Enhanced solid-state multispin metrology using dynamical decoupling

We use multipulse dynamical decoupling to increase the coherence lifetime (T2) of large numbers of nitrogenvacancy (NV) electronic spins in room temperature diamond, thus enabling scalable applications of multispin quantum information processing and metrology. We realize an order-of-magnitude extension of the NV multispin T2 in three diamond samples with widely differing spin impurity environments. In particular, for samples with nitrogen impurity concentration 1 ppm, we extend T2 to >2 ms, comparable to the longest coherence time reported for single NV centers, and demonstrate a tenfold enhancement in NV multispin sensing of ac magnetic fields.