Methods and apparatuses for measuring magnetic flux density and other parameters by means of a plurality of NV centers, and applications thereof

A sensor system (NVMS) comprising:

• a quantum dot with a plurality of paramagnetic centers (NV1), wherein two or more paramagnetic centers (NV1) of the plurality (NVC) of paramagnetic centers (NV1) couple to each other, wherein the plurality of paramagnetic centers (NV1) is included in multiple nanodiamonds, the multiple nanodiamonds having different respective crystal orientations;
• and
• a drive and evaluation device (AWV);
• wherein:
• the drive and evaluation device comprises:
• a first pump radiation source (PL1);
• a first radiation receiver (PD1);
• a correlator (CORR), wherein the correlator includes;
• a sub-device including one or more compensation coils;
• a controller (RG), the controller being a PI controller or functionally equivalent controller;
• the drive and evaluation device (AWV) irradiates the quantum dot with pump radiation (LB) at least temporarily by means of the first pump radiation source (PL1);
• the pump radiation (LB) of the first pump radiation source (PL1) depends on a transmission signal (S5) of the drive and evaluation device (AWV);
• the quantum dot emits fluorescence radiation (FL) upon irradiation with the pump radiation (LB);
• the fluorescence radiation (FL) depends on a magnetic flux density (B) at a location of the quantum dot and/or another physical parameter;
• the drive and evaluation device (AWV) generates, as a function of the fluorescence radiation (FL), by means of a correlator (CORR) which determines a component of a transmitted signal (S5) in a receiver output signal (S0) of the first radiation receiver (PD1), the component of the transmitted signal (S5) in the receiver output signal (S0) being a first output signal (out) which represents a measured value, wherein the correlator includes a synchronous demodulator, an optimal filter, or a matched filter;
• the measured value depends on the value of the magnetic flux density (B) and/or the other physical parameter;
• the drive and evaluation device (AWV) readjusts a sensitivity of the quantum dot for the magnetic flux density (B) and/or the other physical parameter by means of a sub-device in a form of one or more compensation coils (LC);
• a current flow of the compensation coil (LC) depends on the fluorescence radiation (FL) of the quantum dot (NV1);
• the drive and evaluation device (AWV) controls the sensitivity of the quantum dot;
• the drive and evaluation device (AWV) compensatingly readjusting the sensitivity of the quantum dot by means of a dividing device as a function of a control signal of the control and evaluation device (AWV) by means of a controller (RG);
• the compensation coils (LC), as a result of a change in an intensity of the fluorescence radiation (FL) in event of a change in the value of the magnetic flux density (B) or in the event of a change in the value of another physical parameter at the location of the plurality (NVC) of paramagnetic centers (NV1), shift the magnetic flux density (B) at the location of the plurality (NVC) of paramagnetic centers (NV1) in a direction of an operating point by means of a subtraction and/or addition of a coil current;
• and
• the drive and evaluation device (AWV) carries out this readjustment in a compensating manner, such that the receiver output signal (S0) of the first radiation receiver (PD1) no longer has any component of the transmitted signal (S5) in the receiver output signal (S0) except for signal noise and control errors, which means that the receiver output signal (S0) of the first radiation receiver (PD1) has a component of the transmission signal (S5) in the receiver output signal (S0) with an amplitude that is smaller than a predetermined amplitude bandwidth amount.