Lifeboat Foundation

Quantum information relies on the possibility of writing messages in a quantum particle and reading them out in a reliable way. If, however, the particle is relativistic, meaning that it moves with velocities close to the speed of light, it is impossible for standard techniques to decode the message unambiguously, and the communication therefore fails.

Thanks to the introduction of a new method, researchers at the University of Vienna and the Austrian Academy of Sciences have developed reliable decoding of quantum messages transmitted at extremely high speeds. The results, published in the journal Physical Review Letters, opens up new possibilities of technological applications in quantum information and quantum communication.

Imagine the following situation: Anna and Bill want to exchange a message by using a property of a quantum particle, say the spin of an electron, which is an intrinsic form of particle’s rotation. Bill needs Anna’s message as quickly as possible, so Anna has to send the electron at maximum speed, very close to the speed of light. Given that Anna has the electron in her laboratory localized, the Heisenberg uncertainty principle forbids the velocity of the electron to be defined with arbitrary precision. When the electron travels at extremely high speed, the interplay between special relativity and quantum physics causes the spin and the velocity of the electron to become entangled. Due to this correlation, which is stronger than what is classically possible, Bill is not able to read out the spin with the standard method. Can Anna and Bill improve their communication strategy?

Circa 1997

By Michio Kaku

IS THERE a Final Theory in physics? Will we one day have a complete theory that will explain everything from subatomic particles, atoms and supernovae to the big bang? Einstein spent the last 30 years of his life in a fruitless quest for the fabled unified field theory. His approach has since been written off as futile.

Continue reading “Into the eleventh dimension” »

We suggest and motivate a precise equivalence between uncompactified eleven dimensional M-theory and the N = infinity limit of the supersymmetric matrix quantum mechanics describing D0-branes. The evidence for the conjecture consists of several correspondences between the two theories. As a consequence of supersymmetry the simple matrix model is rich enough to describe the properties of the entire Fock space of massless well separated particles of the supergravity theory. In one particular kinematic situation the leading large distance interaction of these particles is exactly described by supergravity.

The model appears to be a nonperturbative realization of the holographic principle. The membrane states required by M-theory are contained as excitations of the matrix model.

Rumour has it that Albert Einstein spent his last few hours on Earth scribbling something on a piece of paper in a last attempt to formulate a theory of everything. Some 60 years later, another legendary figure in theoretical physics, Stephen Hawking, may have passed away with similar thoughts. We know Hawking thought something called “M-theory” is our best bet for a complete theory of the universe. But what is it?

Since the formulation of Einstein’s theory of general relativity in 1915, every theoretical physicist has been dreaming of reconciling our understanding of the infinitely small world of atoms and particles with that of the infinitely large scale of the cosmos. While the latter is effectively described by Einstein’s equations, the former is predicted with extraordinary accuracy by the so-called Standard Model of fundamental interactions.

Our current understanding is that the interaction between physical objects is described by four fundamental forces. Two of them – gravity and electromagnetism – are relevant for us on a macroscopic level, we deal with them in our everyday life. The other two, dubbed strong and weak interactions, act on a very small scale and become relevant only when dealing with subatomic processes.

By Andrew Zimmerman Jones, Daniel Robbins

According to string theory, all particles in the universe can be divided into two types: bosons and fermions. String theory predicts that a type of connection, called supersymmetry, exists between these two particle types.

Under supersymmetry, a fermion must exist for every boson and a boson for every fermion. Unfortunately, experiments have not yet detected these extra particles.

20th century physics has seen two major paradigm shifts in the way we understand Mother Nature. One is quantum mechanics, and the other is relativity. The marriage between the two, called quantum field theory, conceived an enfant terrible, namely anti-matter. As a result, the number of elementary particles doubled. We believe that 21st century physics is aimed at yet another level of marriage, this time between quantum mechanics and general relativity, Einstein’s theory of gravity. The couple has not been getting along very well, resulting in mathematical inconsistencies, meaningless infinities, and negative probabilities. The key to success may be in supersymmetry, which doubles the number of particles once more.

Why was anti-matter needed? One reason was to solve a crisis in the 19th century physics of classical electromagnetism. An electron is, to the best of our knowledge, a point particle. Namely, it has no size, yet an electric charge. A charged particle inevitably produces an electric potential around it, and it also feels the potential created by itself. This leads to an infinite “self-energy” of the electron. In other words, it takes substantial energy to “pack” all the charge of an electron into small size.

On the other hand, Einstein’s famous equation says that mass of a particle determines the energy of the particle at rest. For an electron, its rest energy is known to be 0.511 MeV. For this given amount of energy, it cannot afford to “pack” itself into a size smaller than the size of a nucleus. Classical theory of electromagnetism is not a consistent theory below this distance. However, it is known that the electron is at least ten thousand times smaller than that.

The correspondence between fermions and bosons of identical mass that is postulated to have existed during the opening moments of the big bang and that relates gravity to the other forces of nature… See the full definition.

The theory, which emerged in the 1970s as a way to unify the fundamental forces of nature, has profoundly shaped the landscape of particle physics.