Method for controlling an atom interferometer, atom interferometer and computer program

Abstract

The invention relates to a method in which at least one ensemble of atoms is prepared in an output coupling state (Z1) and, by means of coherent control interventions acting on the at least one ensemble of atoms in an atom interferometer input state that is the same as or, after the application of further manipulation steps, different from the output coupling state (Z1), is changed into subsequent states different from the atom interferometer input state, and a matter-wave interferometry sequence, which may in particular have several loops, is carried out with the at least one ensemble of atoms. The invention further relates to an atom interferometer configured for carrying out such a method and to a computer program for carrying out such a method.

Description

[0001] The invention relates to a method in which at least one ensemble of atoms is prepared in an output coupling state (Z1) and, by means of coherent control interventions acting on the at least one ensemble of atoms in an atom interferometer input state that is the same as or, after the application of further manipulation steps, different from the output coupling state (Z1), is changed into subsequent states different from the atom interferometer input state, and a matter-wave interferometry sequence, which may in particular have several loops, is carried out with the at least one ensemble of atoms. The invention further relates to an atom interferometer configured for carrying out such a method and to a computer program for carrying out such a method.

[0002] Atom interferometry-based sensors can provide highly sensitive, long-term stable, and absolutely accurate measurements of, for example, accelerations and rotations. Both atom interferometric rotation measurements and acceleration measurements, particularly in gravimeters, have been demonstrated. Commercial versions of atom interferometric gravimeters exist, as well as portable versions that have been used in marine and aeronautical gravimetry campaigns. One challenge is the implementation of compact designs.

[0003] Publications: R1: Atom Chip Fountain Gravimeter S. Abend, M. Gebbe, M. Gersemann, H. Ahlers, H. Müntinga, E. Giese, N. Gaaloul, C. Schubert, C. Lämmerzahl, W. Ertmer, WP Schleich, and EM Rasel Phys. Rev. Lett. 117, 203003 - Published November 11, 2016 R2: A transportable quantum gravimeter employing delta-kick collimated Bose-Einstein condensates Nina Heine, Jonas Matthias, Maral Sahelgozin, Waldemar Herr, Sven Abend, Ludger Timmen, Jürgen Müller & Ernst Maria Rasel Published: 25 August 2020 R3: Multi-loop atomic Sagnac interferometry Christian Schubert, Sven Abend, Matthias Gersemann, Martina Gebbe, Dennis Schlippert, Peter Berg & Ernst M. Rasel Published: August 9, 2021 R4: Composite Light Pulse Technique for High-Precision Atom Interferometry P. Berg, S. Abend, G. Tackmann, C. Schubert, E. Giese, WP Schleich, FA Narducci, W. Ertmer, and EM Rasel Published 9 February 2015

[0004] The invention is based on the objective of optimizing such an atom interferometer with a view to an advantageous practical structural implementation.

[0005] This problem is solved in a previously described method for controlling an atom interferometer based on a Cartesian coordinate system with the axes x, y and z, where, for example, when the atom interferometer is operated in a gravitational field, the z-axis can be aligned in the direction of gravity, by moving the at least one ensemble of atoms from a starting position in a first direction that has a spatial component in the xy-plane, whereby the following steps are carried out: a) After traversing a path in the first direction up to a first reversal point, the at least one ensemble of atoms is moved by irradiation with at least one first coherent relaunch control intervention in a second direction modified to the first direction, which also has a spatial component in the xy-plane, b) after traversing a path in the second direction, the at least one ensemble of atoms is moved by irradiation with at least one second coherent relaunch control intervention in the direction of the neighborhood of the first reversal point, such that the at least one ensemble of atoms has a loop-shaped trajectory in the xy-plane, c) Back-and-forth movements of the at least one ensemble of atoms with loop-shaped trajectory in the xy-plane are repeated by means of further coherent relaunch control interventions until a predetermined number of back-and-forth movements of the at least one ensemble of atoms is reached. d) Completing the interferometry sequence by irradiating the at least one ensemble of atoms with at least one final coherent control intervention and detecting the interferometer outputs.

[0006] In this way, an advantageous multi-loop geometry in the xy-plane can be realized independently of a gravitational field. The multi-loop geometry allows for high measurement accuracy and resolution of the interferometry with a small footprint for the atom interferometer. This is made possible by the fact that the at least one ensemble of atoms is not only moved in one and the same spatial direction during the interferometry sequence, thus requiring a relatively large footprint to achieve high resolution, but is moved back and forth in a loop-like fashion multiple times. The number of these back-and-forth movements, i.e., the number of loops or loop-shaped trajectories, can be determined for each specific application. This enables variable scaling of the atom interferometer. In particular, such an atom interferometer can be used as a compact, portable six-axis atom interferometer.Multi-axis inertial sensors can be implemented, also with the possibility for rotation measurements.

[0007] The scaling factor of typical atom interferometers with free-falling atoms depends on the effective wavenumber of the beam splitter light field, which is required for the coherent manipulation of the atoms to shape the interferometer, as well as on the free-fall time or free development time between successive beam splitter pulses during interferometer operation. This time is limited by the size of the vacuum chamber in which the atoms are trapped and manipulated. Possible solutions include trapped or guided interferometers, which entail additional requirements for the setup.

[0008] In contrast, the present invention utilizes the relaunch of the atoms after a certain time, causing them to traverse the vacuum chamber multiple times. Based on this approach, a concept for a rotation sensor is proposed in which repeated relaunch of the atoms results in multiple circumnavigations of an enclosed area, thereby increasing the effectively enclosed area and thus, analogous to a fiber gyroscope, enhancing the scaling factor. This multi-loop concept can, in principle, measure at least one of the three spatial axes on Earth.

[0009] Advantageously, the method according to the invention, unlike the prior art, allows the measurement of rotational movements about at least one, several, or all three spatial axes both in a gravitational field with atoms in free fall and in weightless space. In particular, the method according to the invention does not require gravitational acceleration for the deployment of interferometer surfaces or loops.

[0010] Accordingly, the method according to the invention, as well as the atom interferometer executing the method, can be used either in a gravitational field, e.g., in the Earth's gravitational field, or in weightless space. When operating the atom interferometer in a gravitational field, the z-axis should be aligned in the direction of gravity; in weightlessness, the alignment is irrelevant. In the method according to the invention, spatial movements of the ensemble of atoms in the xy-plane, which is hereinafter also referred to as the horizontal plane or horizontal direction, are advantageously used to define interferometer surfaces or loops. The spatial movements of the ensemble can be influenced by coherent relaunch control interventions, which invert the direction of the ensemble of atoms in the horizontal direction and / or also in the vertical direction (z-direction).

[0011] The aforementioned ensemble of atoms, sometimes referred to in the literature as an atomic ensemble or atomic cloud, can also be described as matter wave(s) or as atoms in a coherent superposition state. In this application, the term "ensemble of atoms" will be used as a general, overarching term.

[0012] The ensemble of atoms initially exists in an out-coupling state (Z1), where the out-coupling state (Z1) describes the state after cooling procedures and / or other preparation steps, or more generally, the state before the subsequent steps, specifically before further control interventions and the coherent control interventions of the matter-wave interferometry sequence. The ensemble of atoms is then transformed into the atom interferometer input state by the aforementioned control interventions, for example, by applying at least one momentum transfer to the ensemble of atoms and / or, if necessary, by performing further preparation steps. The matter-wave interferometry sequence with several coherent control interventions is then carried out, in which the ensemble of atoms can have one or more distinct subsequent states, for example, from the first to the last coherent control intervention.

[0013] Such coherent control interventions can include, for example, the emission of light pulses (e.g., from a laser or other light source), magnetic field gradients, and / or microwave pulses onto at least one ensemble of atoms, or, more generally, any method for the coherent manipulation of the ensemble of atoms—a form of quantum control that utilizes the wave properties of matter to steer the temporal evolution of a quantum system in a desired manner. During the matter-wave interferometry sequence, several coherent control interventions are typically performed. The term "pulse" is understood as a general term for any type of periodic and non-periodic event, and also encompasses momentum, e.g.,in the form of a periodically repeating sequence of impulses, periodically repeating impulse- or shock-like events and / or, in the case of a light pulse, a once-in-time or multiple-time increase and decrease in light output.

[0014] According to an advantageous embodiment of the invention, the coherent superposition states of the atoms, e.g., through at least one ensemble of atoms on loop-shaped trajectories, enclose an area that has a spatial component in the direction of the x-axis and the y-axis. In this way, a horizontal surface is enclosed. This allows an atom interferometer performing the method according to the invention to be used, without modification, either in a gravitational field or in weightless space.

[0015] According to an advantageous embodiment of the invention, the coherent superposition states of the atoms on loop-shaped trajectories form a multi-loop geometry. In particular, the at least one ensemble of atoms can complete several revolutions of the loop-shaped trajectories, e.g., two, three, four, or more loops.

[0016] According to an advantageous embodiment of the invention, the coherent superposition states during the back-and-forth movements are irradiated with at least one coherent deflection control intervention, the direction of action of which is at a non-zero angle, e.g., orthogonal, to the direction of action of the coherent relaunch control interventions. Such deflection control interventions enable comprehensive control of the trajectories of the at least one ensemble of atoms in the horizontal direction. For example, the relaunch control interventions can act in the positive and negative x-direction, and the coherent deflection control interventions in the positive and negative y-direction. The direction of action of the respective coherent control intervention is considered to be the direction of the momentum transfer vector to the at least one ensemble of atoms.

[0017] According to an advantageous embodiment of the invention, the direction of action of the coherent relaunch control interventions and / or the direction of action of the coherent deflection control interventions has at least one spatial component in the direction of the x-axis and / or the y-axis. One or both types of the aforementioned coherent control interventions can thus have at least one spatial component of their direction of action in the horizontal direction.

[0018] According to an advantageous embodiment of the invention, the coherent superposition states of the atoms are not exclusively guided in their movement in the first and second spatial directions. The invention can therefore also be used in unguided interferometers, where at least one ensemble of atoms can move essentially freely, i.e., is not guided in a controlled manner.

[0019] According to an advantageous embodiment of the invention, it is provided that the states of the atoms of the at least one ensemble of atoms are changed by at least one coherent beam splitter control intervention acting on the at least one ensemble of atoms such that their state has at least two partial probabilities of the atoms with different momentum, wherein the components of the different momentum have directional components facing away from each other, each having a spatial component in the xy-plane, wherein control interventions for changing the state can then be applied to the atom interferometer input state, wherein the matter-wave interferometry sequence is then applied, wherein the aforementioned steps a) to d) are applied to the respective partial probabilities of the atoms.This enables the realization of at least two interferometers using the single ensemble of atoms in which the aforementioned coherent beam splitter control intervention is performed. This intervention generates at least two partial probabilities of atoms being located at different momentum points, thus creating, in effect, two independent partial ensembles of atoms. The two interferometers generated in this way can then each be evaluated separately with respect to their interferometer outputs. In this manner, the invention can advantageously be extended to acceleration and rotation measurements of all kinds without significantly increasing the available space.

[0020] The interferometer outputs are understood to be the states of the ensemble of atoms, or rather their partial probability distributions, at the end of the matter-wave interferometry sequence, where the interference of waves can be measured. For example, a camera can be used that can look through a viewing window into a vacuum chamber of the atom interferometer and thereby detect and analyze the ensembles of atoms.

[0021] In an advantageous embodiment of the invention, the at least two partial locations of the atoms with different momentum can perform back-and-forth movements and thereby enclose loop-shaped trajectories, wherein the directions of movement of the partial locations can be opposite to each other on their trajectories, e.g. by the partial locations with their opposing movements each enclosing an area that has a spatial component in the direction of the x-axis and the y-axis (i.e. a horizontal area).

[0022] According to an advantageous embodiment of the invention, a symmetrical or quasi-symmetrical beam splitting of the at least one ensemble of atoms into at least two partial probabilities of the atoms being located in the x-axis and the y-axis is performed. In the case of symmetrical beam splitting, the direction of action of the coherent beam splitter control intervention can be essentially orthogonal to the initial velocity of the at least one ensemble of atoms. In the case of quasi-symmetrical beam splitting, the direction of action cannot be orthogonal, resulting in a symmetrical trajectory.

[0023] According to an advantageous embodiment of the invention, it is provided that symmetrical or symmetrized or quasi-symmetrical beam splitting processes are used for the control interventions or as part of the control interventions for the matter wave interferometry sequence and / or the relaunch control interventions.

[0024] According to an advantageous embodiment of the invention, two separate ensembles of atoms are trapped in separate, spaced-apart atom traps. These separate ensembles of atoms are used to form two separate, partially or fully overlapping interferometers. The separate ensembles of atoms are moved in directions facing away from each other or partially facing away from each other, each having a spatial component in the xy-plane. The steps a) to d) mentioned above are applied to the respective separate ensembles of atoms. This provides an advantageous alternative to dividing the at least one ensemble into the aforementioned at least two partial probabilities of finding the atoms, by utilizing two spaced-apart atom traps and the trapped ensembles of atoms separated from each other therein.In this case, the previously mentioned coherent beam splitter control intervention for splitting into at least two partial residence probabilities is unnecessary.

[0025] According to an advantageous embodiment of the invention, the coherent control interventions of the matter-wave interferometry sequence are applied to the at least one ensemble of atoms in the initial state or in different initial states, either before or after the coherent relaunch control intervention. In the case of light pulses as coherent control interventions, these can, for example, be emitted before or after the relaunch control intervention onto the ensemble of atoms or the partial probability distributions. This allows for a large degree of freedom in the practical implementation of an atom interferometer.

[0026] According to an advantageous embodiment of the invention, acceleration values ​​and / or rotation values ​​in one, several, or all axes x, y, and z are calculated by evaluating the interferometer outputs. In this way, acceleration values ​​and / or rotation values ​​in one, several, or all directions of 3D space can be determined.

[0027] The aforementioned problem is also solved by an atom interferometer with at least one atom trap and at least one controllable coherent signal source for delivering coherent control interventions to the matter-wave interferometry sequence, coherent beam splitter control interventions, coherent deflection control interventions, and / or coherent relaunch control interventions, and with at least one control device for controlling at least one coherent signal source, wherein the control device is configured to execute a method of the type described above. The advantages described above can also be realized in this way. The various types of control interventions mentioned above can be delivered by a single coherent signal source or by different coherent signal sources.The control unit can advantageously be designed as a computer-controlled control unit configured to execute a computer program. In this way, the atom interferometer can be designed with regard to its functionality by appropriately programming the computer program, in particular by means of the computer program to execute a procedure of the type described above.

[0028] The aforementioned task is also solved by a computer program comprising instructions that cause the atom interferometer of the type described above to execute the procedure steps of the type described above when the computer program is executed on a computer of the atom interferometer's control unit. This also allows the previously explained advantages to be realized. The computer program can be stored on a storage medium. The computer program can be implemented as software, firmware, or hardware programming of a PLD (programmable logic device), or as a combination thereof.

[0029] The invention is suitable, for example, for applications in the field of navigation, for rotation and acceleration measurements, e.g., as part of an inertial quantum measuring unit to support or replace conventional inertial measuring units, particularly in areas without a reliable global navigation system (GNSS).

[0030] For the purposes of the present invention, the indefinite term "a" is not to be understood as a numeral. Therefore, when, for example, a component is mentioned, this is to be interpreted as "at least one component". Where angles are specified in degrees, these refer to a circle of 360 degrees (360°).

[0031] Where a computer is mentioned, it may be configured to run a computer program, e.g., in the sense of software. The computer may be a standard commercial computer, e.g., a PC, laptop, notebook, tablet, or smartphone, or a microprocessor, microcontroller, or PLD (programmable logic device), or a combination of such elements.

[0032] The invention includes the possibility of the following properties: 1. By applying multi-loop geometry for rotation measurements, the subject of this invention can measure the third spatial axis or rotation component in terrestrial applications. 2. Compared to existing concepts with free-falling atoms, which can already measure this third spatial axis in a complementary manner, the subject matter of this invention offers the possibility of implementing a multi-loop geometry, i.e., an additional possibility to adjust and increase the scaling factor without requiring a larger vacuum system. 3. The invention can also be used in weightlessness and all three rotation axes can be measured here. 4. In contrast to existing concepts with free-falling atoms, which could already measure all three spatial axes without multiple loops, the subject matter of this invention offers the possibility of implementing a multi-loop geometry, i.e., an additional possibility to adjust and increase the scaling factor without requiring a larger vacuum system.

[0033] The invention is explained in more detail below with reference to exemplary embodiments and drawings.

[0034] They show: Fig. 1. An atom interferometer in schematic representation in the xz-plane, Fig. 2 the atom interferometer according to Fig. 1 in the xy-plane, Fig. 3 a matter-wave interferometry sequence in the xz-plane, Fig. 4 the matter-wave interferometry sequence according to Fig. 3 in the xy-plane, Fig. 5 a matter-wave interferometry sequence with symmetrical beam splitting in a single pass, Fig. 6 a matter-wave interferometry sequence with symmetrical beam splitting in a multi-loop geometry.

[0035] The Fig. 1 and Fig. Figure 2 shows a simplified schematic representation of an atom interferometer 11, particularly with regard to its optical implementation in a sensor head. The atom interferometer 11 has a vacuum chamber 1 with optically transparent viewing windows 2 on several sides. The vacuum chamber 1 can, for example, have a cubic shape. The atom interferometer 11 also has an atom trap 3, for example, an atom chip holder with an atom chip 30, for example, with a highly reflective surface. Alternatively, the atom interferometer 11 can also have a different type of atom trap, for example, an optical dipole trap or a magneto-optical trap (MOT). In the case of an optical dipole trap, the viewing windows 2 can also be transparent to optical dipole trap laser beams and highly reflective to relaunch laser beams or other coherent control interventions.

[0036] The atom interferometer 11 also has a beam shaping optic 4, e.g., for the initial momentum transfer for the transition of the ensemble of atoms 13 trapped in the atom trap 3 to the start state and, if necessary, for further coherent control interventions. The atom interferometer 11 also has a mirror 6, which is arranged diametrically opposite the beam shaping optic 4. The beam shaping optic 4 can, for example, comprise one or more collimators and / or flat-top or top-hat beam shapers. Furthermore, the atom interferometer 11 has a beam shaping optic 5a arranged obliquely to the atom trap 3 and a cooperating mirror 5b, through which the beams of the beam shaping optic 5a are reflected. The beam shaping optic 5a serves for the emission of the relaunch laser beams or, more generally, for the coherent relaunch control interventions.

[0037] The beam-shaping optics 5a and / or the mirror 5b can be fixed or adjustable. They can also be motorized for adjustment, for example, to set the angle of coherent relaunch control interventions. The atom interferometer 11 also has common, well-known elements of such atom interferometers, which are not shown for the sake of simplicity, such as coils and a 2D magneto-optical trap.

[0038] The atom interferometer 11 also has a beam-shaping optic 7a for feeding the coherent control inputs of the matter-wave interferometry sequence. A mirror 7b is arranged opposite the beam-shaping optic 7 in the beam direction. A delay plate 8 can be arranged in front of the mirror 7b, which may or may not be necessary depending on the beam splitter concept. The mirror 7b and / or the mirror 6 can be arranged either inside or outside the vacuum chamber 1.

[0039] The atom interferometer 11 can also have a beam shaping optic 8 for feeding detection light (for absorption recording) into the vacuum chamber 1, as well as at least one camera for detecting the interferometer outputs, e.g., a CCD or CMOS camera with a front-mounted detection optic, e.g., a double lens system for magnification and / or reduction and, if necessary, for stray light suppression, which is described in the Fig. 1 and Fig. Figure 2 is not shown. The atom interferometer 11 has a control unit 12 by which the individual controllable components of the atom interferometer 11 can be controlled. The control unit 12 is configured to execute a procedure of the type described.

[0040] The invention includes the possibility of combining the following elements and functions: 1. A system for the spatially resolved detection of atoms, e.g. by absorption imaging with a camera, e.g. an atom interferometer with a sensor head, comprising a vacuum system with optical access points, and peripheral elements such as beam shaping optics, coils, etc. with the functionalities 1.1. To trap and cool atoms, e.g. with a 3D magneto-optical trap, an optical dipole trap or a magnetic trap or an atom chip, depending on the implementation in single or multiple versions, 1.2. to be able to perform beam splitter operations in at least one axis for the implementation of the interferometer, 1.3. To be able to throw atoms back at defined times and places with defined speed and direction, 1.4. to be able to detect the interferometer outputs. 2. a laser system for providing the laser light or another system for providing coherent control interventions, e.g. for trapping and cooling, for the beam splitter operations, depending on the implementation approach for reflection, 3. an electronic system including control computer, e.g. in the form of the control unit 12, e.g. for the active elements in the sensor head and laser system, execution of the measurement sequences, data acquisition and, if necessary, data processing, 4. each designed to allow multi-loop operation.

[0041] Based on the Fig. 3 and Fig. Section 4 describes a first embodiment of an interferometry method according to the invention, comprising a matter-wave interferometry sequence and a multi-loop geometry. Based on the Fig. Figure 3 first describes the start of two individual interferometers. An ensemble of atoms 13 is initially subjected to a first coherent beam splitter control intervention S at a starting position A, which can be a central location in the vacuum chamber 1. For example, in the case of light pulses, this is a first π / 2 pulse. This divides the ensemble of atoms 13 into two partial probabilities 14, 15 of the atoms, which corresponds to a beam split. These partial probabilities 14, 15 move at velocities of -V SEP , V SEPEach probabilities move to the left and right, i.e., in the positive and negative x-direction. If a gravitational influence is present, the partial probabilities 14 and 15 also move in the direction of gravity g, i.e., in the z-direction. After a certain time, a coherent relaunch control intervention R is applied to the respective partial probabilities 14 and 15 to generate a throwback process of the partial probabilities 14 and 15.

[0042] The Fig. Figure 4 shows the trajectories of the partial probabilities 14, 15 in the xy-plane generated by the various coherent control interventions. The arrows with solid and short-dashed lines indicate the trajectories and directions of rotation of the partial probability 15 starting to the right, and the arrows with dash-dotted and long-dashed lines indicate the trajectories and directions of rotation of the partial probability 14 starting to the left. Multiple rotations of the partial probabilities 14, 15, or more generally, of at least one ensemble of atoms 13, can be generated, each traversing the depicted trajectories that enclose an area in the xy-plane. This is achieved by repeatedly performing the coherent relaunch control interventions R and coherent deflection control interventions L between the relaunch control interventions R.The distraction control intervention L can correspond to the control intervention K2.

[0043] The coherent control interventions of the matter-wave interferometry sequence K1, K2 or L and K3 are executed sequentially. At the end of the matter-wave interferometry sequence, a third coherent control intervention K3 is applied to the respective partial probabilities 14, 15, e.g., in the form of a second π / 2 pulse. Following this, the interferometer outputs 16, 17 of the two interferometers formed by the partial probabilities 14, 15 can be detected and evaluated.

[0044] The Fig. 5 and Fig. Figure 6 shows an implementation of the described multi-loop geometry with symmetrical or quasi-symmetrical beam splitting instead of the symmetrical beam splitting according to the Fig. 3, Fig. 4. Such a configuration enables the operation of the atom interferometer 11 at a non-zero velocity of the atoms relative to the beam splitter light fields, particularly in the y-direction. Fig. Figure 5 shows a single pass of an interferometry sequence as known in the prior art. Fig. Figure 6 shows an embodiment of the invention in multi-loop geometry, i.e., with several back-and-forth movements of the at least one ensemble of atoms 13 with loop-shaped trajectory in the xy-plane, as indicated by the arrows analogous to the Fig. 4 is shown.

[0045] One possible implementation according to the Fig. 3 and Fig. 4 can look like this: 1. An ultracold atomic ensemble, e.g., a Bose-Einstein condensate, is created under an atom chip 3. This is coupled out of the trap and falls downwards (z-direction) [ Fig. 3]. 2. A beam splitting process S generates a superposition of two momentum states (ensembles 14, 15) that move apart with opposite momentum in the x-direction perpendicular to the z-axis [ Fig. 3]. 3. After a free-fall period, the relaunch process (relaunch control interventions R) inverts the motion of the two ensembles 14,15 so that they move towards each other again. An exact inversion is not necessary. This can be adapted according to a suitable implementation [ Fig. 3]. 4. Perpendicular to the z-direction and x-direction (in the y-direction), the beam splitter light fields or other coherent control interventions K1, K2 or L, K3 are applied to set up the interferometer. The first coherent control intervention K1 is a so-called π / 2 pulse, which generates a coherent superposition between two momentum states symmetrically in the y-direction. At or near the apex of the projectile trajectory after a time T, a so-called coherent deflection control intervention L, e.g., a π pulse, is applied, which inverts the momentum of the two ensembles 14, 15 in the y-direction. Fig. 4]. 5. After a further free-fall time T, at or near the point where ensembles 14 and 15 were first thrown back, they are thrown back again by relaunch control interventions R. They are then located at the point where the other ensemble 14 and 15 was previously thrown back. The throwing-back time is chosen such that the two trajectories of the interferometers just intersect. Fig. 4]. 6. At or near the apex of the projectile trajectory after a further free-fall time T, another coherent deflection control intervention L, e.g. a π-pulse, is applied, which inverts the impulses in the y-direction [ Fig. 4]. 7. After a further free-fall time T, at or near the point where the ensembles 14, 15 were first thrown back, where the trajectories just intersect again, two possibilities now arise [ Fig. 4]: 7.1. By applying a coherent control intervention K3, e.g., a π / 2 pulse, the interferometer is closed and the interferometer output 16, 17 can be read out. The total interferometer time is 4T and two loops were completed on the trajectories. 7.2. A further relaunch control intervention R takes place to complete further loops, and the final coherent control intervention K3 is applied after a total interferometer time of 4T plus a multiple of 2T to close the interferometer.

[0046] Depending on the implementation, the first and / or last loop may have a different 2T than the loops in between, e.g., to comply with technical restrictions. All types of coherent control interventions, e.g., the π / 2 and π pulses, can be replaced by composite beam splitter pulses (see Fig.6) Higher-order beam splitter pulses or other methods for increasing the effective wave vector can be used to further increase the scaling factor. In the implementation described, two interferometers are operated in parallel. This allows for the suppression of vibrational noise (acceleration noise). In principle, operation of a single interferometer is also possible, in which case the acceleration noise must be suppressed by other means.

[0047] In microgravity, the reflection only occurs in the x-direction.

[0048] Options for the technical implementation of the recycling process: 1. Beam splitting processes, possibly of higher order, sequentially in the x and z directions with light fields that are irradiated in the x and z directions; the reflection back in the x direction occurs at the intersection point of the trajectories; 2. Beam splitting processes, possibly of a higher order, at a specific angle, e.g. 45° to the atom chip surface; the light field is reflected at the atom chip and then back into itself; the beam guidance and the reflector can optionally be designed so that a change in angle is possible, e.g. via controllable mirror holders. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] S. Abend, M. Gebbe, M. Gersemann, H. Ahlers, H. Müntinga, E. Giese, N. Gaaloul, C. Schubert, C. Lämmerzahl, W. Ertmer, WP Schleich, and EM Rasel Phys. Rev. Lett. 117, 203003 - Published 11 November 2016

[0003]

Claims

Method for controlling an atom interferometer (11), in which at least one ensemble of atoms (13) is prepared in an output coupling state (Z1), wherein the output coupling state (Z1) describes the state after cooling procedures and / or other preparation steps or, more generally, the state before the following steps, and by means of the at least one ensemble of atoms (13) in an atom interferometer input state that is the same as the output coupling state (Z1) or different after the application of further manipulation steps, the state of which is changed into subsequent states different from the atom interferometer input state by means of coherent control interventions (K1, K2, K3, L) acting on the at least one ensemble of atoms (13), including in particular coherent superpositions, and with which a matter-wave interferometry sequence is carried out, characterized in thatthat, based on a Cartesian coordinate system with the axes x, y and z, wherein, when the atom interferometer (11) is operated in a gravitational field, the z-axis may be aligned in the direction of gravitation, the at least one ensemble of atoms (13) is moved from an initial position (A) in a first direction which has a spatial component in the xy-plane, wherein the following steps are carried out: a) after traversing a path in the first direction up to a first reversal point, the at least one ensemble of atoms (13) is moved by irradiation with at least one first coherent relaunch control intervention (R) in a second direction modified from the first direction, which also has a spatial component in the xy-plane,b) After traversing a path in the second direction, the at least one ensemble of atoms (13) is moved towards the vicinity of the first reversal point by irradiation with at least one second coherent relaunch control intervention (R), such that the at least one ensemble of atoms (13) has a loop-shaped trajectory in the xy-plane, c) Back-and-forth movements of the at least one ensemble of atoms (13) with a loop-shaped trajectory in the xy-plane are repeated by means of further coherent relaunch control interventions (R) until a predetermined number of back-and-forth movements of the at least one ensemble of atoms (13) is reached, d) The interferometry sequence is completed by irradiating the at least one ensemble of atoms (13) with at least one final coherent control intervention (K1, K2, K3) and detecting the interferometer outputs. Method according to claim 1, characterized in that the coherent superposition states of the atoms on loop-shaped trajectories enclose an area which has a spatial component in the direction of the x-axis and the y-axis. Method according to one of the preceding claims, characterized in that the coherent superposition states of the atoms on loop-shaped trajectories form a multi-loop geometry. Method according to one of the preceding claims, characterized in that the coherent superposition states during the back-and-forth movements are irradiated with at least one coherent deflection control intervention (L), the direction of action of which is at a non-zero angle, e.g. orthogonal, to the direction of action of the coherent relaunch control interventions (R). Method according to one of the preceding claims, characterized in that the direction of action of the coherent relaunch control interventions (R) and / or the direction of action of the coherent deflection control interventions (L) has at least one spatial component in the direction of the x-axis and / or the y-axis. Method according to one of the preceding claims, characterized in that the coherent superposition states of the atoms are not exclusively guided on their movement in the first and second spatial directions. A method according to one of the preceding claims, characterized in that the states of the atoms of the at least one ensemble of atoms (13) are changed to a transfer state by at least one coherent beam splitter control intervention (S) acting on the at least one ensemble of atoms (13) such that their state has at least two partial probabilities (14, 15) of the atoms with different momentum, wherein the different momenta have at least one directional component facing away from each other, each having a spatial component in the xy-plane, wherein further manipulation steps of claim 1, the matter-wave interferometry sequence of claim 1 and steps a) to d) of claim 1 are subsequently applied to the respective partial probabilities (14, 15) of the atoms. Method according to claim 7, characterized in that a symmetrical or symmetrized or quasi-symmetrical beam splitting of the at least one ensemble of atoms (13) into the at least two partial probabilities of location (14, 15) of the atoms in the direction of the x-axis and the y-axis is carried out. Method according to one of the preceding claims, characterized in that one or more symmetrical or symmetrized or quasi-symmetrical beam splitting processes are used for at least some of the control interventions (K1, K2, K3, L, R). A method according to one of the preceding claims, characterized in that two separate ensembles of atoms (13) are trapped in separate, spaced-apart atom traps, wherein two separate, partially or completely overlapping interferometers are formed using the separate ensembles of atoms (13), wherein the separate ensembles of atoms (13) are moved in directions facing away from each other or partially facing away from each other, each having a spatial component in the xy-plane, wherein steps a) to d) or b) to d) of claim 1 are subsequently applied to the respective separate ensembles of atoms (13). Atom interferometer (11) with at least one atom trap (3) and at least one controllable coherent signal source (4, 5, 5a, 5b) for providing coherent control interventions (K1, K2, K3, L) of the matter wave interferometry sequence including the coherent deflection control interventions (L), coherent beam splitter control interventions (S) and / or coherent relaunch control interventions (R), and with at least one control device (12) for controlling at least one coherent signal source (4, 5, 5a, 5b), characterized in that the control device (12) is configured to carry out a method according to one of the preceding claims. Computer program comprising instructions that cause the atom interferometer according to claim 11 to perform the method steps according to any one of claims 1 to 10 when the computer program is executed on a computer of the control unit of the atom interferometer.

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