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This concept was first described in Two-photon amplitude interferometry for precision astrometry, P.Stankus, A.Nomerotski, A.Slosar and S.Vintskevich, arxiv:2010.09100.

Improved quantum sensing of photon wave-functions could provide high resolution observations in the optical benefiting numerous fields, including general relativity, dark matter studies, and cosmology. It has been recently proposed that stations in optical interferometers would not require a phase-stable optical link if instead sources of quantum-mechanically entangled pairs could be provided to them, potentially enabling hitherto prohibitively long baselines. A new refinement of this idea is developed, in which two photons from different sources are interfered at two separate and decoupled stations, requiring only a slow classical information link between them. We rigorously calculate the observables and contrast this new interferometric technique with the Hanbury Brown & Twiss intensity interferometry. We argue this technique could allow robust high-precision measurements of the relative astrometry of the two sources. A basic calculation suggests that angular precision on the order of 10µas could be achieved in a single night’s observation of two bright stars.


Observations using interferometers provide sensitivity to features of images on angular scales much smaller than any single telescope, on the order of Delta theta ~ l/b where b is the interferometric baseline.  Present-day optical interferometers are essentially classical, interfering single photons with themselves.  However, there is a new wave of interest in interferometry using multiple photons, whose mechanisms are inherently quantum mechanical, which offer the prospects increased baselines and finer resolutions among other advantages.  We will develop and implement recent ideas for quantum-assisted interferometry using the resource of entangled pairs, and specifically a two-photon amplitude technique aimed at improved precision in dynamic astrometry.

It was pointed out by Gottesman, Jennewein and Croke [1] in 2012 that optical interferometer baselines could be extended, without an optical connecting path, if a supply of entangled Bell states between the two stations could be provided. If these states could then be interfered locally at each station with an astronomical photon that has impinged on both stations, the outcomes at the two stations would be correlated in a way that is sensitive to the phase difference in the two paths of the photon, thus reproducing the action of an interferometer. Equivalently, this can be seen as using a Bell state measurement at one station to teleport the state of that station’s astronomical photon to the other station, and interfering it with its counterpart there.