Two-dimensional magneto-optical trap for a cold-atom manipulation system and 2d trapping method

Abstract

The invention relates to a two-dimensional magneto-optical trap (10) for a cold-atom manipulation system. According to the invention, the 2D magneto-optical trap (10) comprises a reflective optical component (40) comprising a first reflective planar face (41) and a second reflective planar face (42), the first face (41) and the second face (42) being perpendicular to each other and parallel to a longitudinal direction (17), and a laser source (3) configured so as to generate an incident laser beam (30) that propagates in a median plane (48) so as to simultaneously illuminate the first face (41) and the second face (42) of the reflective optical component (40) in order to form a first reflected laser beam (31), a second reflected laser beam (32), and a third reflected laser beam (33) overlapping with the incident laser beam (30) in a two-dimensional trapping zone (2) extending in the longitudinal direction (17).

Description

Two-dimensional magneto-optical trap for cold atom manipulation system and 2D trapping method Technical field

[0001] The present invention relates to the technical field of magneto-optical traps for cold atom manipulation system and cold atom trapping methods.

[0002] Such cold atom traps find applications in an atom manipulation system, for example an atomic interferometer, an atomic clock, a quantum processor or a quantum memory.

[0003] An atom interferometer finds applications in particular in an inertial sensor. This inertial sensor can be used in applications for acceleration measurements along a measurement axis. In particular, an atom interferometer is used in an atomic gradiometer or in a gravimeter to measure the local gravitational acceleration with an accuracy of the order of 1 in 1 billion. Prior art

[0004] For the past twenty years, techniques based on the manipulation of cold atoms have enabled the development of new measuring instruments, such as atomic interferometers or atomic clocks and, more recently, the appearance of quantum processors and quantum memories.

[0005] An atom interferometer combines optical and atomic technologies. More specifically, a cold atom interferometer is a system in which matter waves propagate along spatially separated paths that delimit a closed surface. On the one hand, an atom interferometer comprises an atom source and a cold atom trap configured to generate an atom cloud. On the other hand, the atom interferometer comprises a laser source configured to emit a sequence of interrogating laser pulses intended to interact with the fine structure of atoms by photon transfer. The atoms used are generally alkali atoms, for example rubidium, or alkaline earth atoms.

[0006] An atomic interferometer is sensitive to inertial effects such as accelerations and rotations. Atomic interferometers find applications as very high-precision measuring instruments such as gravimeters, gradiometers, accelerometers, gyroscopes, and electromagnetic field sensors. In particular, a gravimeter works by trapping atoms in a magneto-optical trap, then dropping them to measure their free-fall acceleration using a sequence of three laser pulses to create an atom interferometer. Atom interferometer systems have a sensitivity several orders of magnitude higher than that of conventional mechanical sensors.

[0007] The vast majority of atom manipulation systems use a three-dimensional magneto-optical trap, also called 3D-MOT or MOT3D. A 3D-MOT trap is configured to cool and gather atoms into a cloud of cold atoms. By cold atoms, we mean a cloud of atoms arranged at a point in the coordinate space (0, 0, 0) in an orthonormal frame (X, Y, Z). Cold atoms are, for example, atoms of rubidium (Rb), cesium (Cs), potassium (K) or strontium (Sr). Figure 1 shows an example of a 3D-MOT trap 20. The 3D-MOT trap 20 is installed in an ultra-high vacuum chamber 29 in which a weak vapor of atoms that we wish to trap is maintained. The 3D-MOT 20 magneto-optical trap generally comprises six laser beams 21, 22...26 arranged in pairs of opposite beams along the 3 directions of space and a magnetic field having a specific configuration to trap atoms in the three directions of space.The magnetic field is generated, for example, by means of two pairs of anti-Helmholtz coils 28. The trapping zone 9 of the 3D-MOT trap is located at the intersection of the six laser beams and the point where the magnetic field is zero. In a first capture phase, atoms are introduced into the ultra-high vacuum chamber 29 to be trapped there. When one of the atoms from the atom vapor enters the trapping zone of the 3D-MOT trap, it is attracted and retained in the center of the trap.

[0008] Patent document EP2257765B1 describes a cold atom interferometric system, in which a single laser source is used in combination with a pyramid reflector for capture, 3D trapping and atom interferometry sequence.

[0009] The 3D-MOT trap, however, has several drawbacks, including a slow loading speed. In order to load a significant number of atoms into the trap, a large number of atoms must pass into the trapping area and remain there. This constraint encourages the use of a 3D-MOT trap with a large trapping area of ​​a volume of the order of a few mm 3 a few cm away 3 or to maintain a relatively high atomic pressure in the ultra-high vacuum chamber. However, the residual atomic pressure in the chamber may be high enough to disrupt the subsequent atomic interferometry steps or to degrade the components in the chamber, particularly the optical components.

[0010] In order to maintain the atom pressure in the ultra-high vacuum chamber at a low level, it is known to use a two-dimensional magneto-optical trap, or 2D-MOT or MOT2D trap. Figure 1 shows an atom manipulation system according to the prior art, for example of the cold atom interferometer type comprising a 2D-MOT trap 10 connected to the ultra-high vacuum chamber 29 of the 3D-MOT trap 20 by a connecting tube 27. The 2D-MOT trap 10 makes it possible to confine the atoms in only two directions in another vacuum chamber 19. The 2D-MOT trap 10 produces a collimated and slowed atom jet 8 which is directed towards the trapping zone of the 3D-MOT through the narrow connecting tube 27. This configuration makes it possible to maintain a differential pressure between the vacuum chamber 19 of the 2D-MOT trap 10 and the ultra-high vacuum chamber 29 of the 3D-MOT trap 20.The use of a 2D-MOT trap allows both to load the 3D-MOT trap more efficiently and to limit the residual pressure in the ultra-high vacuum chamber so as to limit the pollution of the experimental chamber of the atomic interferometer, and more generally of the atom manipulation system.

[0011] Various 2D-MOT trap technologies are known. Figure 2 illustrates in particular a 2D-MOT trap 10 according to the prior art. An orthonormal XYZ reference frame is also shown. In a known manner, magnetic coils 18 are arranged and configured to generate a zero magnetic field along a longitudinal direction 17 of the 2D-MOT trap, the longitudinal direction 17 being parallel to the Z axis. The 2D-MOT trap 10 comprises two disjoint plane mirrors 4, 5 arranged respectively in the XZ and YZ planes on two faces of the vacuum chamber 19. One or more incident laser beams 11 propagating in the XZ plane, parallel to the X axis, and, simultaneously, one or more incident laser beams 12 propagating in the transverse YZ plane, parallel to the Y axis. The plane mirror 4, respectively 5, receives one or more incident laser beams 11, respectively 12, under normal incidence and reflects beams 14, respectively 15.Advantageously, the laser beams. incident beams 11, 12 are circularly polarized. A quarter-wave plate 49 is placed in front of each plane mirror 4, 5 so that the reflected beams 14, 15 are also circularly polarized, and the incident beams 11 and reflected beams 14 are of mutually opposite polarization, respectively the incident beams 12 and reflected beams 15 are of mutually opposite polarization. The incident beams 11 and reflected beams 14 are superimposed in the XZ plane and the incident beams 12 and reflected beams 15 are superimposed in the YZ plane. The 2D-M0T trap makes it possible to confine the atoms in a trapping zone 2 at the intersection of the laser beams 11, 12, 14 and 15 along two directions in space. The trapping zone 2 extends in a longitudinal direction 17. Another laser beam 13, parallel to the longitudinal direction 17 and transverse to the 2D confinement, makes it possible to push the atoms to generate the atom jet 8 through the connecting tube 27.Such a 2D-M0T trap generally uses three laser beams 11 and 12 in the two confinement directions X and Y and another laser beam 13 in the thrust direction parallel to the Z axis.

[0012] The publication JR Kellogg et al. (“A compact high-efficiency cold atom beam source”, Appl. Phys. B pp. 109:61-64, 2012, DOI 10.1007 / s00340-012-5220-5) discloses a pusher-free 2D-MOT trap based on the use of two laser beams incident in the two confinement directions of the 2D-MOT trap and inclined with respect to the longitudinal direction of the 2D-MOT trap to generate by reflection on two retroreflecting quarter-wave plates a 2D confinement and simultaneously a push along the longitudinal direction.

[0013] US patent document 2017 / 0359888 discloses a 2D-MOT trap based on the use of a single laser beam and a diffraction grating arranged inside the vacuum chamber. However, rubidium atoms are likely to deposit on or damage the surface relief of the diffraction grating and damage it.

[0014] The architecture of prior art 2D-MOT traps is generally complex, bulky and requires very precise optical alignment of many optical components and / or multiple laser beams.

[0015] It is desirable to reduce the footprint of a 2D-MOT trap and to simplify the adjustments of the laser beams and optical components of a 2D-MOT trap, without reducing the throughput of the atom jet. Statement of the invention

[0016] To this end, the invention relates to a two-dimensional magneto-optical trap for a cold atom manipulation system, the two-dimensional magneto-optical trap comprising a vacuum chamber capable of receiving a vapor of alkali or alkaline-earth atoms, means for generating a magnetic field, a laser source and a reflective optical component.

[0017] According to the invention, the reflective optical component comprises a plurality of reflective planar faces, each reflective planar face of the plurality of reflective planar faces being parallel to a longitudinal direction of the two-dimensional magneto-optical trap, the plurality of reflective planar faces being integral with each other and forming a concave surface, the plurality of reflective planar faces comprising a first reflective planar face and a second reflective planar face, the first face being arranged so as to form an angle of 90 ± 5 degrees with the second face, the laser source being configured so as to generate a circularly polarized incident laser beam propagating in a median plane relative to the first face and the second face,the incident laser beam being of suitable dimensions and oriented so as to simultaneously illuminate the first face and the second face of the reflective optical component to form a first reflected laser beam and a second reflected laser beam propagating in mutually opposite directions in a plane transverse to the median plane, and to form a third reflected laser beam propagating in the opposite direction to the incident laser beam in the median plane so that the incident laser beam, the first reflected laser beam, the second reflected laser beam and the third reflected laser beam overlap in a two-dimensional trapping zone extending in the longitudinal direction of the two-dimensional magneto-optical trap.,

[0018] According to a first embodiment, the first face and the second face are contiguous, the second face being capable of reflecting the first reflected laser beam and respectively the first face being capable of reflecting the second reflected laser beam, so as to form the third reflected beam.

[0019] According to a second embodiment, the plurality of reflective planar faces comprises a third face, the third face being disposed between the first face and the second face, the third face being arranged perpendicular to said median plane, a quarter-wave plate being arranged on or in front of the third face, the incident laser beam being oriented so as to illuminate the third face of the reflective optical component through the quarter-wave plate to form the third reflected laser beam.

[0020] According to a particular and advantageous aspect, the incident laser beam is inclined at an angle equal to or between 70 and 90 degrees, and preferably between 80 and 90 degrees, relative to the longitudinal direction of the two-dimensional magneto-optical trap.

[0021] Alternatively, the incident laser beam is perpendicular to the longitudinal direction of the two-dimensional magneto-optical trap, the magneto-optical trap comprising a beam splitter device arranged to receive a source beam from the laser source and to form the incident laser beam and a pusher laser beam separated from the incident laser beam, the pusher laser beam being oriented parallel to the longitudinal direction of the two-dimensional magneto-optical trap.

[0022] Advantageously, the incident laser beam has an elliptical section having a major axis oriented along the longitudinal direction of the two-dimensional magneto-optical trap.

[0023] According to a particular and advantageous aspect, the two-dimensional magneto-optical trap comprises a beam splitter arranged between the laser source and the reflector optical component, the beam splitter being arranged to form the incident laser beam and another incident laser beam parallel to the incident laser beam, the other incident laser beam propagating in the median plane, the other incident laser beam being of suitable dimensions and oriented so as to simultaneously illuminate the first face and the second face of the reflector optical component to form another first reflected laser beam and another second reflected laser beam, so that the other first reflected laser beam overlaps with the other second reflected laser beam in the two-dimensional trapping zone.

[0024] The invention also relates to a system for manipulating cold atoms of the atomic interferometer, atomic clock, quantum processor or memory type. quantum, the cold atom manipulation system comprising a two-dimensional magneto-optical trap according to any of the described embodiments.

[0025] In particular, the present disclosure relates to a gravimeter comprising such a cold atom manipulation system, a connecting device connecting the two-dimensional magneto-optical trap to an ultra-high vacuum chamber of said cold atom manipulation system so as to inject into the ultra-high vacuum chamber a jet of atoms emitted in the longitudinal direction of the two-dimensional magneto-optical trap.

[0026] The invention also relates to a two-dimensional magneto-optical trapping method comprising the following steps: arranging a reflective optical component in a vacuum chamber, the reflective optical component comprising a plurality of reflective planar faces, each reflective planar face of the plurality of reflective planar faces being parallel to a longitudinal direction of the two-dimensional magneto-optical trap, the plurality of reflective planar faces being integral with each other and forming a concave surface, the plurality of reflective planar faces comprising a first face and a second face, the first face being arranged so as to form an angle of 90 ± 5 degrees with the second face; receiving a vapor of alkali or alkaline-earth atoms in the vacuum chamber;generating a magnetic field in the vacuum chamber and generating a circularly polarized incident laser beam propagating in a median plane relative to the first face and the second face, the incident laser beam being of suitable dimensions and oriented so as to simultaneously illuminate the first face and the second face of the reflective optical component, to form a first reflected laser beam and a second reflected laser beam propagating in mutually opposite directions in a plane transverse to the median plane, and to form a third reflected laser beam propagating in the opposite direction to the incident laser beam in the median plane so that the incident laser beam, the first reflected laser beam, the second reflected laser beam and the third reflected laser beam are superimposed in a two-dimensional trapping zone extending in the longitudinal direction of the two-dimensional magneto-optical trap.;

[0027] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Brief description of the drawings

[0028] In addition, various other characteristics of the invention emerge from the appended description given with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0029] Figure 1 schematically represents a prior art atom manipulation system comprising a 3D-MOT trap connected to a 2D-MOT trap;

[0030] Figure 2 schematically represents a 2D-MOT trap of the prior art, respectively in a perspective view, top left, along a transverse section, top right, and along a longitudinal section, bottom,

[0031] Figure 3 schematically represents a 2D-MOT trap according to a first embodiment, respectively in a perspective view, top left, along a transverse section, top right, and along a longitudinal section, bottom,

[0032] Figure 4 schematically represents a 2D-MOT trap according to a second embodiment respectively in a perspective view, top left, along a transverse section, top right, and along a longitudinal section, bottom;

[0033] Figure 5 illustrates another example of operation of a 2D-MOT trap according to any one of the embodiments, respectively in a perspective view, at the top, and along a longitudinal section, at the bottom;

[0034] Figure 6 schematically represents an atom interferometer system in an application to a gravimeter, and comprising a 2D-MOT trap according to the present disclosure.

[0035] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references. Detailed description

[0036] According to the present disclosure, the 2D-MOT trap 10 comprises a single reflector optical component 40 and uses a limited number of incident laser beam(s) propagating in a single plane which contains the longitudinal direction 17 of the 2D-MOT trap.

[0037] More specifically, the reflective optical component 40 comprises a plurality of reflective planar faces, each reflective planar face of the plurality of reflective planar faces being parallel to a longitudinal direction 17 of the two-dimensional magneto-optical trap. In the present disclosure, the term “plurality of reflective planar faces” means two or three reflective planar faces. The different reflective planar faces of the reflective optical component 40 are integral with each other and form a reflective concave surface. Advantageously, the plurality of reflective planar faces advantageously form a continuous reflective surface.

[0038] The reflector optical component 40 can be arranged inside the vacuum chamber 19. Such an arrangement makes it possible to increase the compactness of the 2D-MOT trap and to obtain very good optical quality by limiting shadows. Advantageously, a single porthole on a lateral face of the vacuum chamber 19 is sufficient to couple the incident laser beam. In the case where an axial push laser beam is used, an axial porthole is added. However, this arrangement has disadvantages such as a limited trapping volume and difficulties in changing the reflector.

[0039] Alternatively, the optical reflector component 40 may be arranged outside the vacuum chamber 19, the vacuum chamber being arranged inside the concave surface. Such an arrangement makes it possible to reduce the number of vacuum parts, to increase the trapping volume for an identical vacuum volume and to change the reflector more easily. However, this arrangement has disadvantages such as lower optical quality or greater difficulty in assembly. In addition, this arrangement requires more openings and seals, which implies a risk of leaks in the vacuum enclosure.

[0040] According to another aspect of the present disclosure, one or more incident laser beams are used simultaneously on the different reflective plane faces of the reflective optical component 40, the direction of propagation of these incident laser beams being arranged in a single plane containing the longitudinal direction 17 of the two-dimensional magneto-optical trap.

[0041] In the various embodiments, the magnetic field of the 2D-M0T trap 10 is generated in a conventional manner, for example by means of pairs of anti-Helmholtz coils 18 arranged on the opposite faces of the vacuum chamber 19.

[0042] Figure 3 schematically represents a 2D-MOT trap 10 according to a first embodiment. In the first embodiment, the reflective optical component 40 comprises two reflective planar faces: a first reflective planar face 41 (hereinafter first face 41) and a second reflective planar face 42 (hereinafter second face 42). We note the straight line 44 normal to the first face 41, and, respectively, the straight line 45 normal to the second face 42. The straight line 44 forms a right angle with the straight line 45. In other words, the first face 41 and the second face 42 are arranged perpendicular to each other and form a dihedral angle of 90 ± 5 degrees, and preferably of 90 ± 1 degrees. The first face 41 and the second face 42 are for example machined from a solid material and form a single-piece component.Alternatively, the first face 41 and the second face 42 are formed by the integral assembly of two reflecting plates or two prisms for example. The intersection line 47 between the plane of the first face 41 and the plane of the second face 42 is also called the edge of the dihedron formed by the first face 41 and the second face 42. The edge 47 of the dihedron is here parallel to the Z axis and parallel to the longitudinal direction 17 of the 2D-MOT trap 10. In the first embodiment, the first face 41 and the second face 42 are contiguous along the edge 47 of the dihedron.

[0043] A laser source 3 generates an incident laser beam 30. The incident laser beam 30 is circularly polarized. In a known manner, for example, a quarter-wave plate is used to transform a laser beam from linear polarization to circular polarization.

[0044] As illustrated in Figure 3, the incident laser beam 30 is sized and oriented so as to simultaneously illuminate the first face 41 and the second face 42 of the optical reflector component 40. More precisely, the direction of propagation of the incident laser beam 30 is located in the median plane 48 between the first flat face 41 and the second face 42, this median plane 48 passing through the edge 47 of the dihedron. The incident laser beam 30 is inclined by approximately 45 degrees relative to the straight line 44 normal to the first face 41 which forms a first reflected laser beam 31 oriented perpendicular to the incident laser beam 30. Similarly, the incident laser beam 30 is inclined by approximately 45 degrees relative to the straight line 45 normal to the second face 42 which forms a second reflected laser beam 32 oriented perpendicular to the incident laser beam 30. The first reflected laser beam 31 and the second reflected laser beam 32 propagate in opposite directions to each other in a YZ plane transverse to the median plane 48.

[0045] The first reflected laser beam 31 and respectively the second reflected laser beam 32 are again reflected by the second face 42 and respectively by the first face 41 and combine to form a third reflected beam 33. The incident laser beam 30 and the third reflected beam 33 propagate in opposite directions to each other in the median plane 48 parallel to the XZ plane.

[0046] Two pairs of opposite beams are thus obtained: on the one hand, the first reflected laser beam 31 and the second reflected laser beam 32, and, on the other hand, the incident laser beam 30 and the third reflected beam 33. The incident laser beam 30, the first reflected laser beam 31, the second reflected laser beam 32 and the third reflected beam 33 are superimposed, spatially and temporally, in a two-dimensional trapping zone 2 extending in the longitudinal direction 17 of the two-dimensional magneto-optical trap 10. The longitudinal direction 17 is parallel to the Z axis.

[0047] In the first embodiment, the contiguous arrangement of the first face 41 and the second face 42 of the optical reflector component 40 makes it possible to reflect the entire incident laser beam 30 with virtually no optical losses and thus to improve the efficiency of the two-dimensional magneto-optical trap.

[0048] The first embodiment thus makes it possible to form a two-dimensional magneto-optical trap 10 by using a single incident laser beam 30 on a single reflector optical component 40. This embodiment has the advantage of dispensing with the use of a quarter-wave plate on the reflector optical component 40.

[0049] Figure 4 schematically represents a 2D-MOT trap 10 according to a second embodiment. In the second embodiment, the reflective optical component 40 comprises three reflective planar faces, a third planar face 43 reflecting (hereinafter third face 43) being arranged between the first reflecting plane face 41 and the second reflecting plane face 42. The third face 43 is arranged perpendicular to the median plane 48 relating to the first face 41 and the second face 42.

[0050] In the second embodiment, the third face 43 is contiguous with the first face 41 and with the second face 42. A quarter-wave plate 49 is arranged on or in front of the third reflective face 43. Alternatively, the third face 43 consists of a retroreflective quarter-wave plate 49. The third face 43 forms an angle of 135 degrees with the first face 41 and an angle of 135 degrees with the second face 42. In other words, the straight line 46 normal to the third face 43 forms an angle of 45 degrees with the straight line 44 normal to the first face 41 and with the straight line 45 normal to the second face 42. The straight line of intersection 47 between the plane of the first face 41 and the plane of the second face 42 is here also parallel to the Z axis and parallel to the longitudinal direction 17 of the 2D-MOT trap 10.

[0051] The incident laser beam 30, propagating in the median plane 48, simultaneously illuminates the first face 41, the second face 42 and the third face 43 of the optical reflector component 40. The third face 43 receives a portion of the incident laser beam 30 and reflects it so as to form the third reflected laser beam 33. The third reflected laser beam 33 passes twice through the quarter-wave plate 49 located on or in front of the third face 43.

[0052] Two pairs of opposite beams are thus obtained: on the one hand, the first reflected laser beam 31 and the second reflected laser beam 32 propagating in a YZ plane, and, on the other hand, the incident laser beam 30 and the third reflected beam 33 propagating in the median plane 48 parallel to the XZ plane. The incident laser beam 30, the first reflected laser beam 31, the second reflected laser beam 32 and the third reflected laser beam 33 overlap, spatially and temporally, in the two-dimensional trapping zone 2 which extends along the longitudinal direction 17.

[0053] In the second embodiment, the contiguous arrangement of the first face 41, the second face 42 and the third face 43 of the optical reflector component 40 also makes it possible to reflect the entire incident laser beam 30 with virtually no optical losses and thus to improve the efficiency of the two-dimensional magneto-optical trap.

[0054] The second embodiment thus makes it possible to form a two-dimensional magneto-optical trap 10 using a single incident laser beam 30 on a single reflector optical component 40. The second embodiment allows more flexibility in the geometry at the expense of a more complex reflector optical component 40 with a quarter-wave plate.

[0055] In any of the embodiments, the incident laser beam 30 is for example a laser beam with a Gaussian profile or a top-hat-shaped profile. A single incident laser beam of dimensions adapted to the optical reflector component 40 is thus sufficient to produce a 2D-MOT trap.

[0056] According to a particular and advantageous aspect, illustrated for example in FIG. 5, the incident laser beam 30 has an elongated cross-section along the longitudinal direction 17 of the two-dimensional magneto-optical trap 10. For example, the cross-section of the incident laser beam 30 is elliptical, the major axis of the ellipse being oriented along the longitudinal direction 17. For example, a prism is used to spatially spread the incident laser beam 30. The spreading of the incident laser beam 30 along the longitudinal direction 17 makes it possible to illuminate a large surface of the plurality of planar faces 41, 42, where appropriate 43, in the longitudinal direction 17 of the 2D-MOT trap 10.

[0057] In a complementary or alternative manner, as illustrated in FIG. 3 or 4, a beam splitter 6 is arranged between the laser source 3 and the reflector optical component 40. The beam splitter 6 is configured to separate the source beam 35 from the laser source 3 into several incident laser beams. The beam splitter 6 may be fiber optic or made up of free-space optical components. In a known manner, the beam splitter 6 is adapted to separate the source beam into two incident laser beams or more generally into N incident laser beams, where N is a natural whole number greater than or equal to two. By way of non-limiting example, the beam splitter 6 separates the source beam 35 into an incident laser beam 30 and at least one other incident laser beam 301 and / or 302. Advantageously, the beam splitter is configured to form at least two other incident laser beams parallel to the incident laser beam.The propagation directions of the incident laser beams 30, 301, 302 are all parallel to the median plane 48 relative to the first face. 41 and the second face 42. The incident laser beams 30, 301, 302 are laterally offset relative to each other in the longitudinal direction 17. The plurality of incident laser beams 30, 301, 302 makes it possible to illuminate a larger surface of the first face 41 and the second face 42 in the longitudinal direction 17 of the 2D-M0T trap 10.

[0058] According to a particular and advantageous aspect, illustrated for example in Figures 3 and 4, the incident laser beam(s) 30, 301, 302 are not perpendicular but inclined relative to the longitudinal direction 17 of the two-dimensional magneto-optical trap 10. For example, the angle between the direction of the incident laser beam(s) 30, 301, 302 and the longitudinal direction 17 is for example between 70 degrees and 90 degrees, including equal to 70 degrees or 90 degrees, and preferably between 80 and 90 degrees. The inclination of the incident laser beam(s) 30, 301, 302 relative to the longitudinal direction 17 makes it possible to perform an axial thrust on the atoms located in the trapping zone 2 of the 2D-MOT trap. The inclination of the incident laser beam(s) 30, 301, 302 makes it possible to adjust the speed of the atoms of the atom jet 8 at the exit of the 2D-MOT trap.The speed of atoms in atom jet 8 is between 1 m / s and 50 m / s, for example 10 m / s, 20 m / s, 30 m / s or 40 m / s.

[0059] Alternatively, as illustrated for example in Figure 5, the incident laser beam 30 is perpendicular to the longitudinal direction 17 of the two-dimensional magneto-optical trap 10. In this case, a beam splitter 7 is arranged between the laser source 3 and the reflector optical component 40. The beam splitter 7 is configured to spatially separate the source beam 35 from the laser source 3 into an incident laser beam 30 and a pusher laser beam 34. The incident laser beam 30 propagates in the median plane 48 of the faces 41, 42 perpendicular to the longitudinal direction 17. The pusher laser beam 34 is oriented along the longitudinal direction 17 of the two-dimensional magneto-optical trap. The pusher laser beam 34 makes it possible to apply a thrust to the atoms to generate the atom jet 8 intended to be injected through the connecting tube 27.The beam splitter 7 can be arranged outside or inside the vacuum chamber 19. In an exemplary embodiment, the beam splitter 7 comprises a reflector inclined at 45 degrees relative to the longitudinal direction 17 and perpendicular to the median plane, this reflector. able to be attached to the reflector optical component 40, the reflector being adapted to inject a portion of the laser beam in the longitudinal direction 17.

[0060] As a variant of Figure 5, the incident laser beam is divided into several incident laser beams 30, 301, 302 perpendicular to the longitudinal direction 17 of the two-dimensional magneto-optical trap 10 and a pusher laser beam 34 is oriented along the longitudinal direction 17 of the two-dimensional magneto-optical trap. Adjusting the intensity of the pusher laser beam 34 makes it possible to adjust the speed of the atoms of the atom jet 8 at the outlet of the 2D-MOT trap.

[0061] In the second embodiment, a quarter-wave plate 49 at the wavelength of the incident laser beam 30 is arranged on or in front of the third face 43 of the reflector optical component 40. The incident laser beam 30 is circularly polarized. The incident laser beam 30 illuminates the third face 43 of the reflector optical component 40, so that the third reflected beam 33 is circularly polarized.

[0062] The 2D-MOT trap 10 of the present disclosure offers by construction a great robustness, due to the absence of opto-mechanical adjustment between the reflective planar faces 41, 42, possibly 43, of the optical reflector component 40. The optical reflector component 40 makes it possible to generate reflected beams 31, 32 that are perfectly symmetrical, synchronized and of the same intensity. The optical reflector component 40 has a great opto-mechanical stability which avoids a misalignment between the reflected beams 31, 32. It follows that the optical reflector component 40 makes it possible to limit the fluctuations in relative intensity between the reflected beams compared with an optical device comprising several separate reflectors and several laser sources. This absence of opto-mechanical adjustments makes it possible to arrange the optical reflector component 40 inside the vacuum chamber 19 of the 2D-MOT trap 10.The vacuum chamber 19 requires only one side window to allow the incident laser beam 30 to pass through, unlike prior art 2D-MOT traps which require at least two transversely arranged side windows to allow the incident laser beams to pass through. Reducing the number of windows simplifies assembly and reduces the risk of vacuum leaks. The flat, reflective faces. retain their reflective properties when exposed to atomic vapor unlike a diffraction grating.

[0063] In addition, the number of incident laser beams is greatly reduced compared to the 2D-MOT traps of the prior art. The incident laser beam(s) all propagate in a single plane, the median plane relative to the first face 41 and the second face 42. This configuration simplifies the optomechanical adjustments and reduces the size of the 2D-MOT trap. Indeed, a laser source generating a single laser beam inclined relative to the longitudinal direction of the reflector optical component 40 is sufficient to confine the atoms in a two-dimensional zone of the 2D-MOT part and to apply a longitudinal thrust on the trapped atoms so as to form a jet of atoms 8. The number of collimators and optical fibers between the laser source and the 2D-MOT trap can be reduced by a factor of 3 compared to a conventional configuration.According to different variants, the incident laser beam can be spatially spread or spatially divided along the longitudinal direction of the reflector optical component 40. Alternatively, the source laser beam is divided into one or more beams perpendicular to the longitudinal direction of the reflector optical component 40 to form the two-dimensional trap and a pusher laser beam 34 oriented along the longitudinal direction 17 of the two-dimensional magneto-optical trap to push the atoms.

[0064] Due to the limited number of settings and the limited number of laser beams, the 2D-MOT trap 10 has a reduced footprint. In an exemplary embodiment, the 2D-MOT trap 10 has a length L of between approximately 40 mm and 20 cm in the longitudinal direction 17, and a width W of approximately 30 mm to 10 cm in the transverse direction. The volume of the trapping zone 2 is reduced by approximately a factor of 2 compared to the 2D-MOT traps of the prior art. The 2D-MOT trap of the present disclosure has advantages in terms of compactness, proximity to the MOT3D, and optomechanical robustness.

[0065] The 2D-MOT trap of the present disclosure finds applications for injecting a jet of atoms into the 3D-MOT trap of an atom manipulation system, for example a cold atom interferometer. The compactness of the 2D-MOT trap 10 makes it possible to install the 2D-MOT trap 10 as close as possible to the trapping zone of the MOT3D and the ultra-high vacuum chamber 29 of the atom manipulation system. The compactness of the trap 2D-M0T 10 also limits the loss of atoms during their journey between their exit from the 2D-MOT and the trapping zone of the MOT3D. The atom vapor is generated directly in the vacuum chamber 19 of the 2D-MOT trap. The flow rate of the atom jet 8 at the exit of the 2D-MOT 10 trap is here between 10 7 and 10 11 atoms per second, for example between 10 5 and 10 9 atoms per second.

[0066] A 2D-MOT atom trap according to the present disclosure finds applications in an atom interferometer, which can be used as an inertial sensor. This inertial sensor can be used in applications for acceleration measurements along a measurement axis. In particular, an atom interferometer is used in an atomic gradiometer or in a gravimeter.

[0067] Figure 6 schematically represents a cold atom interferometric system 50 comprising a 2D-MOT trap 10 according to the present disclosure, a connection device 27 and an ultra-high vacuum chamber 29 comprising a 3D-MOT trap. The connection device 27 is arranged in the longitudinal direction 17 of the 2D-MOT trap 10. The connection device 27 connects the vacuum chamber 19 of the two-dimensional magneto-optical trap 10 to the ultra-high vacuum chamber 29 of the cold atom interferometric system. The 2D-MOT trap 10 makes it possible to generate a collimated atom jet 8 in the longitudinal direction 17 towards the connection device 27. The connection device 27 makes it possible to inject the atom jet 8 into the ultra-high vacuum chamber 29 towards the trapping zone 9 of the three-dimensional magneto-optical trap.By way of non-limiting example, the interferometer here comprises a pyramidal reflector 52 illuminated by a single laser beam 51 to enable atoms to be trapped in the 3D trapping zone 9. The 2D-MOT trap thus makes it possible to reduce the loading time of the 3D-MOT trap by a factor of 10, for example to go from a loading time of 500 ms to 50 ms. It is estimated that the loading time of the combination of a 3D-MOT trap and a 2D-MOT according to the present disclosure is approximately 10 times lower than that of the prior art. However, the loading time limits the duration of an interferometric measurement cycle. Reducing the loading time of the 3DMOT trap thus makes it possible to reduce the cycle time of the cold atom interferometer or to increase the measurement rate.

[0068] A cold atom system comprising a 2D trap according to the present disclosure finds other applications in a cold atom interferometer adapted to the measurement of rotations around one or more axes, for example in an on-board inertial navigation system for a mobile application, or in geophysics or fundamental physics testing applications.

[0069] A 2D cold atom trap according to the present disclosure also finds applications in an atomic clock to generate a beam of atoms.

[0070] A 2D cold atom trap according to the present disclosure also finds applications in the field of quantum optics, for example in a quantum processor or a quantum memory. A quantum processor uses quantum algorithms, which are successions of quantum logic operations performed on logical qubits and based on the manipulation of cold atoms. In practice, a quantum algorithm is physically implemented in the quantum processor through interactions between physical entities, such as neutral atoms arranged in quantum registers. The 2D cold atom trap according to the present disclosure can make it possible to load atoms more quickly into the quantum registers of a quantum computer or a quantum memory.

[0071] Of course, various other modifications may be made to the invention within the scope of the appended claims.

Claims

Claims 1. Two-dimensional magneto-optical trap (10) for a cold atom manipulation system, the two-dimensional magneto-optical trap comprising a vacuum chamber (19) capable of receiving a vapor of alkali or alkaline-earth atoms (1), means for generating a magnetic field (18), a laser source (3) and a reflective optical component (40), characterized in that the reflective optical component (40) comprises a plurality of reflective planar faces, each reflective planar face (41, 42, 43) of the plurality of reflective planar faces being parallel to a longitudinal direction (17) of the two-dimensional magneto-optical trap, the plurality of reflective planar faces being integral with each other and forming a concave surface, the plurality of reflective planar faces comprising a first reflective planar face (41) and a second reflective planar face (42),the first face (41) being arranged to form an angle of 90 ±5 degrees with the second face (42), the laser source (3) being configured to generate a circularly polarized incident laser beam (30) propagating in a median plane (48) relative to the first face (41) and the second face (42), the incident laser beam (30) being of suitable dimensions and oriented so as to simultaneously illuminate the first face (41) and the second face (42) of the optical reflector component (40) to form a first reflected laser beam (31) and a second reflected laser beam (32) propagating in mutually opposite directions in a plane transverse to the median plane (48), and to form a third reflected laser beam (33) propagating in the opposite direction to the incident laser beam (30) in the median plane (48) so that the incident laser beam (30), the first reflected laser beam (31),the second reflected laser beam (32) and the third reflected laser beam (33) are superimposed in a two-dimensional trapping zone (2) extending in the longitudinal direction (17) of the two-dimensional magneto-optical trap (10)., 2. Magneto-optical trap according to claim 1 in which the first face (41) and the second face (42) are contiguous, the second face (42) being capable of reflecting the first reflected laser beam (31) and respectively the first face (41) being capable of reflecting the second reflected laser beam (32), so as to form the third reflected beam (33).

3. A magneto-optical trap according to claim 1 wherein the plurality of reflective planar faces comprises a third face (43), the third face (43) being arranged between the first face (41) and the second face (42), the third face (43) being arranged perpendicular to said median plane (48), a quarter-wave plate (49) being arranged on or in front of the third face (43), the incident laser beam (30) being oriented so as to illuminate the third face (43) of the reflector optical component (40) through the quarter-wave plate (49) to form the third reflected laser beam (33).

4. Magneto-optical trap according to one of claims 1 to 3 wherein the incident laser beam (30) is inclined at an angle equal to or between 70 and 90 degrees relative to the longitudinal direction (17) of the two-dimensional magneto-optical trap (10).

5. Magneto-optical trap according to one of claims 1 to 3 wherein the incident laser beam (30) is perpendicular to the longitudinal direction (17) of the two-dimensional magneto-optical trap (10), the magneto-optical trap comprising a beam splitter device (7) arranged to receive a source beam (35) from the laser source (3) and to form the incident laser beam (30) and a pusher laser beam (34) separated from the incident laser beam (30), the pusher laser beam (34) being oriented parallel to the longitudinal direction (17) of the two-dimensional magneto-optical trap.

6. Magneto-optical trap according to one of claims 1 to 5 in which the incident laser beam (30) has an elliptical section having a major axis oriented in the longitudinal direction (17) of the two-dimensional magneto-optical trap (10).

7. Magneto-optical trap according to one of claims 1 to 6 comprising a beam splitter (6) arranged between the laser source (3) and the reflecting optical component (40), the beam splitter (6) being arranged to form the incident laser beam (30) and another incident laser beam (301, 302) parallel to the incident laser beam (30), the other incident laser beam (301, 302) propagating in the median plane (48), the other incident laser beam (301, 302) being of suitable dimensions and oriented so as to simultaneously illuminate the first face (41) and the second face (42) of the reflecting optical component (40) to form another first reflected laser beam and another second reflected laser beam, so that the other first reflected laser beam overlaps with the other second reflected laser beam in the two-dimensional trapping zone (2).

8. Cold atom manipulation system of the atomic interference type, atomic clock, quantum processor or quantum memory, the cold atom manipulation system comprising a two-dimensional magneto-optical trap according to one of claims 1 to 7.

9. Gravimeter comprising a cold atom manipulation system according to claim 8, a connecting device (27) connecting the two-dimensional magneto-optical trap (10) to an ultra-high vacuum chamber (29) of said cold atom manipulation system so as to inject into the ultra-high vacuum chamber (29) a jet of atoms (8) emitted in the longitudinal direction (17) of the two-dimensional magneto-optical trap (10).

10. A two-dimensional magneto-optical trapping method comprising the following steps: arranging a reflective optical component (40) in a vacuum chamber (19), the reflective optical component (40) comprising a plurality of reflective planar faces, each reflective planar face (41, 42, 43) of the plurality of reflective planar faces being parallel to a longitudinal direction (17) of the two-dimensional magneto-optical trap (10), the plurality of reflective planar faces being integral with each other and forming a concave surface, the plurality of reflective planar faces comprising a first face (41) and a second face (42), the first face (41) being arranged so as to form an angle of 90 ± 5 degrees with the second face (42), receiving a vapor of alkali or alkaline-earth atoms (1) in the vacuum chamber (19),generating a magnetic field in the vacuum chamber (19) and generating a circularly polarized incident laser beam (30) propagating in a median plane (48) relative to the first face (41) and the second face (42), the incident laser beam (30) being of suitable dimensions and oriented so as to simultaneously illuminate the first face (41) and the second face (42) of the reflective optical component (40), to form a first reflected laser beam (31) and a second reflected laser beam (32) propagating in mutually opposite directions in a plane transverse to the median plane (48), and to form a third reflected laser beam (33) propagating in the opposite direction to the incident laser beam (30) in the median plane (48) so that the incident laser beam (30), the first reflected laser beam (31), the second reflected laser beam (32) and the third reflected laser beam (33) overlap in an area, two-dimensional trapping element (2) extending along the longitudinal direction (17) of the two-dimensional magneto-optical trap (10).

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