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Out Of Nothing: Dynamical Casimir effect in metamaterial converts vacuum fluctuations into real photons #renewables

Out Of Nothing: Dynamical Casimir effect in metamaterial converts vacuum fluctuations into real photons #renewables | Messenger for mother Earth | Scoop.it

In the strange world of quantum mechanics, the vacuum state (sometimes referred to as the quantum vacuum, simply as the vacuum) is a quantum system's lowest possible energy state. While not containing physical particles, neither is it an empty void: Rather, the quantum vacuum contains fluctuating electromagnetic waves and so-called virtual particles, the latter being known to transition into and out of existence. In addition, the vacuum state has zero-point energy – the lowest quantized energy level of a quantum mechanical system – that manifests itself as the static Casimir effect, an attractive interaction between the opposite walls of an electromagnetic cavity. Recently, scientists at Aalto University in Finland and VTT Technical Research Centre of Finland demonstrated the dynamical Casimir effect using a Josephson metamaterial embedded in a microwave cavity. They showed that under certain conditions, real photons are generated in pairs, and concluded that their creation was consistent with quantum field theory predictions.


Researcher Pasi Lähteenmäki discussed the challenges he and his colleagues – G. S. Paraoanu, Juha Hassel and Pertti J. Hakonen – encountered in their study. Regarding their demonstration of the dynamical Casimir effect using a Josephson metamaterial embedded in a microwave cavity at 5.4 GHz, Lähteenmäki tells Phys.org that the main challenge in general is to get high-quality samples. In addition, Lähteenmäki adds, they had to ensure that the origin of the noise is quantum and not some unaccounted source of excess noise, such as thermal imbalance between the environment and the sample, or possibly leakage of external noise.

 

Modulating the effective length of the cavity by flux-biasing the SQUID (superconducting quantum interference device) metamaterial had its challenges as well. "The pump signal needs to be rather strong, yet at the same time one wants to be sure that no excess noise enters the system through the pump line, Lähteenmäki notes, "and good filtering means high attenuation, which is a requirement contradictory to a strong signal. Also," Lähteenmäki continues, "at 10.8 GHz the pump frequency is rather high – and at that frequency range both the sample and the setup is rather prone to electrical resonances which can limit the usable frequencies." In short, the flux profile needs to be such that the pumping doesn't counteract itself. In addition, trapping flux in SQUID loops can also become a problem, limiting the range of optimal operating points and causing excess loss.

 

The researchers also showed that photons at frequencies symmetric with respect to half the modulation frequency of the cavity are generated in pairs. "In general, with frequency locked signal analyzers today the extraction of this correlation is not particularly problematic – especially since the low noise amplifier noise is not correlated at different frequencies," Lähteenmäki explains. That said, issues related to data collection and averaging include amplifier gain drift and phase randomization of the pump signal (relative to the detection phase) if the state of the generator is changed. "The noise temperature of the low noise amplifier sets some limits to the amount of data that needs to be collected, especially in the case where one is operating in the regime of low parametric gain."


Via Dr. Stefan Gruenwald
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A Wet Way to Better Burning? New catalyst uses energy in sunlight to generate hydrogen gas, a carbon-free fuel

A Wet Way to Better Burning? New catalyst uses energy in sunlight to generate hydrogen gas, a carbon-free fuel | Messenger for mother Earth | Scoop.it
Technology is always looking for ways to make it easier to be green. Now, researchers in New York state report creating a new long-lived catalyst that uses the energy in sunlight to generate hydrogen gas, a carbon-free fuel. With further improvements, the advance could lead to systems that use sunlight to split water molecules, generating a fuel that can power cars and trucks without emitting any greenhouse gases.

 

The idea of using sunlight to convert water into a fuel may sound fanciful. But plants do it: They capture photons of sunlight and use that energy to split water molecules into their constituents of hydrogen and oxygen ions. Pairs of hydrogen ions are then knitted together with a pair of electrons (swiped from the oxygen ions) to make hydrogen molecules (H2).

 

Researchers have actually mimicked this same reaction for many years, but the catalysts they use to do so have been either too expensive or too quick to break down. So the search has been on for cheaper, more rugged catalysts.

 

In the current study, reported online today in Science, researchers at the University of Rochester led by chemists Richard Eisenberg and Todd Krauss coated cadmium selenide nanoparticles with short organic chainlike molecules, abbreviated DHLA. This coating of DHLA chains allowed the nanoparticles to dissolve in water. And the individual chains were so short that they allowed the catalyst's nickel ions—also in the solution—to nuzzle close enough to the nanoparticles to grab the electrons and knit H2 molecules together. The Rochester team found that the catalysts were not only fast actors, knitting as many as 7000 H2 molecules every hour, but kept doing so for weeks on end without falling apart—a major advance over other H2-knitting catalysts.

 

Daniel DuBois, a chemist and hydrogen catalyst designer recently retired from the Pacific Northwest National Laboratory in Richland, Washington, calls the new work "a very nice contribution to the area" and says he's particularly impressed with the catalyst's durability. Even so, the new light harvester-catalyst combo isn't quite ready for the real world. For their current experiment, the Rochester researchers didn't actually split water molecules to generate their hydrogen ions. Rather, they added vitamin C, which readily gives up hydrogen, to their solution. So the Rochester group still needs to show that their H2-making compounds will carry out the same reaction using water. If they do, they may give plants a run for their money in green technology.


Via Dr. Stefan Gruenwald
CineversityTV's insight:

The only thing we are worried about is nano particles, bc they can create cancer.

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