title: Faraday rotation echo spectroscopy and detection of quantum fluctuations.
abstract: Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials.
authors.affiliation: Department of Physics, Centre for Quantum Coherence, & Institute of Theoretical Physics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Shao-Wen
authors.initials: SW
authors.lastname: Chen
authors.affiliation: Department of Physics, Centre for Quantum Coherence, & Institute of Theoretical Physics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ren-Bao
authors.initials: RB
authors.lastname: Liu
references.citation: Phys Rev Lett. 2006 Apr 14;96(14):140604
references.pmid: 16712060
references.citation: Phys Rev Lett. 2009 Nov 27;103(22):220802
references.pmid: 20366085
references.citation: Phys Rev Lett. 2012 Nov 2;109(18):185701
references.pmid: 23215296
references.citation: Science. 2005 Apr 15;308(5720):389-92
references.pmid: 15831752
references.citation: Phys Rev Lett. 1996 Jul 29;77(5):940-943
references.pmid: 10062945
references.citation: Science. 2013 Mar 8;339(6124):1174-9
references.pmid: 23471400
references.citation: Nature. 2010 Mar 4;464(7285):45-53
references.pmid: 20203602
references.citation: Phys Rev Lett. 2010 Jan 22;104(3):036601
references.pmid: 20366666
references.citation: Nature. 2004 Sep 2;431(7004):49-52
references.pmid: 15343328
references.citation: Nat Nanotechnol. 2011 Apr;6(4):242-6
references.pmid: 21358646