Summary: We produced a new system for measuring the small photoelastic constant of a polymer thin film with a small birefringence. Using our mesurement system, we evaluated the photoelastic constant of a polymer film in real time by quantitative analysis. Photoelastic constants of 11.30 Â 10 À12 Pa À1 for a cellulose triacetate film and 78.38 Â 10 À12 Pa À1 for a polycarbonate film were obtained. Furthermore, we obtained a small photoelastic constant of 0.12 Â 10 À12 Pa À1 for a cycloolefin film for liquid crystal displays, using our new measurement system. This value is very small. We emphasize that, if a small change in retardation and stress cannot be detected simultaneously using our system, then we cannot obtain such a small photoelastic constant.

The possibility has been indicated that a piezoelectric polymer with helical chirality (chiral polymer) such as poly-L-lactic acid (PLLA) shows a large linear electrooptical constant (Pockels effect). However, the linear electrooptical constant of a PLLA film may be very small because such a film fabricated by the conventional method has a complex high-order structure with intermingled crystalline and amorphous regions. In order to measure the small linear electrooptical constant of a PLLA film, we developed a new measurement system, which is based on the heterodyne interferometry principle. In this system, the accuracy of retardation is 0.08 nm and the measurement time is 0.1 s. In our attempt to realize a PLLA film with a large linear electrooptical constant, we fabricated a PLLA film, which was heated to 120°C under 320 MPa. Finally, using our new measurement system, we obtained a linear electrooptical constant of 0.070 pm/V in the PLLA film, which is very small compared with those of other famous Pockels materials. However, the linear electrooptical constant of the PLLA film is clarified in this study for the first time.

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Given a bipartite system, correlations between its subsystems can be understood as the information that each one carries about the other. In order to give a model-independent description of secure information disposal, we propose the paradigm of private quantum decoupling, corresponding to locally reducing correlations in a given bipartite quantum state without transferring them to the environment. In this framework, the concept of private local randomness naturally arises as a resource, and total correlations are divided into eliminable and ineliminable ones. We prove upper and lower bounds on the quantity of ineliminable correlations present in an arbitrary bipartite state, and show that, in tripartite pure states, ineliminable correlations satisfy a monogamy constraint, making apparent their quantum nature. A relation with entanglement theory is provided by showing that ineliminable correlations constitute an entanglement parameter. In the limit of infinitely many copies of the initial state provided, we compute the regularized ineliminable correlations to be measured by the coherent information, which is thus equipped with a new operational interpretation. In particular, our results imply that two subsystems can be privately decoupled if their joint state is separable.

The paper covers an issue of method and device for measurement of two-dimensional retardance with high-order and azimuthal direction. The system based on the use of a crossed polarizer by changing spectroscopic polarized light.Sixty-four sets of images are used for birefringence analysis. The spectroscopic interferogram change sinusoidal with wave number and the period is in proportion to birefringence of specimen. The measured results of the two dimensional birefringence distribution of a plastic and standard phase plate of retardation are shown. Fourier transform method and maximum entropy method enable to measure birefringence with high resolution. Two examples, measurement of aligned polymer film, which is laminated as steps, and that of birefringence distribution, are demonstrated.