Quantum Metrology and Quantum Memory Using Defect Sates with Spin -3/2 or Higher Half-Spin Multiplets

A method for creating a quantum memory device, including providing a sample of SiC having at least one spin-3/2 VSi− monovacancy defect therein, the VSi− monovacancy defect having a ground state (GS) and being situated in the presence of nearby nuclei;

• applying a first set of laser pulses to the SiC sample, the first set of laser pulses being configured to cause the VSi− defect to become spin-polarized to produce an initial population of ms=+3/2 states;
• applying a first static magnetic field Bz along a c-axis of the SiC sample, the first magnetic field Bz being configured to bring and keep the SiC sample into an avoided crossing low (ACL) quantum state, the GS of the spin polarized defect being accompanied by two nuclear spins leading to an overall state of |3/2;
• ;
• applying a first B⊥ magnetic field pulse to the SiC sample, the first B⊥ magnetic field pulse being orthogonal to the c-axis of the sample and being configured to bring the spin-polarized ms=±3/2 state of the VSi− defect into a superposition state [|3/2;
• +|−½;
• ]/√{square root over (2)};
• applying a Bϕ magnetic pulse along a c-axis of the defect, the Bϕ pulse creating the form of information that can be encoded in the electron and nuclear spin states;
• applying a second static magnetic field Bz along a c-axis of the SiC sample, the second magnetic field Bz being configured to bring the SiC sample out of the ACL quantum state and prevent further interactions between the electron and nuclear spins, thereby locking the nuclear spin polarizations into their current state where the electron information is stored and writing the information into nuclear memory.