turbid medium

Light from the very beginning of the cosmos has been traveling toward us for 13.8 billion years. During that time, its polarization, the direction of its oscillations, might have been twisted, like a compass needle that someone quietly nudged. Physicists call this phenomenon cosmic birefringence.

A beam of light enters frosted glass and fades — nothing unusual. But physicists have long known how to make light pass through without losing a single photon. This trick is called electromagnetically induced transparency: two light waves cancel each other at the right point, and absorption disappears. Now a similar feat has been pulled off with atoms.

A candle flame flickers in a draft but doesn't go out — the tongue of fire briefly changes shape and then returns. Optical skyrmions behave much the same way — tiny vortices in a light beam, reminiscent of swirling eddies. Until recently, they were created only in the perfect, smooth light of a laser.

A boiling cauldron: steam rises, water churns, and the temperature varies from point to point. So it is in space: the gas clouds around young stars are not smooth spheres but a seething mixture with vortices and density fluctuations. Astronomers long treated such clouds as homogeneous, but this simplification can skew conclusions.

A quantum computer is like an orchestra that can only perform in complete silence. The slightest noise, and the delicate melody falls apart. For quantum devices, heat is that noise: even faint infrared radiation from nearby components heats up the qubits and erases their quantum states.

When light passes through biological tissue or frosted glass, it scatters and loses the image. Researchers at the Paris Institute of Nanosciences have shown that a scattering medium can be tuned to transmit images encoded in the correlations of entangled photons while remaining opaque to classical light.