Snobbish photons forced to pair up and get heavy. Ordinarily, photons—particles of light—don't interact with each other. They interfere, but that's a characteristic that doesn't alter their wavelength or cause them to attract or repel. However, if photons can be induced to interact, it could open up a wide number of applications in quantum computing and optical materials. This sort of radical change can't happen under ordinary circumstances but is possible in special environments. Researchers fabricated just such a medium and produced photons that simultaneously act as though they are massive and mutually attractive.
The key to this weird behavior involved passing light through a cold diffuse gas with strong inter-atomic interactions, properties that are usually exclusive but which can be induced in some circumstances. The atoms in the gas acted as an intermediary, causing photons to form bound pairs. The interactions between the Rydberg atoms produce a bizarre environment. Hot water freezes faster than cold - and now we know why. Hot water seems to freeze faster than cold water, known as the Mpemba effect. The effect was named after the Tanzanian student who in 1963 noticed that hot ice cream mix freezes faster than a cold one. The effect was first observed by Aristotle in the 4th century BC, then later Francis Bacon and René Descartes. Mpemba published a paper on his findings in 1969. Theories for the Mpemba effect have included: faster evaporation of hot water, therefore reducing the volume left to freeze; formation of a frost layer on cold water, insulating it; and different concentrations of solutes such as carbon dioxide, which is driven off when the water is heated.
Unfortunately the effect doesn’t always appear - cold water often does actually freeze faster than hot, as you would expect. Now a team of physicists from the Nanyang Technological University in Singapore, led by Xi Zhang, have found evidence that it is the chemical bonds that hold water together that provide the effect. Tying Light in Knots [Slide Show] Knots can help unravel some knotty (sorry!) Situations. The mathematical study of knotted shapes has proved constructive for many branches of physics, from understanding how fluids flow to developing quantum computers. Now physicists have found that light itself can be knotted by discovering a new set of solutions to the famous Maxwell equations of electromagnetism. In the 1860s Scottish physicist James Clerk Maxwell wrote down a series of equations describing how electric and magnetic fields form and change.
These foundational formulas, still printed in almost every physics textbook, led to the crucial realization that light is an electromagnetic phenomenon. >> View slide show here The researchers worked out a family of solutions to Maxwell’s equations that represent beams of light whose structure is knotted. Knots are not (get it?) Knotted light isn’t merely a theoretical possibility. David Bohm on perception. OVERVIEW. Finding the Universe's cosmological constant using something we can create in the lab. Those of you who know my writing will know that I don't use many analogies. Analogies have a very useful place in helping people understand difficult concepts, but they also have a tendency to be a end up strained beyond their limits.
Now, imagine how I would react to a whole new field of physics that might be best described as "physics by analogy. " The whole field is based on the premise that, when two physically very different situations can be described using the same mathematical model, the conclusions drawn from one situation can be applied to the other. Unfortunately, this is usually applied in situations where the physics in one situation—black holes, for instance—are so extreme that it is difficult, if not impossible, to test any of the conclusions.
It appears I must adjust my attitude and admit that the field as a whole is not useless. You are out by how much? Can we learn anything from physics by analogy? They actually found that the energy and the expansion simply cannot match. Mysterious electron acceleration explained: Computer simulation identifies source of aurora-causing high-speed electrons in space. A mysterious phenomenon detected by space probes has finally been explained, thanks to a massive computer simulation that was able to precisely align with details of spacecraft observations. The finding could not only solve an astrophysical puzzle, but might also lead to a better ability to predict high-energy electron streams in space that could damage satellites. Jan Egedal, an associate professor of physics at MIT and a researcher at the Plasma Science and Fusion Center, working with MIT graduate student Ari Le and with William Daughton of the Los Alamos National Laboratory (LANL), report on this solution to the space conundrum in a paper published Feb. 26 in the journal Nature Physics.
The simulation shows that an active region in Earth's magnetotail, where "reconnection" events take place in the magnetic field, is roughly 1,000 times larger than had been thought. What had puzzled physicists is the number of energetic electrons generated in such events. Two-photon excitation microscopy. Concept[edit] Two-photon excitation employs two-photon absorption, a concept first described by Maria Goeppert-Mayer (1906–1972) in her doctoral dissertation in 1931,[2] and first observed in 1961 in a CaF2:Eu2+ crystal using laser excitation by Wolfgang Kaiser.[3] Isaac Abella showed in 1962 in cesium vapor that two-photon excitation of single atoms is possible.[4] The concept of two-photon excitation is based on the idea that two photons of comparably lower energy than needed for one photon excitation can also excite a fluorophore in one quantum event.
Each photon carries approximately half the energy necessary to excite the molecule. An excitation results in the subsequent emission of a fluorescence photon, typically at a higher energy than either of the two excitatory photons. The probability of the near-simultaneous absorption of two photons is extremely low. Development[edit] A diagram of a two-photon microscope Higher-order excitation[edit] See also[edit] References[edit] Quantum zeno effect explains bird navigation « the physics arXiv blog. Just how birds use the earth’s magnetic field to navigate has puzzled researchers for decades. But in recent years, a growing body of evidence points to the possibility that a weak magnetic field can influence the outcome of a certain type of chemical reaction in bird retinas involving radical ion pairs.
The idea is that the chemical outcome of the recombination of the ion pairs depends on whether the radical electrons are in a singlet or triplet state. A magnetic field creates a bias towards the triplet state which in turn leads to a one chemical output being preferred over another. To test the idea, various experimenters have successfully confused the navigational abilities of birds such as robins by zapping them with magnetic fields specifically designed to disrupt this reaction. Case closed. Not quite. The claim made today by Iannis Kominis at the University of Crete is that the quantum zeno effect explains all. Interesting idea. World's smallest radio stations: Two molecules communicate via single photons. ScienceDaily (Feb. 28, 2012) — We know since the dawn of modern physics that although events in our everyday life can be described by classical physics, the interaction of light and matter is down deep governed by the laws of quantum mechanics.
Despite this century-old wisdom, accessing truly quantum mechanical situations remains nontrivial, fascinating and noteworthy even in the laboratory. Recently, interest in this area has been boosted beyond academic curiosity because of the potential for more efficient and novel forms of information processing. In one of the most basic proposals, a single atom or molecule acts as a quantum bit that processes signals that have been delivered via single photons. In the past twenty years scientists have shown that single molecules can be detected and single photons can be generated. So a team of scientists led by Professor Vahid Sandoghdar made its own.
To generate single photons, a single molecule was excited in the “source” sample. UC San Diego physicists find patterns in new state of matter. Public release date: 29-Mar-2012 [ Print | E-mail Share ] [ Close Window ] Contact: Kim McDonaldkmcdonald@ucsd.edu 858-534-7572University of California - San Diego Physicists at the University of California, San Diego have discovered patterns which underlie the properties of a new state of matter.
In a paper published in the March 29 issue of the journal Nature, the scientists describe the emergence of "spontaneous coherence," "spin textures" and "phase singularities" when excitons—the bound pairs of electrons and holes that determine the optical properties of semiconductors and enable them to function as novel optoelectronic devices—are cooled to near absolute zero. This cooling leads to the spontaneous production of a new coherent state of matter which the physicists were finally able to measure in great detail in their basement laboratory at UC San Diego at a temperature of only one-tenth of a degree above absolute zero. "This is a very interesting discovery," he added.
. [ Print | E-mail. Squeezing what hasn't been squeezed before: Another victory over uncertainty in quantum physics measurements. Most people attempt to reduce the little uncertainties of life by carrying umbrellas on cloudy days, purchasing automobile insurance or hiring inspectors to evaluate homes they might consider purchasing. For scientists, reducing uncertainty is a no less important goal, though in the weird realm of quantum physics, the term has a more specific meaning. For scientists working in quantum physics, the Heisenberg Uncertainty Principle says that measurements of properties such as the momentum of an object and its exact position cannot be simultaneously specified with arbitrary accuracy. As a result, there must be some uncertainty in either the exact position of the object, or its exact momentum. The amount of uncertainty can be determined, and is often represented graphically by a circle showing the area within which the measurement actually lies.
Now physicists at the Georgia Institute of Technology have added another measurement to the list of those that can be squeezed. Replacing electricity with light: First physical 'metatronic' circuit created. The technological world of the 21st century owes a tremendous amount to advances in electrical engineering, specifically, the ability to finely control the flow of electrical charges using increasingly small and complicated circuits. And while those electrical advances continue to race ahead, researchers at the University of Pennsylvania are pushing circuitry forward in a different way, by replacing electricity with light. "Looking at the success of electronics over the last century, I have always wondered why we should be limited to electric current in making circuits," said Nader Engheta, professor in the electrical and systems engineering department of Penn's School of Engineering and Applied Science. "If we moved to shorter wavelengths in the electromagnetic spectrum -- like light -- we could make things smaller, faster and more efficient.
" Now, he and his group at Penn have made this dream a reality, creating the first physical demonstration of "lumped" optical circuit elements. Why quantum computers will be inaccurate: There is more an one kind of nothingness. February 20, 2012, 7:28 PM — If you took enough philosophy in college it's extremely likely you came to despise Jean-Paul Sartre, or at least felt some annoyance at the damage his writing did to both Being and Nothingness. (Briefly – and as accurately as I can bear to relate it – Sartre ruined the reputation of existentialism, of Being and of Nothingness by arguing the only things that can Be are those we perceive and that Nothingness has only itself to blame for our not noticing it, which is the reason it doesn't exist.*) Nothingness, it turns out, is a lot more complicated than that. Worse, it's more complicated even than Sartre made it (though he did stick to the guideline that requires great philosophers to present ideas at least 15 percent more complicated than they are able to write clearly enough for anyone else to understand).
Blasting the photoelectric effect out of the quantum realm with a very intense light source. In 1905, Albert Einstein showed that the photoelectric effect—the ability of metals to produce an electric current when exposed to light—could be explained if light is quantum, traveling in discrete bundles of energy. His model, the photon theory, won him the Nobel Prize in 1921, but it left us with an enigma: why does the classical model of electric fields yield correct experimental results for some systems, but fail so dramatically for the photoelectric effect?
In other words, at what point does the quantum world begin and the classical world end? By directing very intense light to a nanoscale needle-like tip, G. Herink, D. R. Solli, M. Einstein managed to explain the photoelectric effect by suggesting that light's energy is carried in discrete bundles—photons. This is at odds with the pre-quantum view of electromagnetism, where it's the electric field of the light that accelerates electrons. Watching a wavefunction as hydrogen explodes. The wavefunction is a fundamental concept in quantum mechanics, telling us where we're likely to find a particle—the position or momentum of an electron, for example—even though its physical meaning is rather unclear. This concept has turned out to be extremely useful. Where the wavefunction really counts is in things like molecules, where it determines properties like structure and behavior.
Yet determining the spatial properties of the wavefunction inside something like a molecule is not something that is easily done. That is what makes a paper on imaging the wavefunction of an ionized, vibrating hydrogen molecule so interesting. The challenge with measuring the wavefunction of a molecule when it is vibrating is that it is not enough to figure out where the electrons are; you also need to make a precise measurement of where the atomic nuclei are spending their time as well. Blowing up molecular hydrogen So that's the challenge. These sorts of measurements have been around for a while. Quantum optics may remove the uncertainty about quantum gravity. While both quantum physics—in the form of the Standard Model of particles and interactions—and gravitation—formulated in general relativity—are hugely successful theories, making them work together hasn't, well, worked out.
Currently, there's no complete, reliable quantum theory of gravity, though there are many candidates, including superstring theory. In most of these schemes, quantum behavior extends to spacetime itself, setting a fundamental length at which gravitation modifies quantum theory. This fundamental scale, known as the Planck length, is beyond the reach of foreseeable experiments. However, a related quantity known as the Planck mass may provide another way to check for quantum gravity in the laboratory. As proposed by Igor Pikovski, Michael R. The Standard Model of particles and interactions stands as a powerful and successful quantum theory that describes the fundamental building blocks of nature. In ordinary quantum theory, there isn't any fundamental length scale. Particle-wave duality demonstrated with largest molecules yet. Quantum teleportation: Transfer of flying quantum bits at the touch of a button. Leonard Susskind on The World As Hologram.
Science is not the Enemy of the Humanities. 'Time Crystals' Could Upend Physicists' Theory of Time | Wired Science. Quantum computer gets an undo button. Spinning Magnet - Sixty Symbols. Double time-reversal asymmetry could explain weird material behavior. Symphony of Spheres in Microgravity. A simple magnet can control the color of a liquid. A new way to trap light. Club Science. Lecture Notes. Does antimatter fall up? Experiment could provide the answer. Cloud of atoms goes beyond absolute zero - physics-math - 03 January 2013. Super-fine sound beam could one day be an invisible scalpel. The 500 phases of matter: New system successfully classifies symmetry-protected phases. Engineers weld nanowires with light | Engineering. Quantum networks may be more realistic than we thought.
Funneling the sun's energy: New way of harnessing photons for electricity proposed. Invisibility cloaking to shield floating objects from waves. Human brain, Internet, and cosmology: Similar laws at work? Molecules given the big chill. New Physics Discovered by MiniBooNE? Quantum 'kisses 'change the color of space. Model describes universe with no big bang, no beginning, and no end. Quantum entanglement shows that reality can’t be local. Physicists may prove we exist in a computer simulation. Physicists Prove Einstein Wrong with Observation of Instantaneous Velocity in Brownian Particles. Understanding tiny reactions. Richard Feynman videos. Spacetime: A smoother brew than we knew. The dark side of light: negative frequency photons. Dramatic miniaturization of metamaterials? Reluctant electrons enable 'extraordinarily strong' negative refraction.
CSI image enhancement: using evanescent waves to see the invisible. Quantum computing, no cooling required: Room-temperature quantum bits store data for nearly two seconds. Splitting the unsplittable: Physicists split an atom using quantum mechanics precision. Disentangling the wave-particle duality in the double-slit experiment. New Scientist Features - Entropy: The new order. Quantum physicists show a small amount of randomness can be amplified without limit. Earth's Inconstant Magnetic Field. Timing quantum tunneling to attosecond precision. THIS is why we invest in science. This. Physicists Store Short Movie In A Cloud of Gas. Expanding an optical lattice to accelerate particles. Optical trap catches atoms swinging in time to theory. Meet the mother theory.
Startram. New kind of quantum junction. Making a material transparent in order to visualize its internal energy states. Splitting up the indivisible: quasiparticles separate an electron's spin, charge, and orbit. Not-quite-so elementary, my dear electron. Particle accelerators' search for nature's hidden dimensions comes up empty. IBM shows off quantum computing advances, says practical qubit computers are close. Single molecule circuit controlled through quantum interference. Floppy Bose Einstein condensates oscillate free of theory. Crystals May Be Possible In Time As Well As Space. Electron Perfectly Round to One Part in a Million Billion, Experiment Finds.
Electron Holography Produces First Image of a Single Protein Lab mimics Jupiter's Trojan asteroids inside a single atom. What’s in a Femtosecond of Laser Light? A Map of Electron Energy. Collaborative physics: String theory finds a bench mate. Giant Casimir Effect Predicted Inside Metamaterials Tecnología. La NASA estudia formas para hacer realidad el teletransporte. Neutron stars and string theory in a lab: Chilled atoms give clues to deep space and particle physics. According to the Many Worlds Interpretation, every event creates new universes. Where does the energy and matter for the new universes come from.
ISS alerts through Twitter | Twisst. GRIN plasmonics: A practical path to superfast computing, invisibility carpet-cloaking devices. Image Stored on One Photon (photonics.com | Jan 2007 | News & Features) Researchers now able to stop, restart light. Imagining the Tenth Dimension - A Book by Rob Bryanton. Quantum simulator accessible to the world - iPoint. Relativistic Optics at the ANU. Delayed Choice Quantum Eraser. Wheeler's Delayed Choice Experiment" Scientists design an 'antimagnet' stories - io9. Laser light used to cool object to quantum ground state. Gravitational Waves Can Explain Dark Energy And Axis of Evil, Says Cosmologist. Squeezed light a small step forward toward detecting gravitational waves.
Ask a Mathematician / Ask a Physicist | Your Math and Physics Questions Answered. Astronomy Magazine - Interactive Star Charts, Planets, Meteors, Comets, Telescopes.