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arXiv:1507.03897 · Physical Review A

Spectroscopy of cross correlations of environmental noises with two qubits

Piotr Szańkowski, Marek Trippenbach, Łukasz Cywiński

Published Jul 18, 2016• 56 citations
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Abstract

A single qubit driven by an appropriate sequence of control pulses can serve as a spectrometer of local noise affecting its energy splitting. We show that by driving and observing two spatially separated qubits, one can reconstruct the spectrum of cross correlations of noises acting at various locations. When the qubits are driven by the same sequence of pulses, the real part of a cross-correlation spectrum can be reconstructed, while applying two distinct sequences to the two qubits allows for reconstruction of the imaginary part of this spectrum. The latter quantity contains information on either causal correlations between environmental dynamics at distinct locations or the occurrence of propagation of noisy signals through the environment. We illustrate the former case by modeling the noise spectroscopy protocol for qubits coupled to correlated two-level systems. While entanglement between the qubits is not necessary, its presence enhances the signal from which the spectroscopic information is reconstructed.

DOI
10.1103/physreva.94.012109

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