Spin-based quantum sensor

Abstract

The present invention provides spin-based quantum systems and sensors. In particular, the present invention provides means for aligning an alignment element with a spin-based sensing probe, thereby sensitising the probe to a stimulus.

Description

[0001]Quantum Systems Field of the invention The present invention relates to the field of spin-based quantum sensors and sensing probes. In particular, the present invention relates to means for aligning an alignment element with a spin-based sensing probe, thereby sensitising the probe to a stimulus. Background of the invention Spin-based quantum sensors exploit the fact that small changes in stimulus can alter the state of isolated quantum systems known as sensing probes. Spin-based sensing probes comprise one or more electrons with a spin state that is extremely sensitive to stimulus, and are capable of coherently transmitting changes in spin state into a detectable signal. A solid-state example of such a probe is the nitrogen-vacancy (NV-) centre in diamond, a defect which involves a nitrogen atom and an adjacent vacant lattice site in a diamond lattice structure. In this defect, the negatively charged NV- centre forms a spin triplet in the ground state, the energy of which is susceptible to local magnetic and electric fields. The spin state of the NV- centre is highly sensitive to stimuli, and can be determined by a contrast in its fluorescence. As a result, the NV- centre has highly favourable and manipulatable properties of fluorescent signal production, which are sensitive to nanoscale changes in stimulus. Spin- based quantum sensors comprising NV centres have been used to detect changes in magnetic fields of a few nanotesla, as well as changes in electric fields and temperature. Thus, spin-based quantum sensors have been established as a powerful, versatile and low-cost means for sensitively detecting nanoscale stimuli (see e.g. WO2014051886A1, WO2016126436A1, US8885301B1, each of which are incorporated herein by reference). The defect comprised in a spin-based sensing probe possesses a magnetic dipole as a result of its spin, which is oriented along the axis comprising the NV centre in the diamond lattice. To sensitise the probe, a field must be applied (e.g. a magnetic, electric or light field) to bring the magnetic dipole into a state that sensitively responds to changes in the local environment, i.e. wherein the spin-based sensing probe is sensitised. The applied field must have a direction and magnitude relative to the orientation of the magnetic dipole to achieve this. However, as a default, the orientation of the magnetic dipole is unknown due to stochastic placement, and varies for each NV centre. Accordingly, it is necessary to employ a means for aligning the external field with the magnetic dipole of the spin-based sensing probe. Such aligning means must provide extremely precise control of the magnitude and direction of the external field, relative to the spin-based sensing probe. Known aligning means in the art of magnetic field alignment include the use of three-axis solenoid coils and axial translation stages carrying strong permanent magnets. The use of three-axis solenoid coils is the established method to date in this field, which involves placing three individual solenoid coils, one in each of the x, y and z axes, around the spin-based sensing probe and the sample for detection (Fukushige et al., Identification of the orientation of a single nv center in a nanodiamond using a three-dimensionally controlled magnetic field, Applied Physics Letters, 116(26):264002, 2020; Stefan et al. Multiangle reconstruction of domain morphology with all- optical diamond magnetometry, Physical Review Applied, 16(1):014054, 2021). Hence, the use of three-axis solenoid coils aims to produce an overall vector magnetic field on the spin- based sensor probe, by controlling the relative magnitudes of the individual magnetic fields produced by each of the three solenoid coils. Less commonly, axial translation stages have also been used, to move a permanent magnet from point a to point b along a linear or rotational direction in a single axis relative to a spin-based sensing probe (Weggler et al., Determination of the three-dimensional magnetic field vector orientation with nitrogen vacancy centers in diamond, NanoLetters, 20(5):2980–2985, 2020). Due to the cumbersome nature of the alignment process, with this approach the permanent magnet is typically positioned once and then aligned along a set diamond crystalline axis. In order to best isolate and manipulate fragile quantum states, quantum sensors and related technologies often take requirements from the cutting edge of experimental physics. This can include precise and complex optical assemblies, strong vector magnetic fields, high-speed microwave delivery, and compatibility with extremely low temperature environments. In fact, emerging quantum technologies may even combine research from two or more experimental settings, by coupling solid state spins to photonics, nanomechanics or superconducting structures. However, as these proof-of-principle devices become more sophisticated and start to scale, traditional aligning means such as linear translation stages and solenoid coils will no longer provide the flexibility, speed, and precision to meet these constrained and sometimes competing combinations of experimental requirements. For example, the requirement for solenoid coils at three axes around the spin-based sensor probe and the sample for detection severely restricts optical and / or mechanical degrees of freedom. The inherent inflexibility of the axial translation stage approach, which involves a cumbersome, built-in pre-alignment, also poses similar problems. Furthermore, solenoid coils operate hot, which will have adverse implications for using the three-coil approach in biologically sensitive experiments, and the three-coil approach can also only feasibly produce a magnetic field of limited strength. As for the axial stage approach, this entirely precludes the use of nanodiamonds as spin-based sensing probes, where each individual NV centre may have a stochastic orientation. Thus, there are a number of limitations and drawbacks to the established aligning means that are used in spin-based sensing probes, which will only become more impactful as new applications and technologies relating to quantum sensors are developed. The field of robotics has long been developed to operate in inaccessible conditions, such as at the microscale or in very low temperature environments, and benefits from versatility due to sophisticated software stacks and well-developed open-source hardware. In the rapidly advancing field of robotics, classical electromechanical approaches have been superseded by smart dexterous machines. However, to date and to the best of the knowledge of the inventor, no substantive physical use of such robotics, such as robotic aligning means, has been suggested or attempted in the field of quantum information technology, e.g. in a quantum sensor. Summary of the invention The present invention adopts techniques from the field of robotics to demonstrate the use of a robotic aligning means to align a field with the magnetic dipole of a spin-based sensing probe, thereby sensitising the probe to stimulus. In a first aspect, the present invention provides a system comprising: a) a spin-based sensing probe; b) an alignment element; and c) a robotic aligning means configured to movably position the alignment element. In an embodiment, the robotic aligning means is configured to align the alignment element with the spin-based sensing probe, e.g. with a magnetic dipole of the spin-based sensing probe. In an embodiment, the robotic aligning means is configured to movably position the alignment element to a position wherein the spin-based sensing probe is sensitised by the alignment element. In an embodiment, the aligning means is capable of moving (e.g. configurable or configured to move) the alignment element from a first position to a second position via a plurality of different paths, e.g. including via at least one or more non-linear paths. In a second aspect, the present invention provides a robotic aligning means, wherein the robotic aligning means is programmed to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe. In a third aspect, the present invention provides a quantum sensor comprising the system or the robotic aligning means of the invention. In a fourth aspect, the present invention provides a computer-implemented quantum sensing method, comprising programming a robotic aligning means to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe. In a fifth aspect, the present invention provides a method of sensitising a spin-based sensing probe, wherein the method comprises: a) providing a spin-based sensing probe, a robotic aligning means and an alignment element; b) determining a position of the alignment element wherein the spin-based sensing probe is sensitised; and c) using the robotic aligning means to movably position the alignment element to the position wherein the spin-based sensing probe is sensitised. Description of the accompanying Figures Figure 1: Experimental setup and working principles of the exemplified embodiment of the invention. A. Placing a permanent magnet near the NV centre magnetometer produces a magnetic field of a known orientation, defined along its axis (field lines in white). B. One use case is to change the spin resonance of a magnetometer, to operate at its most sensitive regime (linear with respect to detected field) away from the zero-field splitting (marked in grey). As observed, a field along the NV centre Bzaffects this response, whereas off-axial components only contribute unwanted performance degradation. The field Bextshould therefore be approximately aligned to the NV centre magnetic dipole orientation Bz. C. The 6 Degree of freedom (DoF) robot was used to orient the magnet in complex surroundings. The robot base was located at the world origin (x-axis indicated in dark grey, y-axis indicated in light grey, z-axis in black). The Tool Centre Point (TCP axis marked) was translated along the x-axis of the end effector axis (marked) to set the required field strength. The TCP coordinate (x, y, z, αy, αz) was then set to the NV centre position and rotated around the y and z axis, i.e. varying αyand αzof the TCP, to form a defined vector from the end effector to the TCP (the line connecting the TCP and end effector). The robot positions at a range of different (αy, αz) are shown in the inset diagrams. Through this method, the highly-dexterous robot can create fields with arbitrary field strengths and orientations, and align the TCP axis with the NV axis to produce Bz. Figure 2: Robot arm generating arbitrary vector magnetic fields. A. A permanent magnet of varying mass was placed in the tool (left panel). A Hall sensor measured the x−z trajectory of the field produced by the arm (right panel). The trajectory was well-fitted using a model of the field generated by the cylindrical magnet, noting a 15° offset in the x-z crossing from the expect 45° (shown with dotted line) and a varying non-zero offset in y, with this offset resulting in a non-linear trend in field registered with increasing magnetic mass. This initial measurement and model can be used for fine alignment calibration. B. The arm could create a field over the full x − y − z sphere segment (one-eighth) with 3° accuracy. White pixels in the image plots indicate the few unreachable positions. C. The distance r from the end effector to the Tool Center Point produced a field strength fall off in Bxproportional to 1 / r3(top panel), from which points (shown by vertical lines) could then be sampled (middle panel) to create a linear field response with high accuracy (bottom panel). Figure 3: Motion planning in experimental settings. A. Two experimental settings were modelled, a cryostat with optical access and a confocal microscope. Plotted are the simulated collisions with the robot (light grey) and avoided collisions (dark grey). For the confocal, a limited reachable workspace subset was observed. B. An algorithm was developed to replace these unreachable poses with collision-free poses. The procedure is as follows: (i) a desired field vector is measured in a forbidden position, (ii) displacement puts the magnet in an allowed position, (iii) angular orientation sets the correct field vector, (iv) a further displacement corrects the field magnitude. C. Using a dipole source to calculate the rotation, the magnet could be deterministically rotated and there could be recovered the →B vector (title bar) felt at the observer (large grey dot on X axis). D. The designed rotation matched experimentally in minimising the off-axial field at 26°. E. Measuring with the 3D Hall Sensor at each stage following the panels in Fig 1B, the final vector well matched the initial vector (quantified by the similarity function S defined in the corresponding Example). Figure 4: Robot-assisted magnetometry. A. Confocal microscope showing the robot in position. B. Optically accessed cryostat showing the robot in position. C. Confocal image of NV centre located in diamond lens (mounted in setup shown in A.). D. Photoluminescence scan in z of above. E. Optically Detected Magnetic Resonance (ODMR) showing zero-field magnetic field splitting of associated spin in dark grey shading / light grey line when robot arm was approximately 10 cm from sensor, and strong 100 MHz splitting in light grey shading / dark grey line when robot arm was proximal to the spin sensor. F. Fitted splitting for robot trajectory in 5° increments (large circles) and 2° increments (small circles), indicating movement is stable and repeatable. G. Hall sensor data shows Bx, Bycrossover in trajectory. Normalising splitting between resonances by B magnitude reveals σzdependence in Trajectory 1 and Trajectory 2, indicative of angular alignment. Detailed description of the invention Detailed overview of the invention The present invention adopts techniques from the field of robotics to demonstrate the use of a robotic aligning means to align a field with the magnetic dipole of a spin-based sensing probe, thereby sensitising the probe to stimulus. In a particular embodiment, the present invention demonstrates the use of a robotic aligning means to align a magnetic field in the form of a strong permanent magnet with the magnetic dipole of a NV- centre, thereby sensitising the quantum sensor comprising the NV- centre to nanoscale changes in a magnetic field. The robotic aligning means can traverse a highly complex experimental setup, and can provide a robust vector field to sensitise a quantum sensor. The integration of robotics with quantum systems overcomes limitations in complex experimental settings, allowing for increased speed, accuracy and ruggedness in quantum technology applications. In particular, the present invention has proven viability in circumstances where traditional applications of 3- axis coils and translation stages would be infeasible. Thus, the present invention provides a novel robot-assisted approach to spin-based quantum technology. In particular, the present invention provides spin-based quantum sensors comprising a robotic aligning means. To achieve this in the present invention, the robotic aligning means can be configured to movably position an alignment element, such as a strong permanent magnet, thereby aligning the field of the alignment element with the magnetic dipole of a spin-based sensing probe. In a particular embodiment, the present inventor has achieved this using a robotic arm comprised of a set of rigid bodies connected by six joints, with each joint driven by a motor actuator to position a held magnet at a predetermined position and degree of rotation / orientation with six degrees of freedom. Herein, this novel approach has been trialled and validated for the first time, and has unexpectedly been shown to be highly successful. In particular, the use of robotic aligning means according to the present invention provides vastly improved versatility and reproducibility over standard means of aligning the fields of spin-based sensing probes. This has been demonstrated in an embodiment in respect of aligning the magnetic field of a spin- based sensing probe using a strong permanent magnet. However, it will be understood by the skilled person that this approach can also be used for aligning other fields of the spin-based sensing probe, such as electric field or light fields, via the use of appropriate aligning means, e.g. a source of electrons such as an electrode or a source of photons such as a laser or mirror respectively. Moreover, the present approach has been demonstrated in an embodiment to sensitise a spin-based sensing probe to a change in a magnetic field. However, it will be understood by the skilled person that the robotic aligning means of the present invention may be used to sensitise a spin-based sensing probe to many different kinds of stimulus, including changes in electric fields, heat and thermal resistance. Systems and apparatus In a first aspect, the present invention provides a system comprising: a) a spin-based sensing probe; b) an alignment element; and c) a robotic aligning means configured to movably position the alignment element. In an embodiment, the system is a quantum system. In an embodiment, the system is a quantum processing system. In an embodiment, the system is a robot-assisted spin-based quantum system. In an embodiment, the system is a quantum computer. In a preferred embodiment, the system is a quantum sensor. In an embodiment, the system is a spin-based quantum sensor. In an embodiment, the sensor detects changes in local environment through shifts in the resonant energy of the system. In an embodiment, the system is a magnetometer. In an embodiment, the system is for detecting stimuli. In an embodiment, the stimuli are generated by a sample. Accordingly, in an embodiment, the system further comprises a sample that generates a stimulus or stimuli. It will be understood by the skilled person that, while the system of the present invention may detect a single stimulus at minimum, in practice many changes in local conditions and therefore many stimuli may be detected. The basic elements of a spin-based quantum system, such as a spin-based quantum sensor, and variations therein are known and practicable by the skilled person. In an embodiment, the system comprises an excitation means and a signal detection means. In an embodiment, the excitation means is an optical excitation means. In an embodiment, the excitation means is configured to excite the spin-based sensing probe. In an embodiment, the excitation means is configured to emit excitation light. In an embodiment, the spin-based sensing probe is configured to emit a signal when excited by the excitation means. In an embodiment, the signal detection means is a fluorescence detection means. In an embodiment, the signal detection means is configured to detect a signal emitted by the spin-based sensing probe. In an embodiment, the signal emitted by the spin-based sensing probe is modulated by stimuli. In an embodiment, the signal is light, preferably fluorescent light, which is modulated by stimuli. In an embodiment, the intensity of the light is modulated by stimuli. In an embodiment, the stimuli is a change in a magnetic field, electric field or temperature. In an embodiment, the stimuli is a nanoscale change. In an embodiment, the stimuli is the presence or state of single photons. In an embodiment, the stimuli is the presence or state of single spins. For the purposes of the present invention, it will be understood that a stimuli magnetic field is distinct from the magnetic field of the alignment element. In an embodiment, the system further comprises a microwave excitation means. In an embodiment, the system comprises a microwave excitation means in addition to the optical excitation means and the detection means. In an embodiment, the microwave excitation means is configured to excite the spin-based sensing probe. In an embodiment, the microwave excitation means is configured to sensitise the energy state of the spin-based sensing probe. In an embodiment, the spin-based sensing probe resonant frequency is magnetically shifted to match the microwave excitation frequency. In an embodiment, the system further comprises physical constraints. In an embodiment, the system comprises physical constraints that hinder the linear positioning of the alignment element for sensitising the spin-based sensing probe. In an embodiment, the system further comprises constraints that hinder the use of a linear stage for alignment and / or that hinder the placement of solenoid coils at three axes around the sample. In an embodiment, the system further comprises a cryostat or a scanning stage confocal microscope. In an embodiment, the spin-based sensing probe comprises a point-like system with an associated electron spin triplet. In an embodiment, the spin-based sensing probe comprises a solid-state defect. In an embodiment, the spin-based sensing probe is a near-surface defect. In an embodiment, the defect is no more than 1 µm, 500 nm, 400 nm, 300 nm, 200 nm, 100 nm or 50 nm from the surface of the probe, such as the surface of the diamond or nanodiamond. In an embodiment, the spin-based sensing probe comprises a defect in diamond. In an embodiment, the diamond is a nanodiamond. In an embodiment, the spin- based sensing probe comprises a NV- centre. In an embodiment, the spin-based sensing probe comprises an electron comprised in a NV- centre. It will be understood that “NV- centre” herein refers to a negatively charged NV centre, which may also simply be referred to simply as a “NV centre” herein (and generally in the art of quantum information technology) for brevity. In an embodiment, the spin-based sensing probe has an unknown orientation. In an embodiment, the spin-based sensing probe has a random orientation. In an embodiment, the orientation refers to the orientation of an axis of the spin-based probe, e.g. the axis of a NV- centre. In an embodiment, as a default, the spin-based probe is not sensitised. In an embodiment, as a default, the spin-based probe is in need of alignment. In an embodiment, the alignment element is an element that sensitises the spin-based probe when it is aligned with the spin-based sensing probe, i.e. by the robotic aligning means. In an embodiment, the alignment element generates a field, i.e. the alignment element field. In an embodiment, the alignment element is an element that generates a magnetic field. In an embodiment, the alignment element is a magnet. In an embodiment, the magnet is a permanent magnet. In an embodiment, the magnet is a strong permanent magnet. In an embodiment, the magnet is not an induced magnet, such as a magnet emitting a magnetic field that is generated (at least in part) by an electric current, such as a solenoid. In an embodiment, the alignment element is an element that generates an electric field. In an embodiment, the alignment element is a source of electrons. In an embodiment, the source of electrons is an electrode such as a cathode. In an embodiment, the alignment element is an element that generates a light field. In an embodiment, the alignment element is a source of photons. In an embodiment, the alignment element is a light source or mirror. In an embodiment, the robotic aligning means is configured to securably hold the alignment element. In an embodiment, the alignment element is attached to the robotic aligning means. In an embodiment, a securing means secures the alignment element to the robotic aligning means. In an embodiment, the robotic aligning means is merely defined as an aligning means comprising one or more of the features defining the movement of the aligning means herein. In an embodiment, the robotic aligning means is a means for aligning the alignment element with the spin-based sensing probe. In an embodiment, the robotic aligning means and the alignment element do not generate local heat when stationary. A robotic aligning means is “robotic” in the sense that is generally understood as in the field of robotics, and is an “aligning means” as a means that is capable of aligning a first element (e.g. the alignment element) with a second element (e.g. the spin-based sensing probe) by physically, movably positioning the first element such that it is aligned with the second element (e.g. such that the alignment element sensitises the spin-based sensing probe). In an embodiment, the robotic aligning means comprises a robotic appendage, such as a robotic arm. In an embodiment, the robotic aligning means comprises a robotic appendage adapted to hold a tool, preferably an alignment element, preferably a permanent magnet. In an embodiment, the robotic aligning means comprises at least two, at least three, at least four, at least five, at least six or six pivot points. In an embodiment, the robotic aligning means comprises at least two, at least three, at least four, at least five, at least six or six independent joints. In an embodiment, the robotic aligning means has at least two, at least three, at least four, at least five or six degrees of freedom. In an embodiment, this means that the robotic aligning means is configured to move with x degrees of freedom. In an embodiment, this means that the robotic aligning means is configured to move the alignment element with x degrees of freedom. In an embodiment, the robotic aligning means is programmed to position the alignment element. In an embodiment, the robotic aligning means is programmed to position and rotate the alignment element. In an embodiment, the robotic aligning means is capable of non-linear movement. In an embodiment, capable of non-linear movement means capable of moving from a first point to a second point via a non-linear or complex trajectory. In an embodiment, a non-linear trajectory is a trajectory comprising at least one coordinate that is not located on the straight line that is formed by the first and second points. In an embodiment, the non-linear movement is designed to avoid a collision. In an embodiment, the robotic aligning means is capable of aligning the alignment element. In an embodiment, the robotic aligning means is capable of stably positioning the alignment element for an extended duration. In an embodiment, the robotic aligning means is configured to movably position the alignment element in one or more positions wherein the alignment element sensitises the spin-based sensing probe. In an embodiment, “movably position” means that the physical movement of the robotic aligning means directly alters the position of the alignment element. In an embodiment, the robotic aligning means is configured to movably position the alignment element in all three axes of three-dimensional space (x, y and z). In an embodiment, the robotic aligning means is configured to rotate the alignment element about all three axes of three-dimensional space (x, y and z). In an embodiment, the robotic aligning means is configured to position and rotate the alignment element. In an embodiment, the robotic aligning means is configured to movably position the alignment element with non-linear movement. In an embodiment, the robotic aligning means is configured to movably position the alignment element via a non-linear path. In an embodiment, the non-linear movement comprises avoiding collisions against the robotic aligning means and alignment element. Herein, in an embodiment, “configured to” can mean “configurable to”, or “capable of”. In an embodiment, the robotic aligning means is configured to position the alignment element such that the spin-based sensing probe, e.g. the spin state of an electron comprised in the spin-based sensing probe, is aligned. In an embodiment, “aligned” means that the spin-based sensing probe is sensitised. In an embodiment, the robotic aligning means is configured to position and rotate the alignment element such that the spin-based sensing probe is sensitised. In an embodiment, the robotic aligning means is configured to position the alignment element such that the direction (e.g. the vector) and magnitude of the field of the alignment element sensitises the spin-based sensing probe. In an embodiment, sensitises means increases the sensitivity. In an embodiment, the spin-based sensing probe is sensitised in that the transition frequencies thereof are linearly dependent with changes in stimuli, e.g. an external stimulus magnetic field. In an embodiment the spin-based sensing probe is sensitised in that the photonic signal produced by it is enhanced, preferably maximised. In an embodiment the spin-based sensing probe is sensitised in that the signal contrast produced by it is enhanced, preferably maximised. In an embodiment the spin-based sensing probe is sensitised in that the precession of nearby spins are inhibited, preferably minimised. In an embodiment, the spin-based sensing probe is sensitised to nanoscale stimuli, e.g. changes in the local environment. In an embodiment, the stimulus comprises a change in a local magnetic field, electric field or temperature. In an embodiment, the robotic aligning means is configured to position the alignment element such that a field of the alignment element is aligned with an axis of the spin-based sensing probe. In an embodiment, “aligning” with the spin-based sensing probe means aligning with the magnetic dipole of (e.g. that is comprised in) the spin- based sensing probe. In an embodiment, the robotic aligning means is configured to position the alignment element such that a field of the alignment element is aligned with the axis of the NV- centre. In an embodiment, a field of the alignment element being aligned with an axis of the spin-based sensing probe means that the alignment is sufficient to sensitise the spin- based sensing probe. In an embodiment, the field of the alignment element is aligned to within 15° of the axis of the spin-based sensing probe. In an embodiment, the field of the alignment element is aligned to within at most 15°, 14°, 13°, 12°, 11°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, 1°, 0.1°, essentially 0° or 0° of the axis of the spin-based sensing probe. In an embodiment, the alignment element produces a magnetic field of at least 5 mT on the spin-based sensing probe. In an embodiment, “aligning” the field of the alignment element means aligning the direction of the field of the element. In a particularly preferred embodiment of the system of the present invention, the spin-based sensing probe is a NV- centre and the alignment element is a permanent magnet, preferably a strong permanent magnet. In an embodiment of this type, the robotic aligning means is configured to align the magnetic field of the permanent magnet with the axis of the NV- centre. In an embodiment of this type, the robotic aligning means is configured to position the alignment element in all three axes of three-dimensional space, and configured to rotate the alignment element around all of the three axes of three-dimensional space. In an embodiment of this type, the robotic aligning means is a robotic appendage, preferably a robotic arm, having six degrees of freedom. In an embodiment of this type, aligning the magnetic field of the permanent magnet with the axis of the NV- centre sensitises the NV- centre to stimuli. In an embodiment of this type, the stimuli comprises a nanoscale change in a local magnetic field (that is not the magnetic field of the alignment element). In an embodiment of this type, the stimuli comprises a change in temperature. In a second aspect, the present invention provides a robotic aligning means for use in the system of the present invention. In an embodiment, the robotic aligning means is programmed to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe. In an embodiment, the spin-based sensing probe is that of a quantum sensor. In an embodiment, the robotic aligning means is programmed to avoid collisions. It will be understood that the characteristics, features and embodiments applicable to the robotic aligning means comprised in the system described above will also be applicable to the robotic aligning means aspect of the present invention. In a third aspect, the present invention provides a quantum sensor comprising the system or the robotic aligning means of the invention. In an embodiment, the quantum sensor is a quantum magnetometer. In an embodiment, the quantum sensor senses changes in a local magnetic field of a sample. In an embodiment, the quantum sensor senses changes in an electric field of a sample. In an embodiment, the quantum sensor senses changes in the temperature of a sample. In an embodiment, the changes are nanoscale changes. In an embodiment, the changes are in a tissue sample or cell sample. In an embodiment, the sensor is for detecting a cell or molecule. In an embodiment, the sensor is a biosensor. In an embodiment, the sensor is a nuclear mass resonance (NMR) sensor, such as a sensor comprised in a NMR machine. In an embodiment, the aligning means is configured to movably position the alignment element to more than one position in which the spin-based sensing probe is sensitised. Although “a” sensing probe is referred to herein, in an embodiment the system comprises two or more sensing probes. In a preferred embodiment, however, the system comprises a single sensing probe. Methods In a fourth aspect, the present invention provides a computer-implemented quantum sensing method, comprising training a robotic aligning means to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe. In an embodiment, the method comprises training a robotic aligning means to align a field of an alignment element with an axis of the spin-based sensing probe, preferably wherein the spin-based sensing probe is a NV- centre. In an embodiment, the method comprises training the robotic aligning means to movably position the alignment element without colliding with its environment. In an embodiment, the method comprises training the robotic aligning means to movably position the alignment element via non-linear movement. In an embodiment, training the robotic aligning means comprises simulating the workspace of the robotic aligning means and determining positions wherein the alignment element sensitises the spin-based sensing probe. In an embodiment positions and orientations of the alignment element are determined in this respect. In an embodiment, positions resulting in a collision are determined. In an embodiment, training the robotic aligning means comprises an operator manually manipulating the robotic aligning means within the workspace of the robotic aligning means and determining positions wherein the alignment element sensitises the spin-based sensing probe. In an embodiment positions and orientations of the alignment element are determined in this respect. In an embodiment, positions wherein the alignment element sensitises the spin-based sensing probe are determined by measuring the sensitivity of the spin-based sensing probe. In an embodiment, the positions are determined by measuring a signal from a sensor. In an embodiment, the sensor detects a field of the alignment element. In an embodiment, the signal from the sensor is modulated by a field of the alignment element. In an embodiment, the sensor is substituted for the NV- centre, such as being placed in the location of the NV- centre. In an embodiment, the workspace of the robotic aligning means comprises the region of space that is within the reach of the robotic aligning means. In an embodiment, the workspace comprises the quantum sensor of the quantum sensing method. In an embodiment, the workspace comprises the sample on which the method is carried out. In an embodiment, the workspace comprises the other experimental constraints of the quantum sensing method. In an embodiment, the workspace comprises one or more (additional) physical obstructions to the movement of the robotic aligning means. In an embodiment, the aligning means maintains the position of the alignment element throughout the duration of the sensing method. In a related aspect, the present invention provides a data processing apparatus, device or system comprising or a processor configured to perform the method according to the fourth aspect of the present invention. In a related aspect, the present invention provides a computer program comprising instructions which, when executed by a computer, carry out the method according to the fourth aspect of the present invention. In a related aspect, the present invention provides a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to the fourth aspect of the present invention. In a fifth aspect, the present invention provides a method of sensitising a spin-based sensing probe, wherein the method comprises: a) providing a spin-based sensing probe, a robotic aligning means and an alignment element; b) determining a position of the alignment element wherein the spin-based sensing probe is sensitised; and c) using the robotic aligning means to movably position the alignment element to the position wherein the spin-based sensing probe is sensitised. In an embodiment of the method, step b) comprises: i) determining a first position where the alignment element sensitises the spin-based sensing probe, wherein the first position is blocked, and ii) determining a second, different position wherein the alignment element sensitises the spin-based sensing probe, wherein the second position is not blocked; further wherein step c) comprises using the robotic aligning means to movably position the alignment element to the second position wherein the alignment element sensitises the spin- based sensing probe. Herein, “a” or “an” encompasses the singular and also the plural, unless context or explicit limitation dictates otherwise. Herein, an object “comprising” an element indicates that the object has that element but is not limited thereto, and may further comprise additional, unrecited elements. Positional sensor With a positional sensor, environmental mapping, collision avoidance and the achievable set of magnetic field vectors can be determined by the spin-based sensing probe with a robotic aligning means of the present invention, when it is positioned in any arbitrary physical environment or experimental setting without requiring prior knowledge of its environment. This on-the-fly mapping is achieved through an additional sensing instrument (a positional sensor) attached to the end effector of the robotic arm and by then dynamically updating a feedback algorithm with data gathered from this instrument. Accordingly, in an embodiment, the system of the invention comprises a positional sensor, optionally wherein the robotic aligning means comprises the positional sensor. In the context of the present invention, a positional sensor is a sensor configured to collect information on the position of the robotic aligning means and / or alignment element of the present invention. In an embodiment, the methods of the present invention additionally comprises collecting such information and using it to determine the movement of the robotic aligning means. The additional sensing instrument / positional sensor uses either a time-of-flight sensor such as LiDAR (Light Detection and Ranging) or ultrasound, but can also use a camera and machine vision, or an external magnetic field sensor such as Hall sensor or the quantum sensor itself. In some cases, data from combining multiple techniques are used in what is termed multi-fusion sensing. In an embodiment, the positional sensor comprises a LiDAR instrument such as an instrument comprising a LiDAR emitter and / or detector. In an embodiment, the positional sensor comprises an ultrasound instrument such as an instrument comprising an ultrasound emitter and / or detector. In an embodiment, the positional sensor comprises a camera. In an embodiment, the positional sensor comprises a magnetic field sensor. In the simplest case, the robotic end effector will be equipped with a LiDAR instrument. This instrument transmits a light signal and detects it again, following its reflection off a surface / object. By comparing the generated and detected signal, time of flight information reveals the distance of the nearest object surface. The physical environment of the robot is then mapped like this: ^ First the robot is located in a known home position where the end effector is retracted and not in collision with its environment. ^ The end effector is then traversed around a set of points of increasing extension and varying orientation away from this known home position. ^ At each point, the distance to the nearest object is recorded by the LIDAR sensor. This information is used to update knowledge of the physical environment in a collision mesh. ^ The collision mesh is used to intelligently and dynamically update the necessary points for the end-effector to traverse to complete the map of the physical environment. ^ Once the map is complete, the robot returns to its home position. Accordingly, in an embodiment, the methods of the present invention may comprise: The physical environment of the robot is then mapped like this: 1. Locating the robotic aligning means in a known home position, e.g. where the alignment element is retracted and not in collision with its environment; 2. Traversing the alignment element around a set of points of increasing extension and varying orientation away from the known home position; 3. At one or more (preferably each) point, recording the distance to one or more objects, e.g. the nearest object, by a positional sensor, e.g. a LIDAR sensor; 4. Using the recorded distance to update knowledge of the physical environment, e.g. to determine a collision mesh; 5. Using the knowledge of the physical environment, e.g. the collision mesh, to update the necessary points for the alignment element to traverse to complete a map of the physical environment; and 6. Returning the robotic aligning means to its home position, e.g. once the map is complete. In a calibration step, the robot can now be demonstrated to achieve a set of magnetic field vectors by exploiting the map information to generate field vectors at collision-free locations. To replace collision points, alternative locations that generate identical magnetic field vectors are generated by exploiting the fringe field of the magnet as described in the patent. In the calibration step, the robot can show it can achieve a field of a given amplitude |B| with given vectors (|B|, 0, 0), (-|B|, 0, 0), (0, |B|, 0), (0, -|B|, 0), (0, 0, |B|), (0, 0, -|B|) for instance. Ultrasound operates similarly to LiDAR and may be better suited to different experimental conditions. The camera and machine vision is a known alternative strategy exploited in robotic collision detection, providing a richer data set, but requires more intensive data processing from the camera pixel data. Finally, as an alternative, magnetic sensor data can be used simultaneously in combination with the LiDAR at each point at which the map is being constructed, i.e. before the calibration step. This multi-sensor fusion technique could benefit determining wanted magnetic field vectors without requiring the generation of the full map, useful for instance if the environment is dynamically changing. Examples Background Spin-based magnetometers operate by mapping local perturbations in their environment to shifts in the transition (magnetic resonance absorption) frequency of the spin system. The NV centre in diamond is the prototypical solid state quantum sensor on account of its optically accessible spin state which allows optical manipulation and readout of its spin state at room temperature (Optically Detected Magnetic Resonance or ODMR). NV centre magnetometers have rapidly advanced over the past decade and have reached maturity as a quantum magnetometer, with nanotesla (nT) sensitivities at nanoscale resolutions. As magnetic dipole- dipole interactions are weak and confined to the near field, near-surface NV centres are used to image fields from individual spins. Nanoscale inclusions of diamond, or nanodiamond, are used to host the spin-probe in hot and wet biochemical surroundings in applications such as molecule or cell detection. Nanodiamonds typically contribute an additional term Π to the NV centre Hamiltonian H, from lattice strain and local charges: where B⊥ = (Bx, By) and S⊥ = (Sx, Sy), with z defined as the axis comprising the NV centre along the diamond lattice. In Fig 1B, the term leads to a frequency splitting of size 2E (shown in grey), and the NV centre transition frequencies are robust to magnetic field fluctuations to first order. A bias field Bzis thus required bring to the NV centre into the regime (Bz≫ Π / γ) where the transitions are linearly dependent on the magnetic field, which corresponds to the highest sensitivity. Given nanodiamonds typically display Π ∼ 10 MHz, this requires a moderate magnetic field of 5 mT aligned to the NV axis for this application. A misaligned magnetic field (with a residual Bxor Bycomponent) would lead to a mixing of the energy eigenstates, which would result in a reduction of both the fluorescence and contrast (SNR) of the spin-dependent optical readout. A misaligned magnetic field would cause adjacent spin systems, such as C13spins on the diamond lattice, to precess which would result in loss of spin coherence of the NV centre. Thus, means to align a bias field with a spin-based sensing probe (such as a NV centre) are required. Objective The present inventor proposed to surpass known aligning means for spin-based sensing probes with a robotically controlled vectorial field alignment system. This approach was determined to have the following advantages: (1) Increased precision and control. The robot will manipulate the magnet with a high degree of accuracy, ensuring precise alignment of the generated magnetic field. For the present Example, this means better than 15° accuracy. (2) Fast alignment: by employing a robot to move and position the magnet across optimal trajectories, alignment will be more efficient than manual techniques. (3) Long-term stability: employing closed-loop feedback with sufficient torque against gravity will maintain position securely for extended periods, ensuring stable alignment during experiments. (4) Enhanced reproducibility: A robust algorithm can align and realign the magnet between sample exchange or across multiple sites of interrogation. The robot will consistently produce a given orientation field for different sample geometries. (5) Scalability: the robot will have an adaptable routine that is suitable for a wide range of experimental configurations and constraints. This can also be extended to scenarios where two fields with specific orientations need to be simultaneously applied, e.g. an in-plane and out-of-plane field. For positioning of a magnet at a desired location in 3D space with respect to a point of interest, and allowing for rotation about two axes to achieve magnetic field orientation, this Example utilised a robot with at least five degrees of freedom. The robot in this Example was capable of handling a moderate payload, i.e. enough magnet mass to produce an appreciable field (10 mT) at a distance. Example 1: Workspace analysis Workspace analysis is used for robot control and application, as it evaluates the space the robot can access and manipulate with its end-effector, constrained by the robot’s kinematic configuration. This workspace analysis helps to identify the robot’s suitability for specific tasks and environments. Aspects include workspace volume (total 3D space the robot’s end-effector can reach), workspace boundaries (limits of reachable space), singularities (points in the workspace where degrees of freedom are lost), dexterity (ability to precisely position and orient the end-effector), and reachability (ability to access points in the workspace region). In this Example, workspace analysis was carried out on a magnet carrying robotic arm to evaluate its performance in generating vector magnetic fields. The arm consisted of a set of rigid bodies called links, connected by joints, with each joints driven by a motor actuator. An end-effector, in this case a permanent magnet, was attached to the end link. The arm was an open chain robot, with the position and orientation of the end-effector uniquely determined from the joint positions. The common configuration comprises six joints, providing six Degrees of Freedom (DoF). For this, a Niryo NED 2 robot was used, owing to its well-documented open source stack, and ready availability (https: / / docs.niryo.com / product / ned2 / v1.0.0 / en / index.html). The arm had a moderate payload of 300 g, and was thus capable of lifting 40 cm3NdFeB, which could generate a maximum magnetic field of ≈ 800 mT. For ease of adoption, a cylindrical magnetic source with a radial hole was selected, through which it could be fixed by a screw to the tool shaft. Shown in Fig 1C, the robot is first operated by translating the Tool Center Point (TCP) along the x-axis of the end-effector, coaxial with the magnetisation axis of the magnet. This translation set the distance, and hence strength, of the magnet, from the point of interrogation. To create a set vector field, the robot used a Robot Operating System (ROS) kinematic processor to position its joints, in order to compute a desired pose. The robot pose comprised the location and orientation of the TCP relative to a global coordinate frame. Rigid robots possess six state variables (x, y, z, αx, αy, αz), where the latter three coordinates are angles of rotation about the x, y and z axis respectively. The inverse kinematics problem was to find the joint position given a desired pose. In principle, by fixing x, y, and z at the NV centre location, the vector orientation of an applied magnetic field could be modified by varying αyand αzof the pose. In this Example, the cylindrical magnet was symmetric about αx, so this degree of freedom was left unused. In Fig 1C, in RViz, a visualisation software for ROS, it was simulated that the robot was sufficiently dexterous in positioning its joints to achieve a range of orientations, whereby the magnet was rotated around a stationary point. The goal of modifying this pose was to create a desired magnetic vector field. To experimentally verify this, a 3-axis Hall sensor was positioned at the point of interest in order to measure the field generated by the robotic technique. The robot was set roughly collinear with the sensor axis, observed using a camera with a zoom lens. Fig 2A shows the effect of adding magnets to the structure up to 70 % of the payload by setting the robot along an arc trajectory from horizontal to vertical, by rotating the desired pose from αy= 0 to αy= π / 2. Commonly in robotics, camera data is processed to extract information on the desired pose. Here, the 3-axis Hall Sensor provided rich additional vector information, which, coupled with the known dependence of the magnetic field on position, allowed the desired pose to be measured with higher precision than is visually observable. The data were fitted with a closed form expression of the magnetic field observed from the cylindrical magnet, using the six variables of the pose as fitting parameters. A constant 15° offset was measured in αyand observed in the x − z crossing point of the sensor and the robot, which for an aligned system would occur at 45° (marked by a dashed line in the Fig 2A). Additionally, for this trajectory, it was expected that no Byfield would be measured. The non-zero Bycomponent was well fit to a varying non-zero αzoccurring when each magnet was added. This offset resulted in a non- linear relation between the number of magnets added and the observed strength. With an initial calibration trajectory to record this magnetic field information, fine alignment can be achieved either by physically adjusting the robot or by modifying the coordinate frame to correct for the observed error. Following this, in Fig 2B it was observed that by scanning through a dictionary of poses, varying only αyand αz, it was possible to traverse a set of Babs(αy, αz) points on the sphere where Babswas an approximately constant scalar and ṅ was the unit vector. In the image plots, there can be seen the measured Bx, By, and Bzover each pose αy, αzcompared to the designed field. There can be seen a small percentage of white pixels representing poses within the workspace that were unachievable by the kinematic processor. The robot scanned in a meander, alternating +z, −z, and artefacts of this can be seen through scan lines in the measured data. Overall, high angular accuracy was measured with a mean error of 2.9° and modal error of 2.3° and it was confirmed that the robotic arm was able to produce desired field orientations with a high accuracy. For a set vector orientation and magnet mass, some applications require tuning of the field amplitude, for instance so that the ODMR resonance matches a microwave resonator. The amplitude can be controlled by tuning the distance between the magnet and the sample position. However, the magnetic field fall-off with r distance is highly non-linear, characterised by the BiotSavart 1 / r3relation. In addition, the robotic arm performs non-linear displacement, requiring dual movement of two rotational joints per linear step. It was observed in Fig 2C that the displacement of the magnet away from the Hall sensor was sufficiently linear to produce a 1 / x3response in Bx. Because the magnetic field generated by the permanent magnet was large, it could be positioned sufficiently far away from the sensor so that the 10 mm 1 / r3trajectory could be subsampled within the 0.5 mm resolution of the robot (lines shown in the top panel) to create a desired response B(r). In the middle panel it can be observed that a linear field response between 0 and 10 mT was created through this method. In the bottom panel, it can be observed that the error in this sampling technique was typically lower than 0.1 mT. Thus, this Example confirms that the robotic aligning means of the present invention can be used to movably position an alignment element to produce a desired direction and magnitude of a field of the alignment element, i.e. in this Example, the magnetic field of a strong permanent magnet. Example 2: Collision-free motion planning With operation validated in an unconstrained environment, the next step was to navigate the robot around complicated infrastructure. By evaluating intersections with its environment, the robot was able to compute collisions in the ROS simulation using LBKPiece from the Open Motion Planning Library to traverse a tree of possible trajectories to a given pose goal. Two experimental setups were investigated: a cryostat with an optical window and a scanning stage confocal microscope (see Fig 3A), and their spatial meshes were added in simulation to the robot environment. For these complex geometries, it would not be possible to position 3-axis Helmholtz coils for magnetic field alignment due to the competing requirements for optical access to the sample and the need to move the sample in three dimensions. Single microcoils or a permanent magnet mounted on a stage would have limitations in terms of achievable proximity to the sample. However, with the available kinematics of the robotic aligning means, in this Example a 6 DoF robotic arm, the position of the magnet with respect to the sample was far less constrained. In Fig 3A, using LBKPiece, it was simulated that a chosen subset of poses could be traversed with access to the top and back side of the cryostat, generating a −Bx, +By, −Bzsphere segment (one eighth) without collisions. However, it was observed that for the scanning stage confocal microscope, only a subset of any sphere segment was achievable. Poses that cannot be accessed without collision can be seen in light grey and formed a significant part of the subset. From this simulation, it was evident that there would be a collision with the robot when using the specific magnetisation-axis-aligned configuration described in Fig 1C. An important consideration at this point was that the set of poses in this configuration only made up a small subset of the possible joint configurations of the robot, and therefore possible magnetic field vectors. By moving the TCP defined in Fig 1C from the NV centre to the magnet, free control was given on its orientation and position, with access to the fringe fields of the magnetic source. The inventor hypothesised that there existed a set of collision-free poses that would produce a full set of magnetic vectors. This idea makes use of the magnetic inverse problem in field sensing: that there exists a non-unique set of fields B produced by poses p. The algorithm used in this Example is laid out in panels along Fig 2B. Firstly, the unreachable set of poses in the constrained environment were found. For each such pose (first panel), the TCP was translated along x to the magnet centre and the magnet is then linearly translated in either y or z to a new reachable pose (second panel). Next, the new pose was rotated in αyor αzto obtain the same vector field orientation as the original pose (third panel). Finally, the magnet was translated in x to recover the original magnitude (final panel). To calculate the vector rotation in the third panel, the magnet was approximated with a dipole, for which the inverse magnetostatic expression is known. For a powerful permanent magnet, the arm could be withdrawn to sufficient distances so that this dipole approximation became valid. The orientation of a unit dipole →m at a vector →r to create a field at the sensor location →B is given by: where µ0is the vacuum permeability. In Fig 3C, the z displaced magnet was modelled and it was found that the field observed at the sample location (large grey dot on X axis) had a significantly modified orientation (first panel). Equation (ii) was used to calculate the dipole orientation →m to find →B (middle panel). The magnet was then rotated to be coaxial with the calculated dipole orientation and to recover the desired field vector →B with high accuracy, minimising Byand Bz(last panel). In Fig 3D, it can be seen that in the physical experiment, the off-axial field component is indeed minimised when set to the calculated 26° angle, and that this algorithm succeeded within the pose resolution limit of the robot. As well as correcting orientation, for some applications it is important to maintain the field amplitude. This final step in Fig 3B was achieved by using the known 1 / r3Biot-Savart relation of Fig 2C to scale the amplitude, translating the magnet in x. To capture both the orientation and amplitude, a Gaussian kernel similarity function was defined between the target field vector B1and the replacement vector B2, as this is well bounded between zero (least similar) and one (most similar): with d = 3. Each step of the algorithm in Fig 2E was experimentally implemented, and it was observed that the final vector achieved a high similarity to the target vector with S = 0.91. This can be seen by comparing the histograms of the measured field components in the first and last panel. Here, the final amplitude correcting step maintained the desired field vector. In this Example it was determined using this algorithm that it is possible to systematically replace unreachable poses with reachable poses with the same field vector. The full dexterity offered by the robotic links combined with the inverse problem of magnetostatics make this system a powerful tool for setting arbitrary strength magnetic field vectors in highly constrained environments. Example 3: Experimental collision and NV centre alignment To align a spin-based sensing probe requires navigating a highly complex environment with many sensitive optical and mechanical instruments, shown in Fig 4A and 4B. In the technique described, the collision-free positions found in simulation can be downloaded to the physical robot. This requires a fine alignment between the simulation and the real world performance which could be achieved similarly to Fig 2A, for instance. In a highly constrained environment, it was determined that sensor-driven fine angular alignment could be difficult, as the trajectories chosen may not be verified as collision-free until alignment has succeeded. The fast and pragmatic approach employed in this Example was to teach the robot a set of collision-free poses. This was achieved by first switching the torque to each motor off momentarily, allowing the joints to move freely. In this state, the operator grasped the magnet, and guided the robotic arm to a desired location within the geometry, avoiding collision. Whilst doing this, the user monitored the magnetic field produced at the sample location with the Hall sensor. When a desired field was registered, the torque and closed loop feedback were switched on, locking the magnet at its set position. This position (either the pose or the joint state) could then be registered along with the corresponding magnetic field. Through this method, the user can hunt and find locations where, for instance, z is the dominant field component. These poses can be used to gather information to calibrate the source to its experimental surroundings. It is then possible to compare the taught poses with the simulation to calculate collisions, and with the dipole field model, it is possible to locally modify the taught position. As a proof-of-principle experiment, the robot was taught a trajectory across the confocal microscope shown in Fig 4A. In Fig 4C, the confocal was used to locate a collection of milled solid immersion lenses in a polycrystalline diamond sample, and there was observed a bright NV centre in one such lens (Fig 4D). With the robot arm at its home position, 10 cm away from the sample, ODMR was performed on this NV centre. In Fig 4E, there was observed a small 3.7030 MHz splitting, about the central D = 2.8704 GHz, due to an intrinsic splitting as defined in Equation (i) of Π = 1.8515 MHz. Shown in light grey shading / dark grey line, moving the TCP in proximity to the sample resulted in a 100 MHz splitting observed in the ODMR spectra from the presence of the permanent magnet. In this Example, the ability to engage and disengage the robot whilst performing ODMR indicated that the robot can be used in this highly sensitive experiment. In Fig 4F, the ODMR was repeated for a set of robot poses along a collision-free trajectory with αy=20° at 5° increments in αzand the splitting was analysed, which showed a smooth increase as the magnet was moved in front of the objective. The same path was traversed at 2° increments in αzand resonance data showed the same splitting trend, indicating that the trajectory-induced splitting was reproducible. The fitted resonances can be used to extract the polar angle between the NV axis and the magnetic field of interrogation, from the zero-field parameters D and E. This gave a value of 61.0 ± 0.3° for Trajectory 1 and 61.8±0.2° for Trajectory 2. This small polar angle change over the 25° range in αzindicated that the NV centre was near aligned with the z-axis. In Fig 4G, by replacing the diamond sample with the Hall sensor, and focusing the objective at the centre of the sensor area, the field components generated by the trajectory could be mapped. The Bxand Bycomponents crossed, as expected for varying αz. The Hall field amplitude |B| was found in excellent agreement with the ODMR sensed field amplitude. For the trajectory chosen, the robot TCP was not yet fully aligned with the NV or Hall sensor area. In contrast to Fig 2B, the trajectory did not conserve |B|, with a large increasing Bzcomponent, and this was the main contribution to the splitting between the two resonances in Fig 4F. The amplitude data can be used to normalise each splitting to isolate the field component ratios. In Fig 4G, this normalisation resulted in the appearance of a dip from both trajectories, with the phase and contrast of the dip giving an estimation of the NV's orientation. The low contrast, non-zero minima in αzindicated the NV centre was near aligned with the z-axis as previously discussed. Both datasets were well fitted with the characteristic equation for NV centre spin energies (Fukushige et al., Identification of the orientation of a single nv center in a nanodiamond using a three-dimensionally controlled magnetic field, Applied Physics Letters, 116(26):264002) to find αz= 64.1 ± 0.4 °, αy=97.6 ± 0.7 ° for Trajectory 1 and αz= 62.9 ± 0.8 °, αy=97.9 ±1.4 ° for Trajectory 2. In this Example, it has been proven that a robotic aligning means can be used to operate in rapid local movement around sensitive samples to provide stable magnetic fields in order to manipulate a single quantum spin of a spin-based sensing probe, thereby aligning and sensitising the spin-based sensing probe.

Claims

Claims 1. A system comprising: a) a spin-based sensing probe; b) an alignment element; and c) a robotic aligning means configured to movably position the alignment element; d) optionally a positional sensor configured to collect information on the position of the robotic aligning means and / or alignment element.

2. The system of claim 1, wherein the system further comprises an excitation means and a signal detection means.

3. The system of claim 1 or 2, wherein the spin-based sensing probe comprises a solid-state defect, preferably a defect in diamond, preferably a NV- centre.

4. The system of any one of claims 1 to 3, wherein the alignment element is an element that generates a magnetic field, an element that generates an electric field, or an element that generates a light field.

5. The system of any one of claims 1 to 4, wherein the robotic aligning means is configured to movably position the alignment element in one or more positions wherein the alignment element sensitises the spin-based sensing probe.

6. The system of any one of claims 1 to 5, wherein the robotic aligning means has at least two, at least three, at least four, at least five or six degrees of freedom.

7. The system of any one of claims 1 to 6, wherein the robotic aligning means is configured to movably position the alignment element in all three axes of three-dimensional space (x, y and z).

8. The system of any one of claims 1 to 7, wherein the robotic aligning means is configured to rotate the alignment element about all three axes of three-dimensional space (x, y and z).

9. The system of any one of claims 1 to 8, wherein the robotic aligning means is configured to movably position the alignment element with non-linear movement.

10. A robotic aligning means, wherein the robotic aligning means is programmed to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe.

11. A quantum sensor comprising the system of any one of claims 1 to 9, or the robotic aligning means of claim 10.

12. A computer-implemented quantum sensing method, comprising training a robotic aligning means to movably position an alignment element in one or more positions wherein the alignment element sensitises a spin-based sensing probe.

13. The method of claim 12, comprising programming the robotic aligning means to movably position the alignment element without colliding with its environment.

14. A method of sensitising a spin-based sensing probe, wherein the method comprises: a) providing a spin-based sensing probe, a robotic aligning means and an alignment element; b) determining a position of the alignment element wherein the spin-based sensing probe is sensitised; and c) using the robotic aligning means to movably position the alignment element to the position wherein the spin-based sensing probe is sensitised.

15. The method of claim 14, wherein step b) comprises: i) determining a first position where the alignment element sensitises the spin-based sensing probe, wherein the first position is blocked, and ii) determining a second, different position wherein the alignment element sensitises the spin-based sensing probe, wherein the second position is not blocked; further wherein step c) comprises using the robotic aligning means to movably position the alignment element to the second position wherein the alignment element sensitises the spin- based sensing probe.

16. A data processing apparatus, device or system comprising or a processor configured to perform the method according to claim 12 or 13.

17. A computer program comprising instructions which, when executed by a computer, carry out the method according to claim 12 or 13.

18. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to claim 12 or 13.

Images