Genuine Multipartite Entanglement in Positronium-A Potential Quantum Sensor For Detecting Cancer


In hospitals a PET, a Positron-Emission-Tomograph, servers as a device to determine spatial and temporal distributions of concentrations of radio-active substances injected into patients. The back-to-back photons provide local information about the activity inside human bodies, e.g. utilized for detecting cancer. However, positronium atoms can also decay into three photons. The results, published in Scientific Reports (Nature Publishing Group), show that these three photons are entangled, even genuinely multipartite entangled, a strong type of entanglement where all degrees of freedom contribute to the entanglement. This will allow in future to read out not only the classical local information but as well the quantum information in metabolic processes!

In the recent Scientific Report contribution it is shown that the three-photon state with respect to the polarisation degrees of freedom depends on the angles between the photons and exhibits various specific entanglement features. In particular, genuine multipartite entanglement, a type of entanglement involving all degrees of freedom, is subsistent if the positronium was in a definite spin eigenstate. Remarkably, when all spin eigenstates of positronium are mixed equally, entanglement –and even stronger genuine multipartite entanglement– survives. Due to a “symmetrization” process, however, genuine multipartite Dicke-type or W-type entanglement remains whereas GHZ-type entanglement vanishes. The survival of particular entanglement properties in the mixing scenario allows for extracting quantum information of the positronium's environment. In other studies (see publication list) we have shown that, e.g., the lifetime of ortho-positronium (the one decaying in three photons) is greater for cancerous tissues than for healthy tissues from the same patient.