Wydarzenia

Seminarium "Coherence-Correlations-Complexity" (KFT, PWr)

Localization of a magnetic moment using a two-qubit probe

Jan Krzywda

Wydział Fizyki Uniwersytetu Warszawskiego

Spin qubits such as NV centers in diamond are currently used as nanoscale-resolution sensors of magnetic field noise generated by nuclear spins of molecules localized in the qubit's neighbourhood [1,2]. Subjecting the qubit to a periodic sequence of rotations makes it sensitive only to fluctuations of given frequency [3]. Assuming the magnitude of the fluctuating magnetic field (the source) and the form of qubit-source interaction are known, measurement of qubits' decoherence allows one to find a surface on which the source is localized. Using many qubits should allow to pin-point the exact location of the source (cf. the classical triangulation procedure). Here we show that with two qubits, each subjected to a given sequence of rotations, one can localize the fluctuating magnetic moment. The method can be viewed as an application of a general protocol for performing noise cross-correlation spectroscopy [4]. We also consider the situations when the form of the qubit-moment coupling, or when the relative position of the two qubits are not known, then the source localization is also possible, provided that we have control over external magnetic field or over the relative qubit-source position. 

[1] T. Staudacher et al., Science 339, 561 (2013). 
[2] I. Lovchinsky et al., Science. 351, 836 (2016). 
[3] P. Szańkowski et. al., a Topical Review to be published to J. Phys.:Condens. Matter, arXiv:1705.02262 (2017).
[4] P. Szańkowski, et al., Phys. Rev. A 94, 012109 (2016)