[en] We investigate the sensitivity of phase estimation in a Mach–Zehnder interferometer with photon-subtracted two-mode squeezed vacuum states. Our results show that, for given initial squeezing parameter, both symmetric and asymmetric photon subtractions can further improve the quantum Cramér–Rao bound (i.e., the ultimate phase sensitivity), especially for single-mode photon subtraction. On the other hand, the quantum Cramér–Rao bound can be reached by parity detection for symmetric photon-subtracted two-mode squeezed vacuum states at particular values of the phase shift, but it is not valid for asymmetric photon-subtracted two-mode squeezed vacuum states. In addition, compared with the two-mode squeezed vacuum state, the phase sensitivity via parity detection with asymmetric photon-subtracted two-mode squeezed vacuum states will be getting worse. Thus, parity detection may not always be the optimal detection scheme for nonclassical states of light when they are considered as the interferometer states. (paper)

[en] Effect of structure parameter n and its coupling with the connection mode among RuO_6 octahedra of Sr_n_+_1Ru_nO_3_n_+_1 (n = 1, 2, ∞) are investigated. The gradually enhanced rotation and tilting effect with increasing n are observed in Sr_n_+_1Ru_nO_3_n_+_1. Besides, the chemical valence of Ru is not changed, while the one of Sr gradually varies with increasing n, which highlights the great contribution of connection mode to the chemical environment. Our results show a strong n dependence on the connection mode between octahedra in Sr_n_+_1Ru_nO_3_n_+_1 (n = 1, 2, ∞). (paper)

[en] We elucidate the importance of a capping layer on the structural evolution and phase change properties of carbon-doped Ge ₂ Sb ₂ Te ₅ (C-GST) films during heating in air. Both the C-GST films without and with a thin SiO ₂ capping layer (C-GST and C-GST/SiO ₂ ) are deposited for comparison. Large differences are observed between C-GST and C-GST/SiO ₂ films in resistance-temperature, x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectra, data retention capability and optical band gap measurements. In the C-GST film, resistance-temperature measurement reveals an unusual smooth decrease in resistance above 110 °C during heating. X-ray diffraction result has excluded the possibility of phase change in the C-GST film below 170 °C. The x-ray photoelectron spectroscopy experimental result reveals the evolution of Te chemical valence because of the carbon oxidation during heating. Raman spectra further demonstrate that phase changes from an amorphous state to the hexagonal state occur directly during heating in the C-GST film. The quite smooth decrease in resistance is believed to be related with the formation of Te-rich GeTe _4−n Ge_n (n = 0, 1) units above 110 °C in the C-GST film. The oxidation of carbon is harmful to the C-GST phase change properties. (paper)