Quantum anomaly subsurface mapper

Abstract

A quantum measuring system comprises a satellite, a quantum tip, a quantum gravimeter, and a data processing system. The quantum gravimeter and the data processing system are onboard the satellite. The quantum tip comprises spaced apart high precision clocks that are physically supported by the satellite. The quantum tip and the quantum gravimeter are in data communication with the data processing system. The data processing system may be configured to process a combination of structural data collected from an alternative modality sensor and functional data corresponding to gravity-related measurements collected from the quantum tip and the quantum gravimeter.

Description

QUANTUM ANOMAUY SUBSURFACE MAPPERTECHNICAE FIEED

[0001] The present disclosure relates generally to geophysical mapping, and in particular to systems and methods for producing geophysical tomographic maps using quantum physics principles. Particular embodiments have example applications for producing tomographic maps of celestial objects such as the Earth, the Moon, Mars, asteroids, and deep space objects.RELATED APPLICATIONS

[0002] This application claims priority from United States Patent Application No. 63 / 542,743 filed on October 5, 2023 entitled “QUANTUM ATOMIC SUBSURFACE MAPPER”. For the purposes of the United States, this application claims the benefit under 35 U.S.C. §119 of United States Patent Application No. 63 / 542,743 filed on October 5, 2023 entitled “QUANTUM ATOMIC SUBSURFACE MAPPER”. United States Patent Application No. No. 63 / 542,743 is incorporated herein by reference in its entirety for all purposes.BACKGROUND

[0003] Geophysics is an interdisciplinary area of natural science that applies various techniques of mathematics, physics, and chemistry to develop an understanding of various physical properties of the Earth and its surrounding environment. Traditionally, geophysics has been limited to two-dimensional imaging of the surface and subsurface, by using dated methods that measure general changes to density, vibrations, seismology, magnetism, or conductivity below ground to identify areas-of-interest. These methods all rely on classical physics principles and, consequently, produce images with limited range, depth, and resolution.

[0004] Recently, more advanced technologies within the geophysics niche have been developed to support low-resolution three-dimensional (3D) subsurface analysis. These technologies typically involve seismic, induced polarization (IP), magnetic, and classical gravimetric surveys that measure the dispersion of vibrations, conductivity, magnetism, and mass, respectively, to estimate general composition below the surface. Regardless of thespecific method, the current technologies are generally time-consuming to set up, imprecise and can sometimes lead to unnecessary, expensive, and environmentally damaging excavations that regularly frustrate prospectors and geotechnical engineers. For example, seismic and IP surveys require ground contact, while magnetic and gravimetric surveys are more commonly performed from airborne vehicles to increase the range and speed of the survey at the further cost of resolution, thereby necessitating follow-up ground surveys to increase the subsurface detail.

[0005] In space, some large-scale discovery work can be accomplished from orbit by remote sensing technologies such as synthetic aperture radar (SAR), hyperspectral imaging, and classical gravimeters. However, these technologies are limited to surface feature detection and topography with near-zero depth resolution. In particular, while SAR technology has significantly evolved in its capacity to provide detailed and high-resolution topographic maps, there have been little advancements or interest in applying such systems to subsurface tomography imaging.

[0006] Quantum sensing represents a fundamentally novel approach to data collection in geophysics and in space. One example of a quantum sensor currently used for geophysical detection of metallic elements in-ground is the superconducting quantum interference device (SQUID) magnetometer. SQUIDS can sense magnetic fields as nominal as 5x1 O'14T, but have their own limitations. One limitation is their reliance on emitting an electromagnetic field, which not only damages nearby electronics, but remains limited in range by classical physics, making them ineffective from orbit. Other limitations include electronics that are susceptible to being damaged by electromagnetic fields, as well as the detected magnetic field strength signal dissipating at a rate inversely proportional to the square of the distance to the detected object. These limitations render SQUID infeasible for deployment on spacecraft and thus negate their ability to be adapted for collecting geophysical data in space. In addition, electromagnetic fields can often be naturally shielded or reduced, leaving some objects completely unseen by SQUIDs.

[0007] In view of the foregoing shortcomings, there remains a need for systems and methods for capturing or otherwise producing high definition 3D imaging of subsurface composition from a distance. There remains a need for systems and methods which can provide both aterrestrial and geophysical imaging solution that facilitates ground, airborne, and / or spacebome use. The remains a need for systems and methods that leverage artificial intelligence and machine learning (AI / ML) techniques to support 2D and 3D tomography in space with improved speed, range, depth, and resolution.SUMMARY

[0008] One aspect of the invention relates to a quantum measuring system comprising a satellite, a data processing system onboard the satellite, a quantum gravimeter onboard the satellite, and a quantum tip. The quantum tip is physically supported by the satellite and comprises a first high precision clock spaced apart from a second high precision clock. The quantum gravimeter and the quantum tip are in data communication with the data processing system.

[0009] In some embodiments, the quantum measuring system comprises an alternative modality sensor onboard the satellite and in data communication with the data processing system. The data processing system may be configured to process a combination of structural data collected from the alternative modality sensor and functional data corresponding to gravity-related measurements collected from the quantum tip and the quantum gravimeter. In some embodiments, the alternative modality sensor comprises a magnetic sensor and / or an altimeter.

[0010] In some embodiments, the data processing system is configured to process a combination of differential gravity measurements collected by the quantum tip and absolute gravity measurements collected by the quantum gravimeter. The data processing system may be configured to implement a machine learning model to process the combination measurements. The machine learning model may be trained on data collected from previous surveys of subsurface composition of a known geographic region. The machine learning model may be a Bayesian machine learning model. The data processing system may be configured to filter the combined measurements by implementing a Kalman filter.

[0011] In some embodiments, the first and second high precision clocks are atomic clocks. The data processing system may be configured to analyze the differential effects of gravitywells on first and second atomic clocks measured by the quantum tip. The quantum tip may be configured to measure the effects of general relativity on the first and second atomic clocks. In some embodiments, the system comprises one or more spars. In such embodiments, the first atomic clock and the second atomic clock may be spaced apart by a distance defined by the one or more spars, and the satellite may be located between the first and second atomic clocks. The first atomic clock and the second atomic clock may be spaced apart by a length between 8 meters to 12 meters.

[0012] In some embodiments, the quantum gravimeter comprises one or more of an interferometer, an optical tweezer, and a magneto-optical trap. In some embodiments, the quantum gravimeter is an absolute quantum gravimeter. The absolute quantum gravimeter may comprise one or more of: an ultra-high vacuum system, a frequency-locked laser system, an atomic source, and an atomic interferometer.

[0013] Additional aspects of the present invention will be apparent in view of the description which follows.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which:

[0015] FIG. 1 schematically illustrates a quantum anomaly and subsurface mapper (QASM) in accordance with a first embodiment of the invention.

[0016] FIG. 2 is a block diagram of a quantum gravimeter of the FIG. 1 QASM.DETAILED DESCRIPTION

[0017] The description which follows and the embodiments described therein are provided by way of illustration of examples of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation and not limitation of those principles and of the invention.

[0018] Aspects of the invention relate to systems and methods for providing 3D geophysical tomography, which may include details about the subsurface composition of ground, water, ice, minerals, metals, volatiles, underground voids, and hidden dangers. The system may be provided from or hosted on a single orbiting satellite or spacecraft, a constellation of satellites and / or spacecrafts, or other space vehicles. For the purposes of facilitating the description, the term “satellite”, as used herein, is used to refer to any mobile or controlled object in space, including traditional satellites, objects which orbit around a celestial body, space probes, space stations, spacecrafts, and the like. The system may rely on multiple layers of quantum differentials and artificial intelligence or machine learning (AI / ML) techniques to minimize signal noise, collect high-resolution geophysical data, and / or render 3D tomography of the subsurface composition from orbit. In some embodiments, the system relates its orbital position to the displacement of optically cooled, trapped, superposed, and entangled groups of atoms at different states of Raman excitations. In some embodiments, the system utilizes real-time disturbance models to correlate and pre-process signal noise and gravitational data into meaningful geophysical representations. The system may perform the mapping by correlating a multi-instrumental signal that provides a relative or absolute density mapping of the regolith and geological formation.

[0019] Systems described herein comprise one or more of the following components: quantum gravimeters, magneto-optical traps (MOTs), interferometers, optical tweezers, magnetic sensors, high precision clocks (e.g., atomic clocks, nuclear clocks, or optical clocks), gravity gradient booms, quantum tips (QTIP), and general relativity (GR) sensors. The high precision clocks, such as atomic clocks, are important for their timekeeping accuracy, since the smaller the error in time measurement, the smaller the error in distance obtained by multiplying the time by the speed of light (e.g., a timing error of a nanosecond or 1 billionth of a second translates into an almost 30-centimeter (11.8 in) distance and hence positional error).

[0020] Advantageously, systems described herein can provide for transformative dual-use technologies within geophysics that are not bound by classical physics constraints. Some embodiments can be used in the technical fields of terrestrial and planetary mining. Some embodiments can be used to create new applications and markets, such as providing situational information and intelligence to militaries about threats underground, underwater, under ice, onthe surface, in the air, and in space. Some embodiments can be used to track groundwater and aqueduct reserves for agriculture, urban planning, environmental studies, sustainability, and crisis relief Some embodiments can be used for generating 3D maps that can identify the presence of rare earth elements, critical metals, volatiles and threats below the surface. Some embodiments can be used for the purposes of studying deep space artifacts like black holes, quantum gravity, dark matter, gravitational waves, etc. Some embodiments function as inertial measurement units for position, navigation, and timing (PNT) technologies, thereby enabling alternative global positioning system (GPS) solutions that are less susceptible to masking and spoofing attacks compared to traditional GPS systems. The system’s sensitivity to detect changes to gravity wells may allow space agencies and other organizations like the military and its coalitions to detect, identify and track space debris or approaching planetary threats from deep space.

[0021] FIG. 1 illustrates schematically a quantum measuring system 100 in accordance with a first embodiment of the invention. Quantum measuring system 100 is a sensor platform which relies on one or more quantum techniques, including those that may be combined or fused together, to measure quantum anomalies and create mappings of a subsurface (e.g., on Earth, Moon, etc.). Accordingly, quantum measuring system 100 may also be referred to herein as a quantum atomic subsurface mapper or quantum anomaly and subsurface mapper (QASM). Some embodiments of QASM 100 may apply or otherwise incorporate both gravimetry (i.e., measurement of gravitational field strength) and gradiometry (i.e., measurement of variations in gravitational field strength) techniques to increase the system’s sensitivity for anomaly edge detection of subsurface features.

[0022] As depicted in FIG. 1, QASM 100 comprises a general relativity (GR) sensor or quantum tip (QTIP) 101 and a quantum gravimeter 106 for collecting functional data. QTIP101 and quantum gravimeter 106 are physically supported by or otherwise coupled to a satellite102 of a suitable configuration (e.g., a CubeSat, a MicroSat, or a spacecraft). Optionally, QASM 100 may also comprise one or more passive magnetic sensors or other sensor modalities for collecting structural data. Such sensors may also be referred to herein as “alternative modality sensors” and can be used in cooperation with QTIP 101 and quantum gravimeter 106 to better map the underground or subsurface. For example, functional data corresponding togravity-related measurements may be collected from QTIP 101 and quantum gravimeter 106 and combined with structural data collected from other sensor modalities (e.g., a magnetic sensor, an altimeter, etc.) to support the fusion of multiple data sets for subsurface mapping. In general, structural data provides information on the static arrangement of components in a system or region, while functional data provides information on the dynamical processes and interactions that occur within the system or region. The functional data collected by QTIP 101 may, for example, provide information about how various components of a scanned system or region behave, operate, and interact over time. The structural data collected by the alternative modality sensors may, for example, provide information about the physical characteristics (e.g., shape, size, arrangement, etc.) of the components of the scanned system or region.

[0023] Satellite 102 is equipped with means for flying and operating in space or above a celestial body’s surface. For example, satellite 102 may be equipped with means for flying and operating at or above the Earth’s stratosphere. Satellite 102, along with QTIP 101 and quantum gravimeter 106 onboard or coupled thereto, may be flown or otherwise operated at an altitude “h” above a celestial body 200 having a gravitational force (e.g., Earth, Moon, etc.). In some cases, the altitude “h” is in the range of 10km to 300km. In general, the altitude “h” may be dependent on the diameter of celestial body 200. For example, the altitude “h” may be in the range of 160km to 1000km for a satellite 102 flying in a low Earth orbit.

[0024] QTIP 101 comprises high precision clocks in signal or data communication with a data processing system (e.g., an analogue or digital computer). Some embodiments of QTIP 101 comprise two or more atomic clocks. Some embodiments of QTIP 101 may, optionally, comprise other types of clocks, such as nuclear clocks or optical clocks for precision timekeeping and making gravity measurements. QTIP 101 may be physically mounted to or supported by satellite 102 during use. QTIP 101 is configured to measure the effects of general relativity on two or more high precision clocks (e.g., atomic clocks, nuclear clocks, optical clocks, or a combination of any of the foregoing) separated by a fixed distance and maintained at their respective orbital altitudes.

[0025] In the schematically illustrated embodiment, QTIP 101 comprises a first set of quantum atomic clocks 103 and a second set of quantum atomic clocks 104, both in signal or data communication with data processing system 105. Each set of atomic clocks may comprise oneor more atomic clocks and may be referred to herein as “atomic clock” for the purposes of facilitating the description. First atomic clock 103 and second atomic clock 104 may be spaced apart from each other by a fixed distance defined along, for example, a boom or a spar. The tilt and rotation speed of the boom or spar can be measured, by processing system 105 for example, to determine differential movements that can be used to provide a prior distribution for a Bayesian model. The degree of separation between first atomic clock 103 and second atomic clock 104 may be defined or otherwise characterized by a separation distance “D”. The separation distance “D” between the atomic clocks 103, 104 may be in the range of, for example, 5m to 20m in some cases. In general, the more precision the atomic clocks 103, 104 can provide, the lower the separation distance “D” required.

[0026] During operation of QASM 100, first atomic clock 103 and second atomic clock 104 may move in a direction 10 that is generally perpendicular to the direction 12 of a gravitational force or gravitational pull of celestial body 200. Since atomic clocks 103, 104 are separated by a distance “D”, flying satellite 102 at an altitude “h” above celestial body 200 will cause the atomic clocks 103, 104 to experience different gravitational pulls and / or tick at different speeds due to the differential positions within a gravity well (i.e., the pull of gravity that a celestial body in space exerts, which is ~0.17g for the Moon).

[0027] In the schematically illustrated embodiment, first atomic clock 103 is located relatively further away from celestial body 200 (e.g., located at the altitude “h” of satellite 102 plus separation distance “D”), while second atomic clock 104 is located relatively closer to celestial body 200 (e.g., located at the altitude “h”). In such embodiments, first atomic clock 103 may tick at a first frequency, while second atomic clock 104 may tick at a second frequency that is higher than the first frequency, since time passes more slowly at lower gravitational potential (i.e., the closer the atomic clock is to the source of gravitational force, the faster the atomic clock). Atomic clocks 103, 104 may be harmonized or synchronized by processing system 105 to experience time dilation relative to each other. For example, the first atomic clock 103 may experience a first gravitational time dilation, and the second atomic clock 104 may experience a second gravitational time dilation. Gravitational time dilation is a form of time dilation, characterized as an actual difference in elapsed time between two atomic clocks at varying altitudes and / or separation distances from a gravitating mass.

[0028] Using or relying on the principles of general relativity, an alternative modality to the cold atom free fall measurement, QTIP 101 may be configured to measure differential effects of gravity wells on the two atomic clocks 103, 104 that are separated by distance “D” The differential measurements may then be analyzed by data processing system 105, which is typically configured to execute algorithms based on the differential measurements, other inputs, Bayesian machine learning (ML), and / or Kalman filtering. In some embodiments, the machine learning models are trained on data (e.g., high-quality gravimetry data, magnetometry data, seismology data, altimetry data, induced polarization data, etc.) collected from previous surveys where the subsurface composition and density of the geographic region is known.

[0029] In some embodiments, differential measurements from QTIP 101 are combined with absolute measurements from quantum gravimeter 106, and used in combination as either a Bayesian estimate or as a second source of data to be filtered by a filtering system of data processing system 105. The filtering system may include or otherwise implement a Kalman filter. When system 100 is in orbit, the sampling rate may be configured to milliseconds or smaller such that multiple measurements over a region of interest (e.g, on the Earth’s surface) may be used as priors for the Bayesian approach, thereby improving the quality of the 3D subsurface density mapping. In other embodiments, data obtained from QTIP 101 is combined with data obtained from a classical gravimeter. While such embodiments will not provide the same resolution as embodiments with multiple quantum sensors, they can still produce 3D tomography that are improved over existing techniques.

[0030] By analyzing the differential period between the two atomic clocks 103, 104, QTIP 101 can record precise geoidal information. The information can be used to provide or support subsurface tomography from orbit at transformative speeds and higher 3D resolution. The geoidal information may be recorded in the form of the sum of the densities of all underground minerals, ice, and water as well as underground cavities. The geoidal information may be compared to historical information (e.g., the geoid from the International Geophysical Year initiative in 1957). QTIP 101 may comprise memory for storing an independent log of changes to a celestial body’s geoid over predetermined time intervals and multiple orbits. For example, as the mass of celestial body 200 changes, time dilation is observed in the atomic clocks 103,104, which can indicate changes to the density of the celestial body’s elemental composition at precise locations and provide insights into the types of elements contained therein.

[0031] FIG. 2 illustrates a block diagram of a quantum gravimeter 106 according to an example embodiment. Quantum gravimeter 106 is in signal or data communication with data processing system 105. Exemplary types of quantum gravimeters 106 that may be used or adopted by QASM 100 include: a free-falling comer cube, a levitating superconducting element, an optical lattice, and a trapped-atom gyroscope. Compared to conventional gravimeters which must rely on mechanical components to measure the acceleration of a free- falling comer cube with optical interference, quantum gravimeters can achieve improved precision without such mechanical components, thereby offering greater repetition rate and better adaptability to dynamic environments.

[0032] Quantum gravimeter 106 may be designed or otherwise configured to perform one or more of the following tasks: (i) trap and cool atoms to below ImK to create highly entangled states (e.g., Bose-Einstein Condensates); (ii) separate the resulting atoms into two or more groups; (iii) rouse one or more groups into an excited state; and (iv) measure the atom’s atomic states and superposition as they interact with the gravity well.

[0033] Quantum gravimeter 106 may be designed or otherwise configured to measure and identify specific behaviors of the entangled atoms, including variations to flight acceleration within the hard vacuum of space (i.e., changes to the gravity well of 10-8Ag / g (Hz)-l / 2 or more), and phase measurements of the atomic states (i.e., whether the energy of the excited group is being affected by any magnetic or electrical fields). In microgravity, there is an increased timespan with which measurements of the atoms falling through a magneto-optical trap can be made, thereby improving the sensitivity to gravity gradients.

[0034] In some embodiments, quantum gravimeter 106 is configured to isolate relevant signal from noise through performing multiple scale measurements and one or more post-processing steps. To further isolate signal from noise, quantum gravimeter 106 records measurements for two sets of entangled atoms and use the corresponding differential measurements to further isolate the locations and magnitude of disturbances. In some embodiments, quantum gravimeter 106 is configured to measure changes to density of 10-8Ag / g (Hz)-l / 2 or more. In such embodiments, the fusion of quantum techniques and their differential measurements isestimated to perform at 4-8 orders of magnitude above classical instrumentation. In some embodiments, quantum gravimeter 106 is an absolute quantum gravimeter (AQG).

[0035] In the schematically illustrated embodiment, quantum gravimeter 106 comprises one or more interferometers 107, optical tweezers 108, and magneto-optical traps (MOTs) 109. Each of the magneto-optical traps 109 may house two or more sets of entangled atoms.

[0036] In some embodiments, quantum gravimeter 106 operates as a sensing device that can measure small variations in the gravitational field. A manifestation of such a field is through the acceleration of a falling object. At any given point, the magnitude and orientation of such field is the sum of all contributions from all masses around the falling object. If the field around the celestial body is considered, any change in the surface topography or its composition will result in small variations to the gravitational field. The measurement of gravity can be absolute (e.g., the magnitude of the field), or relative (e.g., the difference between two locations). Relative measurements tend to suffer from drift and dependent on a point where the (absolute) gravity is known. Unlike classical gravimeters, quantum gravimeters do not suffer from drift and thus relative measurements that determine the gravity gradient are preferable due to the long-term stability of quantum gravimeters.

[0037] Referring back to FIG. 1, one or more processors 105 onboard satellite 102 may be configured to receive data from QTIP 101 and quantum gravimeter 106. The onboard processor may execute artificial intelligence and machine learning (AI / ML) software to mitigate signal noise and / or generate 3D tomography. Signal noise from disturbances, bias, and drift are inevitable as satellite 102 travels at orbital speeds. However, QTIP 101 and quantum gravimeter 106 can measure gravity in different ways and from different perpendicular axes / dimensions. In some embodiments, data processing system 105 and other onboard processors of QASM 100 may combine high-precision data collected from quantum gravimeter 106 with data collected from Q-TIP 101 and analyze the combined data through one or more Bayesian machine learning algorithms and / or Kalman filters to improve the inverse solution.

[0038] In some embodiments, data processing system 105 is configured to generate a tomographic subsurface map via gravity inversion. Gravity inversion is a geophysical technique used to infer subsurface density distribution from gravity measurements. With gravity inversion, an inverse problem is solved to determine one or more suitable modelparameters that fit the measured gravity data. The gravity inversion techniques implemented by data processing system 105 may involve regularizations, Fast Fourier Transforms, and / or least squares analysis, and may incorporate other types of data (e.g., seismic, magnetic, topographic, etc.).

[0039] Some example benefits provided by QTIP 101 and quantum gravimeter 106 include the following: (i) QTIP 101 and quantum gravimeter 106 do not share any biases or errors apart from white noise; and (ii) QTIP 101 and quantum gravimeter 106 can create a set of 2-qubit Bloch Sphere that enables the potential for radical noise reduction.

[0040] In addition, signal noise in QASM 100 may be mitigated through one or more of the following: (i) analysis of integrated differential measurements; (ii) cooling of the atoms to mK temperatures that will eliminate much of the stochastic noises; (iii) implementation of Bayesian ML and Kalman Filter techniques; and (iv) designs for molecular pumps, acoustic dampers, and expansion correcting structures that enable high-quality reduction of recurring errors and biases. Some of these techniques may be implemented by, for example, data processing system 105 or other onboard computers of satellite 102.

[0041] In some embodiments, a Kalman filtering process and Bayesian statistics of data are used to nearly eliminate or reduce the noise associated with the gravity-related measurements. In some embodiments, a Bayesian machine learning algorithm is used to solve for the inverse solution of multi-modal equations. The solution is then used to generate the 3D geophysical tomography of a subsurface. In some embodiments, QASM 100 is configured to measure the effects of general relativity to capture changes to planetary gravity wells. In some embodiments, QASM 100 incorporates a quantum Kalman filter or equivalent signal filtering algorithms to process one or more datasets.

[0042] In the case of 3D tomography, QASM 100 may comprise multi-satellite gravity sensors used in applications for the Moon and the Earth. Some applications may involve the formation flight of two or more satellites. Some applications may involve positioning the satellites precisely to measure the gravity and gravity gradients for the satellites, which could be complex and could involve biases and noises. In some embodiments, QASM 100 is configured to obtain gravity measurements and the measurement of gravity gradients (or gravity vectors). In some embodiments, QASM 100 is configured to obtain perpendicular gradient measurements (e.g.,three perpendicular vectors in 3 -dimensions), further enhancing the quality of the signal and subsurface resolution.

[0043] In addition to the exemplary aspects described above, the present invention is further described in the following study and description of quantum gravimeters, which are set forth to aid in the understanding of the invention, and should not be construed to limit in any way the scope of the invention as defined in the claims which follow thereafter.QUANTUM GRAVIMETER STUDY

[0044] Based on studies conducted on quantum gravimeters, one approach or method that may be adopted by systems of the type described herein involves observing the atom interference effect of a ballistic trajectory of a cloud of atoms. This method takes advantage of atom interferometry to observe minute variation of a gravitational field. According to the studies, advantages of using this method include: (i) no moving mechanical part; (ii) absolute gravity measurement; (iii) great accuracy (pGal); and (iv) sampling rate suitable for dynamic measurement (few Hz). According to the studies, some disadvantages associated with this method are: (i) complexity: requiring careful tuning of various laser source; (ii) decoupling from vibration and rotation; (iii) sensitive to contaminants (requirement to operate in ultra-high vacuum (UHV) condition) and (iv) sensitive to stray magnetic fields.

[0045] The specifications of some example commercial quantum gravimeters are set forth in Table 1 below.Table 1 : Examples of commercial quantum gravimeters.

[0046] Several parameters are of importance for a space quantum gravimeter: weight, size, repetition rate, precision, lifetime, and power. A spacecraft’s payload and carrying capacity are quite limited. The commercial systems, while possible to carry in a vehicle, would still be costly to launch in orbit. In this regard, M Squared may be the preferred choice. However, the repetition rate is the slowest. This characteristic is highly desirable as a satellite will hover rapidly over a body’s surface. The detection of water or other resources will depend on the resolution of the probed surface.

[0047] The precision of the gravimeter importance is twofold. First, variation of density can indicate the presence of a region of interest. Without sufficient precision, the difference of density due to the presence of a deposit may not be detectable. Second, the gravitational field’s strength is proportional to the distance between the gravimeter and the body. A higher precision will accommodate a greater distance from the surface.ABSOLUTE QUANTUM GRAVIMETERS

[0048] QASM 100 and other systems of the type described herein may comprise one or more absolute quantum gravimeters (AQG). A working principle of the AQG may be achieved as described below. First, a very diluted gas of rubidium may be released from an evaporator reservoir or dispenser. Background thermal atoms may be admitted in a vacuum chamber. AQG requires an ultra-high vacuum environment (10-10 Torr) to operate. An optical push beam directs a fraction of these atoms through a series of transverse counter-propagating optical beams for optical cooling. This creates a flux of rubidium atoms cooled down to about 1.5mK with low transverse velocity profile. This flux then enters a second chamber containing a 3-dimensional Magneto-Optical Trap (3DM0T). With proper timing between the activation of the pusher beam and the loading of the 3DM0T, the trapped atom cloud undergoes a second cooling process called evaporative cooling.

[0049] This creates a Bose-Einstein Condensate (BEC). The BEC is a cloud of coherent slow- moving atoms that share the same lowest energy state. This BEC is then released and free-falls(or is pushed) into an interferometry tube. While accelerating through the tube, a sequence of counter-propagating optical pulses with precise frequencies and timing will manipulate the BEC state across two possible trajectories to create an atomic Mach-Zehnder interferometer.

[0050] The first beam pair acts as an atomic beam splitter that changes the internal state of the atom and applies some ‘recoil’ momentum. The second beam pair acts as a mirror and inverts the internal state and momentum of the atoms. The last pulse recombines the atoms that are now in superposed states. The resulting superposition state depends on the relative phase difference between the different path trajectories (e.g., trajectories which are affected by gravity among other things). Measuring the fraction of atoms in one of the two states will yield an oscillatory function of path difference and this difference may carry information about the gravitational field.

[0051] An AQG requires the integration and simultaneous operation of multiple subsystems to perform its measurement. Most of these systems must work continually during the data acquisition. An AQG may, for example, comprise one or more of the following for operation: (1) an ultra-high vacuum system; (2) a frequency-locked laser system; (3) an atomic source with rubidium evaporator; and (4) an atomic interferometer with an interferometry tube and an atomic absorption detector.

[0052] The ultra-high vacuum system comprises an enclosure and pumps, where the ultra-high differential vacuum system may include the enclosure where atomic flux requires an ultra-high vacuum (ICT10Torr) void of any contaminant to operate. Contaminants affect quality and lifetime of BEC states and are also detrimental to ballistic flight of rubidium atoms. The enclosure should also be made with non-ferromagnetic material. Titanium based alloy and nonmagnetic Stainless Steels are normally used for this application. Titanium have the advantages of: being lightweight, having low-heat capacity, having small thermal dilation, being highly resistive (eddy current), and having good outgassing coefficients. It also has a small thermal dilation coefficient matched to BK7 glass that could be used as windows. The ultra-high vacuum regime is achieved through a combination of different pumps. A first vacuum (down to 10'8mbar) is created with a turbomolecular pump. A second vacuum (down to 10"10mbar) is created with an ion and sublimation pump. The sublimation pump (or getter) is used to help remove noble gas and other contaminants from circulation. Careful placement of a pump willavoid stray magnetic field interfering with the atom flux. A heating element could be used for the initial bake out procedure to accelerate outgassing of the elements.

[0053] The frequency-locked laser system comprises a reference laser, a pusher beam and cooling beams delivery module, and a pulsed Raman lasers module. A laser with stable wavelength emission is used as a reference laser for most of the hyperfine transition of interest. This laser typically has a wavelength of around 780nm. All the other lasers’ emission frequency are measured (beat frequency measurement) against this reference source. The reference laser itself is locked to the transition wavelength using a rubidium cell or a modulation transfer spectroscopy scheme. Pusher and cooling beams are similar in their requirement. Both are made using a narrow line source frequency locked to the reference laser. Both types of beam require linewidth smaller than the atomic transition linewidth of about 6MHz. That source is then frequency shifted using an acousto-optic modulator to be detuned from the transition resonance peak. Laser used for cooling beam frequency is (redshift) detuned from reference laser that is locked on the rubidium resonance peak. The pushing beam requires slightly more detuning that the optical beam. A pulsed Raman system may be used for the manipulation of the internal state of an atom. It is possible to use a combination of counter-propagating Raman beams to control the hyper transition of atoms. The frequency difference between the counterpropagation beams must be that of the target transition. This allows the use of cheaper telecom components and optical amplifiers operating at about 1560nm. The frequency shifting can be achieved using one or more electro-optical modulators.

[0054] The atomic source with rubidium evaporator includes an atom cooling chamber (e.g., 2D-M0T) and a BEC chamber (e.g., 3D-M0T). The rubidium reservoir may be a tube containing a small amount of rubidium metal. The vapor pressure, or the rate of evaporation, is controlled by varying the tube’s temperature with a small heating element. Winding of the heating element may be made in a manner to avoid creation of magnetic field through loop and solenoid. Setting the temperature is a trade-off between having low-background pressure and fast loading of the magneto-optical trap. A pusher beam at the output of the reservoir will accelerate atoms to pass through an optical cooling and differential pressure chamber. Atom flux should be guided through a small opening at the end of the differential pressure chamber to separate the flux from wandering rubidium atoms. One or more ionic pumps workcontinuously to remove scattered rubidium atoms from the system. It is generally desirable to maintain high vacuum level because wandering atoms tend to transfer heat through collision between the walls and the atom cloud.

[0055] The cooling chamber of the atomic source with rubidium evaporator has two pairs of large orthogonal counterpropagating optical beams and a linear quadrupole magnetic field that is constant along the direction of the atom flux. The quadrupole magnetic field is produced using two pairs of racetrack coils in anti-Helmholtz configuration. The combined actions, on the atoms, of the optical and magnetic field generates a 2D confinement in the transverse dimensions of atomic flux propagation vector. The cooling mechanism is mainly through a process of photon emission and reabsorption combined with doppler shifting effect. Other mechanisms involved are the polarisation gradient and Zeeman cooling effects. The beams’ diameter should be large to allow a longer cooling length of the 2D-trapped atoms as they migrate toward the second cooling stage. Surface flatness of the optical element is crucial as any wavefront aberration may create “push zones ”on the atomic flux. The atom flux leaving the chamber is cooled down (to about 1.5 mK) and travels toward a second magneto-optical trap.

[0056] The BEC chamber of the atomic source with rubidium evaporator is another magnetooptical trap. Unlike the cooling chamber, the confinement is 3 -dimensional (3D-M0T). This implies that upon its activation, the atom is trapped around a focal point, further cooled (to the pK range), and form a BEC through an evaporative cooling process. 3D-M0T can be realized using a combination of optical beam and stack of inductive structure called an atomic chip.

[0057] The atomic interferometer has an interferometry tube and an atomic absorption detector. The interferometry tube is part of the enclosure that contains multiple large windows. The interferometry tube also offers multiple vantage points for the observation BEC and for alignment purposes. Those windows should be anti-reflective (AR) coated for both 780nm and 1560nm wavelengths to avoid unwanted reflection in the system. The absorption detector is based on a CCD imaging system mapping the absorption of a near-resonance probe beam. The probe beam is a large collimated beam that crosses the BEC at the end of the interferometry tube. By absorption imaging, the size, shape, density distribution and atom number can be determined.

[0058] Systems of the type described herein may be combined with other systems for use in various geophysical applications and other applications. By way of example, the various teachings of the present application may be readily combined with the various teachings of any of the following documents, which are herein incorporated by reference: the paper entitled "Precision gravity measurements with atom interferometry" by G. Rosi, PhD. University of Pisa, 2012; the paper entitled “Thirty years of progress in absolute gravimetry: a scientific capability implemented by technological advances” by J. E. Faller, Metrologia, vol. 39, p. 425- 428, October 2002; the paper entitled "The superconducting gravimeter" by J. M. Goodkind, Rev. Sci. Instrum., vol. 70, p. 4131- 4152, November 1999; the paper entitled “Long-Lived Bloch Oscillations with Bosonic Sr Atoms and Application to Gravity Measurement at the Micrometer Scale” by G. Ferrari, N. Poli, F. Sorrentino and G. M. Tino, Phys. Rev. Lett., vol. 97, p. 060402, August 2006; the paper entitled “Precision gravimetry with atomic sensors” by M. de Angelis, A. Bertoldi, L. Cacciapuoti, A. Giorgini, G. Lamporesi, M. Prevedelli, G. Saccorotti, F. Sorrentino and G. M. Tino, Meas. Sci. Technol., vol. 20, p. 022001, December 2008; the paper entitled “Multi-loop atomic Sagnac interferometry” by C. Schubert, S. Abend, M. Gersemann, M. Gebbe, D. Schlippert, P. Berg and E. M. Rasel, Sci. Rep., vol. 11, p. 1-9, August 2021 ; the paper entitled “Absolute airborne gravimetry with a cold atom sensor” by Y. Bidel, N. Zahzam, A. Bresson, C. Blanchard, M. Cadoret, A. V. Olesen and R. Forsberg, J. Geod., vol. 94, p. 20-9, January 2020); the paper entitled "Advances toward fieldable atom interferometers" by F. A. Narducci, A. T. Black and J. H. Burke, Advances in Physics: X, vol. 7, p. 1946426, December 2022; the paper entitled “Manipulating atomic velocities using diode lasers” by R. N. Watts and C. E. Wieman, Opt. Lett., vol. 11, p. 291-293, May 1986.

[0059] While the above description describes features of example embodiments, it will be appreciated that some features and / or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. For example, the various characteristics which are described by means of the represented embodiments or examples may be selectively combined with each other. Accordingly, what has been described above is intended to be illustrative of the claimed concept and non-limiting. It will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the invention as defined in the claims appended hereto. The scope of the claims should not be limited by the preferredembodiments and examples, but should be given the broadest interpretation consistent with the description as a whole.Interpretation of Terms

[0060] The terms "including," "comprising," and variations thereof mean "including but not limited to," unless expressly specified otherwise. “Connected,” “coupled,” or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof. “Herein,” “above,” “below,” and words of similar import, when used to describe this specification shall refer to this specification as a whole and not to any particular portions of this specification. “Or” in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. A listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms "a," "an," and "the" mean "one or more," unless expressly specified otherwise.

[0061] The terms "an embodiment," "embodiment," "embodiments," "the embodiment," "the embodiments," "one or more embodiments," "some embodiments," and "one embodiment" mean "one or more (but not all) embodiments of the present invention(s)," unless expressly specified otherwise.

[0062] Where a component is referred to above, unless otherwise indicated, reference to that component should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.

[0063] Furthermore, it will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the example embodiments described herein. However, it will be understood by those of ordinary skill in the art that the example embodiments described herein may be practiced without these specific details. In otherinstances, well-known methods, procedures, and components have not been described in detail so as not to obscure the example embodiments described herein. Also, the description is not to be considered as limiting the scope of the example embodiments described herein.

[0064] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and / or acts with equivalent features, elements and / or acts; mixing and matching of features, elements and / or acts from different embodiments; combining features, elements and / or acts from embodiments as described herein with features, elements and / or acts of other technology; and / or omitting combining features, elements and / or acts from described embodiments.

[0065] Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.

Claims

CLAIMS1. A quantum measuring system comprising: a satellite; a data processing system onboard the satellite; a quantum gravimeter onboard the satellite and in data communication with the data processing system; and a quantum tip comprising a first high precision clock spaced apart from a second high precision clock, wherein the quantum tip is physically supported by the satellite and in data communication with the data processing system.

2. The system of claim 1, comprising an alternative modality sensor onboard the satellite and in data communication with the data processing system.

3. The system of claim 2, wherein the data processing system is configured to process a combination of structural data collected from the alternative modality sensor and functional data corresponding to gravity-related measurements collected from the quantum tip and the quantum gravimeter.

4. The system of claim 2, wherein the alternative modality sensor comprises one or more of a magnetic sensor and an altimeter.

5. The system of claim 1, wherein the data processing system is configured to process a combination of differential gravity measurements collected by the quantum tip and absolute gravity measurements collected by the quantum gravimeter.

6. They system of claim 5, wherein the data processing system is configured to implement a machine learning model to process the combination measurements.

7. The system of claim 6, wherein the machine learning model is trained on data collected from previous surveys of subsurface composition of a known geographic region.

8. The system of claim 6, wherein the machine learning model is a Bayesian machine learning model.

9. The system of claim 5, wherein the data processing system is configured to filter the combined measurements by implementing a Kalman filter.

10. The system of claim 1, wherein the first and second high precision clocks are atomic clocks.

11. The system of claim 10, wherein the data processing system is configured to analyze the differential effects of gravity wells on first and second atomic clocks measured by the quantum tip.

12. The system of claim 10, wherein the quantum tip is configured to measure the effects of general relativity on the first and second atomic clocks.

13. The system of claim 10, comprising one or more spars, wherein the first atomic clock and the second atomic clock are spaced apart by a distance defined by the one or more spars, and wherein the satellite is located between the first and second atomic clocks.

14. The system of claim 10, wherein the first atomic clock and the second atomic clock are spaced apart by a length between 8 meters to 12 meters.

15. The system of claim 1, wherein the quantum gravimeter comprises one or more of an interferometer, an optical tweezer, and a magneto-optical trap.

16. The system of claim 1, wherein the quantum gravimeter is an absolute quantum gravimeter.

17. The system of claim 16, wherein the absolute quantum gravimeter comprises an ultra- high vacuum system.

18. The system of claim 16, wherein the absolute quantum gravimeter comprises a frequency-locked laser system.

19. The system of claim 16, wherein the absolute quantum gravimeter comprises an atomic source.

20. The system of claim 16, wherein the absolute quantum gravimeter comprises an atomic interferometer.

21. Systems having any new and inventive feature, combination of features, or subcombination of features as described herein.

22. Methods having any new and inventive feature, combination of features, or subcombination of features as described herein.

Images