Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant


Enhancing quantum sensing sensitivity by a quantum memory

In quantum sensing, precision is typically limited by the maximum time interval over which phase can be accumulated. Memories have been used to enhance this time interval beyond the coherence lifetime and thus gain precision. Here, we demonstrate that by using a quantum memory also an increased sensitivity can be achieved. To this end, we use entanglement in a hybrid spin system comprising a sensing and a memory qubit associated with a single nitrogen-vacancy center in diamond (see upper figure part). With the memory we retain the full quantum state even after coherence decay of the sensor, which enables coherent interaction with distinct weakly coupled nuclear spin qubits (see lower figure part). To this end we do tomography of the memory’s quantum phase as we increase the interaction time τ with a sample qubit (here: 13C spin, a: cos φ, b: sin φ ). The phase is only accumulated when the sample spin is resonantly driven during the storage time T c. The spectral selectivity is determined by 1/T c which is much narrower than what is possible with the sensor alone. Furthermore, we benchmark the performance of our hybrid quantum system against use of the sensing qubit alone by gradually increasing the entanglement of sensor and memory. Finally, we further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single 13C nuclear spins.

The results of our work are published in:
S. Zaiser, T. Rendler, I. Jakobi, T. Wolf, S.-Y. Lee, S. Wagner, V. Bergholm, T. Schulte-Herbrüggen, P. Neumann, and J. Wrachtrup, Enhancing quantum sensing sensitivity by a quantum memory. Nature Communications 7, 12279 (2016).