Isotropic quantum beats

Mark P. Silverman

xubo liao, Yue Wang, Kangjun Xia +3 more

Abstract Mössbauer nuclei with quadrupole-split levels provide a versatile platform for exploring coherent x-ray light-matter interactions. We theoretically study ensembles of 57 Fe nuclei embedded in thin-film x-ray cavities, explicitly accounting for different orientations of the electric field gradient. By mapping isotropic electric field gradient distributions to an effective equal-weight two-transition model, we derive analytical expressions for the time-dependent reflectivity and reveal the emergence of cavity-mediated quantum beats. The oscillation frequency and temporal profile of these beats can be tuned via the cavity-induced coherent coupling, offering a flexible approach to control collective nuclear dynamics and manipulate nuclear coherence in the x-ray regime.

Patrick Dupré

By analyzing the decaying intensity, leaking out a high-finesse cavity previously ``filled'' by a cw laser source (using the cavity ring-down spectroscopy technique), we observed frequency beating between what we think are two orthogonal eigenpolarization states of the intracavity electromagnetic field. The time decay (ring down) is analyzed by varying the angle of the polarization analyzer located in front of the detector. A full modeling of the observed signal is proposed. It is based on the Jones matrix formalism required for modeling the cavity behavior following a rotated phase shifter. The full transfer function is first established in the frequency domain, and then Fourier transformed to recover the temporal response. The same optical cavity, i.e., constituted of the same set of mirrors, is used at two different wavelengths ($\ensuremath{\sim}800$ and $\ensuremath{\sim}880$ nm). It demonstrates the differences in behavior between a high-finesse cavity $(\ensuremath{\sim}400\phantom{\rule{0.16em}{0ex}}000)$ and a lower finesse cavity $(\ensuremath{\sim}50\phantom{\rule{0.16em}{0ex}}000)$. Beating frequency, characteristics time, and beat amplitude are mainly discussed versus the analyzer angle. A cavity birefringence of $\ensuremath{\sim}1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ rad, resulting from the mirror birefringence is suggested. If the current analysis is in agreement with pulsed CRDS experiments (polarimetry) obtained in an isotropic moderate-finesse cavity, it differs from a recent work report on a high-finesse cavity associated with a source mode locking [Phys. Rev. A 85, 013837 (2012)].

Dmitry V. Kolomoitsev, S. Yu. Nikitin

Le Bin Ho, Yuichiro Matsuzaki, Masayuki Matsuzaki +1 more

Entangled sensors have been attracting a lot of attention recently because they can achieve the sensitivity beyond that of the classical sensors. To exploit entanglement as a resource, it is important to understand the effect of noise because the entangled state is fragile against noise. Here, we provide a Nuclear Magnetic Resonance (NMR) model of an entangled sensor under engineered noise: one can implement an entangled sensor under various noisy environments. In particular, we experimentally investigate the performance of the entangled sensor under the effect of time-inhomogeneous noisy environment with which the entangled sensor holds potential to beat the classical sensors. Our "entangled sensor" consists of a multi-spin molecule solved in isotropic liquid, and we can perform the quantum sensing by using NMR techniques.

Renate Zygan-Maus, H.H. Wolter