Miniature Atomic Gyroscopes

Miniature Atomic Gyroscopes (MAG) employ noble-gas nuclear spins as high-coherence rotation sensors. Advanced prototypes exist but application remains confined to laboratory environments. The primary challenges for MAGs are the long relaxation times that give nuclear-spin devices exquisite long-term stabilities but also lead to narrow resonances that limit the gyroscope operational bandwidth. 

New quantum gyroscopes utilise more drift stable than ever before, paving the way for fully interial navigation and improved safety in highly autonomous driving.

Objective: in macQsimal, partners work closely together to develop, fabricate and test a Compact Atomic Gyroscope demonstrator based on spin-exchange optical pumping (SEOP) in a MEMS cell for target applications in the automotive industry.

Related macQsimal publication

Nuclear Magnetic Resonance Gyroscopes for Precise Positioning
Robert Bosch GmbH (BOSCH), 2020, 1st ZULF NMR Conference, online.

Simulations and Control Theory for Nuclear Magnetic Resonance Gyroscopes
Robert Bosch GmbH (BOSCH), 2020, micro-WOPM 2020, online.

Sensing principle

Atomic rotation sensor detects the angular rate of an object by measuring a shift in the precession frequency of nuclear spins of atomic gas. Typically, the atomic gas is a combination of alkali vapor, e.g. rubidium, and a noble gas, e.g. xenon, confined in a small vapor cell. The nuclear spins of the noble gas are used for rotation detection, whereas the alkali vapor is an auxiliary gas used for initialization and readout via pump and probe laser beams. The applied magnetic fields determine the gyroscope’s measurement axis and drive the atomic spin precession.

Sensing principle, where atomic rotation sensor detects the angular rate of an object.

Vapor cell

We use a gas mixture of rubidium and xenon that is confined in a small vapor cell. We fabricate and investigate various cell designs, ranging from glass-blown vapor cells of different geometries with a volume of about 1 cm³ fabricated by the University of Neuchâtel to MEMS vapor cells that consist of a glass-silicon-glass stack with a volume of 1-10 mm³ fabricated at CSEM.

Glass-blown vapor cells of different geometries containing rubidium and xenon were produced at University of Neuchatel. They allow studying the impact of cell geometry on the gyroscope signal.

Optical setup

The vapor cell s is placed at the center of a magnetic shielding with an integrated triaxial coil system for magnetic field generation. A pump and a probe laser beam optically polarizes and reads out the spin precession, respectively. Electronic data processing and feedback control determines the rotation rate from the optical signal and controls the applied fields.

Within macQsimal project, the team at Bosch research built a large optical setup for proof-of-principle experiments and designed a compact demonstrator suitable for rotation rate measurements.

Laboratory setup of an atomic gyroscope developed at Bosch corporate research. Picture: Martin Stollberg / Bosch

Towards applicability

Precise position data of vehicles are essential for modern mobility solutions. In the case when GPS signals and other systems observing the environment are temporarily unavailable, high-performance inertial sensors will be the only remaining navigation system using dead reckoning i.e. localisation based on a previously determined position and precise directional sensor signals from accelerometers and gyroscopes. Utilisation of quantum effects in atomic vapor cells allows for high precision measurements of rotation rates, and shows great promise for further miniaturisation.

High-performance inertial sensors for future mobility solutions. Source: Tobias Gramsch / Bosch