Retrocausality and Quantum Measurement

A retrocausal interpretation of quantum mechanics is examined and is applied to the problem of measuring an optical qubit before the qubit is actually created. Although the predictions of the retrocausal interpretation are the same as for the conventional causal picture, it provides a new perspective which should give a useful way of understanding some quantum mechanical processes.     

Phase properties of squeezed states of light

Recently introduced unitary and hermitian phase operators are used to examine the phase properties of squeezed states of light with particular reference to the squeezed vacuum. The results differ markedly from previous calculations involving the Susskind and Glogower operators. The new formalism allows the construction of a phase probability density which, on a polar diagram, is a circle for the vacuum state, becomes elliptical with gentle squeezing and collapses to a line through the origin for full squeezing. This probability density together with the calculation of expectation values of various trigonometrical functions of phase show how squeezing impresses phase information onto the vacuum.     

Laser light-scattering spectroscopy on thermally excited capillary waves at liquid-liquid interfaces in binary liquid mixtures near critical end-points

With the aim of testing Widom's recent predictions regarding the surface and interfacial tensions of binary fluid mixtures near critical end-points we have constructed a laser light-scattering spectrometer for studying thermally excited waves at the liquid-liquid interface. This instrument permits the determination of interfacial tensions at temperatures very much nearer the critical temperature T_C than is possible by conventional capillarity. We have measured the interfacial tension of nitroethane+3-methylpentane over a range of temperatures closer by one order of magnitude in ε = |T ? T_C|/T_C to T_C than previously reported; in the region of overlapping ε the two sets of results agree well. The critical index μ is found to be 1.26 ± 0.02 in good agreement with values for pure fluids but somewhat smaller than the value, 1.33 ± 0.03, previously reported for this mixture, possibly reflecting a temperature range dependence of μ.     

Determination of trace elements in food by neutron activation analysis

Neutron activation analysis (NAA) methods have been developed for the determination of major, minor and trace elements in duplicate diets and individual food items. These include a cyclic instrumental NAA (CINAA) method for measuring Se content through its short-lived nuclide^77mSe; epithermal INAA (EINAA) for I and As; conventional INAA for Br, Ca, Cl, Co, Cr, Fe, K, Mg, Mn, Na, Rb, Sb, Sc, Sn and Zn; combination of EINAA and INAA for Al; radiochemical NAA (RNAA) for As, Au, Co, Cu, Fe, Hg, Mo, Sb, Se and Zn; and preconcentration NAA (PNAA) for U and Th. Accuracy of measurements have been evaluated by analyzing a number of biological and diet reference materials. Multielement concentrations of diets and foods have been measured by these methods.     

Proton spin relaxation in some paramagnetic transition-metal acetylacetonate complexes. Comparison between theory and experiment

Proton spin-lattice (T₁) and spin-spin (T₂) relaxation times have been measured for CH₃ protons in a series of paramagnetic transition-metal acetylacetonate complexes and the results interpreted in terms of current relaxation theory, τ_r, the correlation time for molecular reorientation, was estimated from the ¹³C T₁ in the analogous diamagnetic Co(III) and Pd(II) complexes. Using this approach and treating in detail the effects of fast CH₃ group internal motion good agreement is obtained between theory and experiment. In all cases electron-nuclear dipolar coupling dominates T₁ whereas the hyperfine contribution can be important for T₂.     

X-ray absorption studies of the local strontium environments in borosilicate waste glasses

X-ray absorption spectra were collected and analyzed to characterize the strontium environments in borosilicate glass formulations developed for the immobilization of nuclear wastes. Sr can become a major constituent in some radioactive wastes because of the use of Sr-compounds in waste pretreatment processes. Data are presented for 13 borosilicate glasses that are used to simulate the anticipated waste glass compositions, where SrO concentrations range from approximately 2 to 30 wt%. The XANES data are statistically identical for all glasses investigated, and indicate divalent strontium. The EXAFS data for both crystalline standards and glasses appear to provide information only about the inner four to six coordinating oxygens that surround Sr. The data and analyses for all glasses show that the inner coordination environments around Sr have average Sr-O distances near 2.53 Å, which are statistically invariant with respect to glass composition and to various synthesis conditions. Sr-O distances determined for the glasses are within the shorter end of the range of individual Sr-O distances in the SrCO₃ and haradaite (SrVSi₂O₇) crystalline standards.     

Master equation for retrodiction of quantum communication signals

We derive the master equation that governs the evolution of the measured state backwards in time in an open system. This allows us to determine probabilities for a given set of preparation events from the results of subsequent measurements, which has particular relevance to quantum communication.