Various embodiments comprise a magnetic field compensation system. In some examples, the system comprises one or more coil drivers, magnetic field coils, and one or more magnetic field sensors. The one or more coil drivers supply a current to the magnetic field coils to generate a magnetic field. The magnetic field coils receive the current and generate the magnetic field. The magnetic field coils may be arranged in an array. The magnetic field coils individually comprise at least one coil trace pattern that encloses an area. The one or more magnetic field sensors measure the magnetic field generated by the magnetic field coils at a location proximate to the magnetic field coils.

The present disclosure relates to a pH-sensor for determining and/or monitoring a pH value of a medium, having a sensor unit with a wall in contact with the medium, and at least one pH-sensitive material, which has at least one spin state that changes as a function of a pH value. The at least one pH-sensitive material is arranged in or on a region of the wall in such a way that the at least one spin state is subjected to a change in the pH value of the medium. The pH-sensor also includes a spin-sensitive unit, which is configured to detect a variable associated with the at least one spin state, wherein the spin-sensitive unit is arranged in an environment of the at least one pH-sensitive material such that the spin-sensitive unit is subjected to a change in the spin state of the at least one pH-sensitive material.

A method for non-invasive characterisation of a cell for a battery is provided, the method comprising: measuring a magnetic field generated by the cell using a plurality of magnetic field sensors positioned adjacent to the cell, the measuring producing magnetic field sensor data, wherein the measuring is performed while the cell is in a passive state; determining current density profile data across the cell based on the magnetic field sensor data; and determining a condition of the cell using the current density profile data.

In a measurement using a quantum sensor, the range of measurable physical quantities is increased while maintaining sensor sensitivity. A measuring device (10) comprises an irradiation unit (2) that irradiates a quantum sensor element (1) with electromagnetic waves for operating an electron spin state of the quantum sensor element (1) that changes due to interaction (8) with a measurement target (9), in a pulse sequence in which a time τ between n/2 pulses is a variable value; and a physical quantity measuring unit (3) that calculates a physical quantity of the measurement target based on the electron spin state after the interaction with the measurement target (9).

A magnetic field measurement system includes at least one magnetometer having a vapor cell, a light source to direct light through the vapor cell, and a detector to receive light directed through the vapor cell; at least one magnetic field generator disposed adjacent the vapor cell; and a feedback circuit coupled to the at least one magnetic field generator and the detector of the at least one magnetometer. The feedback circuit includes a first feedback loop that includes a first low pass filter with a first cutoff frequency and a second feedback loop that includes a second low pass filter with a second cutoff frequency. The first and second feedback loops are configured to compensate for magnetic field variations having a frequency lower than the first or second cutoff frequency, respectively.

Systems and methods of quantum sensing include obtaining information regarding a target signal in electronic spin states of quantum defects in an ensemble of quantum defects, mapping the information regarding the target signal from the electronic spin states of the quantum defects to corresponding nuclear spin states associated with the quantum defects, applying a light pulse to the ensemble of quantum defects to reset the electronic spin states of the quantum defects, and repeating a readout stage a plurality of times within a readout duration. The readout stage includes mapping the information regarding the target signal back from the nuclear spin states to the corresponding electronic spin states and applying a data acquisition readout pulse to optically measure the electronic spin states of the quantum defects.

A magnetometer includes an electron spin defect body including a plurality of lattice point defects. A microwave field transmitter is operable to apply a microwave field to the electron spin defect body. An optical source is configured to emit input light of a first wavelength that excites the plurality of lattice point defects of the electron spin defect body from a ground state to an excited state. A first optical fiber has an input end optically coupled to the optical source and an output end. The output end is attached to a first face of the electron spin defect body and is arranged to direct the input light into the first face of the electron spin defect body. A second optical fiber has an output end and an input end. A photodetector is optically coupled to the output end of the second optical fiber.

An apparatus useful for creating and measuring states of an entangled system, comprising a pair of interacting multi-level systems, each of systems comprising a state |g>; a state |r>, and state |r*>. One or more first electromagnetic fields excite a first transition between the ground state |g> and the state |r> to create an entangled system. One or more second electromagnetic fields are tuned between the state |r> and the intermediate state |r*> so that any population of the systems in |r*> are dark to a subsequent detection of a population in the systems in |g>, providing a means to distinguish the entangled system in the state |g> and the entangled system in the state |r>. In one or more examples, the systems comprise neutral Rydberg atoms.

An ODMR member is arranged in a measurement target AC magnetic field. A coil applies a magnetic field of a microwave to the ODMR member. A high frequency power supply causes the coil to conduct a current of the microwave. An irradiating device irradiates the ODMR member with light. A light receiving device detects light that the ODMR member emits. A measurement control unit performs a predetermined DC magnetic field measurement sequence at a predetermined phase of the measurement target AC magnetic field, and in the DC magnetic field measurement sequence, controls the high frequency power supply and the irradiating device and thereby determines a detection light intensity of the light detected by the light receiving device. A magnetic field calculation unit calculates an intensity of the measurement target AC magnetic field on the basis of the predetermined phase and the detection light intensity.

A physical state measurement apparatus includes a main solid material which generates fluorescence by excitation light from a light source part. A microwave application part applies microwaves to the main solid material so as to control an electron state of the main solid material. A detection part detects the physical state of an object to be measured by the fluorescence from the main solid material. A feedback part has a solid material for feedback and a control part and detects a difference in amplitude between operating points on a low-frequency side and a high-frequency side of a lowering portion of a spectrum amplitude centered on a resonance frequency of an electron spin resonance spectrum of fluorescence from the solid material for feedback and feedback-controls the microwave application part such that the difference becomes zero.