Abstract
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 an increased sensitivity can also 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 centre in diamond. 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. 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. We further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single 13C nuclear spins.
Highlights
In quantum sensing, precision is typically limited by the maximum time interval over which phase can be accumulated
While the electron spin serves as a magnetic field sensor, the nuclear spin acts as a quantum memory due to its much weaker coupling to the environment
We further test the novel scheme for entangling the memory qubit and a proximal 13C nuclear spin
Summary
Precision is typically limited by the maximum time interval over which phase can be accumulated. 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. We further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single 13C nuclear spins. A long-lived memory is another way which is advantageous when the quantity to be measured has a longer correlation time than the sensor’s coherence time[9,10,11,12]. We demonstrate that entanglement of quantum memory and sensing qubit during the phase accumulation process makes efficient use of the resources at hand. We show that storing the full quantum state allows for improved detection of weakly coupled qubits, and enables coherent interaction and nonlocal gates between memory and distinct weakly coupled qubits
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