A new sensor that measures the local acceleration due to gravity using a Bose–Einstein condensate (BEC) of ultracold atoms has been made by physicists in Germany, the US and Canada.
Quantum technology became a new tool for navigation based on measuring accelerations and rotations. However, the full potential of atom interferometers that operate with ultracold atoms has not yet been exploited. This paper presents current developments in the field of generation and application of Bose–Einstein condensates for inertial navigation. It covers the advancements in the form of atom chip and compact vacuum technology, classical sensor hybridization, and a multi-axis atom interferometry technique. In addition, the synergies of combining quantum sensors with classical inertial measurement units and their implications for navigation trajectories are discussed.
Atom chips are devices used to magnetically trap and manipulate ultracold atoms and Bose-Einstein condensates near a surface. In particular, permanent magnetic film atom chips can allow very tight confinement and intricate magnetic field designs while circumventing technical current noise. Research described in this thesis is focused on the development of a magnetic film atom chip, the production of Bose-Einstein condensates near the film surface, the characterisation of the associated magnetic potentials using rf spectroscopy of ultracold atoms and the realisation of a precision sensor based on splitting Bose-Einstein condensates in a double-well potential. The atom chip itself combines the edge of a perpendicularly magnetised GdTbFeCo film with a machined silver wire structure. A mirror magneto-optical trap collects up to 5 x 108 87Rb atoms beneath the chip surface. The current-carrying wires are then used to transfer the cloud of atoms to the magnetic film microtrap and radio frequency evaporative cooling is applied to produce Bose-Einstein condensates consisting of 1 x 105 atoms. We have identified small spatial magnetic field variations near the film surface that fragment the ultracold atom cloud. These variations originate from inhomogeneity in the film magnetisation and are characterised using a novel technique based on spatially resolved radio frequency spectroscopy of the atoms to map the magnetic field landscape over a large area. The observations agree with an analytic model for the spatial decay of random magnetic fields from the film surface. Bose-Einstein condensates in our unique potential landscape have been used as a precision sensor for potential gradients. We transfer the atoms to the central region of the chip which produces a double-well potential. A single BEC is formed far from the surface and is then dynamically split in two by moving the trap closer to the surface. After splitting, the population of atoms in each well is extremely sensitive to the asymmetry of the potential and can be used to sense tiny magnetic field gradients or changes in gravity on a small spatial scale.
Cold atoms promise versatile atomic chipsUsing a microelectronic chip to hold a cloud of cold atoms hovering above it, physicists in Germany may have developed an "atomic chip" that might eventually shunt Bose-Einstein condensates around an atom chip -just as electrons are shunted around a conventional silicon chip.This tiny circuit creates and manipulates a peculiar state of matter called a Bose-Einstein condensate (p21).Previously these condensates were made using light or magnetic fields to cool and confine a gas of atoms.Electric currents travelling through wires in the atom chip create a confining magnetic field barely 1 mm wide.This field holds a cloud of 1600 rubidium atoms at a height of less than a tenth of 1 mm above the chip surface.Quantum mechanics dictates that atoms, being so small, have wavelike properties.Normally each wave bobs up and down independently.However, in a Bose-Einstein condensate all of the atomic waves are "coherent" -moving in step, in the same quantum state.Instead of behaving like a