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arXiv:2401.14976 · Physical Review Letters

Spin Noise Spectroscopy of a Single Spin Using Single Detected Photons

Manuel Gundín, Paul Hilaire, C. Millet, Elham Mehdi, C. Antón, Abdelmounaïm Harouri, Aristide Lemaître, Isabelle Sagnes, Niccolò Somaschi, O. Krebs, P. Senellart, L. Lanco

Published Jan 24, 2025• 4 citations
arXivHTMLPDF

Abstract

Spin noise spectroscopy has become a widespread technique to extract information on spin dynamics in atomic and solid-state systems, in a potentially nonperturbative way. Here we experimentally demonstrate a new approach in spin noise spectroscopy, based on the detection of single photons. Because of the large spin-dependent polarization rotations provided by a deterministically coupled quantum dot-micropillar device, giant spin noise signals induced by a single-hole spin are extracted in the form of photon-photon cross-correlations. Ultimately, such a technique can be extended to an ultrafast regime probing mechanisms down to few tens of picoseconds.

DOI
10.1103/physrevlett.134.036902

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Interacting multi-component spin systems are ubiquitous in nature and in the laboratory. As such, investigations of inter-species spin interactions are of vital importance. Traditionally, they are studied by experimental methods that are necessarily perturbative: e.g., by intentionally polarizing or depolarizing one spin species while detecting the response of the other(s). Here, we describe and demonstrate an alternative approach based on multi-probe spin noise spectroscopy, which can reveal inter-species spin interactions--under conditions of strict thermal equilibrium--by detecting and cross-correlating the stochastic fluctuation signals exhibited by each of the constituent spin species. Specifically, we consider a two-component spin ensemble that interacts via exchange coupling, and we determine cross-correlations between their intrinsic spin fluctuations. The model is experimentally confirmed using "two-color" optical spin noise spectroscopy on a mixture of interacting Rb and Cs vapors. Noise correlations directly reveal the presence of inter-species spin exchange, without ever perturbing the system away from thermal equilibrium. These non-invasive and noise-based techniques should be generally applicable to any heterogeneous spin system in which the fluctuations of the constituent components are detectable.