Universal Error Correction in Quantum Computation

Physicists have succeeded in entangling five photons for the first time. Although four photons have been entangled before, five is the minimum number needed for universal error correction in quantum computation. Moreover, the same team has demonstrated a process called "open-destination teleportation" for the first time (Z Zhao et al. 2004 Nature 430 54). The results represent a major breakthrough in efforts to exploit the laws of quantum mechanics in quantum information processing.

By taking advantage of quantum phenomena such as entanglement, teleportation and superposition, a quantum computer could, in principle, outperform a classical computer in certain computational tasks. Entanglement allows particles to have a much closer relationship than is possible in classical physics. For example, two photons can be entangled such that if one is horizontally polarized, the other is always vertically polarized, and vice versa, no matter how far apart they are. In quantum teleportation, complete information about the quantum state of a particle is instantaneously transferred by the sender, who is usually called Alice, to a receiver called Bob. Quantum superposition, meanwhile, allows a particle to be in two or more quantum states at the same time

Do We Need a Radically New Spacetime/Quantum Worldview

Whether such a "quantum computer" can realistically be built with a value of L that is large enough to be of practical use is a topic of much debate. However, the mere possibility has led to an explosive renaissance of interest in the host of curious and classically counterintuitive properties associated with entangled states. Other phenomena that rely on nonlocal entanglement, such as quantum teleportation and various forms of quantum cryptography, have also been demonstrated in the laboratory

2004 Promises to be an Exceptionally Exciting Year in General Relativity and Gravitation

But you shouldn't imagine the mood as one of breathless anticipation. At least for the physicists present, a better description would be something like "skeptical curiosity". None of them seemed to believe that Hawking could suddenly shed new light on a problem that has been attacked from many angles for several decades. One reason is that Hawking's best work was done almost 30 years ago. A string theorist I know said that thanks to work relating anti-deSitter space and conformal field theory - the so-called "AdS-CFT" hypothesis - string theorists had become convinced that no information is lost by black holes. Thus, Hawking had been feeling strong pressure to fall in line and renounce his previous position, namely that information is lost. A talk announcing this would come as no big surprise.

I couldn't help but look through previous discussion on the subject here to try and get caught up on who thinks what, and what has been accomplished.




2004 promises to be an exceptionally exciting year in General Relativity and Gravitation: the LIGO/VIRGO/GEO/TAMA network of detectors has begun generating scientific results, ushering in the era of gravitational wave astronomy. These detectors will search for gravitational wave signals of the collision of black holes, neutron star mergers and other astronomical events previously undetectable. The fundamentally new science of gravitational wave astronomy opens up a new window on the universe. Up until now, astronomy has relied on observations of electromagnetic wave signals (e.g. visible light, radio waves). The detection of gravitational waves offers a completely new perspective on the universe: they will enable us to "hear" the cosmic orchestra as well as to see it! GR17 will provide the scientific community with one of the earliest opportunities to discuss the first scientific results of this era.

Mass Transfer to Blackhole

This image is very strong in mind as I read Smolins discriptions of the thing?:)

Consider any physical system, made of anything at all- let us call it, The Thing. We require only that The Thing can be enclosed within a finite boundary, which we shall call the Screen(Figure39). We would like to know as much as possible about The Thing. But we cannot touch it directly-we are restrictied to making measurements of it on The Screen. We may send any kind of radiation we like through The Screen, and record what ever changes result The Screen. The Bekenstein bound says that there is a general limit to how many yes/no questions we can answer about The Thing by making observations through The Screen that surrounds it. The number must be less then one quarter the area of The Screen, in Planck units. What if we ask more questions? The principle tells us that either of two things must happen. Either the area of the screen will increase, as a result of doing an experiment that ask questions beyond the limit; or the experiments we do that go beyond the limit will erase or invalidate, the answers to some of the previous questions. At no time can we know more about The thing than the limit, imposed by the area of the Screen.

Page 171 and 172 0f, Three Roads to Quantum Gravity by Lee Smolin

How shall Gerard Hooft deal with this means of gathering information?


Perhaps Quantum Gravity can be Handled by thoroughly reconsidering Quantum Mechanics itself?

Quickly my mind wanders, to the experiments of Glast, and the gamma ray detection system. How will this informtaion allow such information, to align itself with quantum computer modelling and understand, what is hoped in gathering information from the screen?

No 'Quantum Computer' will ever be able to out perform a 'scaled up classical computer.'

Fundamentals of Quantum Mechanics

To me, Nature is a big jig-saw puzzle, and I see it as my task to try to fit pieces of it together. Click and cut the pieces you see here from the screen and see how they fit, or: read more about it in my book: `Bouwstenen van de Schepping' (Prometheus/Bert Bakker, ISBN 90 351 1327 6) or its English version: `In Search of the Ultimate Building Blocks', Cambridge Univ. Press, Paperback 9.95 pounds, 14.95 US dollars, ISBN 0 521 578833; hardback 27.95 pounds, 39.95 US dollars, ISBN 0 521 550831)

Sound Waves in the CMB

With the discovery of sound waves in the CMB, we have entered a new era of precision cosmology in which we can begin to talk with certainty about the origin of structure and the content of matter and energy in the universe.
Wayne Hu

The Sound Of Gravitational Waves, is located in the archive section of this forum for further considerations.



http://lisa.jpl.nasa.gov/SCIENCE/p5_e0.2_i25_a0.95_hp.wav

Lisa is opening a New Window on the universe too.

The Holographical Principle

I must add a very important note. It is still hard for me to believe that Lee Smolin wrote something that could imply that *he* was the author of the conjecture. Lee Smolin has nothing to do with the discovery of the holographic principle and I hope that he always refers to the real authors properly-and it was just you who did not read carefully enough. The holographic conjecture, based on the Bekenstein's bounds and the Bekenstein-Hawking entropy of the black hole,has been first proposed by Gerard 't Hooft and discussed in more detail by Lenny Susskind:

Information in the Holographic Universe: A Holographic Spacetime

by Jacob D. Bekenstein

TWO UNIVERSES of different dimension and obeying disparate physical laws are rendered completely equivalent by the holographic principle. Theorists have demonstrated this principle mathematically for a specific type of five-dimensional spacetime ("anti–de Sitter") and its four-dimensional boundary. In effect, the 5-D universe is recorded like a hologram on the 4-D surface at its periphery. Superstring theory rules in the 5-D spacetime, but a so-called conformal field theory of point particles operates on the 4-D hologram. A black hole in the 5-D spacetime is equivalent to hot radiation on the hologram--for example, the hole and the radiation have the same entropy even though the physical origin of the entropy is completely different for each case. Although these two descriptions of the universe seem utterly unalike, no experiment could distinguish between them, even in principle.

The Holographic Principle and M-Theory

To them, I said,
the truth would be literally nothing
but the shadows of the images.
-Plato, The Republic (Book VII)

Of course, to Plato this story was just meant to symbolize mankind's struggle to reach enlightenment and understanding through reasoning and open-mindedness. We are all initially prisoners and the tangible world is our cave. Just as some prisoners may escape out into the sun, so may some people amass knowledge and ascend into the light of true reality.

What is equally interesting is the literal interpretation of Plato's tale: The idea that reality could be represented completely as `shadows' on the walls

Tesseract

The tesseract can be unfolded into eight cubes into 3D space, just as the cube can be unfolded into six squares into 2D space. An unfolding of a polytope is called a net. There are 261 distinct nets of the tesseract.^[4] The unfoldings of the tesseract can be counted by mapping the nets to paired trees (a tree together with a perfect matching in its complement)

In geometry, the tesseract, or hypercube, is a regular, convex polychoron with eight cubical cells. It can be thought of as a 4-dimensional analogue of the cube. Roughly speaking the tesseract is to the cube as the cube is to the square.

Generalizations of the cube to dimensions greater than three are called hypercubes or measure polytopes. This article focuses on the 4D hypercube, the tesseract.

In a square, each vertex has two perpendicular edges incident to it, while a cube has three. A tesseract has four. Canonical coordinates for the vertices of a tesseract centered at the origin are (±1, ±1, ±1, ±1), while the interior of the same consists of all points (x0, x1, x2, x3) with -1 < xi < 1. This structure is not easily imagined but it is possible to project tesseracts into three or two dimensional spaces. Furthermore, projections on the 2D-plane become more instructive by rearranging the positions of the projected vertices. In this fashion, one can obtain pictures that no longer reflect the spatial relationships within the tesseract, but which nicely illustrate the connection structure of the vertices. The following examples are provided:

I would have thought artists like Dali and like Escher tried to develope and expand perspective capabilties of mind? To incorporate as much a "higher understanding" of the solid things, as we expect to understand all things around us?:)

Plato was pointing up for a reason, yet he believed in solid geometrical forms?