“Quantum physics enables perfectly secure cloud computing: Researchers have succeeded in combining the power of quantum computing with the security of quantum cryptography and have shown that perfectly secure cloud computing can be achieved using the principles of quantum mechanics. They have performed an experimental demonstration of quantum computation in which the input, the data processing, and the output remain unknown to the quantum computer.
[...] current trend of cloud computing: central remote servers are used to store and process data – everything is done in the “cloud.” The obvious challenge is to make globalized computing safe and ensure that users’ data stays private.
The latest research, to appear in Science, reveals that quantum computers can provide an answer to that challenge. “Quantum physics solves one of the key challenges in distributed computing. It can preserve data privacy when users interact with remote computing centers [...]
The scientists in the Vienna research group have demonstrated the concept of “blind quantum computing” in an experiment: they performed the first known quantum computation during which the user’s data stayed perfectly encrypted. The experimental demonstration uses photons, or “light particles” to encode the data. Photonic systems are well-suited to the task because quantum computation operations can be performed on them, and they can be transmitted over long distances.
The process works in the following manner. The user prepares qubits – the fundamental units of quantum computers – in a state known only to himself and sends these qubits to the quantum computer. The quantum computer entangles the qubits according to a standard scheme. The actual computation is measurement-based: the processing of quantum information is implemented by simple measurements on qubits. The user tailors measurement instructions to the particular state of each qubit and sends them to the quantum server. Finally, the results of the computation are sent back to the user who can interpret and utilize the results of the computation. Even if the quantum computer or an eavesdropper tries to read the qubits, they gain no useful information, without knowing the initial state; they are “blind.”" http://www.eurekalert.org/pub_releases/2012-01/uov-qpe011612.php

Publication: “Demonstration of Blind Quantum Computing” Stefanie Barz, Elham Kashefi, Anne Broadbent, Joseph Fitzsimons, Anton Zeilinger, Philip Walther. DOI: 10.1126/science.1214707

http://arxiv.org/pdf/1110.1381

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The Strong Free Will Theorem

[...] our theorem asserts that if experimenters have a certain freedom, then particles have exactly the same kind of freedom. Indeed, it is natural to suppose that this latter freedom is the ultimate explanation of our own.
[...] It may well be true that classically stochastic processes such as tossing a (true) coin do not help in explaining free will, but [...] adding randomness also does not explain the quantum mechanical effects described in our theorem. It is precisely the “semi-free” nature of twinned particles, and more generally of entanglement, that shows that something very different from classical stochasticism is at play here.
Although the FWT [Free Will Theorem] suggests to us that determinism is not a viable option, it nevertheless enables us to agree with Einstein that “God does not play dice with the Universe.” In the present state of knowledge, it is certainly beyond our capabilities to understand the connection between the free decisions of particles and humans, but the free will of neither of these is accounted for by mere randomness.
[...] determinism may formally be shown to be consistent, there is no longer any evidence that supports it, in view of the fact that classical physics has been superseded by quantum mechanics, a non-deterministic theory. The import of the free will theorem is that it is not only current quantum theory, but the world itself that is non-deterministic, so that no future theory can return us to a clockwork universe.

http://www.ams.org/notices/200902/rtx090200226p.pdf

Cf. http://www.sciencenews.org/view/generic/id/35391/title/Math_Trek__Do_subatomic_particles_have_free_will%3F

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“And yet, even though useful quantum computers might still be decades away, many of their payoffs are already arriving. For example, the mere possibility of quantum computers has all but overthrown a conception of the universe that scientists like Stephen Wolfram have championed. That conception holds that, as in the “Matrix” movies, the universe itself is basically a giant computer, twiddling an array of 1’s and 0’s in essentially the same way any desktop PC does.

Quantum computing has challenged that vision by showing that if “the universe is a computer,” then even at a hard-nosed theoretical level, it’s a vastly more powerful kind of computer than any yet constructed by humankind. Indeed, the only ways to evade that conclusion seem even crazier than quantum computing itself: One would have to overturn quantum mechanics, or else find a fast way to simulate quantum mechanics using today’s computers.” http://www.nytimes.com/2011/12/06/science/scott-aaronson-quantum-computing-promises-new-insights.html?_r=1&ref=science&pagewanted=all

“Carson Chow Says:
Comment #2 December 5th, 2011 at 10:35 pm
Nice article but I am confused about this paragraph:

“For example, the mere possibility of quantum computers has all but overthrown a conception of the universe that scientists like Stephen Wolfram have championed. That conception holds that, as in the “Matrix” movies, the universe itself is basically a giant computer, twiddling an array of 1’s and 0’s in essentially the same way any desktop PC does.”

A quantum universe or a classical universe are both computable aren’t they? It’s just that the quantum universe is exponentially “bigger”. In principle, you could have a classical computer just chug away painfully slowly and simulate the quantum universe, no? There is nothing in the “Matrix” universe that says the computation must be efficient is there? There are still just a countable number of possible quantum universes right?”

“Scott Says:
Comment #5 December 5th, 2011 at 10:59 pm
Carson #2: Yes, as the tagline of my blog says, quantum computers can be simulated classically but with exponential slowdown.

What we learn from quantum computing is that, if both quantum mechanics and the prevailing conjectures in complexity theory are valid, then the physical universe can’t be feasibly simulated by a computer that “twiddles an array of 1’s and 0’s in essentially the same way any desktop PC does.”

(That last clause was meant to indicate that I was talking about efficient simulation by conventional computers — i.e., the Extended Church-Turing Thesis, or what Wikipedia calls the Feasibility Thesis. I wish I knew how to put the point more clearly within the constraints of this article, since you’re right that it might be misinterpreted!)

For what it’s worth, Stephen Wolfram, Ed Fredkin, and other believers in “digital physics,” have been very explicit in saying that they think the universe is a classical cellular automaton—basically, a three-dimensional array of pixels—and that their view would preclude exponential speedups from quantum computation. (Wolfram believes that quantum mechanics is wrong, whereas Fredkin believes that quantum mechanics can be efficiently simulated classically.) So, these viewpoints would indeed be ruled out under the assumptions I mentioned above.

A last remark: the Matrix movies aren’t very clear about what type of computer is being used, other than that it’s powered by human bodies! But since they never mention anything about quantum computing, and since the simulation clearly isn’t astronomically slow, it seems reasonable to assume that Keanu Reeves was trapped in some sort of classical simulation. So maybe he could’ve caused the simulation to crash by building a quantum computer and trying to run Shor’s factoring algorithm! For the version where Keanu is trapped in a quantum computation, we might need to wait for the followup trilogy, “The Unitary Matrix” (har, har).”

“Jiav Says:
Comment #8 December 6th, 2011 at 12:59 am
Nice essay Scott, but how could we know our simulation is not astronomically slow?

I’m curious to see if Greg Egan will comment this one ”

http://www.scottaaronson.com/blog/?p=871

Cf. http://theunitedpersons.org/blog/if-the-answer-is-42-what-is-the-question

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The end of the Space Age – Inner space is useful. Outer space is history http://www.economist.com/node/18897425

An Elegy for the Age of Space http://thearchdruidreport.blogspot.com/2011/08/elegy-for-age-of-space.html

Why Not Space? http://physics.ucsd.edu/do-the-math/2011/10/why-not-space/ Cf. http://science.slashdot.org/story/11/10/18/2258237/space-is-not-the-place-says-professor

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Quantum Mysteries Disentangled: “This paper attempts to dispel some of the “essential mystery” of quantum mechanics (QM) by describing some recent (as of 2001) results in quantum
information theory at a level accessible to the layman. The discussion is motivated by first showing how informal accounts of QM’s mysteries (specifically, entanglement and quantum erasers) lead to a contradiction of relativity. The apparent contradiction is resolved with an elementary mathematical analysis. Finally, I engage in wild philosophical speculation in order to allay fears that a better understanding of QM runs the risk of taking all of the fun out of it.” http://www.flownet.com/ron/QM.pdf

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52 Years and $750M Prove Einstein Was Right “[...] the Gravity Probe results would live forever in textbooks as the most direct measurements [....]

Empty space in the vicinity of Earth is indeed turning, Dr. Everitt reported at the news conference and in a paper prepared for the journal Physical Review Letters, at the leisurely rate of 37 one-thousandths of a second of arc — the equivalent of a human hair seen from 10 miles away — every year. With an uncertainty of 19 percent, that measurement was in agreement with Einstein’s predictions of 39 milliarcseconds.

Likewise, the “sag” should alter the space-time geometry around Earth, warping it from the Euclidean ideal and cutting an inch out of the Gravity Probe’s orbit around it, so that the circumference is slightly less than the Euclidean ideal of pi times the orbit’s diameter, a fact confirmed by the Stanford gyroscopes to an accuracy of 0.3 percent. [...]” http://www.nytimes.com/2011/05/05/science/space/05gravity.html?_r=1

http://einstein.stanford.edu/highlights/status1.html

Update: http://science.slashdot.org/story/11/05/05/0253241/NASA-Gravity-Probe-Confirms-Two-Einstein-Predictions

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3 recent promising papers on the fabric of the universe:

1. Information Physics: The New Frontier

At this point in time, two major areas of physics, statistical mechanics and quantum mechanics, rest on the foundations of probability and entropy. The last century saw several significant fundamental advances in our understanding of the process of inference, which make it clear that these are inferential theories. That is, rather than being a description of the behavior of the universe, these theories describe how observers can make optimal predictions about the universe. In such a picture, information plays a critical role. What is more is that little clues, such as the fact that black holes have entropy, continue to suggest that information is fundamental to physics in general. [...] http://arxiv.org/pdf/1009.5161v1

Cf. http://en.wikipedia.org/wiki/Digital_physics +

[...] it is important to clarify what the problem is not. We are not asking whether the metaphorical interpretation of the universe as a computer is more useful than misleading. We are not even asking whether an informational description of the universe, as we know it, is possible, at least partly and piecemeal. [...] We are asking whether the universe in itself could essentially be made of
information [...] http://num.math.uni-goettingen.de/schaback/info/mat/floridi_open_problems.pdf

2. Primordial weirdness: Did the early universe have 1 dimension? http://www.physorg.com/news/2011-04-primordial-weirdness-early-universe-dimension.html

3. http://theunitedpersons.org/blog/gravity-doesn%E2%80%99t-exist

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Gravity doesn’t exist

With the advent of quantum theory over the past 100 years, scientists have been able to develop an elegant mathematical framework capable of uniting three of the four fundamental forces that are thought to exist in the universe. The fourth, gravity, still remains the fly in the ointment, and has resisted unification to this point. Early last year, Dutch theoretical physicist Erik Verlinde published a manuscript to the arXiv that purports to explain why science cannot reconcile all four fundamental forces. According to him, it is simple: “gravity doesn’t exist.”

http://arstechnica.com/science/news/2011/04/is-gravity-a-result-of-thermodynamics.ars

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Cf. http://theunitedpersons.org/blog/radiation-dose

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The standard cartoon of an electron shows a spinning sphere with positive or negative angular momentum, as illustrated in blue or gold above. However, such cartoons are fundamentally misleading: compelling experimental evidence indicates that electrons are ideal point particles, with no finite radius or internal structure that could possibly “spin”. A quantum mechanical model of electron transport in graphene, a single layer of graphite (shown as a black honeycomb), presents a possible resolution to this puzzle. An electron in graphene hops from carbon atom to carbon atom as if moving on a chessboard with triangular tiles. At low energies the individual tiles are unresolved, but the electron acquires an “internal” spin quantum number which reflects whether it is on the blue or the gold tiles. Thus the electron’s spin could arise not from rotational motion of its substructure, but rather from the discrete, chessboard-like structure of space. (Image: Chris Regan/CNSI) [...]

The electrons in graphene move by hopping from carbon atom to carbon atom, as if hopping on a chessboard. The graphene chessboard tiles are triangular, with the dark tiles pointing “up” and light ones pointing “down.” When an electron in graphene absorbs a photon, it hops from light tiles to dark ones. Mecklenburg and Regan showed that this transition is equivalent to flipping a spin from “up” to “down.”

In other words, confining the electrons in graphene to specific, discrete positions in space gives them spin. This spin, which derives from the special geometry of graphene’s honeycomb lattice, is in addition to and distinct from the usual spin carried by the electron. In graphene the additional spin reflects the unresolved chessboard-like structure to the space that the electron occupies.

“My adviser [Regan] spent his Ph.D. studying the structure of the electron,” Mecklenburg said. “So he was very excited to see that spin can emerge from a lattice. It makes you wonder if the usual electron spin could be generated in the same way.”
“It’s not yet clear if this work will be more useful in particle or condensed matter physics,” Regan said, “but it would be odd if graphene’s honeycomb structure was the only lattice capable of generating spin.”"

http://www.physorg.com/news/2011-03-space-chessboard.html

http://prl.aps.org/abstract/PRL/v106/i11/e116803

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A measure for the multiverse: “[...] Everything we need to know about the multiverse might be right here in our own universe.” http://www.sott.net/articles/show/204004-A-measure-for-the-multiverse

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The Utility of Mathematics: “This essay discusses the best current understanding of the relationship between mathematical and empirical knowledge. It focuses on two questions:

• Does mathematics have some sort of deep metaphysical connection with reality, and
• if not, why is it that mathematical abstractions seem so often to be so powerfully predictive in the real world?” http://www.catb.org/~esr/writings/utility-of-math/

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Why exactly can nothing go faster than the speed of light? http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/ (Cf. http://news.ycombinator.com/item?id=2244304 )

Cf. http://www.amazon.com/Fabric-Cosmos-Space-Texture-Reality/dp/0375727205 Index: ‘speed of light’, p. 564.

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Quantum Entanglement Across Time “[...] In a new paper [ http://arxiv.org/abs/1101.2565 ] posted on the physics preprint website arXiv.org, Olson and Queensland colleague Timothy Ralph perform the math to show how these same tricks can send quantum messages not only from place to place, but from the past to the future.

The equations involved defy simple mathematical explanation, but are intuitive: If it’s impossible to describe one particle without including the other, this logically extends to time as well as space.

“If you use our timelike entanglement, you find that [a quantum message] moves in time, while skipping over the intermediate points,” Olson said. “There really is no difference mathematically. Whatever you can do with ordinary entanglement, you should be able to do with timelike entanglement.”

Olson explained them with a Star Trek analogy. In one episode, “beam me up” teleportation expert Scotty is stranded on a distant planet with limited air supply. To survive, Scotty freezes himself in the transporter, awaiting rescue. When the Enterprise arrives decades later, Scotty steps out of the machine without having aged a day.

“It’s not time travel as you would ordinarily think of it, where it’s like, poof! You’re in the future,” Olson said. “But you get to skip the intervening time.”

According to quantum physicist Ivette Fuentes of the University of Nottingham, who saw Olson and Ralph present the work at a conference, it’s “one of the most interesting results” published in the last year.

“It stimulated our imaginations,” said Fuentes. “We know entanglement is a resource and we can do very interesting things with it, like quantum teleportation and quantum cryptography. We might be able to exploit this new entanglement to do interesting things.” [...]” http://www.wired.com/wiredscience/2011/01/timelike-entanglement/

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American Physical Society announces Physical Review X : “APS announces Physical Review X (PRX), an online, open access, primary research journal for authors in all fields of physics. [...]

PRX will provide validation through prompt and rigorous peer review, and an open access venue in accord with the strong reputation of the Physical Review family of publications.

Articles in PRX will be published under the terms of the Creative Commons Attribution 3.0 License, leaving copyright with the authors. [...]

The funding required to make PRX freely available will derive from article-processing charges of $1500 per article. These will cover the expenses associated with peer review, composition, hosting, and archiving. “APS strives to be among the most cost-effective publishers in physics and is committed to a sustainable model that makes PRX affordable for authors and their funding agencies, nationally and internationally,” said Joseph W. Serene, APS Treasurer/Publisher.

A Call for Papers will be issued in March and the first article published in Fall 2011.” http://www.eurekalert.org/pub_releases/2011-01/aps-aps011911.php

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