We present a protocol to generate and control quantum entanglement between
the states of two subsystems (the system ${\cal S}$) by making measurements on
a third subsystem (the monitor ${\cal M}$), interacting with ${\cal S}$. For
the sake of comparison we consider first an ideal, or instantaneous projective
measurement, as postulated by von Neumann. Then we compare it with the more
realistic or generalized measurement procedure based on photocounting on ${\cal
M}$. Further we consider that the interaction term (between ${\cal S}$ and
${\cal M}$) contains a quantum nondemolition variable of ${\cal S}$ and discuss
the possibility and limitations for reconstructing the initial state of ${\cal
S}$ from information acquired by photocounting on ${\cal M}$.Comment: 12 pages, 3 figures, accepted for publication in Phys. Rev
In this paper we study the nondegenerate optical parametric oscillator with injected signal, both analytically and numerically. We develop a perturbation approach which allows us to find approximate analytical solutions, starting from the full equations of motion in the positive Prepresentation. We demonstrate the regimes of validity of our approximations via comparison with the full stochastic results. We find that, with reasonably low levels of injected signal, the system allows for demonstrations of quantum entanglement and the Einstein-Podolsky-Rosen paradox. In contrast to the normal optical parametric oscillator operating below threshold, these features are demonstrated with relatively intense fields.
This frontline shows how to build a computer-controlled photogate using Snap4Arduino, a programming environment derived from Scratch for controlling the Arduino microcontroller board. The advantages of the proposed photogate are that it is affordable to schools, easy-to-assemble and simple to use by younger students in secondary schools who are not familiar with programming languages. An experiment was conceived to evaluate the device proposed that matched the performance of a commercial photogate. We show that the computer-controlled photogate setup can be used in experiments with objects moving fast (like in free fall) with a good precision.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.