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Polarizing light: to divide (and sometimes conquer)

Polarizing beam splitter and other optics in NIST Spielman laboratory. Credit: E. Edwards/JQI

Polarization refers to the orientation of traveling waves with respect to a well-defined direction. Polarized sunglasses shield your eyes from light having certain orientations. Projectors that display images having different polarizations are used to generate the 3D effects seen in movies. 

Read more to learn more about how polarized light is used in quantum information research.

Atomic transitions: Polarization pops up all over quantum information research. Physicists use polarizing elements like the one shown here, to define the polarization of laser light. This particular element, a polarizing beam splitter, transmits light of one polarization while reflecting the light with the opposite polarization. Why do scientists need to filter or define a given laser beam's polarization?  Because precise manipulation of atomic transitions strictly depends on several factors like laser power, frequency (color), and polarization.

Photonic qubit: Because light can have a well-defined polarization, and even be in combinations of different polarization states, then the light itself can be used by itself for quantum information processing. For instance, just like energy levels for an atom can constitute a qubit, two different polarization states of light can make up a photonic qubit.