Using Quantum Entanglement to Detect Alzheimers in the Brain

Quantum entanglement. Credit: Shutterstock

Neuroscience and quantum mechanics: two scientific disciplines not usually spoken in the same breath. But in a presentation on Tuesday at SPIE Photonics West, Enrique Galvez of Colgate University talked about early work that merges the two fields. Galvez is investigating whether quantum entanglement—the distinct correlations that can only exist among quantum particles—can be harnessed to detect Alzheimer's disease in human brains.

Galvez's approach involves generating pairs of entangled photons, beaming them into samples of brain tissue, and measuring whether the photons are still entangled afterward. Entanglement, often popularly referred to as "spooky action at a distance," is a phenomenon where the fate of two different particles are inextricably linked. A common interpretation of quantum mechanics says that altering or measuring one particle instantly changes the other, even when they are separated extremely far apart.

The work began around 2015, said Galvez. They began investigating thin slices of brain, about 120 microns thick, and found small differences. Then they expanded to thicker slices of brain of about 500 microns.

They generate the entangled photons via a process called parametric downconversion, in which they beam a blue laser into a beta barium borate crystal, which converts a blue photon into two identical entangled infrared photons. As the photons travel through the sample, interactions with the tissue can cause the pairs to no longer be entangled. Galvez's team measures how entangled the photons are after they travel through the tissue using a technique called quantum state tomography.

Galvez's team found that healthy tissue alters the initially entangled photons more. This could be because brains afflicted with Alzheimer's have more holes. They will conduct more experiments to characterize how the light travels through the tissue, including taking reflection measurements, and investigating the role of amyloid-beta, a protein fragment associated with Alzheimer's disease.