« Archives in May, 2014

Quantum Telescope Update

So, I was thinking a bit about how this is supposed to work. Also, I started reading the academic paper that Kellerer wrote on the topic:


She’s not messing with the diffraction limit of the photons, cloned or otherwise. However, if the photons come in one at a time, then you can see each Airy disc (and an image of the entire disc (N photons drawn from the disk distribution), not just a single point drawn at random from the disc) produced by the cloned photons independently of the any other photons from the star. This deconvolves everything in the image. You can then take some average or moment of your disc to recover the center with greater accuracy, improving your angular resolution.

This could be a very big advance in astronomy. For years, what we could resolve was limited by the aperture of the optical system. To resolve something like an extrasolar planet, baselines or primary mirror diameters of hundreds of miles are needed – the sort of baselines that were planned for telescope constellations such as Terrestrial Planet Finder.

If we could increase by some multiple factor the angular resolution of a telescope, we might be able to someday image extrasolar planets with mirrors that aren’t too big to be physically feasable, or in single systems without the need to orchestrate large distributed aperture constellations.

Quantum Telescope

This is an interesting idea:


However, I’m having a hard time figuring out how it is supposed to work. I understand the resolution limit of telescopes in classical terms: Given a wavefront that gets windowed by an aperture, you’ve cut out the longest wavelengths in the fourier transform of the wavefront passing through the apeture, or reflecting off the primary mirror which limits the spot size that it can focus down to at the focal plane.

The same sort of logic should apply to single photons. If you have a photon from a distant star, it’s spread out into a giant wavefront by the time it gets to your primary mirror, the portion of the photon that reflects of the primary mirror is windowed, and can only focus down to a spot of a finite size on your detector (which pixels/entangled superposition of pixels it ends up exciting then becomes a matter of $INTERPRETATION), but N such photons will light up some airy disc of finite size on your detector.

So if you pass the photons through a gain medium (such as for a laser) prior to them hitting your primary mirror, you get N photons with the same wavefront description as the classical case passing through your detector. I can understand why you would get a brighter image from this (more photon counts hitting the detector within the airy disc), but not why the image should have a finer resolution.