A light-trapping geometry enhances the sensitivity of strain, temperature, and/or electromagnetic field measurements using nitrogen vacancies in bulk diamond, which have exterior dimensions on the order of millimeters. In an example light-trapping geometry, a laser beam enters the bulk diamond, which may be at room temperature, through a facet or notch. The beam propagates along a path inside the bulk diamond that includes many total internal reflections off the diamond's surfaces. The NVs inside the bulk diamonds absorb the beam as it propagates. Photodetectors measure the transmitted beam or fluorescence emitted by the NVs. The resulting transmission or emission spectrum represents the NVs' quantum mechanical states, which in turn vary with temperature, magnetic field strength, electric field strength, strain/pressure, etc.

A method includes applying, to a sample exhibiting optical scattering and having a emission particles distributed therein that exhibit spin-dependent fluorescence, a magnetic field to shift a resonance frequency of each emission particle in a position-dependent manner. The method also includes exciting the sample with an excitation beam that causes at least one emission particle to emit spin-dependent fluorescence and detecting the emitted spin-dependent fluorescence. The method also includes estimating a position of the emission particle(s) within the sample based on the spin-dependent fluorescence, the resonance frequency, and the magnetic field. The method also includes estimating optical transmission information for the sample based on a wavefront of the excitation beam and the estimated position. The optical transmission information including a measure of an optical field at each position of an emission particle.

An apparatus for individually trapping atoms, individually imaging the atoms, and individually cooling the atoms to prevent loss of the atoms from the trap caused by the imaging. The apparatus can be implemented in various quantum computing, sensing, and metrology applications (e.g., in an atomic clock).

A method for generating alkali metal in a zero oxidation state includes disposing an alkali metal compound in an ionic liquid, the ionic liquid including an organic cation and an anion; and electrolyzing the alkali metal compound in the ionic liquid to release the alkali metal in the zero oxidation state. The alkali metal in the zero oxidation state can be used in a variety of application including in a vapor cell of a magnetometer.

Microwave resonator readout of the cavity-spin interaction between a spin defect center ensemble and a microwave resonator yields fidelities that are orders of magnitude higher than is possible with optical readouts. In microwave resonator readout, microwave photons probe a microwave resonator coupled to a spin defect center ensemble subjected to a physical parameter to be measured. The physical parameter shifts the spin defect centers' resonances, which in turn change the dispersion and/or absorption of the microwave resonator. The microwave photons probe these dispersion and/or absorption changes, yielding a measurement with higher visibility, lower shot noise, better sensitivity, and higher signal-to-noise ratio than a comparable fluorescence measurement. In addition, microwave resonator readout enables coherent averaging of spin defect center ensembles and is compatible with spin systems other than nitrogen vacancies in diamond.

A cell for a optically pumped magnetic sensor measures magnetic field by setting alkali metal atoms to a predetermined excitation state by a pump beam and detecting the excitation state by a probe beam. The cell is provided with a glass substrate which seals the alkali metal atoms and an enclosing gas and transmits the pump beam and the probe beam and a coating layer provided on an inner surface of the glass substrate. The coating layer is made of an inorganic material.

A magnetometer can include a single, integrated, unitary structure that has a gas cell defining a cavity having a vapor or vaporizable material disposed therein, a collimating element coupled to the gas cell and configured for collimating light directed toward the gas cell, and a lens element coupled the gas cell and configured for redirecting at least a portion of light that has passed through the gas cell. Additionally or alternatively, a gas cell of a magnetometer may be made of sapphire.

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.

The invention concerns a method for the hyperpolarisation of .sup.13C nuclear spin in a diamond, comprising an optical pumping step, in which colour centre electron spins in the diamond are optically pumped. The method further comprises a transfer step in which the polarisation of a long-lived state of the colour centre electron spins is transferred to .sup.13C nuclear spins in the diamond via a long-range interaction.

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.