Quantum sensing using atom interferometry possesses immense potential for application in gravimetry, inertial navigation and for gravitational wave detection, apart from carrying out tests of fundamental physics. Atom interferometry can be used to perform absolute inertial measurements with unprecedented long term stability, unlike classical sensors which are prone to drift and incur calibration errors. However, atom interferometers seldom achieve their fundamental sensitivity due to the coupling of ambient vibrations. It is the dominant noise source that not only impairs performance but also affects its operability. Ideal compensation of the effects due to vibration noise using a versatile accelerometer, while concurrently enabling miniaturized atom interferometer setups has not been pioneered. Such a compact hybrid quantum sensor will enable reliable operation with an enhanced performance in field applications, paving the way for robust atom interferometry beyond laboratory conditions. A novel optomechanical resonator has been designed, developed and successfully hybridized with an atom interferometer to suppress the effects of vibration noise, and the results are presented in this thesis. The optomechanical resonator’s inertial test mass is simultaneously used to create a continuous intracavity optical lattice to sense its displacement, and a pulsed optical lattice to manipulate the atoms. For the first time, a broadband accelerometer is seamlessly hybridized with an atom interferometer via mechanical resonator mediated coupling of the optical lattices to measure acceleration. This enables elimination of vibration induced measurement ambiguity in our atom interferometer with a well defined mechanical transfer function. Vibration noise correlation is demonstrated up to our prototype atom interferometer’s most sensitive operating mode of T = 6 ms using double Bragg diffraction, ultimately limited by its technical noise. The optomechanical resonator measures acceleration with a sensitivity down to 1.1×10−6 ms−2/ √Hz corresponding to a displacement sensitivity of 8.6 × 10−15 m/ √Hz. Substantial 1/f noise suppression due to the developed optical readout scheme enables a measurement bandwidth spanning from sub-hertz frequencies up to several kilohertz. Multiple versions of the optomechanical resonator with different characteristics were developed and hybridized with our atom interferometer. This paves the way for developing tailored optomechanical resonators for specific inertial sensing applications.
Quantum sensing using atom interferometry possesses immense potential for application in gravimetry, inertial navigation and for gravitational wave detection, apart from carrying out tests of fundamental physics. Atom interferometry can be used to perform absolute inertial measurements with unprecedented long term stability, unlike classical sensors which are prone to drift and incur calibration errors. However, atom interferometers seldom achieve their fundamental sensitivity due to the coupling of ambient vibrations. It is the dominant noise source that not only impairs performance but also affects its operability. Ideal compensation of the effects due to vibration noise using a versatile accelerometer, while concurrently enabling miniaturized atom interferometer setups has not been pioneered. Such a compact hybrid quantum sensor will enable reliable operation with an enhanced performance in field applications, paving the way for robust atom interferometry beyond laboratory conditions. A novel optomechanical resonator has been designed, developed and successfully hybridized with an atom interferometer to suppress the effects of vibration noise, and the results are presented in this thesis. The optomechanical resonator’s inertial test mass is simultaneously used to create a continuous intracavity optical lattice to sense its displacement, and a pulsed optical lattice to manipulate the atoms. For the first time, a broadband accelerometer is seamlessly hybridized with an atom interferometer via mechanical resonator mediated coupling of the optical lattices to measure acceleration. This enables elimination of vibration induced measurement ambiguity in our atom interferometer with a well defined mechanical transfer function. Vibration noise correlation is demonstrated up to our prototype atom interferometer’s most sensitive operating mode of T = 6 ms using double Bragg diffraction, ultimately limited by its technical noise. The optomechanical resonator measures acceleration with a sensitivity down to 1.1×10−6 ms−2/ √Hz corresponding to a displacement sensitivity of 8.6 × 10−15 m/ √Hz. Substantial 1/f noise suppression due to the developed optical readout scheme enables a measurement bandwidth spanning from sub-hertz frequencies up to several kilohertz. Multiple versions of the optomechanical resonator with different characteristics were developed and hybridized with our atom interferometer. This paves the way for developing tailored optomechanical resonators for specific inertial sensing applications.
Atom interferometers are among the most sensitive inertial sensors, yet deployment outside the laboratory is limited by vibration noise, conventionally mitigated by external sensors or bulky isolation. Here we demonstrate a hybrid inertial sensor which fuses an optomechanical resonator and an atom interferometer by exploiting the resonator's test mass as the interferometer's reference mirror. This allows for better correlation than with two separate sensors, whose unknown transfer function is replaced by the static response of one mechanical element. The resonator achieves a displacement sensitivity of 8.6⋅10−15 m/Hz with suppressed 1/f noise and yields a minimum acceleration sensitivity of 1.1⋅10−6 m/s2/Hz over a bandwidth extending from sub-Hertz to 2.5 kHz. Under ambient laboratory conditions the integrated system removes vibration-induced phase ambiguity for accelerations up to 50⋅10−3 m/s2 and reaches the interferometer's technical noise limit, which a commercial force-balance accelerometer does not. Because the resonance-tracking readout is largely independent of the mechanical design, the architecture transfers directly to other precision sensing platforms.
Exploiting the quantum nature of atoms through the use of matter-wave interferometry has lead to the development of devices sensitive to, among other things, the local gravitational acceleration. Measurements of the gravitational acceleration have applications ranging from detection of subterranean density di erences to observation of general relativistic e ects. Light-pulse atom interferometers provide an absolute measurement of the gravitational acceleration with a sensitivity competitive and even surpassing the performance of classical sensors. The advantages of atom interferometers as inertial measurement devices have lead to e orts in increasing sensitivity and decreasing the physical dimensions of the measurement head, allowing them to be more transportable for eld use applications. With increasing sensitivity, it becomes more critical to address the noise source limitations a ecting the measurement, speci cally the in uence of ground motion on measurements. Vibrations coupling into the inertial reference add a time varying phase shift uncommon to the paths of the interferometer. This limitation is especially pertinent to transportable atom gravimeters measuring in the eld where inertial noise is typically far higher than in relatively quiet laboratory environments. Within this work, implementation and demonstration of inertial noise post-correction in an atom interferometer is shown within low inertial noise environments and simulated strong motion environments. For a high pulse separation time atom interferometer (T = 78 ms) post-correction yielded an increase in the short term stability from 4.4 x 10 ̄6 m/s2/√Hz to 9.2 x 10 ̄7 m/s2/√Hz. This method was reproduced with a di erent motion sensor to perform post-correction in a high motion environment, generated by introducing additional movement onto the inertial reference. By performing post-correction in the high motion environment, we were able to show an increase of short term stability of γ = 73.8. Current limitations to the post-correction resulted from self noise resolution limitations and spectral resolutions limitations. Beyond corrections with commercially available sensors, this work demonstrates the rst post-correction with a next generation compact optomechanical sensor. This optomechanical sensor is formed from monolithic fused silica capable of sensitively measuring accelerations of a harmonic oscillator test mass, which can be read-out optically. This novel motion sensor has the advantage to any previously shown sensor used for post-correction in the capacity that it is vacuum compatible, insensitive to magnetic elds and has the potential to be implemented directly into the inertial reference. In this work, inertial noise post-correction in a simulated high motion environment is shown, correcting from a short term stability of 8 x 10 ̄3 m/s2/√Hz to 5 x 10 ̄4 m/s2/√Hz. Post-correction was limited by the parasitic cavities within the ber required for optical read-out of the harmonic oscillator displacement and intensity noise uctuations of the source laser. The results shown within this work are congruent with previous works on atom chip gravimeters, both of which help move towards portable hand-held gravimeter measurement heads capable of sensitive inertial measurement.
We present a novel atom interferometer configuration that combines large momentum transfer with the enhancement of an optical resonator for the purpose of measuring gravitational strain in the horizontal directions. Using Bragg diffraction and taking advantage of the optical gain provided by the resonator, we achieve momentum transfer up to 8ℏk with mW level optical power in a cm-sized resonating waist. Importantly, our experiment uses an original resonator design that allows for a large resonating beam waist and eliminates the need to trap atoms in cavity modes. We demonstrate inertial sensitivity in the horizontal direction by measuring the change in tilt of our resonator. This result paves the way for future hybrid atom or optical gravitational wave detectors. Furthermore, the versatility of our method extends to a wide range of measurement geometries and atomic sources, opening up new avenues for the realization of highly sensitive inertial atom sensors.
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.
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).
Atom interferometers are quantum mechanical devices sensitive to gravitational and inertial forces, with applications in fundamental physics and inertial sensing in the field. Their performance is currently limited by the interrogation time available to freely falling atoms in Earth’s gravitational field, as well as noise due to mechanical and acoustic vibrations. Our experiment probes gravitational potentials by holding, rather than dropping, atoms. We realize an interrogation time of 20 seconds by suspending the spatially separated atomic wave packets in an optical lattice. This record coherence is enabled by the smooth lattice wave fronts, which are mode-filtered by an optical cavity. This trapped geometry suppresses phase variance due to vibrations by three to four orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. The later part of the talk describes recent progress in characterizing and reducing dephasing of the interferometer. An upgraded optical lattice interferometer experiment is currently being commissioned, with the goal of increased sensitivity to gravity.