Electromagnetically induced transparency is a quantum interference effect that permits the propagation of light through an otherwise opaque atomic medium; a 'coupling' laser is used to create the interference necessary to allow the transmission of resonant pulses from a 'probe' laser. This technique has been used to slow and spatially compress light pulses by seven orders of magnitude, resulting in their complete localization and containment within an atomic cloud. Here we use electromagnetically induced transparency to bring laser pulses to a complete stop in a magnetically trapped, cold cloud of sodium atoms. Within the spatially localized pulse region, the atoms are in a superposition state determined by the amplitudes and phases of the coupling and probe laser fields. Upon sudden turn-off of the coupling laser, the compressed probe pulse is effectively stopped; coherent information initially contained in the laser fields is 'frozen' in the atomic medium for up to 1 ms. The coupling laser is turned back on at a later time and the probe pulse is regenerated: the stored coherence is read out and transferred back into the radiation field. We present a theoretical model that reveals that the system is self-adjusting to minimize dissipative loss during the 'read' and 'write' operations. We anticipate applications of this phenomenon for quantum information processing.

A Theory of Marital Sexual LifeWhy does the frequency of marital sex decrease with marital duration? Does the probability of involvement in extramarital sex increase or decrease with marital duration, and why? I develop a theory to answer these questions. I apply the law of diminishing marginal utility and human capital theory to explain the basic observed decline in the frequency of marital sex with marital duration. Based on the above explanation, I develop a discussion on the relationship between marital duration and extramarital sex, and I derive two hypotheses, which are supported by statistical analyses of the National Health and Social Life Survey data.It is well known that marital duration negatively affects the frequency of marital sex. However, we know little about how martial duration affects extramarital sex. Extramarital sex has enormous disruptive potential for marriages, and it is frequently cited by divorced persons as a prime reason for the dissolution of their marriages (South & Lloyd, 1995). Therefore, a better understanding of the factors influencing the frequency of marital and extramarital sex should be of great theoretical and practical value. However, factors contributing to these two types of sexual behavior are not well understood. This article develops a theory that explains the basic observed patterns of sex between marital partners and makes two predictions concerning extramarital sex.

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