Optical and Quantum Sensing and Precision Metrology II
Realizing software-defined quantum sensing: experimental demonstration of software-ruggedized atom interferometry for mobile quantum inertial sensing
Jack Saywell, Max Carey, P. S. Light, Stuart S. Szigeti, Alistair R. Milne, Karandeep S. Gill, Michael Goh, Nathanial Wilson, P. J. Everitt, Nicholas P. Robins, R. P. Anderson, Michael Hush, Michael J. Biercuk
Quantum sensors based on cold atoms have enormous potential to unlock new capabilities in GPS-denied navigation, civil engineering, intelligence, and Earth observation. But operating these devices in realistic environments is currently extremely challenging, and for the most part the advantages of choosing a quantum sensor over a conventional alternative are lost in the transition from laboratory to noisy field-based environments. In this work, we demonstrate for the first time in hardware that tailored light pulses, designed and implemented in software using robust control techniques, can substantially mitigate some of the most nefarious effects in a Bragg atom interferometer. We show experimentally that embedding robust control into sensor operation can improve the signal-to-noise ratio of a state-of-the-art Bragg-pulse cold-atom interferometric sensor by a factor of 4× under ideal conditions. In the presence of laser-intensity noise that varies up to 20% from shot-to-shot, commensurate with common platform vibrations, we show experimentally that using the same robust control solutions preserves fringe visibility with minimal degradation while the utility of the primitive Gaussian pulses collapses, delivering an at least 8× improvement in phase-estimation uncertainty compared with primitive pulse schemes. Across all observations, robust control delivers better performance in a noisy environment than the native hardware performance with primitive pulses under approximately ideal conditions. Finally, building on this demonstration we present a validated theoretical concept to extend this performance improvement to compact devices using concatenated sequences of robust pulses designed to enhance the sensor’s scale factor. Time-domain simulations reveal up to 10× performance enhancement in the presence of realistic atomic-cloud effects at 102ℏk momentum separation. These results show for the first time that software-defined quantum sensor operation can deliver useful performance in environmental regimes where primitive operation is impossible, providing a pathway to augment the performance of current and next generation portable cold-atom inertial sensors in real fielded settings.
Quantum sensors based on cold atoms have enormous potential to unlock new capabilities in GPS-denied navigation, civil engineering, intelligence, and Earth observation. But operating these devices in realistic environments is currently extremely challenging, and for the most part the advantages of choosing a quantum sensor over a conventional alternative are lost in the transition from laboratory to noisy field-based environments. In this work, we demonstrate for the first time in hardware that tailored light pulses, designed and implemented in software using robust control techniques, can substantially mitigate some of the most nefarious effects in a Bragg atom interferometer. We show experimentally that embedding robust control into sensor operation can improve the signal-to-noise ratio of a state-of-the-art Bragg-pulse cold-atom interferometric sensor by a factor of 4× under ideal conditions. In the presence of laser-intensity noise that varies up to 20% from shot-to-shot, commensurate with common platform vibrations, we show experimentally that using the same robust control solutions preserves fringe visibility with minimal degradation while the utility of the primitive Gaussian pulses collapses, delivering an at least 8× improvement in phase-estimation uncertainty compared with primitive pulse schemes. Across all observations, robust control delivers better performance in a noisy environment than the native hardware performance with primitive pulses under approximately ideal conditions. Finally, building on this demonstration we present a validated theoretical concept to extend this performance improvement to compact devices using concatenated sequences of robust pulses designed to enhance the sensor’s scale factor. Time-domain simulations reveal up to 10× performance enhancement in the presence of realistic atomic-cloud effects at 102ℏk momentum separation. These results show for the first time that software-defined quantum sensor operation can deliver useful performance in environmental regimes where primitive operation is impossible, providing a pathway to augment the performance of current and next generation portable cold-atom inertial sensors in real fielded settings.
Atom-interferometric quantum sensors could revolutionize navigation, civil engineering, and Earth observation. However, operation in real-world environments is challenging due to external interference, platform noise, and constraints on size, weight, and power. Here we experimentally demonstrate that tailored light pulses designed using robust control techniques mitigate significant error sources in an atom-interferometric accelerometer. To mimic the effect of unpredictable lateral platform motion, we apply laser-intensity noise that varies up to 20% from pulse-to-pulse. Our robust control solution maintains performant sensing, while the utility of conventional pulses collapses. By measuring local gravity, we show that our robust pulses preserve interferometer scale factor and improve measurement precision by 10× in the presence of this noise. We further validate these enhancements by measuring applied accelerations over a 200 μg range up to 21× more precisely at the highest applied noise level. Our demonstration provides a pathway to improved atom-interferometric inertial sensing in real-world settings.
Navigation systems based on quantum sensors are a viable alternative to use of GNSS, however their sensitivity to environmental effects makes deployment in harsh environments challenging. We present results demonstrating that software ruggedization techniques can mitigate these effects and enhance the performance of these systems in real-world environments. Here, we report world-first demonstrations of a dual quantum gravimeter operating in a relevant maritime environment, with an unattended uptime of >144 hours, as well as the first demonstrations of software ruggedized sensing in a real-world motional environment. We demonstrate recovery of signal due to software compensation of motion and a 2X contrast enhancement due to optimized velocity selection. In addition, we present a compact 3-axis quantum inertial sensor capable of high repetition rate operation in extremely harsh environments.
Numerous real-world applications, such as in civil engineering, inertial navigation, and Earth Observation, have demonstrated the utility of quantum sensing with atom interferometers. Today, the biggest challenge to broader market adoption of these sensors is the in-depth knowledge of quantum mechanics required by both the manufacturers and users of these devices. We aim to make the design, construction, and operation of atom interferometers more intuitive using software that incorporates our years of experience in atom interferometry simulation. Here, we provide an overview over our simulation capabilities. Our versatile numerical toolbox enables efficient simulation of atomic test masses interacting with realistic electromagnetic, gravitational and optical forces, as well as prediction of sensor performance in realistic deployment scenarios, e.g., on air, land, and water vehicles.
Quantum control provides a pathway to extract more - and more useful - information from quantum sensors. In this presentation we will highlight a series of experimental and numerical studies demonstrating how quantum control can augment the performance of atomic and solid-state devices for gravimetry, precision navigation, and magnetometry. We begin with demonstrations that a class of cloud-compute-enabled AI agents can be used to autonomously optimize cold-atom loading and BEC production without user intervention. Next, we focus on the application of robust control to mitigate platform noise in fielded atom interferometers. We show 10X improvements interferometer visibility under realistic noise conditions, and also demonstrate up to 1000X improvements in sensitivity under transverse acceleration. Finally, we present novel operating techniques for magnetometry in cluttered environments, in which Slepian window functions are employed to suppress out-of-band sensitivity.
Quantum entanglement has been generated and verified in cold-atom experiments
and used to make atom-interferometric measurements below the shot-noise limit.
However, current state-of-the-art cold-atom devices exploit separable (i.e.
unentangled) atomic states. This perspective piece asks the question: can
entanglement usefully improve cold-atom sensors, in the sense that it gives new
sensing capabilities unachievable with current state-of-the-art devices? We
briefly review the state-of-the-art in precision cold-atom sensing, focusing on
clocks and inertial sensors, identifying the potential benefits entanglement
could bring to these devices, and the challenges that need to be overcome to
realize these benefits. We survey demonstrated methods of generating
metrologically-useful entanglement in cold-atom systems, note their relative
strengths and weaknesses, and assess their prospects for near-to-medium term
quantum-enhanced cold-atom sensing.
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.