Abstract
We consider possible detection of nonclassicality of primordial gravitational waves (PGWs) by applying Hanbury Brown - Twiss (HBT) interferometry to cosmology. We characterize the nonclassicality of PGWs in terms of sub-Poissonian statistics that can be measured by the HBT interferometry. We show that the presence of classical sources during inflation makes us possible to detect nonclassical PGWs with the HBT interferometry. We present two examples that realize the classical sources during inflation. It turns out that PGWs with frequencies higher than 10 kHz enable us to detect their nonclassicality.
Highlights
One of the cornerstones of inflationary cosmology is that the large scale structure of the Universe has a quantum mechanical origin
We considered the possible detection of nonclassicality of primordial gravitational waves (PGWs) by applying HBT interferometry to cosmology
We showed that the initial presence of classical sources induces coherent states during inflation, and the Bunch-Davies vacuum looks like squeezed coherent states from the point of view of the radiationdominated era
Summary
One of the cornerstones of inflationary cosmology is that the large scale structure of the Universe has a quantum mechanical origin. It was shown that the necessary energy scale for generating them can be reduced in the presence of gauge fields during inflation [4]. In this case, the PGWs have circular or linear polarization and carry information about the model of inflation as well. We consider a non-BD vacuum due to the presence of gauge fields as the initial state This initial state becomes a squeezed coherent state and the graviton distribution of the squeezed coherent state shows sub-Poissonian. To predict the frequency range of nonclassical PGWs, we present two examples that realize the presence of gauge fields during inflation. We show that PGWs with frequency higher than 10 kHz enable us to detect their nonclassicality with the HBT interferometry
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