Towards Searching for Entangled Photons in the CMB Sky

Abstract

We explore the possibility of detecting entangled photon pairs from cosmic microwave background or other cosmological sources coming from two patches of the sky. The measurements use two detectors with different photon polarizer directions. When two photon sources are separated by a large angle relative to the earth, such that each detector has only one photon source in its field of view, a null test of unentangled photons can be performed. The deviation from this unentangled background is, in principle, the signature of photon entanglement. To confirm whether the deviation is consistent with entangled photons, we derive a photon polarization correlation to compare with, similar to that in a Bell inequality measurement. However, since photon coincidence measurement cannot be used to discriminate unentangled cosmic photons, it is unlikely that the correlation expectation value alone can violate Bell inequality to provide the signature for entanglement.

5 pages, 2 figure; references added, typos fixed. v3 revised version with more discussions on detection possibilities; added references.v4 published version in PRD

References in corpus (9)

• Cosmic Bell Test: Measurement Settings from Milky Way Stars
• Inflationary Perturbations: the Cosmological Schwinger Effect
• Obstructions to Bell CMB Experiments
• Bell violation in the Sky
• Astrophysical and Cosmological Tests of Quantum Theory
• Possible detection of nonclassical primordial gravitational waves with Hanbury Brown - Twiss interferometry
• Infinite violation of Bell inequalities in inflation
• Bell Inequality in the Holographic EPR Pair
• Entanglement Enabled Intensity Interferometry

Cited by in corpus (9)

• Possible detection of nonclassical primordial gravitational waves with Hanbury Brown - Twiss interferometry
• Nonclassical primordial gravitational waves from the initial entangled state
• Testing ER=EPR
• Gravitational Waves and Possible Fast Radio Bursts from Axion Clumps
• Some measures for fermionic entanglement in the cosmological de Sitter spacetime
• Bell Inequality in the Holographic EPR Pair
• Gravity-induced entanglement between two massive microscopic particles in curved spacetime: II.Friedmann- Lemaître-Robertson-Walker universe
• Violation of Bell inequalities from Cosmic Microwave Background data
• Long-range correlation of CMB temperature fluctuations from the holographic entanglement entropy