Quantum metrology and quantum memory using defect sates with spin-3/2 or higher half-spin multiplets

A method for measuring a strain, comprising:

• providing a mechanical resonator comprising a 4H-SiC thin film membrane containing a spin-3/2 VSi− defect, the resonator the VSi− defect being situated near the surface of the membrane and near to a location on the membrane where a fundamental acoustic mode of the membrane attains a maximum value of the strain;
• calibrating the mechanical resonator to measure an initial zero field splitting (ZFS) of a ground state of the VSi− defect and to cause the VSi− defect to become spin-polarized to produce an initial population of mS=±3/2 states;
• applying first RF/MW fields to the 4H-SiC membrane, the first magnetic fields becoming resonant with transitions between at least one of an mS=±3/2 and an mS=±1/2 spin state of the VSi− defect ground state, wherein the excited mS=±3/2 and/or mS=±1/2 spin states produce a first PL signal PLinit upon their relaxation to a ground state at the resonant frequency, PLinit being received by a photodetector and being indicative of being equal to an energy of the ZFS of the VSi− defect ground state;
• and
• applying second RF/MW fields to the 4H-SiC membrane, the second RF/MW fields producing corresponding PL signals from the relaxation of the mS=±3/2 and/or mS=±1/2 spin states to their respective ground states, the PL signals being received by the photodetector, wherein an RF/MW frequency that corresponds to an absolute maximum PL signal received by the photodetector is recorded by the photodetector as PLout;
• and
• converting a difference (PLout−PLinit) into an expression of the external strain on the membrane.

An apparatus for measuring a temperature, comprising:

• a SiC sample having at least one spin-3/2 VSi− monovacancy defect therein;
• means for calibrating the SiC sample;
• means for applying a varying frequency radiofrequency/microwave (RF/MW) field to the SiC sample,
• a photodetector that receives photoluminescence (PL) signals from the SiC sample;
• and
• a processor that receives data of the PL signals from the photodetector and to convert the data of the PL signals to an expression of a temperature of the SiC sample;
• wherein the means for calibrating the SiC sample measures an initial zero field splitting (ZFS) of a ground state of the VSi− defect, the means for calibrating SiC sample further exciting the VSi− defect from a ground state to an excited state and causing the VSi− defect to become spin-polarized to produce a population of mS=±3/2 and mS=±1/2 spin states in the VSi− defect;
• wherein the means for applying a varying frequency radiofrequency/microwave (RF/MW) field to the SiC sample applies a first RF/MW field to the SiC sample, wherein when the first RF/MW field becomes resonant with a transition between at least one of the mS=±3/2 and mS=±1/2 spin states of the VSi− defect, the excited mS=±3/2 and/or mS=±1/2 spin states produce a first PL signal PLinit upon their relaxation to a ground state at the resonant frequency, PLinit being received by a photodetector and being indicative of being equal to an energy of the ZFS of the VSi− defect ground state;
• wherein the means for applying a varying frequency RF/MW field to the SiC sample further applies second RF/MW fields to the SiC sample when the sample has reached a thermodynamic equilibrium with an environment, the second RF/MW fields producing corresponding PL signals from the relaxation of the mS=±3/2 and/or mS=±1/2 spin states to their respective ground states, the PL signals being received by the photodetector, an RF/MW frequency that corresponds to an absolute maximum PL signal received by the photodetector being recorded by the photodetector as PLout;
• and
• wherein the processor converts a difference (PLout−Pinit) into an expression of the temperature of the SiC sample.

A method for measuring a temperature, comprising:

• providing a SiC sample having at least one spin-3/2 VSi− monovacancy defect therein;
• calibrating the SiC sample to measure an initial zero field splitting (ZFS) of a ground state of the VSi− defect and to cause the VSi− defect to become spin-polarized to produce an initial population of mS=±3/2 states;
• applying first RF/MW fields to the SiC sample, the first magnetic fields becoming resonant with transitions between at least one of an mS=±3/2 and an mS=±1/2 spin state of the VSi− defect ground state, wherein the excited mS=±3/2 and/or mS=±1/2 spin states produce a first PL signal PLinit upon their relaxation to a ground state at the resonant frequency, PLinit being received by a photodetector and being indicative of being equal to an energy of the ZFS of the VSi− defect ground state;
• placing the SiC sample into an environment haying a temperature to be measured, keeping the SiC sample in the environment until the sample reaches thermodynamic equilibrium with the environment;
• and
• applying second RF/MW fields to the SiC sample, the second RF/MW fields producing corresponding PL signals from the relaxation of the mS+±3/2 and/or mS=±1/2 spin states to their respective ground states, the PL signals being received by the photodetector, wherein an RF/MW frequency that corresponds to an absolute maximum PL signal received by the photodetector is recorded by the photodetector as PLout;
• and
• converting a difference (PLout−PLinit) into an expression of the temperature of the SiC sample.