We investigate the limits of our cold atoms interferometer to rotation and acceleration measurements. In contrast with previous atomic setups, emphasis was placed on the long term stability and compactness of the device through the use of laser cooled atoms, as previously shown with the field of atomic clock. It has been designed to give access to all six axes of inertia (three accelerations and three rotations). The expected improvement in stability will enable to consider applications in inertial navigation, geophysics and tests of general relativity as the equivalence principle or Lense-Thirring effect.
We investigate the limits of our cold atoms interferometer to rotation and acceleration measurements. In contrast with previous atomic setups, emphasis was placed on the long term stability and compactness of the device through the use of laser cooled atoms, as previously shown with the field of atomic clock. It has been designed to give access to all six axes of inertia (three accelerations and three rotations). The expected improvement in stability will enable to consider applications in inertial navigation, geophysics and tests of general relativity as the equivalence principle or Lense-Thirring effect.
Inertial sensors based on cold atom interferometry exhibit many interesting features for applications related to inertial navigation, particularly in terms of sensitivity and long-term stability. However, at present the typical atom interferometer is still very much an experiment—consisting of a bulky, static apparatus with a limited dynamic range and high sensitivity to environmental effects. To be compliant with mobile applications further development is needed. In this work, we present a compact and mobile experiment, which we recently used to achieve the first inertial measurements with an atomic accelerometer onboard an aircraft. By integrating classical inertial sensors into our apparatus, we are able to operate the atomic sensor well beyond its standard operating range, corresponding to half of an interference fringe. We report atom-based acceleration measurements along both the horizontal and vertical axes of the aircraft with one-shot sensitivities of 2.3 × 10−4 g over a range of ∼ 0.1 g. The same technology can be used to develop cold-atom gyroscopes, which could surpass the best optical gyroscopes in terms of long-term sensitivity. Our apparatus was also designed to study multi-axis atom interferometry with the goal of realizing a full inertial measurement unit comprised of the three axes of acceleration and rotation. Finally, we present a compact and tunable laser system, which constitutes an essential part of any cold-atom-based sensor. The architecture of the laser is based on phase modulating a single fiber-optic laser diode, and can be tuned over a range of 1 GHz in less than 200 μs.
We report the first operation of a cold atom inertial sensor without dead time. Dead times in conventional cold atom interferometers originate from the preparation of a cold atom source prior to its injection in the interferometer and where information on inertial signals is lost. We use a sequence where we simultaneously prepare a cold atom source and operate a light pulse atom interferometer to circumvent the dead time limitation. Therefore the sensor continuously captures all the dynamics with respect to an inertial frame. We show that the continuous operation does not degrade the sensitivity and stability of the atom interferometer, by demonstrating a rotation sensitivity level of less than 1 nrad/s after 10 000 s of integration time. Such a sensitivity level improves previous results by more than an order of magnitude and opens applications of cold atom gyroscopes in inertial navigation and geophysics.
Atom interferometry has hugely benefitted from advances made in cold atom physics over the past twenty years, and ultra-precise quantum sensors are now available for a wide range of applications [1]. In particular, cold atom interferometers have shown excellent performances in the field of acceleration and rotation measurements [2,3], and are foreseen as promising candidates for navigation, geophysics, geo-prospecting and tests of fundamental physics such as the Universality of Free Fall (UFF). In order to carry out a test of the UFF with atoms as test masses, one needs to compare precisely the accelerations of two atoms with different masses as they fall in the Earth’s gravitational field. The sensitivity of atom interferometers scales like the square of the time during which the atoms are in free fall, and on ground this interrogation time is limited by the size of the experimental setup to a fraction of a second. Sending an atom interferometer in space would allow for several seconds of excellent free-fall conditions, and tests of the UFF could be carried out with precisions as low as 10-15 [4]. However, cold atoms experiments rely on complex laser systems, which are needed to cool down and manipulate the atoms, and these systems are usually very sensitive to temperature fluctuations and vibrations. In addition, when operating an inertial sensor, vibrations are a major issue, as they deteriorate the performances of the instrument. This is why cold atom interferometers are usually used in ground based facilities, which provide stable enough environments. In order to carry out airborne or space-borne measurements, one has to design an instrument which is both compact and stable, and such that vibrations induced by the platform will not deteriorate the sensitivity of the sensor. We report on the operation of an atom interferometer on board a plane carrying out parabolic flights (Airbus A300 Zero-G, operated by Novespace). We have constructed a compact and stable laser setup, which is well suited for onboard applications. Our goal is to implement a dual-species Rb-K atom interferometer in order to carry out a test of the UFF in the plane. In this perspective, we are designing a dual-wavelength laser source, which will enable us to cool down and coherently manipulate the quantum states of both atoms. We have successfully tested a preliminary version of the source and obtained a double species magneto-optical trap (MOT).
Matter-wave interferometry has enabled high precision measurements of inertial forces such as gravity and the Coriolis force. This is facilitated by the long-term stability of the physical properties of atoms and lasers. Recent experiments have demonstrated the operation of portable, robust sensors using atom interferometry. This has potential uses in the context of inertial navigation, where conventional devices suffer from long-term drifts due to bias instability. Furthermore, determining position via dead reckoning requires minimisation of dead time between measurements. This thesis presents the development of an atom interferometer for measuring horizontal accelerations. In this configuration, gravity induces motion across the laser wavefront, which constrains the tolerable level of wavefront distortions. Effective control of the experiment allows the interferometer to be operated at a rate of 4 Hz. A cold ensemble of 10^6 atoms in the same internal state is prepared in 150 ms. The interferometer operates using a sequence of three laser pulses separated by T= 25 ms to achieve sensitivity to horizontal accelerations. Combining this with a classical accelerometer provides a method of correcting for vibration-induced noise, as well as determining the interferometer fringe order. After an integration time of 40 s, the sensitivity to horizontal accelerations is better than 3^-6 m s^-2. Effects which limit this sensitivity are discussed.
Accurate and stable measurement of inertial quantities is essential in geophysics, geodesy, fundamental physics, and inertial navigation. Here, we present an architecture for a compact cold-atom accelerometer-gyroscope based on a magnetically launched atom interferometer. Characterizing the launching technique, we demonstrate 700–parts per million gyroscope scale factor stability over 1 day, while acceleration and rotation rate bias stabilities of 7 × 10 −7 meters per second squared and 4 × 10 −7 radians per second are reached after 2 days of integration of the cold-atom sensor. Hybridizing it with a classical accelerometer and gyroscope, we correct their drift and bias to achieve respective 100-fold and 3-fold increase on the stability of the hybridized sensor compared to the classical ones. Compared to a state-of-the-art atomic gyroscope, the simplicity and scalability of our launching technique make this architecture easily extendable to a compact full six-axis inertial measurement unit, providing a pathway toward autonomous positioning and orientation using cold-atom sensors.
Inertial sensors based on cold atoms and light-pulse interferometry exhibit state-of-the-art sensitivity and ultra-low measurement bias that could revolutionize a variety of fields including geophysics and seismology, gravitational wave detection and fundamental tests of gravity, and inertial navigation. In the latter case, cold-atom interferometers are widely considered as breakthrough technology for future autonomous INSs. Nowadays, absolute quantum inertial sensors are available as commercial and field-deployable devices. Yet, their current size and complexity has not yet reached a technology readiness level compatible with mobile applications or plug-and-play operation by non-specialists. These systems are in desperate need of further development and miniaturization. We will present progress beyond these first experiments while exploring new methods relying on 3D matter-wave manipulation that can lead to interferometer geometries that are simultaneously sensitive to accelerations and rotations in 3D and can discern their vector components within a single measurement. These novel innovations produce additional sensitivity to rotations and gravity gradients which has not yet been exploited experimentally and could be a game changing innovation for future atomic sensors. The ability to measure the full acceleration and rotation vectors with a compact, high-precision, low-bias inertial sensor could strongly impact the fields of inertial navigation, gravity gradiometry, and gyroscopy.