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Nonlocal correlations of polarization-entangled photons through brain tissue (Conference Presentation)

Enrique J. Galvez, Lingyan Shi, R. R. Alfano

Published May 1, 2017• 0 citations
Publisher

Abstract

We investigated the preservation of non-local correlations between polarization-entangled photons when one of them traveled through brain tissue slices of different thicknesses. Using down-converted photons at a wavelength of 802 nm minimized the absorption by the tissue. After the light passed through the tissue samples, we performed quantum state tomography to obtain quantitative measures of the entanglement. We found that entanglement is preserved to a surprising degree, and when it degrades, it does so following a particular path in a tangle versus linear-entropy graph. Such a trajectory reveals direct transfer of probability from entangled to mixed state.

DOI
10.1117/12.2253293

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We investigated the preservation of non-local correlations between polarization-entangled photons when one of them traveled through brain tissue slices of different thicknesses. Using down-converted photons at a wavelength of 802 nm minimized the absorption by the tissue. After the light passed through the tissue samples, we performed quantum state tomography to obtain quantitative measures of the entanglement. We found that entanglement is preserved to a surprising degree, and when it degrades, it does so following a particular path in a tangle versus linear-entropy graph. Such a trajectory reveals direct transfer of probability from entangled to mixed state.
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There is interest in using photon entanglement in biomedical applications. In one application, polarization entangled photons pass through brain tissue. The effect of the brain tissue on the photon entanglement is measured via the decoherence that is imparted on the entangled state. Our current method to obtain a measure of the decoherence involves quantum state tomography, where a minimum of 16 measurements are used in conjunction with tomographic optimization to obtain the density matrix representing the state of the photons. In this work we report on a method to avoid tomographic optimization on behalf of a direct measurement of the elements of the density matrix. We make preliminary comparisons between the two methods.
Quantum correlations are non-classical features of quantum systems that can be harnessed in new technologies. Nonlocality, a unique byproduct of the entanglement of more than one particle, can alter the causal sequence that is present in a classical measurement. In this work, we investigate a nonlocal form of Mueller polarimetry. In the classical method, light prepared in an initial state passes through a sample whose polarization properties are unknown, and the light's modified polarization state is subsequently measured. From a series of measurements, the Mueller matrix is obtained, which contains the polarization properties of the sample. In the nonclassical version of the technique presented here, the initial and final parts of this measurement were split into polarization projections on two polarization-entangled photons, but linked through quantum correlations in the post-selection process. We found the results with samples of known and unknown Mueller matrix using this approach to be equivalent to the classical ones. The nonlocal feature of the measurement can invert the causal order of preparation and measurement in the classical method. We present a study of its limitations when the entangled state of the photons is not the ideal one. From this work, we conclude that the technique is very resilient to imperfections in the quantum state of the photons, making it a feasible alternative to the classical method.