PROJECT DESCRIPTION

Starting from the study carried out for ESO in the frame of Extremely Large Telescopes (ELTs) (QuantEYE), we plan to develop a prototype of the highest time-resolution instrument for optical astronomy, with high quantum efficiency from the blue to the red, a very wide dynamic range (more than 20 mag), and a time tagging capability better than 100 picoseconds for minutes or even hours.

This instrument we have called Iqueye (Italian Quantum Eye) and we want to demonstrate that it is capable to explore astrophysical variability down to the sub-nanosecond scales.
Millisecond resolutions have already permitted to study lunar and stellar occultations, cataclysmic variables, pulsating wide dwarfs, flickering of high luminosity stars, X-binaries oscillations, gamma-ray bursters afterglows, etc.

Iqueye will permit to extend the observational capabilities into regions very close to:

• black holes,
• convection in wide dwarfs,
• acoustical spectra in non-radial oscillations and surface structures of neutron stars,
• photon gas bubbles in accretion flows,
• free electron lasers in magnetars etc.

Correlation spectroscopy down to the nanosecond will allow spectral resolutions R better than R = 10^8, needed to resolve the very narrow spectral lines emitted with lasing mechanisms in Eta Carinae. In addition, we'll obtain novel data on a still unexplored frequency domain of the behavior of the terrestrial atmosphere.
Furthermore, over a narrow bandwith, in a specified polarization state, the capabilities of Iqueye will approach the quantum-optical limit set by Heinseberg uncertainty principle.

Fig. 1 - All of Astronomy on a wavelength - time scale plot. On the left, a list of observable astrophysical phenomena from the millisecond to the nanosecond.

Thus, a further goal of our study is to prove that Iquaye will permit, not only to enlarge by orders of magnitude the presently reachable astrophysical time scales, but also to start the study of photon-stream statistics through second and higher-order correlation functions, which are needed to distinguish quantum states of seemingly identical light.
Under the observational capabilities of present day astronomical instrumentation, which only measure the first order correlation function (either through imaging, or spectroscopy or polarimetry), those different states are a priori indistinguishable.

Iqueye has a further scientific purpose, namely to demonstrate in a real astronomical application the feasibility of a modern version of the Hanbury Brown Twiss Intensity Interferometer (HBTI). Although the sensitivity of the HBTI is intrinsically low, however is has the great advantage not to require a phased array, in the limit, not even an optical link between the two or more telescopes. Furthermore, it is essentially immune to seeing conditions, it tolerates modest optical quality, and its sensitivity covers the blue-yellow region of the spectrum. Thus, it can provide novel data on problems such as the stellar limb darkening, and an unsurpassed spatial resolution.

Our aim in this field is to demonstrate with Iqueye the sensitivity advantage due to the higher quantum efficiency of the detector, the much higher electric bandwidth one can achieve with the precise time tagging capability, and finally the capability to distribute and maintain a very precise common time to distant observers.
Although the signature of quantum phenomena and the sensitivity of HBTI increase with the square of the intensity, implying an enormously increased sensitivity at the future ELTs, however a prototype mounted on an existing telescope (such as TNG, VLT, LBT, the Cerenkov light collector MAGIC, to be decided during the first part of our study) will provide a crucial test-bench for all these concepts, and will also open the new scientific frontier of the nanosecond astrophysics.

Our study aims thus to carry out the crucial steps in all relevant fields of such an ambitious instrument, optics, detectors, time tagging and time distribution devices, data storage and analysis (including quantum computing), in a real astronomical environment.

Our cooperation (Padova-Roma, Cagliari, Catania) includes experts in all these fields, with proven experience from scientific analysis to designing, building, delivering and commissioning frontier instrumentation for ground and space applications. We can furthermore count on several important International collaborations.
At the end of the program, we will be able to move Iqueye to larger telescopes, such as the TNG, VLT and LBT, MAGIC, according to the results of the study. If successful, Iqueye will thus provide a powerful novel instrument to the Italian, and more generally to the European astronomical community.