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Physicists who think carefully about time point to troubles posed by quantum mechanics, the laws describing the probabilistic behavior of particles. At the quantum scale, irreversible changes occur that distinguish the past from the future: A particle maintains simultaneous quantum states until you measure it, at which point the particle adopts one of the states. Mysteriously, individual measurement outcomes are random and unpredictable, even as particle behavior collectively follows statistical patterns. This apparent inconsistency between the nature of time in quantum mechanics and the way it functions in relativity has created uncertainty and confusion.

"Spooky action at a distance," Einstein's summation of quantum physics, has been a criticism of quantum mechanics since the field emerged. So far, descriptions of entangled particles to explain their apparently faster-than-light responses, and even explanations for the phase shifts induced by an electromagnetic field in regions where it is zero-the "Aharonov-Bohm" effect-have mostly addressed these concerns. However, recent theoretical and experimental demonstrations of a "counterfactual" quantum communication protocol have proved difficult to explain in terms of physical cause and effect. In this kind of quantum communication, observers on either side of a "transmission channel" exchange information without any particle passing between them-spooky indeed.

Noise limits the performance of modern quantum technologies. However, particles traveling in a superposition of paths can bypass noise in communication. A collaboration between the Universities of Hong-Kong, Grenoble and Vienna, as well as the Austrian Academy of Sciences, under the lead of Philip Walther, reveals novel techniques to reduce noise in quantum communication. The results, published in the latest issue of Physical Review Research, demonstrate that quantum particles traveling in a superposition of paths enable noise reduction in communications.

As scientists await the highly anticipated initial results of the Muon g-2 experiment at the U.S. Department of Energy's (DOE) Fermi National Accelerator Laboratory, collaborating scientists from DOE's Argonne National Laboratory continue to employ and maintain the unique system that maps the magnetic field in the experiment with unprecedented precision.

Aerosols are suspensions of fine solid particles or liquid droplets in a gas. Clouds, for example, are aerosols because they consist of water droplets dispersed in the air. Such droplets are produced in a two-step process: first, a condensation nucleus forms, and then volatile molecules condense onto this nucleus, producing a droplet. Nuclei frequently consist of molecules different to those that condense onto them. In the case of clouds, the nuclei often contain sulphuric acids and organic substances. Water vapor from the atmosphere subsequently condenses onto these nuclei.

new study uses satellite data over the Southern Hemisphere to understand global cloud composition during the industrial revolution. This research tackles one of the largest uncertainties in today's climate models-the long-term effect of tiny atmospheric particles on climate change.

Anyons have characteristics not seen in other subatomic particles, including exhibiting fractional charge and fractional statistics that maintain a "memory" of their interactions with other quasiparticles by inducing quantum mechanical phase changes.

The physicists who run the world's most sensitive experimental search for dark matter have seen something strange. They have uncovered an unexpected excess of events inside their detector that could fit the profile of a hypothetical dark matter particle called an axion. Alternately, the data could be explained by novel properties of neutrinos. More mundanely, the signal could come from contamination inside the experiment.