Integrated Electrical Spin Readout of Diamond NV Qubits

Physics of NV diamond spin qubits has advanced significantly over the last decade. However, for practical applications, integrating NV diamond into quantum chips and readout electronics remains an ambitious challenge. Here, we present an integrated diamond quantum chip based on photoelectric readout (1,2) and discuss its key characteristics, such as spectral noise density. The diamond chip, combined with a tailor-made transimpedance amplifier, enables detection of ultra-low currents at the level of single NV photocurrents with high bandwidth, compatible with Rabi oscillation measurements and quantum algorithms. The chip can also function as a magnetometer with an electronic detection floor of ~100 pT/√Hz. Additionally, we demonstrate quantum state tomography of single NV electron and nuclear spins, performed on an optical table, achieving high fidelities of up to 99.99% at room temperature. On the technological side, we discuss the fabrication of NV–NV pairs, characterized via double electron–electron resonance.

Acknowledgement: thanks to Philipp Hengel, Michal Kern, Denis Djekic, and Jens Anders from the Institute of Smart Sensors, University of Stuttgart, Germany, as well as Reza Tavakoli Dinani, Boo Carmans, and Abhishek Shukla from Hasselt University, Belgium, for their collaboration. The work was supported by the EU projects Spinus, C-Quens, and ACDC_Q.

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