Lifeboat Foundation

The observation of the onset of turbulence in a gas of bosons allows researchers to explore how turbulence comes to life.

Despite over a century of trying, physicists have yet to develop a complete theory of turbulence—the complex, chaotic motion of a fluid. Now Maciej Gałka of the University of Cambridge and colleagues have taken a step in that direction by witnessing the onset of turbulence in a quantum gas and observing its evolution over roughly 100 ms [1]. The finding could help scientists answer open questions in turbulence, which is observed in systems ranging from ocean waves to star interiors.

An analogue of a tiny, expanding universe has been created out of extremely cold potassium atoms. It could be used to help us understand cosmic phenomena that are exceedingly difficult to directly detect, such as pairs of particles that may be created out of empty space as the universe expands.

Markus Oberthaler at Heidelberg University in Germany and his colleagues cooled more than 20,000 potassium atoms in a vacuum, using lasers to slow them down and lower their temperature to about 60 nanokelvin, or 60 billionths of a degree kelvin above absolute zero.

At this temperature, the atoms formed a cloud about the width of a human hair and, instead of freezing, they became a quantum, fluid-like phase of matter called a Bose-Einstein condensate. Atoms in this phase can be controlled by shining light on them – using a tiny projector, the researchers precisely set the atoms’ density, arrangement in space and the forces they exert on each other.

Quantum chromodynamics (QCD) is one of the pillars of the Standard Model of particle physics. It describes the strong interaction – one of the four fundamental forces of nature. This force holds quarks and gluons – collectively known as partons – together in hadrons such as the proton, and protons and neutrons together in atomic nuclei. Two hallmarks of QCD are chiral symmetry breaking and asymptotic freedom. Chiral symmetry breaking explains how quarks generate the masses of hadrons and therefore the vast majority of visible mass in the universe. Asymptotic freedom states that the strong force between quarks and gluons decreases with increasing energy. The discovery of these two QCD effects garnered two Nobel prizes in physics, in 2008 and 2004, respectively.

High-energy collisions of lead nuclei at the Large Hadron Collider (LHC) explore QCD under the most extreme conditions on Earth. These heavy-ion collisions recreate the quark–gluon plasma (QGP): the hottest and densest fluid ever studied in the laboratory. In contrast to normal nuclear matter, the QGP is a state where quarks and gluons are not confined inside hadrons. It is speculated that the universe was in a QGP state around one millionth of a second after the Big Bang.

The ALICE experiment was designed to study the QGP at LHC energies. It was operated during LHC Runs 1 and 2, and has carried out a broad range of measurements to characterise the QGP and to study several other aspects of the strong interaction. In a recent review, highlights of which are described below, the ALICE collaboration takes stock of its first decade of QCD studies at the LHC. The results from these studies include a suite of observables that reveal a complex evolution of the near-perfect QGP liquid that emerges in high-temperature QCD. ALICE measurements also demonstrate that charm quarks equilibrate extremely quickly within this liquid, and are able to regenerate QGP-melted “charmonium” particle states. ALICE has extensively mapped the QGP opaqueness with high-energy probes, and has directly observed the QCD dead-cone effect in proton–proton collisions. Surprising QGP-like signatures have also been observed in rare proton–proton and proton–lead collisions.

An in-depth survey of the various technologies for spaceship propulsion, both from those we can expect to see in a few years and those at the edge of theoretical science. We’ll break them down to basics and familiarize ourselves with the concepts.
Note: I made a rather large math error about the Force per Power the EmDrive exerts at 32:10, initial tentative results for thrust are a good deal higher than I calculated compared to a flashlight.

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Continue reading “The Spaceship Propulsion Compendium” »

On these timescales, a blink of an eye — one-tenth of a second — seems like eternity.

Researchers from the University of New South Wales have now broken new ground in demonstrating that ‘spin qubits,’ which are the fundamental informational units of quantum computers, can store data for up to two milliseconds. The accomplishment is 100 times longer than prior benchmarks in the same quantum processor for what is known as “coherence time,” the amount of time qubits can be manipulated in increasingly complicated calculations.

Terahertz light, radiation in the far-infrared part of the emission spectrum, is currently not fully exploited in technology, although it shows great potential for many applications in sensing, homeland security screening, and future (sixth generation) mobile networks.

Indeed, this radiation is harmless due to its small photon energy, but it can penetrate many materials (such as skin, packaging, etc.). In the last decade, a number of research groups have focused their attention on identifying techniques and materials to efficiently generate THz electromagnetic waves: among them is the wonder material graphene, which, however, does not provide the desired results. In particular, the generated terahertz output power is limited.

Better performance has now been achieved by topological insulators (TIs)—quantum materials that behave as insulators in the bulk while exhibiting conductive properties on the surface—according to a paper recently published in Light: Science & Applications.

A terahertz camera based on an upconversion mechanism to the visible range can image both THz polarization state and field strength.

A team of scientists from the University of Sciences and Technology of China has proposed a bold solution for the “measurement problem” in quantum mechanics, suggesting the eventual outcome for states of existence is determined by a “game” between the observer and nature.

For over a century, the quantum realm has imposed an abundance of bizarre obstacles along the road to understanding universal existence.

In the microscopic world of atoms and subatomic particles, nature demonstrates unparalleled strangeness, becoming unpredictable and operating in contrast to how it behaves at the macroscopic scale defined by classical physics.

face_with_colon_three circa 2016.

Two basic types of encryption schemes are used on the internet today. One, known as symmetric-key cryptography, follows the same pattern that people have been using to send secret messages for thousands of years. If Alice wants to send Bob a secret message, they start by getting together somewhere they can’t be overheard and agree on a secret key; later, when they are separated, they can use this key to send messages that Eve the eavesdropper can’t understand even if she overhears them. This is the sort of encryption used when you set up an online account with your neighborhood bank; you and your bank already know private information about each other, and use that information to set up a secret password to protect your messages.

The second scheme is called public-key cryptography, and it was invented only in the 1970s. As the name suggests, these are systems where Alice and Bob agree on their key, or part of it, by exchanging only public information. This is incredibly useful in modern electronic commerce: if you want to send your credit card number safely over the internet to Amazon, for instance, you don’t want to have to drive to their headquarters to have a secret meeting first. Public-key systems rely on the fact that some mathematical processes seem to be easy to do, but difficult to undo. For example, for Alice to take two large whole numbers and multiply them is relatively easy; for Eve to take the result and recover the original numbers seems much harder.

Continue reading “Quantum Cryptography Is Unbreakable. So Is Human Ingenuity” »