With this, we have the setup needed for a delayed-choice experiment on a cosmic scale. Using a telescope to capture photons from the Twin Quasar, we can choose to measure which path through the gravitational lens a photon takes—the upper or lower path in the Hubble image—or we can choose to measure a superposition. If we choose to measure its path and we discover, say, that it’s on the upper path, then for almost 14 billion years that photon has been on that path because of a choice we made today. If we had chosen instead to measure a superposition, then that photon would have a different
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We must spend more time on the delayed choice experiment!
