Bias-corrected gyrometer-type cold atom sensor

Abstract

The invention relates to an ultracold atom inertial sensor (10) of the gyrometer type comprising: an atomic chip (ACh) comprising at least one set of a first and a second elementary sensor (SENA, SENB), a power supply device (PSD), the magnetic field generator and the power supply device being configured to apply the magnetic field, the direct currents and the microwave signals according to a predetermined sequence, the arrangement of said group of one or more conductive elements of each sensor and said sequence being further configured so that the trajectory (TR1) associated with the first elementary sensor and the trajectory (TR2) associated with the second elementary sensor are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state, the sensor further comprising a detection system (SDET). Figure to be published: figure 8

Description

Title of the invention: Cold atom sensor of the bias-corrected gyrometer type FIELD OF THE INVENTION

[0001] The present invention lies in the field of inertial sensors and more specifically cold atom interferometric inertial sensors integrated on an atomic chip. More particularly, the invention relates to cold atom sensors on an atomic chip of the gyrometer type using microwave fields and, where appropriate, direct currents for the spatial separation and displacement of the two clouds of atoms according to two internal states, used when measuring inertial parameters (typically the rotation speed). STATE OF THE ART

[0002] Generally speaking, inertial sensors are devices for measuring physical parameters related to movement such as accelerations or angular speeds, which, combined with a clock, allow one to locate oneself in space. A device measuring acceleration and rotational speed is called an inertial unit or inertial measurement unit (IMU).

[0003] On-chip cold atom interferometry technology makes it possible to perform this type of inertial measurements, and tends to demonstrate sufficient compactness and performance for its use in embedded fields.

[0004] The operation of the cold atom gyrometer is based on interferometry, and the measurement of the phase difference of the interferometer makes it possible to obtain a rotation measurement.

[0005] A cold atom interferometer interferes two electronic states, called a first internal state 1a> and a second internal state 1b> of an atom, such as rubidium 87, in a Ramsey-type sequence. A Ramsey-type interferometer sequence measures a phase q> accumulated during the implementation of the sequence, from a measurement of at least one population of a chosen state 1a> or 1b> (preferably a measurement of both populations for greater precision).

[0006] To make this interferometer sensitive to rotations, the two states must both travel a closed trajectory including a non-zero area and this in opposite directions for 1a> and 1b>. Thus, a term dependent on the Sagnac effect and therefore on the rotation speed is added to the energy difference between the two states.

[0007] The operating principle of rotation measurement by interferometry is briefly recalled below, based on a clock-type Ramsey sequence, where the phase of the interferometer at the end of the sequence is proportional to the difference energy of the two states of the interferometer.

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

[0009] cpdock =<pa - q> b = ( œ- Wab ) TR

[0010] With:

[0011] - œ0b

[0012] is the phase of the atoms in the la> state, and % that of the atoms in the b> state,

[0013] œ is the pulsation of the local oscillator,

[0014] is the electronic energy of the level la> and is the electronic energy of the level lb>.

[0015] is the pulsation corresponding to the difference in energy between the states la> and lb>, TR is the duration of free evolution (Ramsey time).

[0016] If during this sequence, we make sure that the atoms in state la> and those in state lb> each describe the same closed trajectory containing a non-zero area but traveled in opposite directions, a phase shift term sensitive to rotations according to the normal to this surface appears due to the Sagnac effect: the clock becomes a gyrometer.

[0017] If the trajectory of state la>, describes for example a rectangle whose trajectory is in the clockwise direction, and state lb>, describes the same trajectory but in the counterclockwise direction then this phase shift is given by:

[0018] = [£2z(raAva) + (£2zAra)2 + «-r <!] dt- ^Jo A v6)+ (Dz A rb)2 + a■ rb] dt

[0019] where is the angular velocity around the z axis, and v« (respectively rb and r*) the position and velocity of the atoms in the state la> (respectively state lb>) in the frame of reference fixed to the sensor and an acceleration that the sensor undergoes, directed along the axis of separation of the two states and which can be measured. m is the mass of the atom and h the reduced Planck constant.

[0020] For a trajectory forming a loop where each state returns to its initial position at the end of the sequence, it can be shown that, if a is constant, the terms in a ' r are equal to 0 and that the terms ( A ra) 2 and (£1- A r^)2 cancel out. The phase shift can then be put in the form (in the case where iX is constant during TR);

[0021] p / A a \ h 4mNa / A T = ~rb^vb )dt= ——Tr

[0022] where A is a vector normal to the surface described by the trajectories of the two states and whose norm is equal to the area and N is the number of complete revolutions that each state has traveled.

[0023] The total phase at the output of the interferometer at the end of the sequence is therefore:

[0024] m , ,n _ \TQ) ^tot ^ck>ck + Kot V h )lR

[0025] Knowledge of this phase Ptc,t as well as the other quantities and parameters of formula (1) makes it possible to go back to the rotation speed along the z axis perpendicular to the plane of the trajectory.

[0026] The operating principle of an ultra-cold atom gyrometer based on an atomic chip is recalled below, which makes it possible to generate the clouds of ultra-cold atoms and the trajectories allowing the implementation of the measurement of the rotation speed via the phase as described above.

[0027] Ultracold atoms are defined as atoms whose temperature is less than 400 nanokelvins, preferably 300 nanokelvins. The temperature of thermal ultracold atoms is, for example for Rubidium atoms, between 50 and 400 nanokelvins and preferably between 100 and 300 nanokelvins.

[0028] The principle is to create a trajectory traveled in a counterpropagative manner by two clouds of magnetically trapped atoms. The creation and movement of the magnetic trap along the trajectory are carried out by conductive wires / elements and microwave guides arranged on and in the atomic chip.

[0029] Different topologies of conductive elements and waveguides are known to those skilled in the art.

[0030] A first example is described in the document US2018 / 0352642 illustrated [Fig. 1].

[0031] The surface of the chip defines an XY plane or measurement plane, normal to a Z axis

[0032] The chip 1 comprises means adapted to generate a first atom trap ul cold traps Tl and a second ultracold atom trap T2, a trap for immobilizing a cloud of ultracold atoms 12 in an internal state different from the other trap, at a predetermined distance h from said measuring plane 13. For example, the trap Tl comprises the atoms in the electronic level or state la> (cloud CL1) and the trap T2 comprises atoms in the state lb> (cloud CL2). The levels la> and lb> are spaced by a frequency wab / 2æFor example, in the case of rubidium 87, these are the two hyperfine levels IF=l,mF=-l> and IF=2,mF=l>, spaced by approximately 6.8 GHz.

[0033] These means also make it possible to move the clouds along the trajectory 16 (also called TZ) located in a plane parallel to the measurement plane 13, at a height h from this plane, as illustrated [Fig.l]. These means consist of waveguides and conductive wires.

[0034] The waveguides CPW1 and CPW2 are suitable for the propagation of microwaves at cob and coa pulses. The waveguides are arranged symmetrically with respect to a Y axis of the measurement plane, preferably parallel. The two waveguides CPW1 and CPW2 are connected to at least one microwave frequency voltage or current generator. For example, each of the waveguides is produced by depositing three parallel conductive wires to produce a coplanar waveguide. In other embodiments, other types of waveguides can be used, in particular waveguides whose manufacture is compatible with microfabrication techniques by deposition or etching. For example, a microstrip line can be produced.

[0035] The conductive wires integrated into the chip 1 are adapted to be crossed by direct currents. The conductive wires are distributed into a conductive wire WIz along an axis of symmetry Y perpendicular to X and included in the measurement plane 13, and into a plurality of n conductive wires Wldi, i index varying from 1 to n, parallel to each other and parallel to the axis X, n being at least equal to 2. In the example of [Fig.l] n=3, i.e. three conductive wires Wldl, WId2 and WId3. The wires are arranged so as to define n crossing points Ci (crossing between WIz and Wldi) located on the axis Y, here 3 crossing points Cl, C2, C3.

[0036] Each conductive wire is connected to one or more current and / or voltage generators, themselves connected to a processing unit comprising at least one microprocessor. The voltage and / or current generators make it possible to control both direct currents and alternating currents in the wires. In particular, direct currents are controlled in the conductive wires.

[0037] In the sensor, the atom chip 1 is placed in a vacuum chamber maintained, for example, using an ion pump and preferably comprising magnetic shielding. The sensor comprises a device for generating ultracold atoms which comprises:

[0038] - an atom emitter (dispenser in English), for example produced by a heating filament delivering a rubidium vapor;

[0039] -a primary atom trap (optical and / or magnetic), making it possible to pre-cool and arrange a cloud of ultracold atoms in the vicinity of the chip, to load the magnetic traps T1 and T2 described later with atoms.

[0040] The sensor also comprises a magnetic field source, external to the chip 1. It makes it possible to impose a homogeneous and stationary magnetic field Bc over a thickness at least of the order of a height h above the measurement plane 13. Advantageously, the direction of the homogeneous magnetic field is parallel to the measurement plane.

[0041] In [Fig.l] the dotted trajectory 16 illustrates the trajectory of the ultracold atom clouds 12. This closed trajectory defines an area denoted A. A distance h separates the plane of the trajectory 16 and the measurement plane 13 of the chip. Preferably h is between 500 nm and 1 mm, and preferably between 5 pm and 500 pm.

[0042] [Fig.2] illustrates the geometry of the guides and wires of the atomic chip as well as the Tl and T2 traps. The specific arrangement of the conductive wires and waveguides, combined with the homogeneous magnetic field source, makes it easy to obtain two Tl and T2 traps as illustrated in part a) of [Fig.2]. Each Tl and T2 trap has a non-zero and identical minimum VO value, and an identical curvature, a necessary condition for the sensor to work. Indeed, when a direct current is applied to at least two conductive wires of a crossing point, the minimum potential is located vertically above this crossing point. When microwave power is then sent into the waveguides, the central minimum transforms into two minima on either side of the initial minimum in the direction of the waveguides. If the initial minimum is not located strictly at an equal distance from the two waveguides, the two potential minima created will not have exactly the same value of the minimum VO and the same curvature.

[0043] Part c) of [Fig.2] illustrates the arrangement of the conductive wires defining the initial crossing point C1 and the waveguides (top view). Part b) of [Fig.2] describes the corresponding arrangement of the conductive wires and the waveguides printed on a chip in profile view, in section along the conductive wire Wld1 which crosses the conductive wire WIz along the axis of symmetry Y. The waveguides CPW1 and CPW2 are coplanar waveguides located on a first level N1. The insulating layer 18 advantageously makes it possible to flatten the measurement plane. The material of the electrical insulating layer may be, for example, silicon dioxide, silicon nitride or benzocyclobutene. A conductive material is used for the manufacture of the conductive wires, for example gold, and is deposited on a substrate 15, forming a second level N2. The substrate may be, for example, made of silicon, aluminum nitride or silicon carbide.

[0044] In part a) we see the symmetrical separation of ultracold atoms, specific to the internal state of the ultracold atoms, and more precisely the variations in potentials as a function of the X axis of chip 1.

[0045] Curve "a" shows a potential well corresponding to the association of the homogeneous magnetic field and the field created by two intersecting conductive wires, the wire WIz carried by the current Iz and the wire Wldl carried by the current Idl. This results in a local potential well, initial potential Vini forming an atomic trap T in three dimensions. A cloud of ultracold atoms can be trapped and cooled there.

[0046] Curve "b" schematically shows the potential created by the transmission of microwaves at the cob frequency in the CPW1 waveguide. The field emitted by the passage of microwaves at the cob frequency makes it possible to modify the energy of the ultracold atoms and to move the atoms of internal states lb>. Curve "e" illustrates the potential seen by the internal states lb> due to the contributions of the potentials illustrated by curve "a" and by curve "b". Curve "e" shows a local minimum of potential making it possible to locally trap a cloud of ultracold atoms of internal states lb>.

[0047] Similarly, curve “d” schematically presents the potential created by the transmission of microwaves at frequency coa in the CPW2 waveguide. The field emitted by the passage of microwaves at frequency coa allows the energy of the ultracold atoms to be modified and the atoms of internal states la> to be displaced. Curve "c" illustrates the potential seen by the atoms of internal states la> due to the contributions of the potentials illustrated by curve "a" and by curve "d". Curve "c" shows a local energy minimum allowing a cloud of ultracold atoms of internal states la> to be locally trapped.

[0048] The combination of a DC magnetic trap (created by the direct currents in the wires and the homogeneous field Bc) and a microwave field creates what is called a "dressed" trap. By "dressed" is meant a trap created at least in part by an oscillating microwave, radio-frequency or optical field. Changes in the microwave fields (power, frequency and guide in which they propagate) make it possible to move this dressed trap and therefore to move the atoms. The DC magnetic trap is represented in [Fig.2] by curve a. The microwave field at coa is represented in [Fig.2] by curve d and the microwave field at cob is represented in [Fig.2] by curve b. The dressed trap Tl (combination of curves a and d for the state la> is represented by curve c and the dressed trap T2 (combination of curves a and b) for the state lb> is represented by curve e.

[0049] The ultracold atom clouds of internal states 1a> and 1b> can be separated and trapped symmetrically with respect to the Y symmetry axis by simultaneously imposing the propagation of waves of frequency coa in CPW2 and cob in CPW1. To obtain two traps whose minima are of the same value V0 and whose curvatures are of the same value, it is important that the crossing point Cl is arranged at an equal distance from CPW1 and CPW2, on the Y symmetry axis.

[0050] The frequencies coa and cob are chosen as a function of the frequencies of the states la> and lb> co Oa and œOb.

[0051] [Fig. 3] illustrates the principle of generation of trajectory 16. Part a) of [Fig. 3] schematically presents a sequence of the displacement of each of the clouds of ultracold atoms at characteristic times t1 to t9. Part b) illustrates in a complementary manner a sequence of the different currents applied to the conductive wires, of the powers applied to the waveguides and of the frequencies imposed on the waveguides, for the times corresponding to those of part a).

[0052] In the sequence shown in [Fig.3], the current Iz, not shown, flowing in WIz is stationary, at a constant value. In part b) the values ​​of the currents, powers and frequencies are arbitrary. The ordinate ô frequency corresponds to a variation in frequency expressed in arbitrary units, around an average value of the frequency. The currents flowing through the conductive wires can be between 100 pA and 10 A, and the pulses injected into the waveguides can be between 6.6 GHz and 7 GHz in the case of the use of rubidium atoms.

[0053] In a step AO, there is a phase of preparation of the atoms. A cloud of ultracold atoms 12 is generated, including phases of emission of said atoms, of cooling of said atoms, of initialization of said atoms in at least one internal state la> and of trapping of a cloud of said ultracold atoms in a local minimum of potential, at a distance h from the measurement plane (trap T, curve “a” of [Fig.2] part a)). The height h is different from 0 because the homogeneous magnetic field Bc is non-zero.

[0054] Trapping is carried out by passing direct currents through the wire WIz and through one of the wires Wldi, the intersection point of these two wires defining the starting point (here Cl with Wldl). At the same time, a bias magnetic field Bc parallel to the plane of the atomic chip is applied, which is superimposed on the magnetic field created by the two previous wires. The cloud of atoms is then trapped by the potential Vini vertically above Cl, the intersection of the wires Wlz and Wldl.

[0055] In a step B0 the internal states are initialized by coherently superimposing the ultracold atoms between the states 1a> and 1b> by a first 7T / 2 pulse. This pulse can be produced by a laser, microwave emission, or more generally by a method emitting waves at a suitable transition frequency. The currents Iz and Idi are imposed respectively on the conductive wires WIz and Wldl. The two internal states 1a> and 1b> are coherently and spatially superimposed in line with the crossing point CL.

[0056] In a step C0, a cloud of atoms of internal state 1a> in a trap T1 is spatially separated from a cloud of atoms of internal state 1b> in another trap T2 and the traps are moved in opposite directions along a closed trajectory 16 contained in a plane perpendicular to the measurement axis Z. The cloud of atoms of internal states 1a> is symbolized by a disk of light texture and the cloud of atoms of internal states 1b> is symbolized by a disk of darker texture. This step is carried out in the example of [Fig.3] from ti to t9.

[0057] Between t1 and t2, the microwave power injected into the waveguides CPW1 and CPW2 gradually increases from 0 to its maximum value. A cob pulse is sent into the waveguide CPW1 and a coa pulse is sent into the waveguide CPW2, which makes it possible to separate the two clouds of different internal states on either side of the axis of symmetry Y, by a distance d, up to the positions shown diagrammatically in t2. The ultracold atom trap T described previously at time ti is then transformed into two ultracold atom traps Tl and T2, each trap making it possible to immobilize a cloud of ultracold atoms with internal states different from the other trap (in this case internal states la> in one of the traps, for example Tl, and internal states lb> in the other trap T2, as described in part a) of [Fig.2].

[0058] A crossing point Ci corresponds to the crossing of the wire WIz with the wire Wldi.

[0059] Between t2 and t3, the current Idi is gradually cut off and Id2 is gradually increased to its maximum value (the time interval separating t2 and t3 is typically of the order of 10 ms and can be between 0.1 ms and 100 ms: the two traps T1 and T2 are moved to the right to the positions shown in t3.

[0060] Between t3 and t4 the current Id2 is gradually cut off and Id3 is gradually brought to its maximum value: the two traps are moved to the right to the positions shown in t4.

[0061] Between t4 and t5, the microwave power is gradually cut: the two traps are brought back to the same location on the chip, shown schematically in t5.

[0062] At t5, the pulsations of the two microwave guides are modified: the coa pulsation is imposed in CPW1 and the cob pulsation is imposed in CPW2.

[0063] Between t5 and t6, the power in the two waveguides gradually increases from 0 to its maximum value: the traps are separated in the vertical direction as shown schematically in figure t6.

[0064] Between t6 and t7, the current Id3 is gradually cut off and Id2 is gradually brought to its maximum value: the two traps T1 and T2 are moved to the left to the positions shown diagrammatically in t7.

[0065] Between t7 and t8, the current Id2 is gradually cut off and Idi is gradually brought to its maximum value: the two traps are moved to the left to the positions shown in t8. This operation can be repeated several times with other first conductive wires to increase the area included in the trajectory 16.

[0066] Between t8 and t9, the microwave power in the waveguides is progressively cut off. The two traps T1 and T2 move until they merge into a single trap located at the starting point shown diagrammatically in tb

[0067] Direct currents are thus applied to the two wires corresponding to the initial crossing point Cl, and over time these currents are successively applied to the different crossing points Ci located on the axis of symmetry, while simultaneously applying microwave power to the waveguides.

[0068] During step C0 the direct currents applied to the different wires Wldi vary continuously (increase and decrease) between 0 and a maximum value Idimax (normalized to 1 in [Fig.3]), while the magnetic field Bc and the current Iz remain constant during the sequence. Throughout the sequence A0, B0 and C0 the two traps Tl and T2 remain at altitude h.

[0069] The two traps T1 and T2 move in the direction of "ignition" of the crossing points: from the crossing point Cl to the crossing point Cn. The return is carried out by inverting the microwave frequencies and by lighting the direct currents successively in the wires corresponding to the different crossing points by traveling from Cn to Cl. The traps are thus made to travel the closed trajectory 16.

[0070] In a step DO, the internal states 1a> and 1b> are recombined by applying a second pulse tt / 2 to the ultracold atoms, which transfers the phase difference to the populations of the two atomic levels. Then, the density of atoms in an internal state chosen from at least 1a> and 1b> is measured.

[0071] Finally, in a step E0, the Sagnac phase of the ultracold atoms (phase of the interferometer) is determined and the rotation speed of the sensor along the Z axis is calculated.

[0072] To measure a rotation speed along an axis, it is necessary to generate a trajectory in a plane perpendicular to this axis.

[0073] A second example of chip topology is described in the document US2023 / 0178262 illustrated [Fig.4],

[0074] The atomic chip comprises a first pair of waveguides (CPWX1, CPWX2) parallel in themselves and arranged symmetrically with respect to an axis X and a second pair of waveguides (CPWY' 1, CPWY'2) parallel in themselves and arranged symmetrically with respect to an axis Y', which in this non-limiting example is perpendicular to X and equal to the axis Y. the axis Y' is different from the axis X, the two pairs of guides are sequential and define a parallelogram. The chip also comprises two conductive wires W1 and W2 which cross at point O. When the two wires are crossed by a direct current they generate the potential Vini which has a minimum at point O. The starting cloud CL is thus trapped above point O. For reasons of symmetry, point O is preferably coincident with the center of the parallelogram.

[0075] In this document, trajectories perpendicular to X (TX trajectory) and Y (TY trajectories) are produced. To measure the rotation speed Qx along the X axis, the TX trajectory is generated via the waveguides, the conductive wires and the B0 field. Similarly, to measure the rotation speed Qy' along the Y' axis, a TY' trajectory is generated via the waveguides, the conductive wires and the B0 field.

[0076] The path of the atoms for the realization of the trajectory TX is illustrated [Fig.5]. The Ramsey sequence begins at t0 (direct currents are applied to the two conducting wires W1 and W2 for the generation of Vini). At t1 the clouds are separated, the separation of the two clouds is carried out in the same way as in US document US2018 / 0352642 (application of microwave signals to the guides). At t2 the clouds CL1 and CL2 are “raised” from a height hl to a height h2 by modifying the value of the current flowing in the wires and / or by modifying the value of the field B0. A substantially vertical portion of the trajectory is then covered, over a distance w = h2-hl (see this document for an example of a timing diagram describing the sequence of application of the different signals). Then at t3 the two clouds are brought back onto the X axis still at the height h2 by progressively decreasing until cancellation of the power applied to the waveguides. The other part of the second portion of the trajectory at h2 on the other side of the X axis (t4, t5) is obtained by inverting the values ​​of the microwave frequencies applied to the guides CPWX1 and CPWX2. Then a descent to the height hl at t5 is carried out by returning to the initial values ​​of the currents circulating in the conductive wires and / or to the initial value of the magnetic field. The two clouds finally join at L by cancellation of the microwave power applied to the guides.

[0077] The geometry of the chip of document US2018 / 0352642 can be combined with that of document US2023 / 0178262 by integrating additional wires defining crossing points inside the parallelogram defined by the guides. This produces an interferometric inertial sensor allowing the measurement of the three rotation speeds Qx, Qy and Qz.

[0078] Document US2023 / 0178262 describes the production of an AchMO matrix chip allowing the production of several elementary sensors. [Fig.6] illustrates an example of a 6x6 matrix. The waveguides along 6 axes Xn and along 6 axes Ym form the columns and rows of the matrix (in another geometry described in this document the waveguides form the diagonals). Each pixel (n,m) of the matrix corresponds to a potential elementary sensor. For example the chips in column C1 measure ax, the chips in column C2 measure Qy, the chips in row L1 measure ay and the chips in row L2 measure Qx. As a measurement requires a particular sequence for the coplanar guides, these cannot be shared for two simultaneous measurements of two distinct inertial parameters. Thus the pixels 4 surrounded by a circle are not used.The matrix chip is thus reconfigured according to the needs: the type of measurement desired (ax, ay, Qx, Qy, t), the desired precision (function of the number of chips simultaneously carrying out the measurement), etc. Parallel, redundant and / or complementary measurements are thus carried out on the same matrix chip.

[0079] According to another atomic chip geometry described in document US2022 / 0397396, trajectories are produced along the three axes using additional pairs of waveguides and a flared conductive wire defining a DC plane. Particular sequences of microwave signals are applied to the different pairs, including signals at a frequency coa, a frequency cob and signals including both frequencies, signal noted coa+cob and called the “sum” signal. An effect of the application of a “sum” signal (signal resulting from the sum of a signal at the frequency coa and a signal at the frequency cob) is to push the two clouds away from the side opposite to that where the guide in which this signal circulates is located, for the production of a trajectory for the measurement of a rotation speed along the Z axis (see for example figures 16 to 18 of this document). In this document is also described a passage from a height hl to a height h2 when two guides arranged on either side of the clouds are simultaneously traversed by the “sum” signal, for the creation of trajectories for the measurement of a rotation speed along the X and Y axes (see for example figures 20 and 22 of this document).

[0080] Another chip geometry is described in document US2022 / 0397397, comprising two intersecting conductive strips whose intersection is at least partly included in the parallelogram defined by the two pairs of waveguides. The trajectories are produced by applying a specific sequence of microwave signals in the guides, also using the "repellent" effect of "sum" signals.

[0081] The two preceding chip geometries are also compatible with a matrix architecture.

[0082] To obtain a more precise measurement of a rotation around a certain axis, it is possible to use measurement redundancy (use of several sensors, for example with a sensor matrix architecture such as described previously).

[0083] Thus a sensor based on a matrix chip comprising a plurality of elementary sensors according to the various geometries described above makes it possible to:

[0084] Carry out on a single chip the clock function, the measurement of the acceleration along two orthogonal axes and the measurement of the rotations along three orthogonal axes two by two,

[0085] Duplicate the elementary geometry on the same atomic chip to carry out all the previously mentioned measurements in parallel and implement redundancy between the different measurements.

[0086] However, this solution does not allow the elimination of measurement biases or error correction.

[0087] Every measurement is associated with an uncertainty that results in an error in the measurement. This error can be due to random factors that are unavoidable and cannot be corrected (however, their amplitude can be estimated), but also to systematic factors due to imperfections in the sensor or imperfect measurement conditions. It is this last type of error that is also called bias.

[0088] An aim of the present invention is to remedy the aforementioned drawbacks by proposing an inertial sensor and a measurement method allowing the correction of certain biases, in order to obtain better performance of the sensor. DESCRIPTION OF THE INVENTION

[0089] The present invention relates to an interferometric ultracold atom inertial sensor of the gyrometer type comprising: • an atomic chip placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to a Z axis, and comprising at least one assembly of a first and a second elementary sensor, each elementary sensor comprising: at least a first pair of waveguides parallel to each other and at least a second pair of waveguides parallel to each other and intersecting with the first pair, a group of one or more conductive elements, 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, said initial clouds being located near said XY plane of said chip, a generator of a homogeneous magnetic field, 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 microwave signals to said waveguides and direct currents to said conductive elements, the magnetic field generator and the power supply device being configured to apply the magnetic field, the direct currents and the microwave signals in a predetermined sequence, an arrangement of said group of one or more conductive elements and said sequence being configured, upon implementation of each sensor, to: generate an initial trapping potential of said initial cloud of ultracold atoms, spatially separating the initial cloud into a first cloud of ultracold atoms in a first internal state from a second cloud of ultracold atoms in a second internal state, respectively forming a first and second ultracold atom trap, and moving said traps along a closed trajectory parallel or perpendicular to XY traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud of ultracold atoms, the arrangement of said group of one or more conductive elements of each sensor and said sequence being further configured so that the trajectory associated with the first elementary sensor and the trajectory associated with the second elementary sensor are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state, the sensor further comprising 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, a rotation speed being determined completed from a difference between the first and second phase.

[0090] According to one embodiment, the power supply device is further configured to apply direct currents to said waveguides.

[0091] According to one embodiment, the sensor according to the invention comprises at least three assemblies configured respectively to carry out a rotation measurement along three orthogonal axes.

[0092] According to one embodiment, the atomic chip has a matrix structure whose pixels define potential elementary sensors, a set comprising two pixels of the matrix.

[0093] According to one embodiment, the sets of a first and a second elementary sensor have a pair of waveguides in common or at least one conductive element in common.

[0094] According to another aspect, the invention relates to an inertial unit comprising at least three gyrometer-type sensors according to the invention configured to respectively perform a rotation speed measurement along three orthogonal axes, the atomic matrix chip further comprising pixels configured to perform at least one clock measurement and pixels configured to perform an acceleration measurement along at least two orthogonal axes.

[0095] According to another aspect, the invention relates to a method for measuring a rotation speed by an interferometric ultracold atom inertial sensor comprising an atomic chip placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to a Z axis, and comprising at least one set of a first and a second elementary sensor, each elementary sensor comprising: • at least a first pair of parallel waveguides therein and at least a second pair of waveguides • a group of one or more conductive elements, the method comprising the steps of: 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, said initial clouds being located near said XY plane of said chip, B. Generate a homogeneous magnetic field, C. Generate an initial trapping potential for said initial cloud of ultracold atoms, D. For each sensor initialize a first internal state and a second internal state by a first pulse n / 2 E. For each sensor, spatially separate the initial cloud into a first cloud of ultracold atoms in the first internal state of a second cloud of ultracold atoms in the second internal state, respectively forming a first and second ultracold atom trap, F. For each sensor, move said traps along a closed trajectory parallel or perpendicular to XY traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud of ultracold atoms, • steps B to F are carried out by applying, according to a predetermined sequence, a homogeneous magnetic field, direct currents to said conductive elements and microwave signals to said waveguides, • the arrangement of said group of elements of one or more conductive elements and said predetermined sequence being further configured so that the trajectory associated with the first elementary sensor and the trajectory associated with the second elementary sensor are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state, A. Recombine said first and second internal states by applying to said ultracold atoms a second pulse ji / 2, B. Measure at least a first phase of the first elementary sensor and a second phase of the second elementary sensor, a rotational speed being determined from a difference between the first and second phases.

[0096] According to one embodiment, step C comprises the application of direct currents in at least one conductive element.

[0097] According to one embodiment, step E comprises the application of microwave signals in the first pair of waveguides.

[0098] According to one embodiment, step F comprises the application of microwave signals in at least one waveguide of the second pair.

[0099] According to one embodiment, step F comprises the application of direct currents to certain conductive elements.

[0100] The following description presents several exemplary embodiments of the device of the invention: these examples are not limiting of the scope of the invention. These exemplary embodiments present both the essential characteristics of the invention as well as additional characteristics linked to the embodiments considered.

[0101] The invention will be better understood and other characteristics, aims and advantages thereof will appear during the detailed description which follows and with regard to the appended drawings given as non-limiting examples and in which:

[0102] The [Fig. 1] already cited illustrates a first example of atomic chip topology according to the state of the art.

[0103] The [Fig.2] already cited illustrates the geometry of the guides and wires of the atomic chip as well as the ultracold atom traps and the associated potentials according to the state of the art.

[0104] The [Fig.3] already cited illustrates the principle of trajectory generation. Part a) schematically presents a sequence of the displacement of each of the ultracold atom clouds at characteristic times t1 to t9. Part b) illustrates in a complementary manner a sequence of the different currents applied to the conductive wires, the powers applied to the waveguides and the frequencies imposed on the waveguides, for the times corresponding to those of part a).

[0105] The [Fig.4] already cited illustrates a second example of atomic chip topology according to the state of the art.

[0106] The [Fig.5] already cited illustrates the path of the atoms for the realization of the trajectory illustrated [Fig.4].

[0107] The [Fig.6] already cited illustrates an example of a matrix atomic chip according to the state of the art.

[0108] [Fig.7] illustrates the path of the two trajectories in opposite directions according to the invention through the clouds of atoms.

[0109] [Fig.8] illustrates the ultracold atom interferometric inertial sensor according to the invention.

[0110] [Fig.9] illustrates a first way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Qz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the movement of the clouds takes place with conductive wires.

[0111] [Fig. 10] illustrates a second way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Wz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the movement of the clouds is carried out by applying direct currents to conductive wires.

[0112] [Fig. 11] illustrates a third way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Wz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the movement of the clouds is carried out by applying direct currents to conductive wires.

[0113] [Fig. 12] illustrates a fourth way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Wz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the displacement of the clouds is carried out by applying microwave signals to waveguides.

[0114] [Fig. 13] illustrates a fifth way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Wz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the movement of the clouds takes place by applying microwave signals to waveguides.

[0115] [Fig. 14] illustrates a sixth way of producing two trajectories TZ1 and TZ2 contained in the XY plane (measurement of Wz) traveled in opposite directions by each cloud in an internal state la> or lb>, in which the displacement of the clouds is carried out by applying microwave signals to waveguides. DETAILED DESCRIPTION OF THE INVENTION

[0116] The idea of ​​the invention is to use two elementary sensors configured in a particular way to eliminate measurement bias.

[0117] Formula (1) stated above corresponds to a direction of travel of the cloud of atoms CL1 (and CL2 in the opposite direction) on a trajectory as described previously. For illustration purposes, we consider that the trajectory is a rectangle R traveled in a clockwise direction by CL1 (state la>) and in an anticlockwise direction by CL2 (state lb>) as illustrated [Fig.7] part A.

[0118] For a gyrometer, the sign of the phase shift induced by the presence of a rotation during the interferometry phase depends on the way in which the two clouds of atoms travel the same geometric trajectory. The sign of the phase shift depends on the direction of travel of each of the states relative to the direction of rotation.

[0119] Either everyone goes in the same direction (to the right [Fig.9], to the left [Fig.10]), and then the direction of separation must be reversed. Either one goes to the right, the other to the left, and the direction is the same ([Fig.l 1]).

[0120] Consider two cold atom gyrometers arranged on the same chip with separation / displacement of the traps using a movable trapping potential, each being oriented so that it is sensitive to rotations around the same axis (e.g. the z axis). This means that the two trajectories followed by the clouds are arranged in the same plane. If the direction of travel of the atomic states used on these sensors is opposite, each gyrometer will accumulate the same phase shift to within a difference in sign. By carrying out these two measurements simultaneously, it is possible to eliminate the presence of measurement bias as explained below.

[0121] Thus starting from [Fig.7] part A, if we reverse the directions of propagation of the atoms of each state (i.e. the trajectory of state la> describes the rectangle in the counterclockwise direction, and state lb> describes the same trajectory but in the clockwise direction) as illustrated in [Fig.7] part B, then this phase shift changes sign.

[0122] Let ^tot-si be the phase accumulated during the interferometric sequence corresponding to figure 7 part A and ^tot~S2 the phase accumulated during the interferometric sequence corresponding to [Fig.7] part B. We have by taking formula (1):

[0123] m M (2A)

[0124] = m - m Early IF ^clock ^rot \ <lh fl        r

[0125] en considérant que la mesure est entachée d’un biais, on a:

[0126] =" 1">rr„+^„

[0127]

[0128] With ^bias additional phase due to the bias present in any measurement (so-called “additive” bias).

[0129] If a (non-negligible) bias is present, the determination of ^tot-SX - ^tot^sz allows it to be eliminated:

[0130] )(3) ™rot 2 Y tot_S\. toi_S2

[0131] To perform a measurement that eliminates the bias, two interferometric sequences must be performed in parallel with two sensors on the same chip.

[0132] The ultracold atom interferometric inertial sensor 10 according to the invention uses this property and is illustrated [Fig.8]. It comprises an atom chip ACh placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to the Z axis. The chip comprises at least one set of a first elementary sensor SENA and a second elementary sensor SENB. Each elementary sensor comprises at least a first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least a 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 as illustrated [Fig.4]. The atom chip also comprises a group of one or more IEC conductive elements.

[0133] 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 of ultracold atoms associated with the second elementary sensor SENB. The initial clouds are located near said XY plane of the chip. The sensor also comprises a generator GB of a homogeneous magnetic field Bc and a power supply device PSD. The power supply device comprises at least one microwave generator GMW configured to apply microwave signals to the waveguides and at least one direct current generator configured to apply direct currents to the conductive elements. The magnetic field generator GB and the power supply device PSD being configured to apply the magnetic field Bc, the direct currents and the microwave signals according to a predetermined sequence.

[0134] The arrangement of the group of one or more conductive elements and the predetermined sequence are configured, during the implementation of each sensor, to carry out the different steps described above on the clouds.

[0135] This involves firstly 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 (CL1A for SENA and CL1B for SNEB) in a first internal state of a second cloud of ultracold atoms (CL2A for SENA and CL2B for SENB) in a second internal state, respectively 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).

[0136] Then the traps are moved along a closed trajectory parallel or perpendicular to XY traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud of ultracold atoms.

[0137] The arrangement of the group of one or more conductive elements and the predetermined sequence are further configured so that the trajectory TRIA associated with the first elementary sensor and the trajectory TR2A associated with the second elementary sensor are identical and traveled simultaneously and in reverse directions by the clouds of ultracold atoms associated with the same internal state. This involves applying the principle of the two trajectories traveled in reverse directions illustrated [Fig.7].

[0138] The sensor further comprises a detection system SDET adapted to measure at least a first phase of the first elementary sensor and a second phase Vtotjsz of the second elementary sensor. The rotation speed is determined from a difference between the first and second phases (property expressed with formula (2)). When implementing the sensor according to the invention, a double simultaneous measurement of the same parameter is therefore carried out, the phase accumulated during the interferometric sequence.

[0139] By using the property of the interferometer explained by formulas (2A) (2B) and (3) the rotation speed thus determined is corrected for the so-called "additive" bias which affects each measurement in an identical manner. This reduction in measurement bias leads to a reduced measurement uncertainty of the gyrometer according to the invention, i.e. better sensitivity, which makes it possible to obtain longer inertial navigation times.

[0140] The sensor according to the invention is compatible with any atomic chip geometry comprising the two pairs of microwave guides allowing the generation of so-called dressed traps (see state of the art), i.e. the generation of a trapping potential, and the selective displacement of these traps as a function of the internal states along a closed trajectory.

[0141] Thus the IEC conductive elements of the chip can be arranged in different ways. What matters is the generation of a trapping potential resulting from the combination of the DC fields generated by the conductive elements carrying direct currents and the microwave fields generated by the waveguides carrying microwave signals, this trapping potential being able to be displaced to produce the closed trajectory.

[0142] For example, the sensor according to the invention is compatible with all chip geometries described in the state of the art, associated with the different addressing modes, i.e. with particular sequences of application of the magnetic field, direct currents and microwave fields.

[0143] Typically according to the state of the art:

[0144] The initial trapping potential is generated by applying direct currents in the conductive elements, typically two wires crossing at point O, or two ribbons crossing, or a flared wire...

[0145] The separation of the two traps T1 and T2 is carried out by applying microwave signals to the different waveguides,

[0146] The movement of the traps, carried out by moving the minimum of the trapping potential, is carried out:

[0147] either by applying direct currents to other conductive wires (US2018 / 0352642), to the same wires and / or by application of a different magnetic field (US2023 / 0178262),

[0148] either by applying microwave signals to the guides according to a particular sequence of switching on and off the guides with signals of different frequencies, in association with a particular geometry of conductive elements: flared wire (US2022 / 0397396); two intersecting ribbons (US2022 / 0397397).

[0149] In fact, either the minimum of the DC magnetic field (resulting from the direct current in the wires and the homogeneous magnetic field) is moved, which moves the minimum of the trap resulting from the combination of the DC magnetic field and the MW field (resulting from the passage of microwave signals in the waveguides), or the DC magnetic field is fixed and the MW magnetic field is changed, which moves the trap resulting from the combination of the DC magnetic field and the MW field.

[0150] According to another embodiment, once the clouds have been separated, the microwave signals applied to the waveguides are replaced by direct currents. This embodiment is described for the gyrometer application in document FR2306475 (not yet published on the filing date). The PSD power supply device is in this case further configured to apply direct currents to the waveguides. This replacement makes it possible to reduce the measurement noise.

[0151] The sensor according to the invention is thus independent of the geometry of the atomic chip and of the selective separation / displacement method of the traps used. The chip may have another geometry of conductive elements associated with the waveguides not described in the aforementioned documents, as well as additional waveguides. The implementation of the sensor may use other methods (sequences) of separation / displacement allowing the realization of a displaceable trapping potential (i.e. the minimum of which can be moved) than those described in the documents aforementioned.

[0152] We will now describe non-limiting examples of embodiments of the sensor according to the invention.

[0153] Figures 9 to 16 illustrate different ways of producing two trajectories TRI and TR2 contained in the XY plane (measurement of Qz) traveled in opposite directions by each cloud in an internal state la> or lb>. The position of the different clouds is represented for a series of characteristic times ti to t7: ti starting situation; t2 separation; t3 displacement; t4 recombination; t5 separation (in the opposite direction); t6 displacement; t7 recombination. The color or texture of a guide illustrates its “off” state (no signal applied; black) or “on” state (signal applied; different grays). The direction of the arrow on the trajectories for the last time t7 illustrates the direction of travel of the trajectories for the cloud in the internal state la> (dark gray). Other trajectories in the XY plane and in the other planes (XZ and YZ) can be obtained in a non-limiting manner with the geometries and sequences described in the state of the art.

[0154] Figures 9 to 11 illustrate the case in which the displacement of the traps is carried out by applying direct currents in two crossing points. Figures 12 to 14 illustrate the case in which the displacement of the traps is carried out by a "repellent" effect by applying a "sum" signal to one of the guides of the pair which is not used for separation. For all the figures, the displacement of the traps is carried out horizontally along the X axis and the separation is carried out vertically along Y by applying a microwave field in the guides along X CPWX1 and CPWX2. In these examples we have Y'=Y, the first pair and the second pair of waveguides are perpendicular to each other for each sensor of the set.

[0155] In [Fig.9] the direction of separation of the two states is opposite for the two trajectories (cloud CL1A in the state la> of SENA upwards, cloud CL1B in the state la> of SENB downwards) and each pair of clouds associated with an elementary sensor moves in the same direction, here the right.

[0156] In [Fig. 10] the direction of separation of the two states is opposite for the two trajectories (cloud CL1A in state la> of SENA upwards, cloud CL1B in state la> of SENB downwards) and each pair of clouds associated with an elementary sensor moves in the same direction, here the left.

[0157] In [Fig.l 1] the direction of separation of the two states is identical for the two trajectories (cloud CL1A in the state la> of SENA and cloud CL1B in the state la> of SENB upwards) and the two pairs of clouds associated with the two elementary sensors move in an opposite direction, the left for SENA (clouds CL1A and CL2A) and the right for SENB (clouds CL1B and CL2B).

[0158] In [Fig. 12] the direction of separation of the two states is opposite for the two trajectories (cloud CL1A in the state la> from SENA upwards, cloud CL1B in the state the> of SENB downwards) and each cloud pair associated with an elementary sensor moves in the same direction, here the right. For this a “sum” signal is applied to the guide along Y on the side opposite to the movement, i.e. on the left side.

[0159] In [Fig. 13] the direction of separation of the two states is opposite for the two trajectories (cloud CL1A in the state la> of SENA upwards, cloud CL1B in the state la> of SENB downwards) and each pair of clouds associated with an elementary sensor moves in the same direction, here the left. For this a "sum" signal is applied to the guide along Y on the side opposite to the movement, i.e. on the right side.

[0160] In [Fig. 14] the direction of separation of the two states is identical for the two trajectories (cloud CL1A in the state la> of SENA and cloud CL1B in the state la> of SENB upwards) and the cloud pairs associated with the two elementary sensors move in an opposite direction, left for SENA and right for SEN B. For this a “sum” signal is applied to the guide along Y on the right side for SENA and to the guide along Y on the left side for SENB.

[0161] According to one embodiment, the sensor according to the invention comprises at least three assemblies configured respectively to carry out a rotation measurement along three orthogonal axes. For this, for each assembly, the first pair and the second pair of waveguides are perpendicular to each other. For example, the first assembly is configured to measure Qz with the generation of a trajectory perpendicular to Z, the second assembly is configured to measure Qx with the generation of a trajectory perpendicular to X, and the third assembly is configured to measure Qy with the generation of a trajectory perpendicular to Y (in fact, we have Y'=Y).

[0162] According to one embodiment, the different sets are organized in a matrix. According to one embodiment, the atomic chip of the sensor according to the invention has a matrix structure whose pixels define potential elementary sensors. An assembly according to the invention comprising two sensors SENA and SENB corresponds to two pixels of the matrix.

[0163] The structure of the matrix is ​​for example as described in the state of the art. According to one embodiment it is the arrangement of the pairs of waveguides which defines the columns and the rows of the matrix, as illustrated [Fig.6]. According to another embodiment it is the arrangement of the conductive elements (wires / ribbons / flared wires) which defines the rows and the columns, the pairs of guides being typically along the diagonals of the matrix (see examples in document US2023 / 0178262).

[0164] In order to optimize the measurements, according to one embodiment, the sets of a first and a second elementary sensor have a pair of waveguides in common or at least one conductive element in common. It is thus possible to use a same sequence applied to the guides or to the elements in common to measure the two phases according to the invention.

[0165] Typically in the figures illustrating different examples, we see that for certain configurations the waveguides along X can be common to the two sensors ([Fig. 11] and 14), or the guides along Y can be common ([Fig.9], 10, 11, 12 and 13), which optimizes the matrix arrangement.

[0166] The invention also relates to an inertial unit on an atomic matrix chip comprising at least three gyrometer-type sensors according to the invention configured to respectively perform a rotation speed measurement along three orthogonal axes, the atomic matrix chip further comprising pixels configured to perform at least one clock measurement and pixels configured to perform an acceleration measurement along at least two orthogonal axes.

[0167] According to another aspect, the invention relates to a method for measuring a rotation speed by an interferometric ultracold atom inertial sensor 10 comprising an ACh atomic chip placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to a Z axis, and comprising at least one set of a first and a second elementary sensor (SENA, SENB), each elementary sensor comprising: • at least a first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least a second pair of waveguides (CPWY' 1, CPWY'2) parallel to each other and intersecting with the first pair, • a group of one or more conductive elements,

[0168] The method comprises a first step A consisting of generating an initial cloud of ultracold atoms associated with the first elementary sensor SENA and an initial cloud of ultracold atoms associated with the second elementary sensor SENB, the initial clouds being located near said XY plane of said chip. In a step B a homogeneous magnetic field is generated and in a step C an initial trapping potential Vini of the initial cloud of ultracold atoms is generated.

[0169] Then for each sensor in a step D we initialize the first internal state la> and the second internal state lb> by a first pulse / 2.

[0170] Then for each sensor in a step E the initial cloud is spatially separated into a first cloud (CL1A, CL1B) of atoms in the first internal state from a second cloud (CL2A, CL2B) of ultracold atoms in the second internal state, respectively forming a first ultracold atom trap (T1A, T1B) and a second ultracold atom trap (T2A, T2B).

[0171] Then for each sensor, in a step F, the traps are moved along a closed trajectory parallel or perpendicular to XY, traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud. of ultracold atoms.

[0172] Steps B to F are carried out by applying, according to a predetermined sequence, a homogeneous magnetic field in the vicinity of the chip, direct currents to the conductive elements and microwave signals to the waveguides.

[0173] The arrangement of the group of elements of one or more conductive elements and said predetermined sequence are further configured so that the trajectory TRIA associated with the first elementary sensor and the trajectory TR2A associated with the second elementary sensor are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state.

[0174] In a step G the first and second internal states are recombined by applying a second pulse ji / 2 to the ultracold atoms.

[0175] Finally, in a step H, at least a first phase (Ptot_si of the first elementary sensor and a second phase Vtotjv of the second elementary sensor are measured, the rotation speed being determined from a difference between the first and second phases.

[0176] According to one embodiment, step C comprises the application of direct currents in at least one conductive element.

[0177] According to one embodiment, step E comprises the application of microwave signals in the first pair of waveguides. According to one embodiment, step F comprises the application of microwave signals in at least one waveguide of the second pair.

[0178] According to one embodiment, step F comprises the application of direct currents to certain conductive elements.< / lh>

Claims

Claims

1. Ultra-cold atony inertial sensor (10) of the gyrometer type comprising: • an atomic chip (ACh) placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to a Z axis, and comprising at least one set of a first and a second elementary sensor (SENA, SENB), each elementary sensor comprising: • at least a first pair of waveguides (CPWX1, CPWX2) parallel to each other and at least a second pair of waveguides (CPWY' 1, CPWY'2) parallel to each other and intersecting with 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 the first elementary sensor (SENA) and an initial cloud of ultracold atoms associated with the second elementary sensor (SENB), said initial clouds being located near said XY plane of said chip, • a generator (GB) of a homogeneous 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 being configured to apply microwave signals to said waveguides and direct currents to said conductive elements, • the magnetic field generator and the power supply device being configured to apply the magnetic field, the direct currents and the microwave signals in a predetermined sequence, • an arrangement of said group of one or more conductive elements and said sequence being configured, during the implementation of each sensor, to: i. generate an initial trapping potential (Vini) 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 from a second cloud (CL2A, CL2B) of ultracold atoms in a second internal state, respectively forming a first (T1A, T1B) and second (T2A, T2B) ultracold atom trap, iii. and moving said traps along a closed trajectory parallel or perpendicular to XY traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud of ultracold atoms, • the arrangement of said group of one or more conductive elements of each sensor and said sequence being further configured so that the trajectory (TRI) associated with the first elementary sensor and the trajectory (TR2) associated with the second elementary sensor are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state, • the sensor further comprising a detection system (SDET) adapted to measure at least a first phase (^iot_s2) of the first elementary sensor and a second phase (^iot_s2) of the second elementary sensor, a rotation speed being determined from a difference between the first and the second phase.

2. Sensor according to the preceding claim wherein the power supply device (PSD) is further configured to apply direct currents to said waveguides.

3. Sensor according to one of claims 1 or 2 comprising at least three assemblies configured respectively to carry out a rotation measurement along three orthogonal axes.

4. Sensor according to one of the preceding claims in which the chip atomic presents a matrix structure whose pixels define potential elementary sensors, a set comprising two pixels of the matrix.

5. Sensor according to the preceding claim in which sets of a first and a second elementary sensor have a pair of waveguides in common or at least one conductive element in common.

6. Inertial unit comprising at least three gyrometer-type sensors according to one of claims 4 to 5 configured to respectively perform a rotation speed measurement along three orthogonal axes, the atomic matrix chip further comprising pixels configured to perform at least one clock measurement and pixels configured to perform an acceleration measurement along at least two orthogonal axes.

7. Method for measuring a rotational speed by an interferometric ultracold atom inertial sensor (10) comprising an atom chip (ACh) placed in a vacuum chamber, comprising an XY plane called the measurement plane normal to a Z axis, and comprising at least one set of a first and a second elementary sensor (SENA, SENB), each elementary sensor comprising: • 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, • a group of one or more conductive elements, the method comprising the steps of: A. Generating an initial cloud of ultracold atoms associated with the first elementary sensor (SENA) and an initial cloud of ultracold atoms associated with the second elementary sensor (SENB), said initial clouds being located near said XY plane of said chip, B.Generate a homogeneous magnetic field, C. Generate an initial trapping potential (Vini) of said initial cloud of ultracold atoms, D. For each sensor initialize a first internal state and a second internal state by a first pulse rr / 2. E. For each sensor, spatially separate the initial cloud into a first cloud (CL1A, CL1B) of ultracold atoms in the first internal state from a second cloud (CL2A, CL2B) of ultracold atoms in the second internal state, respectively forming a first (T1A, T1B) and second (T2A, T2B) ultracold atom trap, F. For each sensor, moving said traps along a closed trajectory parallel or perpendicular to XY traveled in one direction by the first cloud of ultracold atoms and in the opposite direction by the second cloud of ultracold atoms, steps B to F being carried out by applying, according to a predetermined sequence, a homogeneous magnetic field, direct currents to said conductive elements and microwave signals (IMW) to said waveguides, the arrangement of said group of elements of one or more conductive elements and said predetermined sequence being further configured so that the trajectory associated with the first elementary sensor (TRIA) and the trajectory associated with the second elementary sensor (TR2A) are identical and traveled simultaneously and in opposite directions by the clouds of ultracold atoms associated with the same internal state, G. Recombine said first and second internal states by applying to said ultracold atoms a second pulse 2, H. Measure at least one first phase of the first elementary sensor and a second phase (^tot_s2) of the second elementary sensor, a rotation speed being determined from a difference between the first and second phases.

8. Method according to the preceding claim in which step C comprises the application of direct currents in at least one conductive element.

9. A method according to one of claims 7 or 8 wherein step E comprises applying microwave signals into the first pair of waveguides.

10. Method according to the preceding claim in which step F comprises applying microwave signals into at least one waveguide of the second pair.

11. Method according to one of claims 7 to 10 in which step F comprises the application of direct currents to certain conductive elements.

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