- Substitutional nitrogen atom in the diamond lattice, next to a missing carbon atom (vacancy)
- At the vacancy, some electrons trapped and form an electron spin → quantum bit
- Advantages
- Very long coherence time, even at room temperature
- Electron spin couples to nuclear spins in the environment → extra qubits
- Interacts with photons (light particles)
- Hybrid system of photons and spins → quantum networks
- Diamond made in the shape of hemisphere
- Acts as lens, counter the total internal reflection, more photons to escape the qubit
Operations on NV center qubits
- Single-qubit rotation
- Wire running next to the qubit emits an AC electromagnetic field on resonance with the qubit’s frequency
- Readout
- Light with a specific frequency shined → get excieted to the next energy level only if it was in the spin-up state
- After waiting,
- Detect light → spin-up
- No llight → spin-down
- Control multiple nuclear spin qubits
- Nuclear spins - source of decoherence
- Flip-flop around randomly
- Create a slowly-varying magnetic field on the NV-center
- Changes the NV energy levels → phase evolution to be random → quantum state lost
- Solution - Spin echo : apply a pulse that inverts the state of the NV
- Flip → inverts the effect of the magnetic field on the spin → affect exactly cancelled
- Dipolar magnetic field of the electron spin → unique energy splitting to differently positioned nuclear spins → selective control
- Nuclear spin’s dependence on the electron spin state → can create a controlled quantum gate, CNOT
- Each NV center becomes a system of 5 or even more qubits
- Use photons to create a network & entanglement between two distant NV centers
- Beam splitter
- Similarly shine a laser on the other NV center
- Let the photons, emitted due to electrons falling back, interfere
- Measure the photons, entangle the two NV centers
- Nuclear spins - source of decoherence
전자와 광자의 interaction을 사용한다는게 신기하긴 한데 솔직히 100% 이해는 못하겠다… 물리랑 화학 지식이 부족하다. 공부 더 하고 다시 봐야겠다.
NUS CS'25