We report the operation of a cold-atom inertial sensor which continuously captures the rotation signal. Using a joint interrogation scheme, where we simultaneously prepare a cold-atom source and operate an atom interferometer (AI), enables us to eliminate the dead times. We show that such continuous operation improves the short-term sensitivity of AIs, and demonstrate a rotation sensitivity of 100  nrad/sec/sqrt[Hz] in a cold-atom gyroscope of 11  cm^{2} Sagnac area. We also demonstrate a rotation stability of 1  nrad/sec at 10^{4}  sec of integration time, which represents the state of the art for atomic gyroscopes. The continuous operation of cold-atom inertial sensors will lead to large area AIs at their full sensitivity potential, determined by the quantum noise limit.

Continuous cold atom inertial sensor with 1 nrad/s rotation stability

We present the scientific motivation for future space tests of the equivalence principle, and in particular the universality of free fall, at the $10^{-17}$ level or better. Two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed.

Exploring the Foundations of the Universe with Space Tests of the Equivalence Principle

Very Long Baseline Atom Interferometry corresponds to ground-based atomic matter-wave interferometry on large scales in space and time, letting the atomic wave functions interfere after free evolution times of several seconds or wave-packet separation at the scale of meters. As inertial sensors, e.g., accelerometers, these devices take advantage of the quadratic scaling of the leading-order phase shift with the free-evolution time to enhance their sensitivity, giving rise to compelling experiments. With shot-noise-limited instabilities better than 10−9 m/s2 at 1 s at the horizon, Very Long Baseline Atom Interferometry may compete with state-of-the-art superconducting gravimeters, while providing absolute instead of relative measurements. When operated with several atomic states, isotopes, or species simultaneously, tests of the universality of free fall at a level of parts in 1013 and beyond are in reach. Finally, the large spatial extent of the interferometer allows one to probe the limits of coherence at macroscopic scales as well as the interplay of quantum mechanics and gravity. We report on the status of the Very Long Baseline Atom Interferometry facility, its key features, and future prospects in fundamental science.

Matter Wave Interferometry for Inertial Sensing and Tests of Fundamental Physics

The recent development of Micro-Electro-Mechanical System (MEMS) technology has provided new methods for researchers to design and fabricate seismometers and geophones in small scale which will enable seismic sensors achieve higher sensitivity with a larger frequency band when compared with traditional instruments. In this paper, we review the development of various types of MEMS based geophones and seismometers by dividing them into two types according to the state of inertial mass (liquid or solid type). Within all types of seismic sensors, emphasis has been put on the highly sensitive electrochemical sensors and the frequently used capacitive seismic sensors. The working principles, detailed fabrication processes, as well as the advantages or limitations are also summarized. Moreover, the levelling system assembled with the seismic sensors is also included in this review. They are added to help seismometers work properly when tilted. Since MEMS fabrication technology with small mass also brings magnified intrinsic noise to the seismic sensors, self-noise issues and some possible modifications on structures or signal processing circuits to reduce this noise are discussed.

MEMS based geophones and seismometers

We present the scientific motivation for future space tests of the equivalence principle, and in particular the universality of free fall, at the 10− 17 level or better. Two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed. This publication is a White Paper written in the context of the Voyage 2050 ESA Call for White Papers.

/pdf/exploring-the-foundations-of-the-physical-universe-with-3b9m375kiy.pdf

Exploring the Foundations of the Physical Universe with Space Tests of the Equivalence Principle

Matter-wave interferometry and spectroscopy of optomechanical resonators offer complementary advantages. Interferometry with cold atoms is employed for accurate and long-term stable measurements, yet it is challenged by its dynamic range and cyclic acquisition. Spectroscopy of optomechanical resonators features continuous signals with large dynamic range, however it is generally subject to drifts. In this work, we combine the advantages of both devices. Measuring the motion of a mirror and matter waves interferometrically with respect to a joint reference allows us to operate an atomic gravimeter in a seismically noisy environment otherwise inhibiting readout of its phase. Our method is applicable to a variety of quantum sensors and shows large potential for improvements of both elements by quantum engineering. Precise gravity sensing in dynamic environments is challenging. Here, the long-term stability of a matter-wave gravimeter and high bandwidth of an optical resonator are combined in a compact gravity sensor with high seismic noise suppression.

/pdf/optomechanical-resonator-enhanced-atom-interferometry-1jy2lr2mu0.pdf

Optomechanical resonator-enhanced atom interferometry

Matter-wave interferometry and spectroscopy of optomechanical resonators offer complementary advantages. Interferometry with cold atoms is employed for accurate and long-term stable measurements, yet it is challenged by its dynamic range and cyclic acquisition. Spectroscopy of optomechanical resonators features continuous signals with large dynamic range, however it is generally subject to drifts. In this work, we combine the advantages of both devices. Measuring the motion of a mirror and matter waves interferometrically with respect to a joint reference allows us to operate an atomic gravimeter in a seismically noisy environment otherwise inhibiting readout of its phase. Our method is applicable to a variety of quantum sensors and shows large potential for improvements of both elements by quantum engineering.

/pdf/optomechanical-resonator-enhanced-atom-interferometry-42otblraij.pdf

The stability of matter-wave sensors benefits from interrogating large-particle-number atomic ensembles at high cycle rates. The use of quantum-degenerate gases with their low effective temperatures allows constraining systematic errors towards highest accuracy, but their production by evaporative cooling is costly with regard to both atom number and cycle rate. In this work, we report on the creation of cold matter-waves using a crossed optical dipole trap and shaping it by means of an all-optical matter-wave lens. We demonstrate the trade off between residual kinetic energy and atom number by short-cutting evaporative cooling and estimate the corresponding performance gain in matter-wave sensors. Our method is implemented using time-averaged optical potentials and hence easily applicable in optical dipole trapping setups.

/pdf/all-optical-matter-wave-lens-using-time-averaged-potentials-2jgllv8203.pdf

Ashwin Rajagopalan

Papers

Optomechanical resonator-enhanced atom interferometry

Optomechanical resonator-enhanced atom interferometry

All-Optical Matter-Wave Lens using Time-Averaged Potentials