Cold-atom and light-pulse interferometric system and method, for the on-board measurement of acceleration or rotation

Abstract

The invention relates to a cold-atom and light-pulse interferometric system (100) comprising a vacuum chamber (7) containing a cloud of cold atoms (8), a planar retro-reflective optical component (5), a laser source (6) suitable for generating a sequence of laser pulses, and a detection system (17) able to perform an inertial measurement by atom interferometry. According to the invention, the interferometric system (100) comprises an actuating device (13) that mechanically connects the optical component (5) to a plate (4), and a rotation sensor (1, 2) which is suitable for providing a measurement of the rotation of the vacuum chamber (7) about an axis transverse to the axis of the laser at each interrogation time in said sequence, the actuating device (13) being able to angularly incline the optical component (5) relative to said plate (4) during each interrogation time in said sequence on the basis of said rotation measurement.

Description

Cold atom and light pulse interferometric system and method for on-board measurement of acceleration or rotation technical field

[0001] The present invention relates to the technical field of inertial sensors based on an atomic interferometer for acceleration and / or rotation measurements.

[0002] It relates more specifically to an inertial sensor based on an atomic interferometer for measurements of acceleration, gravity and / or rotation along a measurement axis, these measurements being corrected for the rotations of the inertial sensor.

[0003] It relates more specifically to an inertial sensor for acceleration and rotation, based in particular on an atomic interferometer. This inertial sensor finds applications in an atomic gravimeter or gradiometer, in an embedded inertial navigation system for a mobile application, or in geophysical applications or fundamental physics testing. Previous technique

[0004] For about twenty years, atomic interferometry techniques have enabled the development of new measuring instruments, such as gravimeters, gradiometers, accelerometers, gyroscopes, atomic clocks and electromagnetic field sensors.

[0005] An atomic interferometer combines optical and atomic technologies. More specifically, a cold atom interferometer is a system in which matter waves propagate along spatially separated paths that define a closed surface. An atomic interferometer is sensitive to inertial effects such as accelerations and rotations.

[0006] On the one hand, an atomic interferometer comprises an atom source and a cold atom trap configured to generate an atom cloud. On the other hand, the atomic interferometer includes a laser source emitting a sequence of interrogation laser pulses designed to interact with the fine structure of atoms by photon transfer.

[0007] Atomic interferometer systems have a sensitivity several orders of magnitude greater than that of conventional mechanical sensors. However, these atomic interferometry systems face limitations in terms of robustness to tilt and vibration. Furthermore, atomic interferometry systems currently have a reduced sensitivity range (or dynamic range) compared to conventional sensors.

[0008] Depending on the orientation of the atom source and the atomic interferometer, it is possible to measure acceleration and / or rotation along a specific direction. Atomic interferometers allow for extremely precise measurements. They find applications in inertial sensors such as gravimeters, gradiometers, accelerometers, and cold-atom gyroscopes.

[0009] A particularly important application of atomic interferometry concerns cold atom accelerometers (CAAs). Most cold atom accelerometers (CAAs) are built in a gravimeter configuration, the purpose of which is to measure gravitational acceleration as accurately as possible. The measurement axis of an atomic interferometer is defined by the normal to the surface of a retroreflective mirror positioned to reflect the interrogation field back towards the cloud of cold atoms. The retroreflective mirror thus establishes a reference frame for the cold atom inertial sensor. In the case of a gravimeter or gradiometer, this normal is aligned with the vertical direction. These cold atom interferometers rely critically on this reference frame.

[0010] In mobile applications, such as inertial navigation, several factors primarily limit the operation and performance of cold-atom accelerometers. First, the interferometer ceases to function when its orientation varies randomly or its movements are random. This is because the movements of the inertial system compromise the stability of the reflecting surface. Second, in the case of a gravimeter or gradiometer, a misalignment between the normal to the mirror and the local vertical axis introduces a systematic measurement error. These issues are technical in nature and result from using cold-atom inertial sensors outside their nominal operating range.

[0011] In particular, a loss of contrast (C) is observed in the atomic interferometry fringes. This loss of contrast leads to a loss of sensitivity in the atomic interferometer. If the contrast (C) decreases significantly, the interferometer ceases to function. However, this loss of contrast can have various causes.

[0012] The publications Shau-Yu Lan et al., "Influence of the Coriolis Force in Atom Interferometry", PRL 108, 090402 (2012), and Alex Sugarbaker et al., "Enhanced Atom Interferometer Readout through the Application of Phase Shear", PRL 111, 113002 (2013), describe a cold atom interferometer (CAI) used for highly sensitive inertial measurements (gyrocompass, or gravity gradient measurement) in which a tilting stage is used to compensate for the Earth's rotation. While these systems are effective for stable laboratory experiments, they are not suitable for onboard inertial measurement applications where the motions experienced are unpredictable.

[0013] The publication by Yuan Zhao et al., "Extension of the rotation-rate measurement range with no sensitivity loss in a cold-atom gyroscope", Phys Rev A, 104.013312 (2021), describes a cold-atom gyroscope mounted horizontally on a vertically rotating table. This gyroscope uses three spatially separated Raman pulses to interrogate two counter-propagating atom clouds. All beams are reflected by a single mirror mounted on a tiltable stage, which compensates for the table's rotation and thus mitigates the loss of contrast. This system is effective for a horizontal configuration with atoms moving orthogonally to the beams, where the table's rotation signal also controls the stage's tilt.

[0014] However, these cold atom interferometer systems are not suitable for mobile operation, where the system is highly integrated to be mounted on a mobile vehicle and remains subject to unpredictably varying vibrations, accelerations, and rotations in multiple directions.

[0015] One of the aims of the invention is to provide a cold-atom interferometer system corrected for the aforementioned drawbacks. In particular, the invention provides a cold-atom interferometer system usable outside its nominal range of operation, which exhibits both very high sensitivity and high measurement accuracy over a wide measurement range. Description of the invention

[0016] To remedy the aforementioned drawbacks of the prior art, the present disclosure proposes a cold atom and light pulse interferometric system, the interferometric system comprising a vacuum chamber, a laser source fixed relative to the vacuum chamber, a planar retroreflector optical component, an electronic system and a detection system, the vacuum chamber being suitable for containing a cloud of cold atoms, the laser source being adapted to generate a sequence of laser pulses in the direction of the cold atom cloud along an axis of the laser, the retroreflector optical component being arranged to reflect the sequence of laser pulses in the direction of the cold atom cloud, the laser pulse sequence comprising N successive light pulses where N is an integer greater than or equal to three, the successive light pulses of the sequence being temporally separated from each other by an interrogation time T;the retroreflector optical component having a normal to its plane defining a measurement axis aligned with the laser axis at an initial instant of the sequence; the electronic system and the detection system being configured to perform an inertial measurement by atomic interferometry of the atom cloud along the measurement axis, the inertial measurement being integrated during the laser pulse sequence.

[0017] According to the invention, the interferometric system comprises an actuation device mechanically linking the optical component to a stage, the stage being fixed relative to the vacuum chamber, and at least one rotation sensor fixed relative to the vacuum chamber. The at least one rotation sensor and the electronic system are adapted to provide at least one rotation measurement of the vacuum chamber about at least one axis transverse to the laser axis at each interrogation time of said sequence. The electronic system and the actuation device are capable of angularly tilting the optical component relative to said stage during each interrogation time of said sequence as a function of said at least one rotation measurement acquired by the rotation sensor during said interrogation time of said sequence, so as to compensate for a rotation of the vacuum chamber transverse to the laser axis at each successive light pulse of the sequence relative to an orientation of the vacuum chamber at the initial time of the sequence.

[0018] Advantageously, the electronic system is adapted to adjust an optical phase of the laser source emitting the pulse sequence as a function of a Coriolis acceleration measurement induced by a compensating rotation of the optical component.

[0019] According to a particular aspect, the actuation device includes a first actuator capable of tilting the optical component relative to said plate around an axis of rotation transverse to the laser axis and / or a second actuator capable of tilting the optical component relative to said plate around another axis of rotation transverse to the laser axis.

[0020] In a particular and advantageous way, at least one rotation sensor includes a first gyroscope capable of acquiring a measurement of the rotation speed of the vacuum chamber around a first axis transverse to the laser axis and / or a second gyroscope capable of acquiring a measurement of the rotation speed of the vacuum chamber around a second axis transverse to the laser axis.

[0021] According to a particular and advantageous embodiment, the first gyroscope is a fiber optic gyroscope and the second gyroscope is a fiber optic gyroscope.

[0022] Advantageously, each optical fiber gyroscope has a sensitivity of at least 1 prad / s / ^Hz.

[0023] Preferably, the first actuator and the second actuator are configured to tilt the turntable with an angular resolution of less than 1 prad.

[0024] In a particularly advantageous way, the interrogation time is between 1 ms and several seconds, the first gyroscope and the second gyroscope being configured to acquire the rotation measurement, for example at an acquisition frequency between 100 Hz and several kHz.

[0025] In one particular aspect, the interferometric system includes a conventional sensor, the conventional sensor comprising a first adapted accelerometer to acquire an acceleration measurement of the stage along an axis transverse to the laser axis, a second accelerometer adapted to acquire an acceleration measurement of the stage along another axis transverse to the laser axis and / or a third accelerometer attached to the stage adapted to acquire an acceleration measurement of the stage along the measurement axis or the laser axis, and the electronic system is adapted to hybridize the measurements of the conventional sensor with the measurements of the interferometric system.

[0026] Advantageously, the conventional sensor includes a third gyroscope capable of acquiring a measurement of the rotational speed of the stage around the laser axis.

[0027] Advantageously, inertial measurement by atomic interferometry is suitable for measuring an acceleration and / or a rotation of the vacuum chamber.

[0028] This disclosure also relates to a cold atom, light-pulse interferometric method comprising the following steps: generating a sequence of laser pulses directed at a cloud of cold atoms in a vacuum chamber, the laser pulse sequence comprising N successive light pulses, where N is an integer greater than or equal to three, the successive light pulses of the sequence being temporally separated by an interrogation time T, the light pulses being reflected off a retroreflective optical component, a normal to the plane of the retroreflective optical component defining a measurement axis and being aligned with the laser axis at an initial time in the sequence; at the end of the laser pulse sequence, performing an inertial atomic interferometry measurement of the atom cloud along the measurement axis, the inertial measurement being integrated during the laser pulse sequence;measure at least one rotation of the vacuum chamber around at least one axis transverse to the laser axis at each interrogation time of said sequence; at each interrogation time, tilt the optical component angularly relative to the vacuum chamber according to the rotation measured during said interrogation time of said sequence, so as to compensate for a rotation of the vacuum chamber transverse to the laser axis at each successive light pulse of the sequence relative to an orientation of the vacuum chamber at the initial instant of the sequence.

[0029] Advantageously, the rotation measurement includes a rotation speed measurement which is integrated over time to determine a measurement of the chamber's rotation angle over a determined time interval.

[0030] In a particularly advantageous way, the process includes the following steps: acquiring a Coriolis acceleration measurement induced by a residual rotation of the mirror, resulting from the rotation of the chamber from which the compensating rotation of the optical component is subtracted, and adjusting an optical phase of the laser source emitting the pulse sequence to compensate for the Coriolis acceleration measurement.

[0031] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways as long as they are not incompatible or mutually exclusive. Brief description of the drawings

[0032] Furthermore, various other features of the invention become apparent from the attached description made with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0033] Figure 1 schematically represents a cold atom interferometer according to one embodiment of the present disclosure;

[0034] Figure 2 schematically represents the operation of a cold atom interferometer according to one embodiment of the present disclosure;

[0035] Figure 3 schematically represents simulation curves of contrast of the fringes of a cold atom interferometer as a function of an uncompensated rotation speed, and for different interrogation durations, in an inertial navigation application;

[0036] Figure 4 schematically represents simulation curves of fringe contrast of a cold atom interferometer as a function of an uncompensated rotation speed, and for different interrogation times, in a space application;

[0037] Figure 5 schematically represents a cold atom interferometer subjected to an uncompensated rotation of its measurement axis and shows the trajectories of the wave packets during a conventional three-pulse laser interrogation sequence;

[0038] Figure 6 schematically represents in perspective the trajectories of wave packets during a conventional three-pulse laser interrogation sequence in a cold atom interferometer subjected to uncompensated rotation transverse to its measurement axis;

[0039] Figure 7 schematically represents a three-pulse laser interrogation sequence and shows rotation speed measurements acquired by a gyroscope between each of the successive light pulses in the sequence;

[0040] Figure 8 schematically represents the same interrogation sequence as in Figure 7, in which the rotation speed measurements are integrated over time to provide, in real time, rotation angle measurements of the interferometer measurement axis during the sequence and tilt angle commands to the mirror;

[0041] Figure 9 schematically represents a cold atom interferometer in which a rotation transverse to its measurement axis is corrected and shows the trajectories of wave packets during a three-pulse laser interrogation sequence;

[0042] Figure 10 schematically represents in three dimensions the trajectories of wave packets during a three-pulse laser interrogation sequence in a cold atom interferometer corrected for a rotation transverse to its measurement axis.

[0043] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references. Detailed description

[0044] Figure 1 schematically represents a cold atom interferometric system with light pulses according to one embodiment. In a known manner, the cold atom interferometric system comprises an atom source and a cold atom trap configured to generate and trap a cloud of cold atoms. Alkali atoms, such as atoms of cesium (Cs), rubidium (Rb), and / or potassium (K). As an example, patent document WO2018 / 154254 Al describes an atomic interferometer. The cloud of cold atoms 8 is confined within a vacuum chamber 7 or experimental chamber. In applications to an accelerometer or gravimeter, the cloud of cold atoms 8 has zero initial velocity. In an application to an atomic gyroscope, the trap's laser beams are adapted to launch the cloud of cold atoms 8 along a predetermined initial propagation direction with an initial velocity. In an inertial navigation application, the vacuum chamber is mounted on a mobile vehicle.

[0045] On the other hand, the interferometric system 100 comprises a laser source 6, a planar retroreflector optical component 5, and a detection system 17. The laser source 6 and the detection system 17 are fixed relative to the experimental chamber 7. Advantageously, the planar retroreflector optical component 5 is a mirror, as illustrated in Figure 1. Alternatively, the planar retroreflector optical component 5 is a two-dimensional diffraction grating as described in patent document FR 3109221. The normal to the surface of the planar retroreflector optical component 5 is aligned with the measurement axis of the atomic interferometer, which is denoted The laser source 6 emits a laser beam 11. A collimator collimates the laser beam 11. The retroreflector optical component 5 receives the laser beam 11 and forms a reflected laser beam 12. The laser beam 11, and the reflected laser beam 12 respectively, propagates with a wave vector ki, and k respectively. In vector form, the measurement axis is defined by the vector k e ^ = k ± — k2■ Therefore, the wave vector k e The measurement axis ff is always aligned with the axis normal to the plane of the mirror 5. The experimental chamber 7 is equipped with a window to allow the laser beam 11 emitted by the laser source 6 to pass through.

[0046] The axis of the laser source 6, or laser axis, is denoted ït / . The laser axis is defined by the optical collimator, which is fixed to the experimental chamber. The laser axis is fixed in the frame of reference of the experimental chamber 7.

[0047] As is well known, an atomic interferometry measurement relies on the emission of a sequence of laser pulses. The successive light pulses of a The sequences are generally spaced temporally apart by an interrogation time T. A sequence of three light pulses, called the "n / 2 - n - n / 2" sequence, is commonly used, as illustrated, for example, in Figures 5 to 10. The "n / 2" pulses, each with a duration of T, allow the matter waves associated with the atoms to be separated or recombined. The "n" pulses, each with a duration of 2T, allow the matter waves to be deflected. Other sequences comprising more than three pulses are also used, notably a sequence of four light pulses, "n / 2 - n - n - n / 2". In all cases, a first light pulse 21 interacts with the cloud of cold atoms 8 in such a way as to spatially separate the wave associated with each atom into a first wave of atoms 31 traveling along a first path and, respectively, a second wave of atoms 32 traveling along a second path.At least one second light pulse 22 interacts with the two separated atomic waves 31, 32 to redirect them. Finally, a last light pulse 29 spatially recombines the two atomic waves 31, 32. The area defined by the paths of the two atomic waves 31, 32 between separation and recombination defines an atomic interferometry area. The sensitivity of the atomic interferometer is generally proportional to the area delimited by the two paths. The detection system 17 makes it possible to measure the accumulated atomic interferometry phase shift between the two atomic waves 31, 32 on their respective paths between separation and recombination. The detection system 17 is pointed at the center of the chamber towards the atomic cloud 8, maximizing the observed field. The detection system 17 records a fluorescence signal emitted by the atoms in an isotropic manner.The detection system 17 is mechanically attached to the experimental chamber 7 and therefore to the collimator defining the laser axis. Advantageously, the detection system records an average over the entire atom cloud 8.

[0048] On the one hand, an inertial frame of reference, or absolute inertial frame of reference, is defined as external to the interferometric system 100. This inertial frame of reference is fixed relative to the part, the laboratory, or relative to a geocentric frame of reference where the atomic interferometer is located, for example, on a mobile vehicle. We know the orientation of chamber 7 and the position of mirror 5 at an initial instant to = 0 for each sequence of laser pulses relative to the inertial reference frame.

[0049] On the other hand, a moving or rotating frame of reference, also known as an inertial reference frame, is defined, which moves with chamber 7 during the interferometry sequence. Experimental chamber 7 defines the rotating frame of reference relative to the inertial frame. The rotating frame of reference is defined by the laser axis θ and by two axes transverse to the laser axis, for example, the X and Y axes. The measurement signal detection system 17 is fixed to experimental chamber 7 and therefore to the rotating frame of reference. Atomic interferometry measurements are performed in the rotating frame of reference. The normal to mirror 5 is aligned with the laser axis at an initial instant t₀ = 0.

[0050] The inertial frame of reference is not linked to the rotating frame of reference. Unlike the rotating frame of reference, the inertial frame of reference does not experience inertial effects such as the acceleration and rotation of the moving object. Initially, that is to say at the beginning of each interferometry sequence, the laser axis and the measurement axis of the atomic interferometer are aligned, in other words the angle α between the laser axis η and the measurement axis is zero. In an interferometric system without rotation compensation, the laser axis and the measurement axis remain aligned throughout the interferometry sequence. According to this disclosure, as described in detail below, a rotation is applied to the mirror 5 during each interrogation time between two successive light pulses of the same interferometry sequence to compensate for a rotation of the experimental chamber accumulated over the entire interrogation time relative to the inertial frame of reference. The rotation applied to the mirror results in a misalignment between the laser axis and the measurement axis. the measurement axis during the interferometry sequence. Therefore, the angle α can vary during an interferometric measurement. At the end of each interferometry sequence, the normal to the optical component 5 is realigned with the axis of the laser 6 to return to its initial position.

[0052] The interferometric system 100 includes a detection system 17 of an inertial measurement signal by atomic interferometry relative to the inertial reference frame. Depending on the configuration, the detection system 17 can be located inside or outside the experimental chamber 7. The detection system 17 includes a point detector that detects all the atoms. Alternatively, the detection system 17 includes a camera that forms an image of the overlap of the two atom clouds and allows for the observation of spatially resolved interferometric fringes. In general, the detection system 17 detects, for example by fluorescence, a signal representative of the quantum state of the atoms after recombination of the two atom clouds at the end of the interferometric sequence, as described in patent document WO 2019 / 102157 A1. For example, the reading of the interference state of the atoms is performed in two steps, using two new laser reading pulses. The first laser reading pulse is wavelength-adjusted to one of the atom states.A photoreceptor detects a fluorescence signal resulting from the absorption of the first laser reading pulse. A second laser reading pulse measures the overall fluorescence signal to determine the total number of atoms. These two successive measurements provide information on the relative interference state between atoms. The detection of the two atomic populations (one in one state and the total population) yields a ratio that is then plotted against this atomic phase shift to observe interferometric fringes.

[0053] The interferometric system 100 also includes an electronic system 3, for example of the FPGA (field programmable gate array) type. As detailed below, the electronic system 3 controls and commands the various elements of the interferometric system 100, such as the sequence of laser pulses and the orientation of the optical component 5. In addition, the electronic system 3 receives signals from the detection system 17 of the atomic interferometer and from various sensors 1, 2 and / or 9, in order to process them to apply feedback to certain elements and extract very high-precision atomic interferometry measurements.

[0054] As mentioned in the technological background, in mobile applications, for example in the space domain or inertial navigation, the acceleration and / or rotational movements experienced by the interferometric system limit the operation and performance of a cold atom interferometer. A loss of contrast is observed, for example, when detecting all the atoms on a point detector. This loss of contrast leads to a loss of sensitivity in the atomic interferometer. If the contrast drop is significant, the interferometer ceases to function. More generally, in all cases, the contrast is zero (C=0) when the atomic wave packets no longer overlap at the output of the atomic interferometer. There are methods known to those skilled in the art for measuring contrast and monitoring a decrease in contrast.

[0055] In the case of rotations in particular, a change in the orientation of the reflective surface of the optical component 5 during an interferometry sequence leads to a decrease in the contrast C of the interferometry fringes when all the atoms are detected on a point detector. This decrease in contrast is modeled by the following expression:

[0056] [Math. 1]

[0057] Where k e ff represents the effective wave vector of the laser, o vThe velocity distribution of the atomic wave packet, T the interrogation time of the interferometer, and Q the rotation speed of the experimental setup, including the experimental chamber 7 and the laser 6, around an axis transverse to the measurement axis. Such behavior is simulated in Figures 3 and 4. Depending on the targeted sensitivity range, which is related to the interrogation time T, a relatively low rotation speed Q can nevertheless lead to a total loss of contrast C in the measurement signal of the atomic interferometer.

[0058] Figures 3 and 4 show simulation curves of the contrast C of the fringes of a cold atom interferometer as a function of a transverse rotation speed around the measurement axis of the atomic interferometer. This rotation is not compensated, respectively in an inertial navigation application (Figure 3) and a spatial navigation application (Figure 4). The dashed curve corresponds to a 10% contrast loss relative to the maximum contrast C=l. This curve demonstrates that even low rotation speeds are sufficient to degrade the interferometric measurement over the interrogation time.

[0059] In an inertial navigation application (Figure 3), the transverse rotation speed around the measurement axis is, for example, within a range of 0 to 100 mrad / s (this range is by no means limiting, but chosen here for clarity). Figure 3 shows different curves corresponding to different interrogation times T of an atomic interferometry sequence: 3.0 ms (disk-shaped markers), 5.0 ms (squares), 10.0 ms (diamonds), and 20.0 ms (crosses). For an interrogation time of 3.0 ms, the atomic interferometer can operate with limited contrast loss (i.e., remaining above the contrast ratio C = 0.9) up to a transverse rotation speed of approximately 93 mrad / s. For an interrogation duration of 5.0 ms, the limiting transverse rotation speed is approximately 34 mrad / s. For an interrogation duration of 10.0 ms, the limiting transverse rotation speed is approximately 8 mrad / s.For an interrogation duration of 20.0 ms, the limiting transverse rotation speed is approximately 2 mrad / s. Therefore, a very rapid decrease in contrast is observed, especially as the interrogation duration increases.

[0060] In a spatial application (Figure 4), the transverse rotation speed around the measurement axis is, for example, within a range of 0 to 0.0010 mrad / s (this range is by no means limiting, but chosen here for clarity). Figure 4 shows different curves corresponding to different interrogation times T of an atomic interferometry sequence: 1000 ms (disks), 2000 ms (squares), 3000 ms (rhombuses), 5000 ms (crosses). For an interrogation time of 1000 ms, the atomic interferometer can operate with limited contrast loss (i.e., remaining above the contrast ratio C = 0.9) up to a transverse rotation speed of approximately 0.0008 mrad / s. For an interrogation duration of 2000 ms, the limiting transverse rotation speed is approximately 0.0002 mrad / s. For an interrogation duration of 3000 ms, the limiting transverse rotation speed is approximately 0.0001 mrad / s.For an interrogation duration of 5000 ms, the limiting transverse rotation speed is approximately 0.00005 mrad / s. Here too, we observe a very rapid decrease in C contrast, especially as the interrogation duration increases.

[0061] Indeed, as schematically illustrated in Figure 5, it is assumed that the assembly formed by the experimental chamber 7, the optical component 5 and the stage 4 undergoes a rotation of its measurement axis by an angle of rotation 9 with respect to the inertial reference frame external to each interrogation time T of an interferometry sequence "JC / 2 - 7t - 7t / 2". For clarity, we consider here the specific case of a rotation at constant speed during the duration of the interferometry sequence. Between the time t=0 of the first pulse 21 and the time t=T of the second pulse 22 of the interferometry sequence, the moving frame has therefore rotated through an angle 9 with respect to the external inertial frame. Similarly, between the time t=T of the second pulse 22 and the time t=2T of the last pulse 29 of the interferometry sequence, the moving frame has rotated through an angle 9 with respect to the external inertial frame. Between the initial time t=0 and the time t=2T, the moving reference frame has therefore rotated by an angle 29. In figure 6, we observe that at time t= 2T, the two packets of atoms 31 and 32 do not overlap spatially because of the angle of rotation 29 of the measurement axis.This explains the loss of contrast C in the atomic interferometry fringes. A partial overlap of the two atom packets 31 and 32 at time t = 2T results in a decrease in contrast C compared to the theoretical maximum value of C=1, when all the atoms are detected on a point detector. If a camera is used, spatially resolved interferometry fringes can be detected. However, if the wave packets 31 and 32 are completely separated, the contrast is strictly zero (C=0).

[0062] More generally, the rotation speed of the interferometer can be random and even variable during the interferometry sequence. In this case, there may be a rotation of angle 0i before the second pulse 22 and a rotation of angle 02 between the second pulse 22 and the third pulse 23, with 02 different from 0i.

[0063] Figure 6 shows the same interferometry sequence as Figure 5 in perspective. The paths of the two atom packets 31 and 32 are represented by solid lines. The projection of the paths of atom packets 31 and 32 onto the (Y, t) and (Z, t) planes is represented by dashed lines. Here again, we observe that the paths of the two atom packets 31 and 32 do not completely overlap at time t=2T, due to rotation around an arbitrary axis, provided that this rotation has a component transverse to the measurement axis.

[0064] However, a rotation of the inertial reference frame around its measurement axis has no effect on the contrast of atomic interferometry measurements.

[0065] This disclosure proposes to measure and compensate in real time, during a sequence of pulses, the effects of a rotation around any axis transverse to the interferometric measurement axis.

[0066] For this purpose (see Figures 1-2), the planar retroreflector optical component 5 is mounted on a stage 4. The stage 4 is rigidly mechanically connected to the experimental chamber 7. The laser 6 is also attached to the vacuum chamber 7. An actuation device 13, 14 mechanically connects the optical component 5 to the stage 4. The actuation device 13, 14 comprises, for example, one or two piezoelectric actuators. The actuation device 13, 14 allows the optical component 5 to be tilted relative to the stage 4, i.e., relative to the inertial reference frame. An orthonormal coordinate system XYZ is considered, linked to the inertial reference frame. Preferably, the orthonormal coordinate system of the inertial reference frame comprises the laser axis and two axes X and Y orthogonal to the laser axis, with the X axis being orthogonal to the Y axis.

[0067] At the beginning of each interferometry sequence, the laser axis and the measurement axis (i.e., the normal to the surface of the optical component 5) are aligned. Optionally, particularly in the case of a gravimeter or gradiometer, the measurement axis is aligned along a local vertical axis before the start of an interferometry sequence.

[0068] The actuation device 13, 14 is chosen to allow the optical component 5 to be oriented with high precision, high stability, and a wide bandwidth. For example, a first piezoelectric actuator 13 allows the optical component 5 to be tilted by rotation or pivoting around a first axis of rotation transverse to the laser axis. Advantageously, a second piezoelectric actuator 14 allows the optical component 5 to be tilted by rotation or pivoting around a second axis of rotation transverse to the laser axis ït^ and transverse to the first axis of rotation. The measurement axis pivots simultaneously with optical component 5. Advantageously, the first axis of rotation is orthogonal to the second axis of rotation. Initially, the measurement axis The laser axis ït^ is orthogonal to the first and second axes of rotation. However, detector 17 remains fixed to chamber 7 and therefore to the rotating frame of reference. The mirror is the only component that rotates, thanks to the compensation system.

[0069] In an example application to inertial navigation, actuators 13 and 14 are chosen with a resolution on the order of microrads in closed loop and on the order of a hundred nanorads in open loop. The repeatability of the actuators is on the order of microrads and their bandwidth on the order of kHz. The angular dynamic range is on the order of 35 mrad. Those skilled in the art adapt the choice of actuators according to the requirements to increase one or more of these technical characteristics, sometimes at the expense of one or more of the others. In an example application in the space domain, the order of magnitude of these value ranges is generally divided by 100.

[0070] We are particularly interested in an application of the atomic interferometer 100 to an acceleration measurement along an acceleration axis denoted a. In Figure 1, the acceleration vector a represents the total acceleration vector applied to the atoms 8 in the experimental chamber 7. Figure 1 is a simplified view projected into two dimensions for better understanding. This total acceleration vector a is the sum of the local gravitational force g and the other accelerations experienced by the atoms 8 in the experimental chamber 7. Consequently, the total acceleration vector a can have a random orientation in space. The atomic interferometer 100 measures a projection of the acceleration vector a onto the measurement axis, which is normal to the reflecting surface of the optical component 5.

[0071] The interferometric system 100 further comprises at least one rotation sensor 1, 2 fixed to the inertial reference frame, for example to the stage 4. Alternatively, at least one rotation sensor 1, 2 is fixed to the experimental chamber 7. In the example illustrated in Figure 1, the interferometric system 100 comprises, for example, a first gyroscope 1 arranged and configured to acquire a measurement of the rotational velocity Qx of the stage 4 about a first axis X transverse to the laser axis and a second gyroscope 2 arranged and configured to acquire a measurement of the rotational velocity QY of the stage 4 about a second axis Y transverse to the laser axis. We denote ' c'that the laser axis ït^ remains fixed relative to stage 4 and gyroscopes 1 and 2. Stage 4 being fixed relative to the experimental chamber, each rotation sensor 1, 2 therefore allows the measurement of a rotation of the experimental chamber around an axis transverse to the measurement axis. Particularly advantageously, gyroscopes 1, 2 are fiber optic gyroscopes which present at the They possess high sensitivity, precision, and a wide measurement dynamic range. As a non-limiting example, gyroscopes 1 and 2 have a sensitivity on the order of 100 nrad / s / Hz, a precision on the order of 5 prad / s, and a dynamic range greater than 0.1 rad / s.

[0072] As illustrated in Figures 1 and 2, the first gyroscope 1 transmits to the electronic system 3 the measurement of rotational speed x around the first axis X and, respectively, the second gyroscope 2 transmits to the electronic system 3 the measurement of rotational speed y around the second axis Y. The electronic system 3 acquires at least one measurement of rotational speed on each gyroscope at each interrogation time T of a sequence.

[0073] For example, as illustrated in Figure 7, for each X or Y axis, the electronic system 3 acquires the rotational velocity x,y(t) of one of the gyroscopes 1, 2 as a function of time t over an interferometry sequence. The rotational velocity X,Y(t) varies slowly during a sequence. In general, this disclosure applies to a rotational velocity x,y(t) varying arbitrarily during an interferometry sequence. For clarity, a simplified example is considered in which the rotational velocity x,y(t) varies linearly over the considered interrogation time. During each interrogation time T of an interferometry sequence, the electronic system 3 receives at least one rotational velocity measurement, preferably for each X, Y axis.Thus, during the first interrogation time T of an interferometry sequence, the electronic system 3 receives a rotational velocity measurement x,y(ti) at a time ti located between the first laser pulse 21 and the second laser pulse 22. Similarly, during the second interrogation time T of the same interferometry sequence, the electronic system 3 receives a rotational velocity measurement x,y(ftz) at a time t? located between the second laser pulse 22 and the last laser pulse 29. The time ti, or tz respectively, is located, for example, at a time tdei after the end of the first pulse 21, or the second laser pulse 22 respectively. The time tdei is less than the interrogation time T. The time tdei represents a delay adjusted to find the best compromise between the time located exactly between two successive pulses (best estimate of the average) and a sufficient time before the next pulse. to stabilize the orientation of mirror 5 taking into account the response time of the actuators. For example, for an interrogation time T equal to 10 ms, tdei=2.5 ms is used.

[0074] As illustrated in Figure 8, the electronic system 3 integrates these rotational speed measurements x,y(t) as a function of time, to deduce a measurement of the rotation angle 0^ Y(t) of the inertial reference frame, as a function of time t, around the first X-axis or, respectively, the second Y-axis, relative to its position at the initial time t0 = 0 of the interferometry sequence. The solid curve represents the rotation of the reference frame in the inertial reference frame. Advantageously, these measurements are performed in parallel for both the X and Y axes of gyroscopes 1 and 2. Thus, for each axis, the electronic system 3 calculates an evaluation of the rotation angle 9 of the inertial reference frame at time t = T + 2i of the second pulse as a function of the rotation velocity measurement(s) between the first pulse 21 and the second pulse 22. This evaluation can be based on a time integration over the interrogation time T.

[0075] In the simplified case of a linear approximation of the rotational velocity x,y(t) over the interrogation time T, the rotation angle 9 can be calculated from a single measurement of the rotational velocity x,y(ti) which, once integrated over the entire interrogation time T, gives us an angle that can be extrapolated as the angle of rotation during this time. The setpoint for the rotation angle 0^ Y (T) to be applied to the optical component 5 before the second pulse 22 is calculated relative to its initial position defined by an angle 0^, (to) at time to = 0 of the interferometry sequence, i.e., the start time of the first laser pulse 21. In the example shown in Figure 8, the rotation angle 0^ is applied. Y(T) to the actuators of mirror 5 from time ti to time t?. The applied rotation angle ) is equal in absolute value and opposite in sign to x,v(ti).T. Similarly, the electronic system 3 calculates an evaluation of the rotation angle 0 of the inertial reference frame at time t=2T of the last pulse as a function of the rotation speed measurement(s) between the second pulse 22 and the last pulse 29. In the simplified particular case of a linear approximation of the rotation speed x,y(t) over the interrogation time T between the second pulse 22 and the Last pulse 29, the rotation angle 9 can be calculated from a single measurement of rotational speed x,Y(tz) at time t?, this measurement being extrapolated over the interrogation time T. The setpoint for the rotation angle 0^ Y (2T) to be applied to optical component 5 is calculated with respect to its angular position 0^ Y(T) at the time of the second laser pulse 22 of the same interferometry sequence. In the example shown in Figure 8, the rotation angle 0^(2T) is applied to the actuators of mirror 5 from time t? until the end of the interferometry sequence. The applied rotation angle 0^(2T) is equal in absolute value and opposite in sign to x,Y(tz).T. Two successive angle jumps are thus performed during the same interferometry sequence.

[0076] In order to physically compensate for the effect of these rotations, the electronic system 3 applies to the piezoelectric actuators 13, 14 a rotation angle 0^(T) from time ti, and respectively a rotation angle 0'^(2T) from time tz, of the same amplitude and opposite sign to the angle 0^ Ycalculated during the first interrogation period, and respectively during the last interrogation period. More precisely, the rotation angle 9 is compensated before the application of the second pulse 22. Similarly, the rotation angle 9 is compensated before the application of the last pulse 29. The opposites of the setpoints are represented by dashed lines in Figure 8 and are relative to the last angular position: the mirror is initially aligned with the laser, then rotated by 0^ Y (T) during the interrogation time between the first two pulses and finally during the interrogation time between the last two, then returned to its reference orientation after the interferometry sequence (aligned with the laser).

[0077] Thus, the electronic system 3 makes it possible to compensate for the rotations undergone by the interferometric system 100 in real time, that is to say during each interrogation time of a sequence of laser pulses.

[0078] Of course, it is possible to acquire several rotational speed measurements on each X, Y axis during each interrogation time T, and, depending on the response time of the electronic system and the actuators, to calculate more precisely the rotation angle to be applied before each successive laser pulse 22, 29 to compensate in real-time rotations of the inertial reference frame, especially when the assumption of linearity of the rotational speed is not applicable.

[0079] More generally, for an interferometry sequence comprising N successive laser pulses, at least one rotation angle measurement is acquired during each interrogation time Tj between pulse i-1 and pulse i, successively for each value of i = 2, ..., N. Before each pulse i, the rotation angle 0j over the interrogation time between pulse i-1 and pulse i is evaluated as a function of at least one rotation velocity measurement acquired between pulse i-1 and pulse i. And before each pulse i, a rotation angle command is successively applied to the actuator in question so as to compensate for the rotation angle 0i over the interrogation time Ti.

[0080] The timing of actuator rotation is generally dictated by the actuators' technical characteristics. In one example, the actuators rotate shortly after pulse i-1, for instance, after 2.5 ms for an interrogation time T of 10 ms. In another example, the actuators rotate at time t=T / 2 between two successive pulses, or just before pulse i. Alternatively, the actuators rotate several times between two successive laser pulses. The key point is that the rotation angle 0 of the experimental chamber 7, accumulated between two successive laser pulses i-1 and i, is corrected as accurately as possible at the moment pulse i is delivered, that is, at the moment the laser and the atoms interact.

[0081] For example, consider an interferometer with a three-pulse interferometry sequence "JC / 2 - 7t - TC / 2". In this way, at each instant t of an atomic interferometer sequence, t between t0 = 0 and t = 2T+4T, the signals from the gyroscopes 1, 2 are integrated over time to provide the new tilt angle of the reference mirror 5 according to the following equation.

[0082] [Math. 2]

[0083] where fl x represents the rotational speed measured by the first gyroscope 1 around the X-axis, fl r represents the rotational speed measured by the second gyroscope 2 around the Y-axis, and fl z represents the rotational speed around the Z-axis, optionally measured by a third gyroscope. The vector 0 mis the vector opposite to the rotation of the experimental chamber 7, in other words, the time-integrated rotation velocity vector. The Z-axis here coincides with the measurement axis. Note, however, that rotations around the measurement axis do not affect the contrast loss or the correction of the mirror 5's orientation. Furthermore, the duration T of the laser pulses is generally negligible compared to the interrogation duration T.

[0084] From this rotation vector of the experimental chamber 7, the FPGA 3 algorithm determines an associated rotation angle matrix 0 to be applied to the vector k defining the normal to the surface of the optical component 5, so as to align this vector k with its initial position at time t0 of the sequence. The vector k is here identical to k e ff or to the measurement axis In other words, as schematically illustrated in Figures 9 and 10, this compensation for rotations of the measurement axis transverse to this axis allows for better spatial overlap of the atomic wave packets at the end of the interferometry sequence, and consequently increases the fringe contrast. The interferometric system thus resolves the technical problem of contrast loss induced by rotation of the experimental chamber 7 relative to the inertial frame of reference.

[0085] In an example application, after rotation compensation according to this disclosure, a contrast C of 97% of its maximum value (without rotations) is obtained for T = 10 ms and respectively of 95% of its maximum value (without rotations) for T = 15 ms for a rotation speed between 150 and 200 mrad / s.

[0086] Optionally, and particularly advantageously, the optical component 5 and / or the piezoelectric actuators 13, 14 include a servo control device equipped with orientation sensors that allow the actual angle to be measured. eai around the first axis, respectively G^eai around the second axis, of the optical component 5 with respect to the rotation angle setpoint 9 et around the first axis, respectively 0 et around the second axis. The electronic system 3 can thus effectively control in real time the position of the optical component 5 as a function of the rotations undergone by the inertial reference frame.

[0087] Optionally, a conventional inertial sensor 9 is attached to the plate 4. The conventional inertial sensor 9 is positioned to be sensitive to acceleration or rotation about its measurement axis, denoted Let y be the angle formed between of the classic inertial sensor 9 and the axis of the acceleration vector a.

[0088] Advantageously, since the atomic interferometer 100 is used in an application for measuring acceleration or gravity, the conventional inertial sensor 9 includes an accelerometer to measure the acceleration along the axis Alternatively, the conventional inertial sensor 9 includes three accelerometers arranged to measure acceleration along three orthonormal axes. As an alternative or complement, the conventional inertial sensor 9 includes a third gyroscope to measure rotation around

[0089] According to another variant, the atomic interferometer 100 is used in an application to rotation measurements around and the third conventional inertial sensor 9 includes an accelerometer and / or a third gyroscope to measure the acceleration, respectively the rotation with respect to the measurement axis of the classic inertial sensor 9.

[0090] Since the conventional inertial sensor 9 is fixed to the stage 4, which is rigidly connected to the vacuum chamber 7, the initial angle P between the laser axis ït / and the measurement axis of the conventional inertial sensor 9 is known. The initial angle α between the measurement axis of the atomic interferometer is also known. laser it / .

[0091] The measurements from the conventional inertial sensor 9 are not used for mirror 5 compensation. Advantageously, the conventional inertial sensor 9 is used to hybridize the atomic interferometer measurements with the conventional acceleration or rotation measurements from the conventional inertial sensor 9, as described in French patent FR 1751457. For example, the measurements from the conventional inertial sensor 9 are used to determine the interference fringe corresponding to the acceleration measurement via the atomic interferometer. The measurements from the conventional inertial sensor 9 are also used to correct for phase shifts due to vibrations.

[0092] According to this disclosure, the phase correction also includes, specifically within the context of rotation correction, the Coriolis phase shift and the misalignments detailed below. Indeed, a Coriolis acceleration is an acceleration induced by the interaction between atoms falling in a straight line under the effect of gravity relative to the inertial frame of reference (the laboratory, geocentric, in any case a fixed frame that does not experience inertial effects) and the mirror 5, which rotates relative to this same inertial frame of reference. In this context, we observe an acceleration induced by the rotation of the vacuum chamber 7 relative to the inertial frame of reference, since the mirror experiences the rotational velocity, and another acceleration induced by the rotation of the mirror relative to the chamber.Therefore, in the context of this disclosure, phase correction corresponds to a Coriolis acceleration induced by a residual rotational speed (zero if the rotation of the mirror perfectly compensates that of the chamber).

[0093] According to a particular and interesting aspect of this disclosure, a phase term introduced by both the rotations of the vacuum chamber 7 and the angular compensation of the mirror 5 is calculated in real time. For this purpose, we consider the motion of atoms, for example falling in a straight line in the inertial frame of reference, relative to the vacuum chamber 7, which is itself rotating relative to the inertial frame of reference. The Coriolis term, defined by the following equation, appears in the acceleration measurement:

[0094] [Math. 3]

[0095] Or m represents the actual rotational velocity vector of mirror 5 in the inertial frame of reference and v at is the speed of the wave packets of atoms. m corresponds to a residual rotational speed of the mirror resulting from the rotation of the chamber, from which the applied compensation is subtracted.

[0096] Using a sensitivity function formalism, we determine the phase shift omega induced by this Coriolis acceleration a(t). This phase shift can be approximated, assuming negligible pulse duration, by the following equation:

[0097] [Math. 4]

[0098] Where v(t) represents the integral of a(t), namely the speed of the mirror relative to the atoms. When measuring the phase output of the atomic interferometer, this phase shift is subtracted to avoid fringe blurring. This is a random phase term, which corresponds to measurement noise if this effect is not corrected. The fringe blurring phenomenon is unrelated to the contrast loss; it is possible to avoid contrast loss while still having completely blurred fringes.

[0099] This formula is calculated for an interferometry sequence defined over an interval [-T; T]. This formula is valid with and without correction, using Q for the rotational speed. m (t): m(t) = cosh(t) without angular correction of mirror 5 and m(t) = cosh(t) - cosh(t) with angular correction of mirror 5, where cosh(t) represents the rotational speed of the vacuum chamber and Cor(t) represents the correction applied to mirror 5. Thus, when the orientation of mirror 5 is corrected, the rotational speed considered corresponds to a residual rotational speed due to an imperfect correction. The phase shift induced by the Coriolis acceleration is calculated in real time. The optical phase adjustment of the laser source can be done in several ways, but it seems simpler and faster to communicate the final value of the phase shift accumulated during the interferometry sequence only once, before the last pulse.

[0100] Other effects can be taken into account when compensating for rotations. In particular, the angular orientation of the optical component 5 relative to the laser axis during an atomic interferometry sequence leads to multiple misalignments. Let y be the angle between the measurement axis. of the conventional inertial sensor 9 and the acceleration vector a (see figure 1). We also consider the angle P between the laser axis and the measurement axis of the conventional inertial sensor 9, and the angle α between the measurement axis of the atomic interferometer and the laser axis The phase shift induced by this misalignment of the optical component 5 with respect to the laser axis is expressed as follows, in the approximation where a, P «1.

[0101] [Math. 5]

[0102] The interferometric system allows the reference optical component 5 to be realigned to its initial position between each interferometry sequence. This system prevents loss of contrast in the measured interferometric signals. It thus enables atomic interferometry measurements to be performed in a moving environment subject to randomly varying rotations without requiring a complex and bulky stabilization system.

[0103] In addition, the system allows for the reconstruction of atomic interferometry fringes in real time during a sequence and for correcting the laser phase before the last pulse of an interferometry sequence so that the total phase at the end of the interferometry sequence takes this term into account.

[0104] This correction can advantageously be combined with a hybridization scheme as described in patent document WO 2018 / 154254 A1, to simultaneously compensate for vibrations and rotations. For this purpose, the conventional inertial sensor 9 includes a third gyroscope to measure the rotation around the axis. The third gyroscope is based on MEMS, laser gyroscope, or fiber optic gyroscope technology. This dual correction preserves the recentering or tracking of the central fringe of the interferogram.

[0105] Of course, various other modifications can be made to the invention within the scope of the attached claims.

Claims

Claims Cold atom and light pulse interferometric system (100), the interferometric system (100) comprising a vacuum chamber (7), a laser source (6), a planar retroreflector optical component (5), an electronic system (3) and a detection system (17), the vacuum chamber (7) being suitable for containing a cloud of cold atoms (8), the laser source (6) being adapted to generate a sequence of laser pulses in the direction of the cold atom cloud (8) along a laser axis (UL), the retroreflector optical component (5) being arranged to reflect the sequence of laser pulses in the direction of the cold atom cloud, the laser pulse sequence comprising N successive light pulses where N is an integer greater than or equal to three,the successive light pulses of the sequence being temporally separated from each other by an interrogation time T; the retroreflective optical component having a normal to its plane defining a measurement axis aligned with the laser axis at an initial instant of the sequence; the detection system (17) and the electronic system (3) being configured to perform an inertial measurement Ile by atomic interferometry of the atom cloud along the measurement axis, characterized in that the interferometric system (100) comprises: an actuation device (13) mechanically connecting the optical component (5) to a stage (4), the stage (4) being fixed relative to the vacuum chamber (7), and at least one rotation sensor (1, 2) fixed relative to the vacuum chamber (7), the at least one rotation sensor (1,2) and the electronic system (3) being adapted to provide at least one measurement of the rotation of the vacuum chamber (7) about at least one axis transverse to the laser axis at each interrogation time of said sequence, the electronic system (3) and the actuation device (13) being capable of angularly tilting the optical component (5) relative to said stage (4) during each interrogation time of said sequence as a function of said at least one measurement of rotation acquired by the rotation sensor during said interrogation time of said sequence, so as to compensate for a rotation of the vacuum chamber transverse to the laser axis at each successive light pulse of the sequence relative to an orientation of the vacuum chamber at the initial instant of the sequence. An interferometric system according to claim 1, wherein the electronic system (3) is adapted to adjust an optical phase of the laser source (6) emitting the pulse sequence as a function of a Coriolis acceleration measurement induced by a compensating rotation of the optical component (5). An interferometric system according to claim 1 or 2, wherein the actuation device (13) comprises a first actuator capable of tilting the optical component (5) relative to said stage (4) about an axis of rotation transverse to the laser axis and / or a second actuator capable of tilting the optical component (5) relative to said stage (4) about another axis of rotation transverse to the laser axis.An interferometric system according to any one of claims 1 to 3, wherein at least one rotation sensor comprises a first gyroscope (1) capable of acquiring a rotational velocity measurement (x) of the vacuum chamber (7) about a first axis (X) transverse to the laser axis and / or a second gyroscope (2) capable of acquiring a rotational velocity measurement (Qy) of the vacuum chamber (7) about a second axis (Y) transverse to the laser axis. An interferometric system according to claim 4, wherein the first gyroscope (1) is a fiber optic gyroscope and the second gyroscope (2) is a fiber optic gyroscope. An interferometric system according to any one of claims 4 to 5, wherein the interrogation time is between 1 ms and several seconds, the first gyroscope (1) and the second gyroscope (2) being configured to acquire the rotational measurement.Interferometric system according to any one of claims 1 to 6 comprising a conventional sensor (9) fixed to the stage (4), the conventional sensor (9) comprising a first accelerometer adapted to acquire an acceleration measurement of the stage along an axis transverse to the laser axis, a second accelerometer adapted to acquire an acceleration measurement of the stage along another axis transverse to the laser axis and / or a third accelerometer adapted to acquire an acceleration measurement of the stage along the laser axis and wherein the electronic system is adapted to hybridize the measurements of the conventional sensor (9) with the measurements of the interferometric system (100). An interferometric system according to claim 7, wherein the conventional sensor (9) comprises a third gyroscope capable of acquiring a measurement of the rotational velocity (Qz) of the stage about the laser axis. Use of an interferometric system according to any one of claims 1 to 8 for measuring an acceleration or rotation of the vacuum chamber. A cold atom, light-pulse interferometric method comprising the following steps: generating a sequence of laser pulses directed towards a cloud of cold atoms (8) in a vacuum chamber, the laser pulse sequence comprising N successive light pulses where N is an integer greater than or equal to three, the successive light pulses of the sequence being separated temporally by an interrogation time T, the light pulses being reflected off a planar retroreflector optical component (5).a normal to the plane of the retroreflector optical component (5) defining a measurement axis and aligned with the laser axis at an initial time in the sequence; at the end of the laser pulse sequence, perform an inertial measurement by atomic interferometry of the atom cloud along the measurement axis, the inertial measurement being integrated during the laser pulse sequence; measure at least one rotation of the vacuum chamber around at least one axis transverse to the laser axis at each interrogation time of said sequence; at each interrogation time, tilt the optical component (5) angularly relative to the vacuum chamber according to the rotation measured during said interrogation time of said sequence,in order to compensate for a rotation of the vacuum chamber transverse to the laser axis at each successive light pulse of the sequence relative to an orientation of the vacuum chamber at the initial instant of the sequence. A method according to claim 10 comprising the following steps: acquiring a Coriolis acceleration measurement induced by a compensating rotation of the optical component and adjusting an optical phase of the laser source (6) emitting the pulse sequence to compensate for the Coriolis acceleration measurement.

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