Long spin coherence lifetimes are realized for ensembles of electronic spin impurities in solid state spin systems, for example NV color centers in diamond, by using spin-control RF pulse sequences to provide dynamic decoupling of the ensembles of spin impurities from environmental sources of decoherence such as dipolar and hyperfine interactions with proximal spin and other paramagnetic impurities in diamond. In this way, the measurement sensitivity of the coherent evolution of ensembles of solid state spin impurities are increased. Using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, the spin coherence lifetimes of NV ensembles can be extended to more than 2 ms in room temperature diamond, and sensitivity of magnetometry that uses NV ensembles can be increased.

Improved loop-gap resonators applicable to Electron-Spin Resonance spectroscopy and to quantum computing employ interdigitated capacitor structures to dramatically increase the capacitance of the resonator, along with corresponding decreases in loop size to enable measurements of small-volume samples or individual quantum bits (qubits). The interdigitated-capacitor structures are designed to minimize parasitic inductance.

Improved loop-gap resonators applicable to Electron-Spin Resonance spectroscopy and to quantum computing employ interdigitated capacitor structures to dramatically increase the capacitance of the resonator, along with corresponding decreases in loop size to enable measurements of small-volume samples or individual quantum bits (qubits). The interdigitated-capacitor structures are designed to minimize parasitic inductance.

A magnetic measuring device includes: a determination part configured to identify four maximum inclination points in an average value in a visual field of a light detection magnetic resonance spectrum and configured to determined a degree of decrease in relative fluorescence intensity and a microwave frequency at each of the maximum inclination points; a setting part configured to set a reference decrease degree of the relative fluorescence intensity in a predetermined area and configured to set operating point frequency initial values at four points at which the reference decrease degree is achieved, near the microwave frequencies at the respective maximum inclination points; a frequency update part configured to update operating point frequencies at the four points; and a frequency correction part configured to input the updated operating point frequencies to a microwave oscillator as corrected operating point frequencies.

A coupling device is provided for coupling microwave radiation from a first microwave structure, in particular a microwave waveguide, into a second microwave structure, in particular a microwave resonant cavity, wherein the first and second microwave structures share a common wall, through an iris opening in said wall in front of which the coupling device is positioned on the side of the first microwave structure, in particular wherein the coupling device is of a basically cylindrical shape, characterized in that the coupling device comprises N electrically conducting conductor loops, with N≥3, preferably 3≤N≤20, that the conductor loops are arranged coaxially in an array along a z-axis, and that axially neighboring conductor loops are separated by a dielectric. The inventive coupling device allows for a larger coupling coefficient, and in particular allows for a larger dynamic range.

A coupling device is provided for coupling microwave radiation from a first microwave structure, in particular a microwave waveguide, into a second microwave structure, in particular a microwave resonant cavity, wherein the first and second microwave structures share a common wall, through an iris opening in said wall in front of which the coupling device is positioned on the side of the first microwave structure, in particular wherein the coupling device is of a basically cylindrical shape, characterized in that the coupling device comprises N electrically conducting conductor loops, with N≥3, preferably 3≤N≤20, that the conductor loops are arranged coaxially in an array along a z-axis, and that axially neighboring conductor loops are separated by a dielectric. The inventive coupling device allows for a larger coupling coefficient, and in particular allows for a larger dynamic range.

A diamond probe is suitable to be attached to an Atomic Force Microscope and is created with a tip that incorporates a one or more Nitrogen Vacancy (NV) centers located near the end of the tip. The probe arm acts as an optical waveguide to propagate the emission from the NV center with high efficiency and a beveled end directs excitation light to the NV center and directs photoluminescence light emanating from the NV center into the probe arm. The probe tip is scanned over an area of a sample with an electric charge, such as a field effect transistor or flash memory. Optically Detected Spin Resonance (ODMR) is measured as the probe tip is scanned over the area of the sample, from which a characteristic of the area of the sample with the electric charge may be determined.

A diamond probe is suitable to be attached to an Atomic Force Microscope and is created with a tip that incorporates a one or more Nitrogen Vacancy (NV) centers located near the end of the tip. The probe arm acts as an optical waveguide to propagate the emission from the NV center with high efficiency and a beveled end directs excitation light to the NV center and directs photoluminescence light emanating from the NV center into the probe arm. The probe tip is scanned over an area of a sample with an electric charge, such as a field effect transistor or flash memory. Optically Detected Spin Resonance (ODMR) is measured as the probe tip is scanned over the area of the sample, from which a characteristic of the area of the sample with the electric charge may be determined.

An electron-nuclear double resonance resonator, having a loop-gap resonator and an elongated lead; the loop-gap resonator comprises a plurality of arc-shaped conductive plates, and the elongated lead connects the arc-shaped conductive plates into a radio-frequency coil; the loop-gap resonator resonates at an electron resonance frequency, and the radio-frequency coil resonates at a nuclear resonance frequency; with the structure of the loop-gap resonator, the separation between an electric field and a magnetic field can be accelerated to ensure the maximization of the ratio of the magnetic field to the electric field inside a resonant resonator; and with the elongated lead, the impact of the lead to a resonance frequency and the mode of the loop-gap resonator is prevented as much as possible, and meanwhile the conductive plates of the loop-gap resonator can be connected into the radio-frequency coil.

An electron-nuclear double resonance resonator, having a loop-gap resonator and an elongated lead; the loop-gap resonator comprises a plurality of arc-shaped conductive plates, and the elongated lead connects the arc-shaped conductive plates into a radio-frequency coil; the loop-gap resonator resonates at an electron resonance frequency, and the radio-frequency coil resonates at a nuclear resonance frequency; with the structure of the loop-gap resonator, the separation between an electric field and a magnetic field can be accelerated to ensure the maximization of the ratio of the magnetic field to the electric field inside a resonant resonator; and with the elongated lead, the impact of the lead to a resonance frequency and the mode of the loop-gap resonator is prevented as much as possible, and meanwhile the conductive plates of the loop-gap resonator can be connected into the radio-frequency coil.