Download Using Pink Diamond to Detect Small Magnetic Fields and Break

UsingPinkDiamondtoDetectSmallMagneticFieldsandBreak
ComputerCodes
Diamond is the hardest substance known. It is used extensively in jewelry and also in industry as a cutting tool, semiconductor etc. Pure diamond is colorless (transparent); however presence of impurity can give color to diamonds. Depending on the type of impurity present diamonds can have color like yellow (Nitrogen impurity), blue (Boron impurity), pink (NV center impurity) etc. Diamond is a crystalline allotrope of carbon where each carbon atom is bonded to four other carbon atoms giving it a tetrahedron shape with each carbon atom sitting at the center of the tetrahedron. However, if one carbon atom is replaced by a nitrogen atom and there is also an absence of carbon atom to this neighboring nitrogen, then this vacancy is called a Nitrogen Vacancy (NV) center. The NV center impurity makes diamond pink in color. This defect is found in naturally occurring diamond. NV centers are very sensitive to magnetic fields and can be used to sense very low magnetic fields. Also, they are potential candidates for qubits which are needed to construct a quantum computer. Quantum computers are predicted to be more powerful than classical computers and can break any security codes easily. We will use a technique called EPR to study pink diamonds. EPR is a method which will measure how good pink diamond is to act as sensitive magnetic field sensors. It will also help us to characterize pink diamond as a qubit and evaluate its performance in a quantum computer. EPR is a technique used to study samples that have unpaired spins. Spin is a property of quantum particles and there is no classical equivalence of this property. A particle can have fractional spin (e.g. Spin=1/2 for an electron) or whole spin (e.g. Spin=1 for a photon). Two spins can add up, for example two electrons can form a state with total spin S=1 (triplet) or S=0 (singlet). If a particle has Spin S=m, then the projection of spin Sz on z axis can take all values from +m to –m. Hence for the NV center Sz=1, 0,‐1. In the absence of any external field all these states should have same energy (degenerate). However, due to the presence of a field inside the diamond crystal, the state Sz=0 and Sz=1,‐1 will have a small energy gap. Introducing an external magnetic field will bring the state Sz=‐1 close to Sz=0 and Sz=1 will move away from Sz=0. Applying electromagnetic radiation (visible light and microwave are two examples of electromagnetic radiation) to this will cause transitions of spin from lower to higher energy states. Applying EM radiation of right energy (corresponding to the difference of low and high energy state) will cause absorption; hence by measuring the intensity of the radiation coming out of the sample, we can determine the energy gap. We will have a simple EPR spectrometer built for studying ensemble NV center spins at room temperature using microwave frequency in the range of 300 MHz‐1300 MHz in presence of 1000 Gauss magnetic field. You will be using this apparatus to understand the workings of various components, taking readings and interpreting the results. Apart from this you will also have the opportunity to observe building of a high frequency EPR spectrometer with 12 Tesla superconducting magnets. The project will enable you to observe quantum mechanics at work. The goal of the project is to provide high school students an opportunity to observe and participate in scientific projects in labs which have impacts on everyday life. We hope that this experience will encourage the student to study science in college and fill the shortage of highly skilled well paid scientific workers in this country. Knowledge of high school Physics and Math is helpful but not necessary for joining this program. Further Reading: Group’s Website: http://www‐bcf.usc.edu/~susumuta/index.html Group’s research page: http://www‐bcf.usc.edu/~susumuta/research.html Contact: Anirban Das Email: [email protected], [email protected]