Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: quantum physics – Page 892

Uncertain Propulsion Breakthroughs?

Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.

By marc millis, george hathaway, martin tajmar, eric davis, & jordan maclay

It’s time to weigh in about the controversial EmDrive. I say, controversial, because of its profound implications if genuine, plus the lack of enough information with which to determine if it is genuine. A peer-reviewed article about experimental tests of an EmDrive was just published in the AIAA Journal of Propulsion and Power by Harold (Sonny) White and colleagues: White, H., March, P., Lawrence, J., Vera, J., Sylvester, A., Brady, D., & Bailey, P. (2016), “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum,” Journal of Propulsion and Power, (print version pending, online version here.

Testing Predictions of the Quantum Landscape Multiverse 2: The Exponential Inflationary Potential [CEA]

The 2015 Planck data release tightened the region of the allowed inflationary models. Inflationary models with convex potentials have now been ruled out since they produce a large tensor to scalar ratio. Meanwhile the same data offers interesting hints on possible deviations from the standard picture of CMB perturbations. Here we revisit the predictions of the theory of the origin of the universe from the landscape multiverse for the case of exponential inflation, for two reasons: firstly to check the status of the anomalies associated with this theory, in the light of the recent Planck data; secondly, to search for a counterexample whereby new physics modifications may bring convex inflationary potentials, thought to have been ruled out, back into the region of potentials allowed by data. Using the exponential inflation as an example of convex potentials, we find that the answer to both tests is positive: modifications to the perturbation spectrum and to the Newtonian potential of the universe originating from the quantum entanglement, bring the exponential potential, back within the allowed region of current data; and, the series of anomalies previously predicted in this theory, is still in good agreement with current data. Hence our finding for this convex potential comes at the price of allowing for additional thermal relic particles, equivalently dark radiation, in the early universe.

Read this paper on arXiv…

E. Valentino and L. Mersini-Houghton Wed, 28 Dec 16 26/46.

Generating tunable terahertz radiation with a novel quantum dot photoconductive antenna

Creating tunable terahertz radiation.

Indium arsenide quantum dots in gallium arsenide wafers offer wider pump-wavelength range, significantly higher thermal tolerance, and higher conversion efficiency than typical terahertz radiation sources.

The terahertz (THz) range of electromagnetic waves (0.1–10THz)—which lies between the microwave and optical regions—is of great interest. This is mainly because this band of the electromagnetic spectrum includes the frequencies of rotational and vibrational spectra of complex (e.g., biological) molecules. Most dielectric materials are transparent in the THz region, and THz waves are already used in many biomedical applications (e.g., for the detection of dangerous and illicit substances, as well as for the diagnosis and treatment of diseases). Photoconductive antennas are the most-developed room-temperature sources of THz radiation. However, ultrafast low-temperature-grown gallium arsenide (GaAs)—which is typically used as a substrate for such antennas—suffers (because of its large band gap) from low thermal efficiency, low carrier mobility, and a pump limit at a wavelength of about 850nm.

The Science and Engineering of Quantum Dot Lasers

Since their development in 1960, lasers have become an indispensable tool supporting our modern society, finding use in fields such as medicine, information, and industry. Thanks to their compact size and energy efficiency, semiconductor lasers are now one of the most important classes of laser, making possible a diverse range of applications. However, the threshold current of a typical semiconductor laser—the minimum electrical current required to induce lasing—increases with temperature. This is one of a number of disadvantages that can be overcome by using quantum dot lasers. Professor Yasuhiko Arakawa of the Institute of Industrial Science at the University of Tokyo has been researching quantum dot lasers for about 35 years, from their conception to commercialization.

An electron trapped in a microscopic box

Sunlight is composed of light of various colors. The property that determines the color of light is its wavelength, or in other words, the distance between two successive wave peaks or troughs. The location of the peaks and troughs in the waveform is known as its phase. As a laser emits light waves in a uniform phase at the same wavelength, the light can be transmitted as a beam over long distances at high intensity.

Ultra-Small Nanocavity Advances Technology for Quantum-Based Data Encryption

What’s next? Nanocavities in a diamond for small devices.

Researchers have developed a new type of light-enhancing optical cavity that is only 200 nanometers tall and 100 nanometers across. Their new nanoscale system represents a step toward brighter single-photon sources, which could help propel quantum-based encryption techniques under development.

Quantum encryption techniques, which are seen as likely to be central to future data encryption methods, use individual photons as an extremely secure way to encode data. A limitation of these techniques has been the ability to emit photons at high rates. “One of the most important figures of merit for single-photon sources is brightness — or collected photons per second — because the brighter it is, the more data you can transmit securely with quantum encryption,” said Yousif Kelaita of Stanford University.

In the journal Optical Materials Express, from The Optical Society (OSA), Kelaita and his colleagues show that their new nanocavity significantly increased the emission brightness of quantum dots — nanometer-scale semiconductor particles that can emit single photons.

Physicists Achieve Quantum Teleportation of Photon Over 25 Kilometers

For the first time, a team of physicists have successfully teleported a quantum state of a photon to a crystal over 25 kilometers away through a fiber optic cable. This effectively showed that the photon’s quantum state, not its composition, is important to the teleportation process. The team was led by Nicolas Gisin of the University of Geneva and the results were published in the journal Nature Photonics. With this new paper, Gisin’s team has successfully squashed the previous record they set a decade ago by teleporting a quantum state of a proton 6 kilometers.

The quantum state of the photon is able to preserve information under extreme conditions, including the difference between traveling as light or becoming stored in the crystal like matter. The photon’s state acts as information that can be teleported along great distances using the optical fiber, and can be stored within the crystal. This was achieved due to a phenomenon in quantum mechanics known as entanglement, where two particles have a correlation, despite the fact that they aren’t touching and transmitting information to one another.

To test this and ensure what they were observing was actually happening, one photon was stored in a crystal while the other was sent along optical fiber, over a distance of 25 kilometers. The photon that was sent along the optical fiber collides with a third photon, which was assumed to destroy them both. However, the information from the first photon was transferred to the third photon in the collision, like the transfer of energy when one billiard ball hits another. The information from the third photon came back to the crystal where it could be measured to ensure the information was preserved between the first and the second.

Russia offers technology to keep hackers at bay

Russian Quantum Center (RQC) said that it is ready to collaborate with India and offer its quantum technology that will prevent hackers from breaking into bank accounts. RQC plans to offer ‘quantum cryptography’ that could propel India to the forefront of hack proof communication in sectors such as banking and national and homeland security.

“We are ready to work with Indian colleagues. It (the technology) can’t be bought from the United States as it deals with the government and security,” said Ruslan Yunusov, chief executive at RQC, in an interview.

Established by Russia’s largest global technology hub, Skolkovo in 2010, RQC conducts scientific research that could lead to a new class of technologies. These include developing ‘unbreakable cryptography’ for the banks and the government organisations. It also involves research in areas such as materials with superior properties and new systems for ultrasensitive imaging of the brain. The research is mostly funded by the government money.