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Institute: search.filters.UBSInstitut.Zentrum für Angewandte Quantentechnologie (ZAQuant)Author: search.filters.author.Dasari, Durga Bhaktavatsala Rao

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    ItemOpen Access
    Anti-Zeno purification of spin baths by quantum probe measurements
    (2022) Dasari, Durga Bhaktavatsala Rao; Yang, Sen; Chakrabarti, Arnab; Finkler, Amit; Kurizki, Gershon; Wrachtrup, Jörg
    The quantum Zeno and anti-Zeno paradigms have thus far addressed the evolution control of a quantum system coupled to an immutable bath via non-selective measurements performed at appropriate intervals. We fundamentally modify these paradigms by introducing, theoretically and experimentally, the concept of controlling the bath state via selective measurements of the system (a qubit). We show that at intervals corresponding to the anti-Zeno regime of the system-bath exchange, a sequence of measurements has strongly correlated outcomes. These correlations can dramatically enhance the bath-state purity and yield a low-entropy steady state of the bath. The purified bath state persists long after the measurements are completed. Such purification enables the exploitation of spin baths as long-lived quantum memories or as quantum-enhanced sensors. The experiment involved a repeatedly probed defect center dephased by a nuclear spin bath in a diamond at low-temperature.
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    Dopant-assisted stabilization of negatively charged single nitrogen-vacancy centers in phosphorus-doped diamond at low temperatures
    (2023) Geng, Jianpei; Shalomayeva, Tetyana; Gryzlova, Mariia; Mukherjee, Amlan; Santonocito, Santo; Dzhavadzade, Dzhavid; Dasari, Durga Bhaktavatsala Rao; Kato, Hiromitsu; Stöhr, Rainer; Denisenko, Andrej; Mizuochi, Norikazu; Wrachtrup, Jörg
    Charge state instabilities have been a bottleneck for the implementation of solid-state spin systems and pose a major challenge to the development of spin-based quantum technologies. Here we investigate the stabilization of negatively charged nitrogen-vacancy (NV - ) centers in phosphorus-doped diamond at liquid helium temperatures. Photoionization of phosphorous donors in conjunction with charge diffusion at the nanoscale enhances NV 0 to NV - conversion and stabilizes the NV - charge state without the need for an additional repump laser. The phosphorus-assisted stabilization is explored and confirmed both with experiments and our theoretical model. Stable photoluminescence-excitation spectra are obtained for NV - centers created during the growth. The fluorescence is continuously recorded under resonant excitation to real-time monitor the charge state and the ionization and recombination rates are extracted from time traces. We find a linear laser power dependence of the recombination rate as opposed to the conventional quadratic dependence, which is attributed to the photo-ionization of phosphorus atoms.