The Secret of Long Life for Quantum Memory in Diamond ⚡ экспресс
Spin and optical properties of single NV centers in diamond grown along the (111) direction with isotope engineering were investigated. The growth process ensures precise control over 13C concentration and nitrogen content at the level of a few ppb. By suppressing 50 Hz noise with a real-time feedforward scheme and adapted decoupling sequences, spin coherence times reached T2 = 6.8(1) ms for Hahn echo and T2^DD = 11.2(8) s under dynamical decoupling. Optical transitions show a homogeneous linewidth of 16.9(4) MHz, close to the lifetime limit, with detailed analysis of spectral diffusion. These results open new possibilities for controlling spin qubits in quantum networks and other quantum technologies, as well as for studying impurity incorporation in diamond.
A spinning top, set in motion on a perfect surface, topples from the slightest tremor. Likewise, a quantum bit, created at a defect in a diamond, has its state destroyed by magnetic disorder from impurities and external interference. To keep this 'top' spinning, scientists grew a diamond almost free of the carbon-13 isotope—tiny magnets that create noise. Compensating electronics catch the electrical hum (like the 50 Hz mains buzz) and slightly rotate the spin in the opposite phase, while fast laser pulses average out the harmful jolts.
As a result, the quantum state lives for 11.2 seconds—in that time, light can travel to the Moon and back eight times. Spectral measurements showed an almost perfectly narrow line of coupling with light, which is necessary for quantum repeaters—the future 'relay stations' of the quantum internet.
🎯 In 11.2 seconds, light travels 3.36 million kilometers—a distance equal to eight round trips to the Moon.
🎬 Diamond spins in a quantum network are a step toward 'ansibles' from science fiction—devices for instantaneous communication via entanglement.