Tuesday, 2 December 2014
There was a time when states of matter were simple: Solid, liquid, gas. Then came plasma, Bose -Einstein condensate, supercritical fluid and more. Now the list has grown by one more, with the unexpected discovery of a new state dubbed “dropletons” that bear some resemblance to liquids but occur under very different circumstances.
The discovery occurred when a team at the University of Colorado Joint Institute for Lab Astrophysics were focusing laser light on gallium arsenide (GaAs) to create excitons.
Excitons are formed when a photon strikes a material, particularly a semiconductor. If an electron is knocked loose, or excited, it leaves what is termed an “electron hole” behind. If the forces of other charges nearby keep the electron close enough to the hole to feel an attraction, a bound state forms known as an exciton. Excitons are called quasiparticles because the electrons and holes behave together as if they were a single particle.
If this all sounds a bit hard to relate to, consider that solar cells are semiconductors, and the formation of excitons is one possible step to the production of electricity. A better understanding of how excitons form and behave could produce ways to harvest sunlight more efficiently.
Graduate student Andrew Almand-Hunter was forming biexcitons – two excitons that behave like a molecule, by focusing the laser to a dot 100nm across and leaving it on for shorter and shorter fractions of a second.
“But the experiment didn’t behave at all in the way we expected,” Almand-Hunter said. When the pulses were lasting less than 100 millionths of a second exciton density reached a critical threshold. “We expected to see the energy of the biexcitons increase as the laser generated more electrons and holes. But, what we saw when we did the experiment was that the energy actually decreased!”
The team figured that they had created something other than biexcitons, but were not sure what. They contacted theorists at Philipps-University, Marburg who suggested they had made droplets of 4, 5 or 6 electrons and holes, and constructed a model of these dropletons' behavior.
The dropletons are small enough to behave quantum mechanically, but the electrons and holes are not in pairs, as they would be if the dropleton was just a group of excitons. Instead they form a “quantum fog” of electrons and holes that flow around each other and even ripple like a liquid, rather than existing as discrete pairs. However, unlike liquids we are familiar with, dropletons a finite size, outside which the electron/hole association breaks down.
The discovery has been published in Nature. Perhaps the most remarkable thing is that the dropletons are stable, by the standards of quantum physics. While they can only survive inside solid materials, they last around 25 trillionths of a second, which is actually long enough for scientists to study the way their behavior is shaped by the environment. At 200nm wide the dropletons are as large as very small bacteria – a size that can be seen by conventional microscopes.
"Classical optics can detect only objects that are larger than their wavelengths, and we are approaching that limit," Mackillo Kira of Philipps-University who provided much of the theoretical grounding told Scientific American. "It would be really neat to not only detect spectroscopic information about the dropleton, but to really see the dropleton."
JILA lab leader Professor Steven Cundiff says, “Nobody is going to build a quantum droplet widget." However, the work could help in the understanding of systems where multiple particles interact quantum mechanically.
Friday, 17 January 2014
How it worksDigital cinema has taken place of historical motion picture film projection. Nearly all the multiplex are using digital cinema projection technique now - a - days. Even a single screen theater like Galaxy (Rajkot ,gujrat [INDIA] ) is using the digital cinema projection....
In addition to the equipment already found in a film-based movie theatre a DCI-compliant digital cinema screen requires a digital projector and a computer known as a "server".
Movies are supplied to the theatre as a digital file called a Digital Cinema Package(DCP). For a typical feature film this file will be anywhere between 90 and 300GB of data (roughly two to six times the information of a Blu-ray disc) and may arrive as a physical delivery on a conventional computer hard-drive or via Currently (Dec 2013) physical deliveries are most common and have become the industry standard. Trailers arrive on a separate hard-drive and range between 200 and 400MB in size.
satellite or fibre-optic broadband.
Regardless of how the DCP arrives it first needs to be copied onto the internal hard-drives of the server, usually via a USB port, a process known as "ingesting". DCPs can be, and in the case of feature films almost always are, encrypted. The necessary decryption keys are supplied separately, usually as email attachments and then "ingested" via USB. Keys are time limited and will expire after the end of the period for which the title has been booked. They are also locked to the hardware (server and projector) that is to screen the film, so if the theatre wishes to move the title to another screen or extend the run a new key must be obtained from the distributor.
The playback of the content is controlled by the server using a "playlist". As the name implies this is a list of all the content that is to be played as part of the performance, the playlist will be created by a member of the theatre's staff using proprietary software that runs on the server. In addition to listing the content to be played the playlist also includes automation cues that allow the playlist to control the projector, the sound system, auditorium lighting, tab curtains and screen masking (if present) etc. The playlist can be started manually, by clicking the "play" button on the server's monitor screen, or automatically at pre-set times.
Digital Cinema Initiatives
Briefly, the specification calls for picture encoding using the ISO/IEC 15444-1 "JPEG2000" (.j2c) standard and use of the CIE XYZ color space at 12 bits per component encoded with a 2.6 gamma applied at projection. Two levels of resolution for both content and projectors are supported: 2K (2048×1080) or 2.2 MP at 24 or 48 frames per second, and 4K (4096×2160) or 8.85 MP at 24 frames per second. The specification ensures that 2K content can play on 4K projectors and vica-versa
For the sound component of the content the specification provides for up to 16 channels of uncompressed audio using the "Broadcast Wave" (.wav) format at 24 bits and 48 kHz or 96 kHz sampling.
Playback is controlled by an XML-format Composition Playlist, into an MXF-compliant file at a maximum data rate of 250 Mbit/s. Details about encryption, key management, and logging are all discussed in the specification as are the minimum specifications for the projectors employed including the color gamut, the contrast ratio and the brightness of the image. While much of the specification codifies work that had already been ongoing in the Society of Motion Picture and Television Engineers (SMPTE), the specification is important in establishing a content owner framework for the distribution and security of first-release motion picture content.
In addition to DCI's work, the National Association of Theatre Owners (NATO) released its Digital Cinema System Requirements.
The document addresses the requirements of digital cinema systems from the operational needs of the exhibitor, focusing on areas not addressed by DCI, including access for the visually impaired and hearing impaired, workflow inside the cinema, and equipment interoperability. In particular, NATO's document details requirements for the Theatre Management System (TMS), the governing software for digital cinema systems within a theatre complex, and provides direction for the development of security key management systems. As with DCI's document, NATO's document is also important to the SMPTE standards effort.
The Society of Motion Picture and Television Engineers (SMPTE) began work on standards for digital cinema in 2000. It was clear by that point in time that HDTV did not provide a sufficient technological basis for the foundation of digital cinema playback. (In Europe and Japan however, there is still a significant presence of HDTV for theatrical presentations. Agreements within the ISO standards body have led to these systems being referred to as Electronic Cinema Systems (E-Cinema).)
Digital cinema projectors
For these reasons all projectors intended to be sold to theaters for screening current release movies must be approved by the DCI before being put on sale. Because feature films in digital form are encrypted and the decryption keys are locked to the make, model and serial number of the projector used, an unapproved projector simply will not work if an attempt is made to use it to screen current release feature films from a DCP.
DLP cinema projectors
Initially DCI-compliant DLP projectors were available in 2K only, but from early 2012, when TI's 4K DLP chip went into full production, DLP projectors have been available in both 2K and 4K versions. Manufacturers of DLP-based cinema projectors are now offering 4K upgrades to many of their more recent 2K models.
Early DLP Cinema projectors, which were deployed primarily in the U.S., used limited 1280×1024 resolution or the equivalent of 1.3 MP (megapixels). Digital Projection Incorporated (DPI) designed and sold a few DLP Cinema units when TI's 2K technology first debuted but then abandoned the D-Cinema market while continuing to offer DLP-based projectors for non-cinema purposes. Although based on the same 2K TI "light engine" as those of the major players they are so rare as to be virtually unknown in the industry. They are still widely used for pre-show advertising but not usually for feature presentations.
TI's technology is based on the use of Digital Micromirror Devices (DMDs).These devices are manufactured from silicon using similar technology to that of computer memory chips. The surface of these devices is covered by a very large number of microscopic mirrors, one for each pixel, so a 2K device has about 2.2 million mirrors and a 4K device about 8.8 million. Each mirror vibrates several thousand times a second between two positions, in one light from the projector's lamp is reflected towards the screen, in the other away from it. The proportion of the time the mirror is in each position varies according to the required brightness of each pixel.
Three DMD devices are used, one for each of the primary colors. Light from the lamp, usually a Xenon similar to those used in film projectors with a power between 1 kW and 7 kW, is split by colored filters into red, green and blue beams which are directed at the appropriate DMD. The 'forward' reflected beam from the three DMMDs is then re-combined and focused by the lens onto the cinema screen.
Sony SXRD projectors
Live broadcasting to cinemasDigital cinemas can deliver live broadcasts from performances or events. For example, there are regular live broadcasts to movie theaters of Metropolitan Opera performances. In February 2009, Cinedigm screened the first live multi-region 3D broadcast through a partnership with TNT. Previous attempts have been isolated to a small number of screens. In December 2011, the series finale of the BBC dance competition series Strictly Come Dancing was broadcast live in 3D in selected cinemas.
List of digital cinema companies
- Barco — digital projector manufacturer
- Blackmagic Design — digital cinema camera and distribution equipment manufacturer
- Christie — digital projector manufacturer
- Deluxe Digital Studios — distributor and theater system integrator
- Dolby Laboratories — theater system integrator
- Doremi Labs — Digital server and theater management system manufacturer
- GDC Tech — Digital server and theater management system manufacturer
- IMAX — digital projector manufacturer
- Kinoton — manufacturer of digital projection solutions
- Kodak — theater system integrator
- NEC — digital projector manufacturer
- MasterImage 3D — 3D cinema and mobile display technology
- Panavision 3D — 3D cinema display technology
- Qube Cinema — Digital Cinema mastering, distribution and server products manufacturer
- RealD Cinema — 3D cinema display technology
- RED Digital Cinema Camera Company — digital cinema camera manufacturer
- Silicon Imaging — digital cinema camera manufacturer
- Sony — manufacturer of 4K digital projector, cinema camera manufacturer and digital cinema servers and theater system integrator
- Technicolor — distributor and theater system integrator
- Texas Instruments — developers of DLP Cinema projector technology
- UFO Moviez — world's largest satellite based Digital Cinema
- dcinex — theater system integrator & digital server manufacturer
Thursday, 6 June 2013
You’re looking at is the first direct look of an atom’s electron orbits which can be mathematically described by Atom's Real wave function! To take the photo, Scientists utilized A quantum microscope — an incredibly Innovative device that helps scientists to look into the quantum world.!
An orbital structure is the space in an atom that’s occupied by an electron. But describing these super-microscopic properties of matter, scientists have to depend on wave functions — a mathematical way of describing the quantum states of particles, basically, quantum physicists use formulas like the Schrödinger equation to describe these states, often coming up with complex numbers and Strange graphs!
Up until this point, scientists have never been able to actually observe the electron orbit. Trying to get an atom’s exact position or the momentum of its alone electron direct observations have this obstacle of quantum coherence. So to get a full quantum state We need tool that can statistically average many measurements over time And to magnify this results scientists needs the quantum microscope — a device that uses photoionization microscopy to visualize atomic structures directly.
Aneta Stodolna of the FOM Institute for Atomic and Molecular Physics (AMOLF) in the Netherlands describes how she and her team get a picture of the nodal structure of an electronic orbital of a hydrogen atom placed in a static (dc) electric field in Physical Reviw Letter..
After zapping the atom with laser pulses, ionized electrons escaped and followed a particular trajectory to a 2D detector (dual microchannel plate [MCP] detector placed perpendicular to the field itself). There are many trajectories that can be taken by the electrons to reach the same point on the detector, thus Scientist got the set of interference patterns — patterns that shows the nodal structure of the wave function.
And the they have done this by using an electrostatic lens that magnified the outgoing electron wave more than 20,000 times.
Image: Examples of four atomic hydrogen states. The middle column shows the experimental measurements, while the column at right shows the time-dependent Schrödinger equation calculations.
Physicists have long known that quantum mechanics tells a strange connection between quantum particles "Entanglement" In which measuring one particle can instantly set "state," of another particle—even if it's light years away. Now, experiments have shown that they can entangle two photons that don't even exist at the same time even.....!!!
Entanglement is a kind of order that leis within the uncertainty of quantum theory. Suppose you have a quantum particle of light, or photon. It can be polarized so that it either vertically or horizontally. The quantum realm is also hazed over with unavoidable uncertainty, and thanks to such quantum uncertainty, a photon can also be polarized vertically and horizontally at the same time. If you then measure the photon, however, you will find it either horizontally polarized or vertically polarized,
Entanglement can come in if you have two photons. Each can be put into the uncertain vertical-and-horizontal state. However, the photons can be entangled so that their polarizations are correlated even while they remain undetermined. For example, if you measure the first photon and find it horizontally polarized, you'll know that the other photon has instantaneously collapsed into the vertical state and vice versa—no matter how far away it is. Because the collapse happens instantly, Albert Einstein dubbed the effect "spooky action at a distance." It doesn't violate relativity, though: It's impossible to control the outcome of the measurement of the first photon, so the quantum link can't be used to send a message faster than light.
Now Eli Megidish, Hagai Eisenberg, and colleagues at the Hebrew University of Jerusalem have entangled two photons that don't exist at the same time. They start with a scheme known as entanglement swapping. To begin, researchers zap a special crystal with laser light a couple of times to create two entangled pairs of photons, pair 1 and 2 and pair 3 and 4. At the start, photons 1 and 4 are not tangled. But they can be if physicists play the right trick with 2 and 3.
The key is that a measurement "projects" a particle into a definite state -- just as the measurement of a photon collapses it into either vertical or horizontal polarization. So even though photons 2 and 3 start out unentangled, physicists can set up a "projective measurement" that asks, are the two in one of two distinct entangled states or the other? That measurement entangles the photons, even as it absorbs and destroys them. If the researchers select only the events in which photons 2 and 3 end up in, say, the first entangled state, then the measurement also entangles photons 1 and 4. (See diagram, top.) The effect is a bit like joining two pairs of gears to form a four-gear chain: Enmeshing to inner two gears establishes a link between the outer two.
In recent years, physicists have played with the timing in the scheme. For example, last year a team showed that entanglement swapping still works even if they make the projective measurement after they've already measured the polarizations of photons 1 and 4. Now, Eisenberg and colleagues have shown thatphotons 1 and 4 don't even have to exist at the same time, as they report in a paper in press at Physical Review Letters.
To do that, they first create entangled pair 1 and 2 and measure the polarization of 1 right away. Only after that do they create entangled pair 3 and 4 and perform the key projective measurement. Finally, they measure the polarization of photon 4. And even though photons 1 and 4 never coexist, the measurements show that their polarizations still end up entangled. Eisenberg emphasizes that even though in relativity, time measured differently by observers traveling at different speeds, no observer would ever see the two photons as coexisting.
The experiment shows that it's not strictly logical to think of entanglement as a tangible physical property, Eisenberg says. "There is no moment in time in which the two photons coexist," he says, "so you cannot say that the system is entangled at this or that moment." Yet, the phenomenon definitely exists. Anton Zeilinger, a physicist at the University of Vienna, agrees that the experiment demonstrates just how slippery the concepts of quantum mechanics are. "It's really neat because it shows more or less that quantum events are outside our everyday notions of space and time."
So what's the advance good for? Physicists hope to create quantum networks in which protocols like entanglement swapping are used to create quantum links among distant users and transmit uncrackable (but slower than light) secret communications. The new result suggests that when sharing entangled pairs of photons on such a network, a user wouldn't have to wait to see what happens to the photons sent down the line before manipulating the ones kept behind, Eisenberg says. Zeilinger says the result might have other unexpected uses: "This sort of thing opens up people's minds and suddenly somebody has an idea to use it in quantum computing or something."
- Jenish Kansagra
- New Delhi, New Delhi, India
- is a Cisco Certified Internetworking Expert. He is working in the domain of Routing & switching also working with Next Generation Networks implementation. Apart from that he is actively involved in String Theory Development and Quantum Physics research.