. A chip-based atomic clock scheme is presented, utilising state-dependent guiding around a ring shaped trap. The chip design to form the trap and operate the interferometer is presented, and a vacuum compatible PCB has been designed and commercially manufactured to provide atomic transport and compression towards an atom chip. This project is part of the larger MatterWave project. In collaboration with Birmingham and Crete, the Matterwave project aims to develop ultra-sensitive matter-wave interferometry for compact devices.
We describe our progress in the development of an atom based rotation sensor, which employs state-dependent trapping potentials to transport ultracold atoms along a closed path and perform Sagnac interferometry. Whilst guided atom interferometers are sought after to build miniaturized devices that overcome size restrictions from free-falling atoms, fully trapped interferometers also remove free-propagation along an atomic waveguide. This provides additional control of motion, e.g. removing wave-packet dispersion and enabling operation that remains independent of external acceleration. Our experimental scheme relies on radio-frequency and microwave-fields, which are partly generated via atom-chip technology, providing a step towards implementing a small, robust, and eventually portable atomic-gyroscope.
We describe a Sagnac interferometer suitable for rotation sensing, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap. The atom wave packets are split and recombined by standing-wave Bragg lasers, and the trapping potential steers the packets along circular trajectories with a radius of 0.2 mm. Two conjugate interferometers are implemented simultaneously to provide common-mode rejection of noise and to isolate the rotation signal. With interference visibilities of about 50%, we achieve a rotation sensitivity comparable to Earth's rate in about 10 min of operation. Gyroscope operation was demonstrated by rotating the optical table on which the experiment was performed.