Accelerometer-type offset correction ultra-cold atom sensor

Abstract

The invention relates to an interferometric ultra-cold atomic inertial sensor (10) of the accelerometer type, comprising:-an atomic chip (ACh) comprising at least one set of first and second elementary sensors (SENA, SENB):-an atomic generation device (ACG); -a generator (GB) for generating a uniform magnetic field (Bc); -a power supply device (PSD); -wherein the arrangement of the set of one or more electrically conductive elements of each sensor and the sequence are further configured such that the tracks (TR1A, TR2A) associated with the first base sensor and the tracks (TR1B, TR2B) associated with the second base sensor are parallel to each other, have the same length, are covered simultaneously, and are not parallel to each other. And such that the departure directions of the first clouds from the first base sensor and the second base sensor, respectively, are opposite; -The sensor further comprises a detection system (SDET).

Description

Technical Field

[0001] The present invention relates to the field of inertial sensors and more specifically to cold atom interferometry inertial sensors integrated on an atom chip. More specifically, the present invention relates to cold atom sensors of the accelerometer type on an atom chip used in measuring inertial acceleration parameters, which use microwave fields to spatially separate two atomic clouds according to two internal states. Background Art

[0002] In general, an inertial sensor is a device used to measure physical parameters related to movement, such as acceleration or angular velocity, which is used together with a clock to determine the orientation in space. Devices that measure acceleration and rotational velocity are called inertial units or inertial measurement units (UMIs).

[0003] Interferometry techniques using cold atoms on a chip allow this type of inertial measurement to be performed and are often compact enough and have sufficient performance capabilities to be used in the embedded space.

[0004] The operation of cold atom accelerometers is based on interferometry, and measuring the phase difference of the interferometer can be used to derive acceleration measurements.

[0005] Cold atom interferometry causes two electronic states of an atom (such as rubidium 87) (called the first internal state |a> and the second internal state |b>) to interfere in a Ramsey-type sequence. The Ramsey-type interferometer sequentially measures the phases accumulated from measurements of at least one population (preferably, for greater precision, measurements of both populations) of the selected states |a> or |b> in achieving the sequence.

[0006] In order for the interferometer to be sensitive to acceleration, both states must cover straight return trajectories from the same departure point DP, with the two trajectories and the departure point being aligned along the straight line Dr. Therefore, a term is added to the energy difference between the two states, which term depends on the difference in the potential acceleration energy between the positions of the two states |a> and |b>, and thus the phase of the interferometer depends on the acceleration.

[0007] The operating principle for measuring acceleration using interferometry based on a clock-type Ramsey sequence is briefly provided below by way of hint, wherein the phase of the interferometer at the end of the sequence is proportional to the energy difference between two states of the interferometer.

[0008] In the case of a clock, the phase of the interferometer is provided by:

[0009]

[0010] in:

[0011] is the phase of the atom in the |a> state, and is the phase of the atom in the |b> state;

[0012] ω ab =ω 0a -ω 0b

[0013] is the energy of the |a> state, and is the energy of the |b> state;

[0014] ω ab is the angular frequency corresponding to the energy difference between the |a> and |b> states;

[0015] ω is the angular frequency of the local oscillator;

[0016] T R is the duration of free evolution (Ramsey time).

[0017] If during this sequence the atom in the |a> state and the atom in the |b> state are each made to describe a straight return trajectory as described above, then due to the difference in the potential acceleration energy between the positions of the two states |a> and |b>, a phase shift term appears that is sensitive to the acceleration along the straight line Dr: the clock becomes an accelerometer.

[0018] If separation occurs along the X axis (the line Dr along X), and the state is separated for the entire duration T sep If there is an acceleration ac in the interferometer, an additional phase shift appears at the output of the interferometer:

[0019]

[0020] in:

[0021] x a (t) is the position of the |a> state along the line Dr, and x b (t) is the position of the |b> state along the line Dr;

[0022] m is the mass of the atom, and is the reduced Planck constant.

[0023] In fact, the energy levels of the two states of the interferometer have been shifted by energy. This shift in energy levels is caused by the spatial separation of the two states; as a result of their spatial separation, the two states are no longer at the same acceleration potential energy level.

[0024] To simplify the equation, the separation and recombination durations are considered negligible compared to the duration during which the separation is maintained (T sep ≈T R ), x a and x b Therefore, is no longer a function of time, and the previous equation can be rewritten as follows:

[0025] where Δx = x a -x b

[0026] Therefore, the total phase output from the interferometer is:

[0027]

[0028] Knowing the phase As well as the other quantities and parameters in formula (1) make it possible to deduce the acceleration along the X axis.

[0029] The following provides, by way of suggestion, the operating principle for an ultracold atom accelerometer based on an atom chip, which is used to generate a cloud of ultracold atoms and a trajectory that enables the measurement of acceleration via phase, as described above.

[0030] Ultracold atoms are defined as atoms having a temperature below 400 nanoKelvin and preferably below 300 nanoKelvin. The temperature of hot ultracold atoms (e.g. for rubidium atoms) ranges between 50 and 400 nanoKelvin, and preferably between 100 and 300 nanoKelvin.

[0031] The principle involves creating two aligned and straight return tracks, each covered by two clouds of magnetically trapped atoms. The magnetic trap is moved along the tracks by wires / elements and microwave guides arranged on and in the atom chip.

[0032] exist Figure 1 An example of an atom chip is shown in .

[0033] The surface of the chip defines an XY plane or measurement plane 13 which is perpendicular to the Z axis.

[0034] The chip 1 comprises a unit suitable for generating a first ultracold atom trap T1 and a second ultracold atom trap T2, wherein the trap allows a cloud of ultracold atoms to be fixed in an internal state different from another trap at a predetermined distance h from the measurement plane 13. For example, the trap T1 comprises atoms (cloud CL1) in the electronic level or |a> state, while the trap T2 comprises atoms (cloud CL2) in the |b> state. The levels |a> and |b> are separated by a frequency ω ab / 2π. For example, in the case of rubidium 87, two hyperfine levels are involved |F=1,m-F =-1> and |F=2,m- F =1>, which are separated by approximately 6.8 GHz.

[0035] These units also allow the cloud to move along trajectories TR1 and TR2 lying in a plane parallel to the measurement plane 13 and at a height h from this plane, as Figure 1 These units are made of waveguides and wires.

[0036] The waveguides CPW1 and CPW2 are suitable for the angular frequency ω b and ω a The microwaves are propagated. The waveguides are arranged symmetrically, preferably in parallel, with respect to the Y axis of the measurement plane. The two waveguides CPW1 and CPW2 are connected to at least one generator for generating a voltage or a current at microwave frequencies. For example, each of these waveguides is produced by depositing three wires in parallel so that a coplanar waveguide is formed. In other embodiments, other types of waveguides can be used, in particular waveguides manufactured so as to be compatible with deposition or etching microfabrication processes. For example, a microstrip line can be produced.

[0037] The wires integrated into the chip 1 are suitable for circulating direct current. The wires are divided into wires WIz, for example, along a symmetry axis Y perpendicular to X and located in the measurement plane 13, and wires Wld parallel to the X axis. The wires are arranged so as to define an intersection C (intersection between Wlz and Wld) located on the Y axis.

[0038] Each conductor is connected to one or more current and / or voltage generators, which are themselves connected to a processing unit comprising at least one microprocessor. The voltage and / or current generators allow both direct current and alternating current to be driven through the conductor. In particular, direct current is driven through the conductor.

[0039] In the sensor, the atom chip 1 is placed in a vacuum chamber, the vacuum of which is maintained, for example, using an ion pump and preferably includes magnetic shielding. The sensor includes an ultracold atom generation device, which includes:

[0040] - an atom distributor, for example produced by a heated filament generating rubidium vapor;

[0041] - A primary (optical and / or magnetic) atom trap, which allows precooling of the cloud of ultracold atoms and is arranged near the chip (with the loading view described below of the magnetic traps T1 and T2 with atoms).

[0042] The sensor also comprises a magnetic field source external to the chip 1. It allows generating a uniform and static magnetic field Bc over a thickness of the order of at least a height h above the measurement plane 13. Advantageously, the direction of the uniform magnetic field is parallel to the measurement plane.

[0043] exist Figure 1 , the trajectories TR1 and TR2 shown as dashed lines show the trajectories of the clouds CL1 and CL2 of ultracold atoms, respectively. A distance h separates the plane of the trajectories and the measurement plane 13 of the chip. Preferably, h ranges between 500 nm and 1 mm, and preferably between 5 μm and 500 μm.

[0044] Figure 2 The geometry of the waveguides and wires of the atom chip and the wells T1 and T2 are shown. The specific arrangement of the wires and waveguides associated with the uniform magnetic field source allows to easily obtain Figure 2 The two wells T1 and T2 shown in part a) of . Each well T1 and T2 has the same non-zero minimum value V0 and the same curvature, which is a necessary condition for the sensor to operate. In fact, when a direct current is applied to the two wires crossing at C, the minimum of the potential is located vertically from the intersection. Of course, when microwave power is then sent through the waveguide, the central minimum is converted into two minima located on either side of the initial minimum toward the waveguide. If the initial minimum is not strictly located at an equal distance from the two waveguides, the two potential minima created will not have strictly the same minimum value V0 and the same curvature.

[0045] Figure 2 Part c) shows the layout of wires and waveguides (seen from above) defining the initial crossing point C. Figure 2 Part b) of the diagram describes the corresponding layout of the conductors and waveguides printed on the chip as a cross-section through the conductor WId (which intersects the conductor WIz along the symmetry axis Y). The waveguides CPW1 and CPW2 are coplanar waveguides located on the first layer N1. The isolation layer 18 advantageously allows the measurement plane to be flattened. The material of the electrical isolation layer can be, for example, silicon dioxide, silicon nitride or benzocyclobutene. A conductive material (for example gold) is used to manufacture the conductors and is deposited on the substrate 15, thereby forming the second layer N2. The substrate can be made of, for example, silicon, aluminum nitride or silicon carbide.

[0046] Part a) shows the symmetric separation of the ultracold atoms, which is specific to the internal state of the ultracold atoms, and more specifically the potential variation as a function of the X-axis of the chip 1 .

[0047] Curve "a" shows the relationship between a uniform magnetic field and a current I Z The potential well corresponds to the correlation of the field created by the wire WIz through which the current Id passes and the wire WId through which the current Id passes. This leads to a local potential well (initial potential Vini), thus forming a three-dimensional atomic well T. Clouds of ultracold atoms can be trapped in it and cooled.

[0048] Curve "b" schematically shows the frequency ω of the b The electric potential created by sending microwaves. b The field emitted by the passage of allows to modify the energy of the ultracold atoms and to move the atoms of the internal state |b>. Curve "e" shows the potential observed by the internal state |b> as a result of the contribution of the potentials shown by curves "a" and "b". Curve "e" has a local potential minimum that allows the cloud of ultracold atoms of the internal state |b> to be locally trapped.

[0049] Similarly, curve "d" schematically shows the frequency ω of the a The electric potential created by sending microwaves. a The field emitted by the passage of allows to modify the energy of the ultracold atoms and to move the atoms of the internal state |a>. Curve "c" shows the potential observed by the atoms of the internal state |a> as a result of the contribution of the potentials shown by curves "a" and "d". Curve "c" has a local energy minimum that allows the cloud of ultracold atoms of the internal state |a> to be locally trapped.

[0050] The correlation of the DC magnetic trap (created by the DC current in the wire and the uniform field Bc) and the microwave field creates a so-called "dressed" trap. The term "dressed" is understood to mean a trap created at least in part by a microwave, radio frequency or optical oscillating field. Variations in the microwave fields (power, frequency and the waveguides in which they propagate) allow this dressed trap and therefore the atoms to be moved. Figure 2 The DC magnetic trap is shown by curve a in FIG. Figure 2 The curve d shows that a The microwave field at Figure 2 The microwave field at ωb is shown by curve b in FIG. The trimmed well T1 for the |a> state is shown by curve c (correlation of curves a and d), and the trimmed well T2 for the |b> state is shown by curve e (correlation of curves a and b).

[0051] The cloud of ultracold atoms with internal states |a> and |b> can be simultaneously a The wave propagates through CPW2 and makes the frequency ω b The waves propagating are separated and trapped symmetrically with respect to the symmetry axis Y by CPW1. In order to obtain two wells with the same value of minimum V0 and with the same value of curvature, it is important that the intersection point C is placed on the symmetry axis Y at an equal distance from CPW1 and CPW2.

[0052] Frequencyω a and ω bis the frequency ω of the states |a> and |b> 0a and ω 0b The function is selected.

[0053] Figure 3 In its lower part b) an example of applying various signals to the wires and waveguides according to the prior art in order to cover the linear trajectories at the two wells T1 and T2 (and therefore at the two clouds of trapped atoms) in the case of an accelerometer type sensor is shown, and in its upper part a) the positions of the two clouds corresponding to selected times are shown. Figure 3 Part a) schematically shows the sequence of movement of each cloud of ultracold atoms at characteristic times t1 to t3. Part b) shows the sequence of various currents applied to the wire, powers applied to the waveguide, and frequencies applied to the waveguide at times corresponding to the times of part a). Figure 3 In the sequence shown, the current Iz (not shown) flowing through WIz is static and at a constant value. The current applied to WId is also constant throughout the sequence.

[0054] In step A0, there is a stage of preparing atoms. A cloud of ultracold atoms is generated, comprising the stages of distributing the atoms, cooling the atoms, initializing the atoms in at least one internal state |a>, and trapping the cloud of ultracold atoms at a distance h from the measurement plane (well T, Figure 2 Curve "a", part a)). The height h is different from 0, because the uniform magnetic field Bc is non-zero. The trapping is achieved by applying a direct current (Vini generation) in the wire WIz and in the wire WId. At the same time, a magnetic bias field Bc is applied parallel to the plane of the atomic chip, which is superimposed on the magnetic field created by the two aforementioned wires. The atomic cloud is then trapped by the potential Vini perpendicular to C, which is the intersection of the wires Wlz and Wld. This step is achieved by Figure 3 The portion between 0 and t1 in part b) is shown.

[0055] In step B0, the internal state is initialized by coherently superimposing the ultracold atoms between states |a> and |b> via a first pulse π / 2. This pulse can be generated by a laser, a microwave transmitter or more generally using a method in which a wave is emitted at a suitable transition frequency. The current I Z and I d are applied to the wire WIz and the wire WId, respectively. The two internal states |a> and |b> are coherently superimposed on the intersection C and vertically in space.

[0056] In step C0, the initial cloud is spatially separated into a first ultracold atomic cloud CL1 in a first internal state |a> and a second ultracold atomic cloud CL2 in a second internal state |b>, thereby forming a first ultracold atomic well T1 and a second well T2. This step is performed by Figure 3 The portion between t1 and t′1 in part b) is shown.

[0057] In step D0, at time T S The two wells are kept separate for (t'1 to t'2) and then the wells are recombined at the exit point (t'2 to t3).

[0058] During steps C0 and D0 , the two clouds cover respectively a first linear trajectory TR1 and a second linear trajectory TR2 parallel to the XY plane from the departure point DP.

[0059] In step E0, the internal states |a> and |b> are recombined by applying a second pulse π / 2 to the ultracold atoms, which transfers a phase difference to the two atomic-level populations. The pulse π / 2 can be sent to the atoms via a microwave guide or via a separate microwave transmitter.

[0060] The sequence ranging from the first pulse to the second pulse π / 2 comprises the Ramsey sequence (see above).

[0061] Then, in step F0, the phase due to the difference in potential acceleration energy between the two states |a> and |b> of the ultracold atom is measured and the acceleration of the sensor along the X axis is calculated.

[0062] Only the duration T between t1 and t3 is considered R Ramsey order, initially at t1, no power is applied to the waveguide and the cloud is trapped above point C. Between t1 and t'1, the microwave power injected into the waveguides CPW1 and CPW2 gradually increases from 0 to its maximum value, and then the value remains maximum and constant between t'1 and t'2 (through t2). The angular frequency ω is transmitted through the waveguide CPW2 a , and transmits the angular frequency ω through the waveguide CPW1 b , thereby separating the two clouds with different internal states on either side of the symmetry axis Y, until the positions schematically shown at t2, where these positions are maintained throughout the duration t'2-t'1 (which can be short). Between t'2 and t3, the microwave power in the waveguide is gradually reduced. The two traps T1 and T2 move until they merge into a single trap located at the exit point schematically shown at t3 (part a)).

[0063] To implement the above method, the ultracold atomic sensor that allows acceleration measurement ac includes:

[0064] - an atomic chip 1 with waveguides and wires as described above;

[0065] - an atom generation device for generating a cloud of ultracold atoms close to the measurement plane 13 of the atom chip;

[0066] - a generator for generating a uniform magnetic field Bc;

[0067] - at least one direct current or voltage generator suitable for controlling the current in the conductor and for generating microwaves connected to the waveguide

[0068] at least one generator of current or voltage;

[0069] - a detection system, typically for detecting optical intensities, suitable for measuring at least one ultracold atomic population in an internal state, wherein the

[0070] The measurement allows the determination of the phase and therefore the acceleration ac due to the difference in the potential acceleration energy between the two states |a> and |b>.

[0071] In order to obtain more accurate measurements of inertial parameters (time, acceleration, rotation speed), measurement redundancy can be used. An architecture integrating several sensors, clocks, accelerometers and gyroscopes is described in document US 2023 / 0178262. The sensor is based on an AchM0 matrix array chip that allows the generation of several basic sensors.

[0072] Figure 4 An example of a 6x6 matrix from the document is shown. Waveguides along the 6 axes Xn and along the 6 axes Ym form the columns and rows of the matrix. Each pixel (n, m) of the matrix corresponds to a potential elementary sensor that can be configured as needed. For example, the chip in column C1 measures the acceleration ax along X, while the chip in column C2 measures the rotational velocity Ωy around axis Y, the chip in row L1 measures the acceleration ay along Y, while the chip in row L2 measures the rotational velocity Ωx around axis X. Since the measurements require a specific order for the coplanar waveguides, the waveguides cannot be shared for two simultaneous measurements of two different inertial parameters. Therefore, the pixel 4 surrounded by the circle is not used. Therefore, the matrix array chip is reconfigured as needed: the desired measurement type (ax, ay, Ωx, Ωy, t), the desired accuracy (which depends on the number of chips performing the measurement simultaneously), etc. Therefore, parallel, redundant and / or complementary measurements are performed on the same matrix array chip. It should be noted that, given a specific sequence for applying a direct current and / or a magnetic field and / or a microwave field, measurement of Ωz is also possible (if necessary) (see, for example, documents US2023 / 0178262 and US2022 / 0397396).

[0073] Figure 4 continued Another example of a 6x6 matrix from document US2023 / 0178262 is shown, in which the waveguides form diagonals, which are numbered (D1 to D6, then D1' to ...). The rows and columns are formed by DC wires W1n and W2m. The pixels on the southeast-northwest diagonal D5 measure ax, and some pixels on the diagonal D6 measure Ωy. The southwest-northeast diagonal D6' measures Ωx, while the southwest-northeast diagonal D7' measures ay. Therefore, for the same reasons as above, the basic chip 5 surrounded by a circle is not used.

[0074] Sensors based on matrix array chips comprising a plurality of elementary sensors having the various geometries described above allow:

[0075] Implementing on a single chip clock functionality, measurement of acceleration along two orthogonal axes, and measurement of rotation along pairs of three orthogonal axes;

[0076] The basic geometry is replicated on the same atom chip in order to perform all the aforementioned measurements simultaneously and to achieve redundancy between the various measurements.

[0077] However, this solution does not allow to eliminate measurement biases or correction errors.

[0078] Each measurement has an associated uncertainty, which is represented by an error in the measurement. This error may be due to random factors that are unavoidable and cannot be corrected (although their magnitude can be estimated), and to systematic factors that are due to sensor defects or imperfect measurement conditions. The latter type of error is also called bias.

[0079] The present invention aims to overcome the above mentioned drawbacks by proposing an inertial sensor of the accelerometer type and a measurement method which allow to correct some deviations in order to improve the performance capabilities of the sensor. Summary of the invention

[0080] The object of the present invention is an interferometric ultracold atomic inertial sensor of the accelerometer type, comprising:

[0081] - an atomic chip placed in a vacuum chamber, comprising an XY plane, called measurement plane, perpendicular to the Z axis, and comprising at least one set of first elementary sensors and second elementary sensors, wherein each elementary sensor comprises:

[0082] o at least one first pair of waveguides parallel to each other and at least one second pair of waveguides parallel to each other and intersecting the first pair;

[0083] ○ A group of one or more conductive elements;

[0084] - an atom generation device configured to generate an initial cloud of ultracold atoms associated with the first elementary sensor and an initial cloud of ultracold atoms associated with the second elementary sensor, wherein the initial clouds are positioned close to the XY plane of the chip;

[0085] - a generator for generating a uniform magnetic field (Bc);

[0086] - a power supply device comprising at least one microwave generator and at least one direct current generator, the power supply device being configured to apply a microwave signal to the waveguide and to apply a direct current to the conductive element;

[0087] - the magnetic field generator and the power supply device are configured to apply the magnetic field, the direct current and the microwave signal in a predetermined sequence;

[0088] - wherein when implementing each sensor, the arrangement of the set of one or more conductive elements and the order are configured as:

[0089] i) generating an initial trapping potential for a defined departure point of said initial cloud of ultracold atoms;

[0090] ii) spatially separating the initial cloud into a first cloud of ultracold atoms in a first internal state and a second cloud of ultracold atoms in a second internal state by forming a first ultracold atom trap and a second ultracold atom trap, respectively, and such that the first cloud, the second cloud and the exit point are aligned along a measurement axis;

[0091] iii) At time T S maintaining the separation of the first trap and the second trap within a certain period of time, and then recombining the traps at the exit point so that the first cloud and the second cloud cover a first linear trajectory and a second linear trajectory parallel to the XY plane from the exit point, respectively;

[0092] - wherein said arrangement of said set of one or more conductive elements of each sensor and said order are further configured so that a track associated with said first elementary sensor and a track associated with said second elementary sensor are parallel to each other, have the same length, are covered simultaneously, and so that said exit directions of said first cloud from said first elementary sensor and said second elementary sensor, respectively, are opposite;

[0093] - the sensor further comprises a detection system adapted to measure at least a first phase of the first elementary sensor and a second phase of the second elementary sensor, wherein the acceleration is determined from the difference between the first phase and the second phase.

[0094] According to an embodiment, the power supply device PSD is further configured to apply a direct current to the waveguide.

[0095] According to one embodiment, the first pair of waveguides and the second pair of waveguides are perpendicular to each other, and the sensor comprises at least two components configured to perform acceleration measurements along two orthogonal axes, respectively.

[0096] According to one embodiment, the atomic chip has a matrix structure, the pixels of which define potential elementary sensors, wherein a set comprises two pixels of the matrix.

[0097] According to one embodiment, the set of first and second elementary sensors have at least one conductive element in common.

[0098] According to another aspect, the present invention relates to an inertial unit comprising at least two accelerometer-type sensors according to the present invention, which are configured to perform acceleration measurements along two orthogonal axes, respectively, wherein the matrix atomic chip also includes pixels configured to perform at least one clock measurement and pixels configured to perform rotational speed measurements along three orthogonal axes.

[0099] According to another aspect, the invention also relates to a method for measuring acceleration using an interferometric ultracold atomic inertial sensor, the interferometric ultracold atomic inertial sensor comprising an atom chip placed in a vacuum chamber, the atom chip comprising an XY plane, referred to as the measurement plane, perpendicular to the Z axis, and comprising at least one set of a first elementary sensor and a second elementary sensor, wherein each elementary sensor comprises:

[0100] o at least one first pair of waveguides parallel to each other and at least one second pair of waveguides parallel to each other and intersecting the first pair;

[0101] ○ A group of one or more conductive elements;

[0102] The method comprises the following steps:

[0103] A. generating an initial cloud of ultracold atoms associated with the first elementary sensor and an initial cloud of ultracold atoms associated with the second elementary sensor, wherein the initial clouds are positioned close to the XY plane of the chip;

[0104] B. Generate a uniform magnetic field;

[0105] C. generating, for each sensor, an initial trapping potential for said initial cloud of ultracold atoms;

[0106] D. for each sensor, initializing a first internal state and a second internal state via a first pulse π / 2;

[0107] E. for each sensor, spatially separating the initial cloud into a first cloud of ultracold atoms in the first internal state and a second cloud of ultracold atoms in the second internal state by forming a first ultracold atom trap and a second ultracold atom trap, respectively, and making the first cloud, the second cloud and the exit point aligned along a measurement axis;

[0108] F. For each sensor, at time T S maintaining the separation of the first trap and the second trap within a certain period of time, and then recombining the traps at the exit point so that the first cloud and the second cloud cover a first linear trajectory and a second linear trajectory parallel to the XY plane from the exit point, respectively;

[0109] Steps B to F are performed by applying a uniform magnetic field and a direct current to the conductive element in a predetermined sequence and applying a microwave signal (I MW ) is applied to the waveguide to perform;

[0110] wherein said arrangement of said set of one or more conductive elements and said predetermined order are further configured such that a track associated with said first elementary sensor and a track associated with said second elementary sensor are parallel to each other, have the same length, are covered simultaneously, and such that said departure directions of said first cloud from said first sensor and said second sensor, respectively, are opposite;

[0111] G. recombining the first internal state and the second internal state by applying a second pulse π / 2 to the ultracold atoms;

[0112] H. Measuring at least a first phase of the first elementary sensor and a second phase of the second elementary sensor, wherein acceleration is determined based on a difference between the first phase and the second phase.

[0113] According to one embodiment, step C comprises applying a direct current to at least one conducting element.

[0114] According to one embodiment, steps E and F involve applying a microwave signal in a pair of waveguides in order to measure acceleration along a measurement axis perpendicular to the waveguides of the pair.

[0115] According to one embodiment, in step E and step F, applying a microwave signal comprises:

[0116] - for the first elementary sensor, applying a frequency ω in one of the waveguides a signal, and in another waveguide a frequency ω is applied b ;

[0117] - for the second sensor, applying a frequency ω in one of the waveguides b signal, and in another waveguide a frequency ω is applied a ;

[0118] Among them, the frequency ω a and ω b is determined according to the resonant frequencies of the first internal state and the second internal state.

[0119] According to one embodiment, step F comprises the sub-step of switching off the microwave signal and the sub-step of applying a direct current to said waveguide.

[0120] The following description presents several embodiments of the device of the invention: these embodiments do not limit the scope of the invention. These embodiments also contain the features essential to the invention as well as additional features associated with the embodiment under consideration. BRIEF DESCRIPTION OF THE DRAWINGS

[0121] The invention will be better understood and other features, objects and advantages of the invention will become apparent throughout the following detailed description, which is provided with reference to the accompanying drawings, which are provided by way of non-limiting examples and in which:

[0122] Figure 1 An example of an atom chip according to the prior art is shown;

[0123] Figure 2 shows the geometry of waveguides and wires and magnetic traps of an atom chip according to the prior art;

[0124] Figure 3 In its lower part b) an example of applying various signals to the wires and the waveguide in order to cover a linear trajectory at two wells in the case of an accelerometer type sensor according to the prior art is shown, and in its upper part a) the positions of the two clouds corresponding to a selected time are shown;

[0125] Figure 4 A first alternative embodiment of a matrix array chip for producing several elementary sensors according to the prior art is shown;

[0126] Figure 4 continued A second alternative embodiment of a matrix array chip for producing several elementary sensors according to the prior art is shown;

[0127] Figure 5 The principle of a sensor according to the invention is shown, the sensor comprising a first elementary sensor shown in part a) and a second elementary sensor shown in part b);

[0128] Figure 6 shows the time sequence of measurements made with two sensors, namely SENA for the upper part a) and SENB for the lower part b);

[0129] Figure 7 An ultracold atom interferometry inertial sensor of the accelerometer type according to the present invention is shown;

[0130] Figure 8 An example of a chip topology comprising two intersecting strips compatible with the creation of a basic sensor according to the invention is shown;

[0131] Fig. 9 Another example of a chip topology including flared wires compatible with the production of a basic sensor according to the present invention is shown;

[0132] Fig.10 An example of an implementation according to the invention for two acceleration measurements along the same axis using two elementary sensors on the same chip is shown. For greater clarity, only one pair of waveguides is shown, namely the waveguides parallel to the Y axis for measuring acceleration along the X axis. DETAILED DESCRIPTION

[0133] The idea of ​​the invention is to use two elementary sensors which are specifically configured to eliminate measurement deviations.

[0134] Formula (1) set forth above corresponds, for example, to a sensor SENA for which the trajectory TR1A is covered by cloud CL1 and the trajectory TR2A is covered by cloud CL2, as in Figure 5 As shown in the upper part a) of FIG. 1A , cloud CL1A leaves from departure point DPA in departure direction S1A (and cloud CL2A leaves from departure point DPA in departure direction S2A). Figure 5 (not shown). Figure 5 a), the departure direction S1A is upward (direction S2A is downward). The abscissas of the endpoints of the trajectory TR1A (cloud CL1A in state |a>) and TR2A (cloud CL2A in state |b>) of the sensor SENA are denoted by x aA and x bA , where Δx A =|x aA –x bA |.

[0135] For an accelerometer, the sign of the phase shift induced by the presence of acceleration during the interferometry phase depends on how the two clouds of atoms cover the two trajectories. The sign of the phase shift depends on the direction in which the two clouds depart from the departure point.

[0136] Consider two cold atom accelerometers SENA and SENB arranged on the same chip, where the traps are separated using a shiftable trapping potential, each cold atom accelerometer is oriented so that it is sensitive to acceleration along the same axis (e.g., the X axis in this example). This means that the straight line DrA on which the trajectories TR1A and TR2A of sensor SENA are based and the straight line DrB on which the trajectories TR1B and TR2B of sensor SENB are based are parallel to each other and parallel to X. The abscissas of the endpoints of the trajectories TR1B (cloud CL1B in state |a>) and TR2B (cloud CL2B in state |b>) of sensor SENB are denoted as x respectively. bB and x aB , where Δx b =|x bB –x aB |(See Figure 5 Part b)).

[0137] Assuming that for sensor SENB, the departure direction S1B of the first cloud CL1B is opposite to the departure direction S1A of the first cloud CL1A of sensor SENA, then S1B=-S1A, that is, in this case, the first cloud CL1B leaves downward. Of course, this condition is also satisfied for the second clouds CL2A and CL2B. Figure 5 The cloud CL1B departing from the departure point DPB towards S1B departs downwards.

[0138] When the direction of travel of the atomic states used in these sensors is reversed, e.g. Figure 5 As shown, each accelerometer will accumulate the same phase shift as the most recent sign difference.

[0139] This result is obtained for trajectories that are parallel to each other, have the same length and are covered simultaneously, and such that the departure directions of clouds CL1A and CL1B are opposite: Δx A =Δx B =Δx.

[0140] Figure 6 The time sequence of measurements made with two sensors (i.e. SENA for the upper part a) and SENB for the lower part b) is shown. After the first pulse π / 2 (duration τ), the two pairs of clouds separate simultaneously from t1 (the start of the Ramsey sequence) and then remain separated for a time Ts and are then recombined. Finally, the second pulse π / 2 ends with a total duration T R By making two measurements simultaneously (one for each sensor), it is possible to eliminate the presence of measurement bias, as explained below.

[0141] set up For Figure 5 The phase accumulated during the interferometric measurement sequence corresponding to part a) of For Figure 5 Part b) corresponds to the phase accumulated during the interferometric measurement sequence. Using formula (1), we have:

[0142]

[0143] Assuming the measurement is subject to bias, then:

[0144]

[0145] in, is the additional phase due to the bias present in any measurement (called "additive" bias).

[0146] If there is a (non-negligible) deviation, then determine eliminate:

[0147]

[0148] Therefore, in order to perform bias-free measurements, two interferometric measurement sequences must be performed simultaneously using two sensors on the same chip.

[0149] The ultracold atom interferometry inertial sensor 10 according to the present invention uses this characteristic and Figure 7 It includes an atomic chip ACh placed in a vacuum chamber, which includes an XY plane perpendicular to the Z axis, and the XY plane is called the measurement plane. The chip includes at least one set of a first basic sensor SENA and a second basic sensor SENB. Each basic sensor includes at least one first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least one second pair of waveguides (CPWY'1, CPWY'2) parallel to each other and intersecting with the first pair. The intersection of the two pairs defines a parallelogram. The atomic chip also includes a set of one or more conductive elements CE1.

[0150] The sensor further comprises an atom generation device ACG configured to generate an initial cloud of ultracold atoms associated with the first elementary sensor SENA and an initial cloud CLB of ultracold atoms associated with the second elementary sensor SENB. The initial cloud is positioned close to said XY plane of the chip. The sensor further comprises a generator GB for generating a uniform magnetic field Bc and a power supply device PSD. The power supply device comprises: at least one microwave generator GMW configured to apply a microwave signal to the waveguide; and at least one direct current generator configured to apply a direct current to the conductive element. The magnetic field generator GB and the power supply device PSD are configured to apply a magnetic field Bc, a direct current and a microwave signal in a predetermined order.

[0151] When each sensor is implemented, the arrangement and predetermined order of the set of one or more conductive elements is configured to perform the various steps described above on the cloud.

[0152] This initially involves: generating an initial trapping potential Vini of said initial cloud of ultracold atoms, then spatially separating the initial cloud into a first cloud of ultracold atoms in a first internal state (CL1A for SENA and CL1B for SNEB) and a second cloud of ultracold atoms in a second internal state (CL2A for SENA and CL2B for SENB), forming a first ultracold atom trap (T1A for SENA and T1B for SENB) and a second ultracold atom trap (T2A for SENA and T2B for SENB), respectively. Furthermore, the first cloud, the second cloud and the exit point are aligned along the measurement axis:

[0153] The departure point DPA for SENA, where CL1A, DPA and CL2A are aligned along the straight line DrA;

[0154] The departure point DPB for SENB, wherein CL1B, DPB and CL2B are aligned along the straight line DrB.

[0155] The departure point DPA for the SENB and the DPB for the SENB are preferably located in the center of a parallelogram which is a rectangle when the pairs are perpendicular (axis Y'=Y).

[0156] like Figure 5 As shown, for each sensor, the first cloud, the second cloud and the exit point are aligned along the measurement axis.

[0157] Then, at time T S The first and second wells are kept separated within the cloud and then recombined at the exit point so that the first cloud and the second cloud cover respectively the first and second linear trajectories parallel to the XY plane from the exit point.

[0158] The arrangement of the group of one or more conductive elements of each sensor and the order for applying a direct current in the conductive element, applying a microwave signal in the waveguide, and applying a magnetic field near the atomic chip Ach are also configured so that the tracks (TR1A and TR2A) associated with the first basic sensor and the tracks (TR1B and TR2B) associated with the second basic sensor are parallel to each other, have the same length, and are covered simultaneously. In addition, the departure directions of the first clouds from the first basic sensor and the second basic sensor, respectively, are opposite. If S1A is the departure direction of CL1A and S2A is the departure direction of CL1B, then S1B=-S1A. The same condition is also satisfied for the second clouds CL2A and CL2B.

[0159] The sensor further comprises a detection system SDET adapted to measure at least a first phase of a first elementary sensor and the second phase of the second elementary sensor The acceleration ac is determined from the difference between the first phase and the second phase (characteristic expressed by formula (3)). Thus, when using the sensor according to the invention, a double simultaneous measurement of the same parameter (phase accumulated during the interferometric measurement sequence) is performed.

[0160] By using the characteristics of the interferometer explained by formulas (2A), (2B) and (3), the acceleration determined in this way is corrected for "additive" deviations that affect each measurement in the same way. This reduction in measurement deviations leads to a reduced measurement uncertainty (i.e. improved sensitivity) for the accelerometer according to the invention, which allows longer inertial navigation times to be obtained.

[0161] Preferably, the first pair of waveguides and the second pair of waveguides are perpendicular to each other. For example, the waveguides of the first pair are parallel to the X axis and the waveguides of the second pair are parallel to the Y'=Y axis. Thus, the set of two accelerometers (SENA and SENB) is able to measure acceleration along two orthogonal axes. They measure either acceleration without bias, depending on the order in which they are applied.

[0162] According to one embodiment, the sensor comprises at least two components respectively configured to measure acceleration along two orthogonal axes. Thus, the measurement of acceleration acx along X without bias is performed by the first component, and the measurement of acy along Y without bias is performed by the second component. Thus, the measurement of acx and acy without bias can be performed simultaneously.

[0163] The sensor according to the invention is compatible with any atomic chip geometry comprising: two pairs of microwave guides for generating "tailored" traps (see prior art), i.e. the generation of trapping potentials, and the selective separation of these traps (as a function of the internal state) along a linear trajectory as described above.

[0164] Therefore, the conductive elements CE1 of the chip can be arranged in different ways. What is important is to generate a trapping potential resulting from the combination of the DC field generated by the conductive element through which the direct current flows, and the microwave field generated by the waveguide through which the microwave signal flows, wherein the trapping potential can be moved in order to create a separation and therefore a linear track.

[0165] For example, the sensor according to the invention is compatible with all chip geometries described in the prior art associated with various solution modes, ie with a specific sequence for applying magnetic field, direct current and microwave field.

[0166] Conductive element geometries have been described for gyroscope applications. These geometries are applicable in this case because they allow the two clouds to separate from the departure point. Accelerometers do not require the well to move along a closed trajectory.

[0167] Typically, according to the prior art, the initial trapping potential is generated by applying a direct current in the conductive element.

[0168] According to one embodiment, these conductive elements are two wires crossing at point C, such as Figure 7 As shown (point CA for SENA and CB for SENB).

[0169] According to another embodiment, the conductive element comprises two intersecting strips W1 and W2, such as Figure 8 Shown and described in document US2022 / 0397397.

[0170] According to another embodiment, the conductive element includes a flared wire W2, such as Fig. 9 As shown and described in document US2022 / 0397396. For the accelerometer according to the present invention, Fig. 9 The additional pairs of waveguides (CPWX1', CPWX2') and (CPWY1', CPWY2'), the second wire W1, and the load wires W1C and W2C shown in FIG. 1 are optional.

[0171] The two wells T1 and T2 are separated by applying a microwave signal to each waveguide.

[0172] According to one embodiment, separation is maintained by keeping the microwave signals on individual waveguides.

[0173] According to another embodiment, once the cloud is separated, the microwave signal applied to the waveguide is replaced by a direct current. This embodiment is described for a gyroscope application in document FR 2306475 (not yet published at the filing date). In this case, the power supply device PSD is also configured to apply a direct current to the waveguide. This replacement allows to reduce the measurement noise.

[0174] The sensor according to the invention is therefore independent of the geometry of the atomic chip and of the method for holding the trap. The chip may assume another geometry of conductive elements associated with waveguides not described in the aforementioned document and of additional waveguides. The implementation of the sensor may use separation / holding methods (sequences) for generating a displaceable trapping potential (i.e., whose minimum value may be displaced) other than those described in the aforementioned document.

[0175] In fact, Fig.10 An example of using two basic sensors on the same chip to achieve two acceleration measurements by shifting each state asymmetrically is shown in Fig.10 is based on Figure 3 The operating principle of the accelerometer shown in . For greater clarity, only one pair of waveguides is shown, namely the waveguides parallel to the Y axis for measuring acceleration along the X axis.

[0176] For each sensor, the potential Vini is generated by two wires for SENA (W1A and W2A) and two wires for SENB (W1B and W2B), through which a direct current flows. The two wires cross at a point set at an equal distance from the two waveguides. In this way, the DC lines of the same sensor (with an external bias field Bc) can be used to create a magnetic trap for manipulating and storing atoms, especially during the interferometry phase.

[0177] The coplanar waveguide allows to selectively move atoms by pushing them according to their current electronic state when a microwave signal (at the right power and frequency) is injected inside.

[0178] Fig.10 Various moments of the interferometry sequence are schematically shown in order to better visualize the shifts induced in the atomic states due to the various DC and microwave currents being injected simultaneously into the two sensors.

[0179] At t=0, the atoms of sensor SENA are in the |a> state and the atoms of sensor SENB are also in the |a> state. The cloud of each of these sensors is prepared under identical conditions so that they will have identical properties (number of atoms, temperature, state, etc.). Each sensor has a cloud of atoms trapped in a magnetic trap created by the two DC wires of the sensor corresponding thereto. The coplanar waveguide is currently closed. The interferometry sequence for each sensor starts simultaneously at t=0 under identical conditions with a pulse of π / 2 (for each sensor) of duration τ and ends at t1, as Figure 6 This pulse places each cloud into a coherent superposition with equal weight for the two states of the interferometer.

[0180] At t1( Fig.10 Part a)) and t2( Fig.10 Between the parts b), the coplanar waveguides of the two sensors are gradually connected, such as Fig.10 In practice, each state needs to selectively move in opposite directions. The subtle difference lies in the frequency used in the waveguide of each sensor.

[0181] In the coplanar waveguide of the sensor SENA (on the left), the tailored microwave frequency ω corresponding to the |a> state a is injected into the waveguide at the positive x position and the trimmed microwave frequency ω corresponding to the |b> state b Injected into the waveguide at a negative x position.

[0182] In the coplanar waveguide of the sensor SENB (right), the trimmed microwave frequency ω corresponding to the |a> state a is injected into the waveguide at the negative x position and the trimmed microwave frequency ω corresponding to the |b> state b Injected into the waveguide at the positive x position.

[0183] Thus, sensor SENA will therefore shift the |b> state to a positive x position and the |a> state to a negative x position, while sensor SENB will shift the |a> state to a positive x position and the |b> state to a negative x position. Thus, the selective displacement of the states occurs asymmetrically between the two sensors, i.e., the departure direction of each type of cloud is opposite for the two sensors.

[0184] After the duration for maintaining separation, Fig.10 At time t3 in (part c), the recombination of the clouds over both sensors is completed by closing all waveguides simultaneously, and a second pulse of π / 2 (one for each sensor) can start.

[0185] Finally, all magnetic fields are turned off to release the atoms, and the atomic population at each sensor is detected to determine and Then by eliminating the measurement bias, according to To calculate the acceleration acx according to X.

[0186] Using a pair of waveguides along X (at Fig.10 (not shown), the acceleration acy along the Y axis is measured according to the same reasoning.

[0187] According to one embodiment, the atomic chip has a matrix structure, whose pixels define underlying elementary sensors, and a set of two sensors (SENA and SENB) comprises two pixels of the matrix. Figure 4 An example of a matrix array chip topology is shown in Figure 4 continued Another example is shown in .

[0188] For the implementation of the invention, two pixels of the matrix are configured to form an assembly for measuring acceleration according to the invention.

[0189] Since various microwave signals are applied to the two sensors SENA and SENB, they cannot have a common waveguide. According to one embodiment, the set of first elementary sensors and second elementary sensors have at least one conductive element in common. According to Figure 4 continued A topology is preferred, where the sensors SENA and SENB are selected in the matrix so as to share the same wire instead of the same waveguide.

[0190] According to another aspect, the present invention relates to an inertial unit, comprising at least two accelerometer-type sensors according to the present invention, which are configured to perform acceleration measurements along two orthogonal axes, respectively, wherein the matrix atomic chip also includes pixels configured to perform at least one clock measurement and pixels configured to perform rotational speed measurements along three orthogonal axes.

[0191] According to another aspect, the invention relates to a method for measuring acceleration using an interferometric ultracold atom sensor 10 according to the invention as described above.

[0192] The method comprises steps A to F for each sensor. In step A, an initial cloud of ultracold atoms associated with a first elementary sensor SENA and an initial cloud CLB of ultracold atoms associated with a second elementary sensor SENB are generated, wherein the initial cloud is positioned close to the XY plane of the chip. In step B, a uniform magnetic field Bc is generated near the chip. Steps A and B may be simultaneous. In step C, an initial trapping potential Vini of the initial cloud of ultracold atoms is generated (for each sensor). Then, for each sensor, in step D, a first internal state and a second internal state are initialized by a first pulse π / 2.

[0193] In step E, for each sensor, the initial cloud is spatially separated into a first cloud of ultracold atoms in a first internal state (CL1A for SENA, CL1B for SENB) and a second cloud of ultracold atoms in a second internal state (CL2A for SNA, CL2B for SNB) by forming a first trap of ultracold atoms (T1A for SENA, T1B for SENB) and a second trap of ultracold atoms (T2A for SNA, T2B for SNB), respectively. For each sensor, the first cloud, the second cloud and the exit point are aligned along the measurement axis.

[0194] For each sensor, at time T S The separation of the first well and the second well is maintained within the chip, and then the wells are recombined at the exit point so that the first cloud and the second cloud cover the first linear track (TR1A for SENA, TR1B for SENB) and the second linear track (TR2A for SNA, TR2B for SNB) from the exit point, respectively. The tracks are parallel to the XY plane of the chip.

[0195] By applying a uniform magnetic field near the chip, applying a current to the conductive element CE1 and transmitting a microwave signal S MW Apply to the waveguide to perform steps B to F.

[0196] In order to be able to measure the same phase with opposite signs, the arrangement and predetermined order of one or more conductive elements of a set of elements are also configured so that the tracks (TR1A and TR2A) associated with the first basic sensor and the tracks (TR1B and TR2B) associated with the second basic sensor are parallel to each other, have the same length, are covered at the same time, and so that the departure directions of the first clouds CL1A and CL1B from the first sensor SENA and the second sensor SENB, respectively (i.e., departure from points DPA and DPB) are opposite.

[0197] Then, in step G, the first internal state and the second internal state are recombined by applying a second pulse π / 2 to the ultracold atoms. In step H, at least a first phase of the first elementary sensor is measured. and the second phase of the second elementary sensor The acceleration is determined based on the difference between the first phase and the second phase.

[0198] According to one embodiment, step C comprises applying a direct current to at least one conducting element.

[0199] According to one embodiment, steps E and F consist of applying a microwave signal in a pair of waveguides so as to measure the acceleration along a measurement axis perpendicular to the waveguide of the pair under consideration.

[0200] According to one embodiment, in step E and step F, applying a microwave signal comprises:

[0201] - For the first elementary sensor SENA, a frequency ω is applied in one of the waveguides a signal, and in another waveguide a frequency ω is applied b ;

[0202] - For the second sensor SENB, a frequency ω is applied in one of the waveguides b signal and applies a frequency ω in another waveguide a .

[0203] Frequencyω a and ω b It is determined according to the resonant frequencies of the first internal state and the second internal state.

[0204] For the sensor SENB, the choice as to which frequency is applied to which waveguide is determined in order to obtain a reversal of the exit direction relative to that of the SNA.

[0205] According to one embodiment, in order to reduce the measurement noise, step F comprises a sub-step of switching off the microwave signal and a sub-step of applying a direct current to the waveguide instead of the microwave signal.

Claims

1. An accelerometer-type interferometric ultracold atomic inertial sensor (10), comprising: - an atom chip (ACh) placed in a vacuum chamber, which includes an XY plane perpendicular to the Z axis, called the measurement plane, and comprises at least one set of a first basic sensor and a second basic sensor (SENA, SENB), wherein each basic sensor comprises: o at least one first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least one second pair of waveguides (CPWY'1, CPWY'2) parallel to each other and intersecting the first pair; ○ A group of one or more conductive elements; an atom generation device (ACG) configured to generate an initial cloud of ultracold atoms associated with said first elementary sensor (SENA) and an initial cloud of ultracold atoms (CLB) associated with said second elementary sensor (SENB), wherein said initial clouds are positioned close to said XY plane of said chip; - a generator (GB) for generating a uniform magnetic field (Bc); - a power supply device (PSD) comprising at least one microwave generator (GMW) and at least one direct current generator (GDC), The power supply device is configured to apply a microwave signal to the waveguide and a direct current to the conductive element; - the magnetic field generator and the power supply device are configured to apply the magnetic field, the direct current and the microwave signal in a predetermined sequence; - wherein when implementing each sensor, the arrangement of the set of one or more conductive elements and the order are configured as: i) generating an initial trapping potential for a defined departure point of said initial cloud of ultracold atoms; ii) spatially separating the initial cloud into a first cloud (CL1A, CL1B) of ultracold atoms in a first internal state and a second cloud (CL2A, CL2B) of ultracold atoms in a second internal state by forming a first ultracold atom trap (T1A, T1B) and a second ultracold atom trap (T2A, T2B), respectively, and such that the first cloud, the second cloud and the exit point are aligned along a measurement axis; iii) At time T S maintaining the separation of the first trap and the second trap within a certain period of time, and then recombining the traps at the exit point so that the first cloud and the second cloud cover a first linear trajectory and a second linear trajectory parallel to the XY plane from the exit point, respectively; - wherein said arrangement of said set of one or more conductive elements of each sensor and said order are also configured so that a track (TR1A, TR2A) associated with said first elementary sensor and a track (TR1B, TR2B) associated with said second elementary sensor are parallel to each other, have the same length, are covered simultaneously, and so that said exit directions of said first cloud from said first elementary sensor and said second elementary sensor, respectively, are opposite; - said sensor further comprises a detection system (SDET) adapted to measure at least a first phase of said first elementary sensor and the second phase of the second basic sensor The acceleration is determined based on the difference between the first phase and the second phase.

2. A sensor according to the preceding claim, wherein: The power supply device PSD is further configured to apply a direct current to the waveguide.

3. A sensor according to any one of the preceding claims, wherein: The first pair of waveguides and the second pair of waveguides are perpendicular to each other, and wherein the sensor includes at least two components configured to perform acceleration measurements along two orthogonal axes, respectively.

4. A sensor according to any one of the preceding claims, wherein: The atomic chip has a matrix structure whose pixels define potential elementary sensors, wherein a set comprises two pixels of the matrix.

5. The sensor according to the preceding claim, wherein The set of the first elementary sensor and the second elementary sensor have at least one conductive element in common.

6. An inertial unit comprising at least two accelerometer-type sensors according to any one of claims 3 to 5, which are configured to perform acceleration measurements along two orthogonal axes respectively, wherein the matrix atomic chip also includes pixels configured to perform at least one clock measurement and pixels configured to perform rotational speed measurements along three orthogonal axes.

7. A method for measuring acceleration using an interferometric ultracold atom inertial sensor (10), the interferometric ultracold atom inertial sensor (10) comprising an atom chip (ACh) placed in a vacuum chamber, the atom chip (ACh) comprising an XY plane perpendicular to the Z axis, referred to as the measurement plane, and comprising at least one set of first and second elementary sensors (SENA, SENB), wherein each elementary sensor comprises: o at least one first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least one second pair of waveguides (CPWY'1, CPWY'2) parallel to each other and intersecting the first pair; ○ A group of one or more conductive elements; The method comprises the following steps: A. generating an initial cloud of ultracold atoms associated with the first elementary sensor (SENA) and an initial cloud of ultracold atoms (CLB) associated with the second elementary sensor (SENB), wherein the initial clouds are positioned close to the XY plane of the chip; B. Generate a uniform magnetic field; C. generating, for each sensor, an initial trapping potential (Vini) for the initial cloud of ultracold atoms; D. for each sensor, initializing a first internal state and a second internal state via a first pulse π / 2; E. for each sensor, spatially separating the initial cloud into a first cloud (CL1A, CL1B) of ultracold atoms in the first internal state and a second cloud (CL2A, CL2B) of ultracold atoms in the second internal state by forming a first ultracold atom trap (T1A, T1B) and a second ultracold atom trap (T2A, T2B), respectively, and making the first cloud, the second cloud and the exit point aligned along the measurement axis; F. For each sensor, at time T S maintaining the separation of the first trap and the second trap within a certain period of time, and then recombining the traps at the exit point so that the first cloud and the second cloud cover a first linear trajectory and a second linear trajectory parallel to the XY plane from the exit point, respectively; Steps B to F are performed by applying a uniform magnetic field and a direct current to the conductive element in a predetermined sequence and applying a microwave signal (I MW ) is applied to the waveguide to perform; wherein said arrangement of said set of one or more conductive elements and said predetermined order are further configured such that a track (TR1A, TR2A) associated with said first elementary sensor and a track (TR1B, TR2B) associated with said second elementary sensor are parallel to each other, have the same length, are covered simultaneously, and such that said departure directions of said first cloud from said first sensor and said second sensor, respectively, are opposite; G. recombining the first internal state and the second internal state by applying a second pulse π / 2 to the ultracold atoms; H. Measure at least the first phase of the first elementary sensor and the second phase of the second basic sensor The acceleration is determined based on the difference between the first phase and the second phase.

8. A method according to the preceding claim, wherein: Step C comprises applying a direct current in at least one conductive element.

9. The method according to any one of claims 7 or 8, wherein: Steps E and F involve applying a microwave signal in a pair of waveguides in order to measure acceleration along a measurement axis perpendicular to the waveguides of the pair.

10. The method according to the preceding claim, wherein: Applying the microwave signal in step E and step F comprises: - for the first elementary sensor, applying a frequency ω in one of the waveguides a signal, and in another waveguide a frequency ω is applied b ; - for the second sensor, applying a frequency ω in one of the waveguides b signal, and in another waveguide a frequency ω is applied a ; Wherein the frequency ω a and ω b is determined according to the resonant frequencies of the first internal state and the second internal state.

11. The method according to any one of claims 6 to 10, wherein: Step F includes the sub-step of cutting off the microwave signal and the sub-step of applying a direct current to the waveguide.

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