Quantum investigation: propagation of entangled photons through cortex tissue

Medical techniques for scanning the brain enable imaging of its structure or function of the brain. There is growing interest in using quantum light for tissue scanning. A precise investigation of this quantum mechanical phenomenon can lead to new medical diagnostics and brain imaging techniques. In this study, we employed quantum photon pair’s, created by spontaneous parametric down-conversion. The technique involved preparing pairs of photons in maximally-entangled Bell states in the polarization degree of freedom. One part of the entangled photons was focused on rat brain tissue. The state of the photons passing through the brain was measured. We compared the preservation of the photon pairs’ quantum correlation in polarization via Bell parameter measurement of the transmitted entangled photons. Our results show a distinct difference in the entanglement preservation among different regions of the rat brain. The cortex tissue meaningfully preserved the photons’ correlation to a high degree despite the scattering effect , while the inner part, like the amygdala, degraded the entanglement and the Bell parameter declined to 1.31. The gradual decrease of the Bell parameter, indicating the decoherence of entangled photons in the tissue, can serve as a proper criterion to describe the characteristics of biological media. This study can be a major step toward a modern imaging method and brain mapping in the future.