We experimentally address the significance of fidelity as a figure of merit in quantum state reconstruction of discrete (DV) and continuous variable (CV) quantum optical systems. In particular, we analyze the use of fidelity in quantum homodyne tomography of CV states and maximum-likelihood polarization tomography of DV ones, focussing attention on nonclassicality, entanglement and quantum discord as a function of fidelity to a target state. Our findings show that high values of fidelity, despite well quantifying geometrical proximity in the Hilbert space, may be obtained for states displaying opposite physical properties, e.g. quantum or semiclassical features. In particular, we analyze in details the quantum-to-classical transition for squeezed thermal states of a single-mode optical system and for Werner states of a two-photon polarization qubit system.

We suggest and demonstrate a scheme to reconstruct the symmetric two-mode squeezed thermal states of spectral sideband modes from an optical parametric oscillator. The method is based on a single homodyne detector and active stabilization of the cavity. The measurement scheme have been successfully tested on different two-mode squeezed thermal states, ranging from uncorrelated coherent states to entangled states.PACS numbers: 03.65. Wj, 42.50.Lc, 42.50.Dv Introduction -Homodyne detection (HD) is an effective tool to characterize the quantum state of light in either the time [1][2][3][4][5][6][7][8] or the frequency [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] domain. In a spectral homodyne detector, the signal under investigation interferes at a balanced beam splitter with a local oscillator (LO) with frequency ω 0 . The two outputs undergo a photodetection process and their photocurrents are combined leading to a photocurrent continuously varying in time. The information about the spectral field modes at frequencies ω 0 ± Ω (sidebands) is then retrieved by electronically mixing the photocurrent with a reference signal with frequency Ω and phase Ψ. Upon varying the phase θ of the LO, we may access different field quadratures, whereas the phase Ψ can be adjusted to select the symmetric S or antisymmetric A balanced combinations of the upper and lower sideband modes.

Wind‐formed features are abundant in Oxia Planum (Mars), the landing site of the 2022 ExoMars mission, which shows geological evidence for a past wet environment. Studies of aeolian bedforms at the landing site were focused on assessing the risk for rover trafficability, however their potential in recording climatic fluctuations has not been explored. Here we show that the landing site experienced multiple climatic changes in the Amazonian, which are recorded by an intriguing set of ridges that we interpret as Periodic Bedrock Ridges (PBRs). Clues for a PBR origin result from ridge regularity, defect terminations, and the presence of preserved megaripples detaching from the PBRs. PBR orientation differs from superimposed transverse aeolian ridges pointing toward a major change in wind regime. Our results provide constrains on PBR formation mechanisms and offer indications on paleo winds that will be crucial for understanding the landing site geology.

No abstract