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"In June 1999 the act of measuring a photon repeatedly without destroying it has was achieved for the first time, enabling researchers to study an individual quantum object with a new level of non-invasiveness. Physicists have long realized that it is possible to perform non-destructive observations of a photon with a difficult-to-execute technique known as a "quantum non-demolition" (QND) measurement. After many years of experimental effort, researchers in France (Serge Haroche, Ecole Normale Superieure) have demonstrated the first QND measurement of a single quantum object, namely a photon bouncing back and forth between a pair of mirrors (a "cavity"). A conventional photodetector measures photons in a destructive manner, by absorbing the photons and converting them into electrical signals. "Eating up" or absorbing photons to study them is not required by fundamental quantum mechanics laws and can be avoided with the QND technique demonstrated by the French researchers. In their technique, a photon in a cavity is probed without absorbing any net energy from it. (Of course, Heisenberg's Indeterminacy Principle ensures that counting a photon still disturbs the "phase" associated with its electric and magnetic fields.) In the experiment, a rubidium atom passes through a cavity. If a photon is present, the atom acquires a phase shift which can easily be detected. Sending additional rubidium atoms through the cavity allowed the researchers to measure the photon repeatedly without destroying it or. This technique can allow physicists to study the behavior of a photon during its natural lifespan; it can potentially allow researchers to entangle an arbitrary number of atoms and build quantum logic gates (Nogues et al., Nature, 15 July)"

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So the question is: If all it takes is ONE photon to communicate between the stars, how do we know that some of the stray photons from distant stars are not entangled with photons trapped in an alien transmitter? After all, single photons are received from the most distant stars and galaxies.