Lifeboat Foundation

Finding evidence of many-body localization in a closed quantum system.

During equilibration ordinary many-body systems lose all information about the initial state. Every morning we experience an example for this behaviour. Milk poured into a cup of coffee mixes perfectly and after some time it is impossible to say how exactly the two fluids were put together. The same behaviour holds for almost all quantum systems. However, recently a new phenomenon called “many-body localization” has been predicted theoretically, which allows well insulated quantum systems to preserve memory of the initial state forever. Now a team of scientists around Dr. Christian Groß and Professor Immanuel Bloch (Director at MPQ and Chair of Quantum Optics at LMU Munich), in cooperation with David Huse (Princeton University), has obtained evidence of such a behaviour in a two-dimensional quantum system of cold rubidium atoms trapped in an optical lattice.

The scientists observed that – beyond a certain degree of disorder imprinted on the particle ensemble in the beginning – the system would relax into a steady state still containing detailed microscopic information about its past. “We were able to observe the transition from a thermalized state into a many-body localized phase”, Christian Groß points out. “It is the first observation of that kind in a regime that is not accessible with state-of-the-art simulations on classical computers.” The experiment is not only of fundamental interest; the results might also lead to new ways for storing quantum information.

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When the bang became a bounce.

How the universe began is one of the most brain-breaking questions you could possibly ask, and the Big Bang is probably the answer most people accept. But what if the infinitely dense point from which the entire universe burst forth wasn’t the beginning of everything, but merely the middle of an ongoing cycle? That’s the theory of the Big Bounce, which suggests that the universe regularly cycles through periods of expansion and contraction, meaning the Big Bang may have been preceded by an earlier universe collapsing in on itself. A new study details how this might be possible.

The idea of the Big Bounce has been bouncing around since 1922, but explaining just how the universe transitions between expanding and contracting has always been an issue. What’s to stop a universe just contracting into a point and collapsing completely? According to researchers from Imperial College London and the Perimeter Institute for Theoretical Physics in Canada, it may be the same quantum mechanics that prevent atoms from deteriorating into nothing.

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Listen up all my QC buddies; the air force wants to hear from you. You have QC ideas for fighter jets they want you.

Guess I need to submit them some of mine.

The Air Force wants white papers that describe new ways quantum computing could help achieve its mission, according to an amended Broad Agency Announcement posted Friday. Eventually, the government could provide a test-bed where a contractor might install, develop and test a quantum computing system, according to the announcement.

Last year, the Air Force announced it had about $40 million available to fund research into, and the eventual maintenance and installation of a quantum system — a branch of emerging computing technology that relies on the mechanics of atomic particles to process complex equations.

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So-called “zero-point energy” is a term familiar to some cinema lovers or series fans; in the fictional world of animated films such as “The Incredibles” or the TV series “Stargate Atlantis”, it denotes a powerful and virtually inexhaustible energy source.

Whether it could ever be used as such is arguable. Scientists at Jülich have now found out that it plays an important role in the stability of nanomagnets. These are of great technical interest for the magnetic storage of data, but so far have never been sufficiently stable. Researchers are now pointing the way to making it possible to produce nanomagnets with low zero-point energy and thus a higher degree of stability (Nano Letters, “Zero-Point Spin-Fluctuations of Single Adatoms”).

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Why is gravity so much weaker than the other fundamental forces? A small fridge magnet is enough to create an electromagnetic force greater than the gravitational pull exerted by planet Earth. One possibility is that we don’t feel the full effect of gravity because part of it spreads to extra dimensions. Though it may sound like science fiction, if extra dimensions exist, they could explain why the universe is expanding faster than expected, and why gravity is weaker than the other forces of nature.

In our everyday lives, we experience three spatial dimensions, and a fourth dimension of time. How could there be more? Einstein’s general theory of relativity tells us that space can expand, contract, and bend. Now if one dimension were to contract to a size smaller than an atom, it would be hidden from our view. But if we could look on a small enough scale, that hidden dimension might become visible again. Imagine a person walking on a tightrope. She can only move backward and forward; but not left and right, nor up and down, so she only sees one dimension. Ants living on a much smaller scale could move around the cable, in what would appear like an extra dimension to the tightrope-walker.

Nice.

Abstract: Researchers have developed a way to use less platinum in chemical reactions commonly used in the clean energy, green chemicals, and automotive industries, according to a paper in Science.

Led by the University of New Mexico in collaboration with Washington State University, the researchers developed a unique approach for trapping platinum atoms that improves the efficiency and stability of the reactions.

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While there are several forms of ion propulsion, the version Brophy used on Dawn involves two grids, each about a foot wide and spaced half a millimeter apart. An electrical system powered by a solar array on the spacecraft passes a current through both grids, and the resulting voltage differential between the two is what accelerates the xenon particles as they pass through the grids. Each accelerating particle only provides a tiny amount of thrust — roughly equivalent to the pressure of a piece of paper lying in your hand — but in the airless and frictionless environment of space, a steady stream of that tiny thrust can build up to monumental speeds of about 24,000 miles-per-hour.

What Brophy and his coworkers aimed to do was build a grid and propulsion system that could pull this off, and demonstrate that the setup was durable enough to survive the whole mission. So before both Deep Space 1 and Dawn, they ran versions of the ion system here on Earth continuously for years to demonstrate their lifespan.

Finally, the Dawn mission became possible when Ceres and Vesta reached a once-every-17-years alignment, allowing the mission to visit them both. “That was really a great boon for space exploration to do the two largest asteroids in the asteroid belt with one mission,” Russell explains.

Continue reading “This innovation could change space travel forever” »

Robots so small they can enter the bloodstream and perform surgeries are one step closer, a research team from Monash University has discovered.

Led by Dr Zhe Liu, the Monash Engineering team has focused on graphene oxide — which is a single atom thick — as an effective shape memory material.

Graphene has captured world scientific and industrial interest for its miracle properties, with potential applications across energy, medicine, and even biomedical nano-robots.

Continue reading “Fantastic voyage to the nanoverse one step closer” »

“Nothing is impossible!” In line with this motto, physicists from the Quantum Dynamics Division of Professor Gerhard Rempe (director at the Max Planck Institute of Quantum Optics) managed to realise a quantum logic gate in which two light quanta are the main actors. The difficulty of such an endeavour is that photons usually do not interact at all but pass each other undisturbed. This makes them ideal for the transmission of quantum information, but less suited for its processing. The scientists overcame this steep hurdle by bringing an ancillary third particle into play: a single atom trapped inside an optical resonator that takes on the role of a mediator. “The distinct feature of our gate implementation is that the interaction between the photons is deterministic”, explains Dr. Stephan Ritter. “This is essential for future, more complex applications like scalable quantum computers or global quantum networks.”

In all modern computers, data processing is based on information being binary-coded and then processed using logical operations. This is done using so-called logic gates which assign predefined output values to each input via deterministic protocols. Likewise, for the information processing in quantum computers, quantum logic gates are the key elements. To realise a universal quantum computer, it is necessary that every input quantum bit can cause a maximal change of the other quantum bits. The practical difficulty lies in the special nature of quantum information: in contrast to classical bits, it cannot be copied. Therefore, classical methods for error correction cannot be applied, and the gate must function for every single photon that carries information.

Because of the special importance of photons as information carriers – for example, for communicating quantum information in extended quantum networks – the realisation of a deterministic photon-photon gate has been a long-standing goal. One of several possibilities to encode photonic quantum bits is the use of polarisation states of single photons. Then the states “0” and “1” of a classical bit correspond to two orthogonal polarisation states. In the two-photon gate, the polarisation of each photon can influence the polarisation of the other photon. As in the classical logic gate it is specified beforehand which input polarisation leads to which output polarisation. For example, a linear polarisation of the second photon is rotated by 90° if the first one is in the logic state “1”, and remains unchanged if the first one is in “0”.