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The quantum superposition principle has been tested on a scale as never before in a new study by scientists at the University of Vienna in collaboration with the University of Basel. Hot, complex molecules composed of nearly two thousand atoms were brought into a quantum superposition and made to interfere. By confirming this phenomenon – “the heart of quantum mechanics”, in Richard Feynman’s words – on a new mass scale, improved constraints on alternative theories to quantum mechanics have been placed. The work was published in Nature Physics on September 23, 2019.

Quantum to classical?

The superposition principle is a hallmark of quantum theory which emerges from one of the most fundamental equations of quantum mechanics, the Schrödinger equation. It describes particles in the framework of wave functions, which, much like water waves on the surface of a pond, can exhibit interference effects. But in contrast to water waves, which are a collective behavior of many interacting water molecules, quantum waves can also be associated with isolated single particles.

Geneva. Arts at CERN announces two open calls for art residencies – Collide Geneva/Dance and Accelerate Finland – and the arrival of the winners of Collide International, Rosa Menkman, and Collide Pro Helvetia, Christina Hemauer and Roman Keller. The art residency programmes are based on the particle physics laboratory’s cultural strategy, which aims to foster networks between local and international organisations through platforms that engage art and science.

“Arts at CERN plays an important role in augmenting the interest seen in the interaction of the arts and sciences in recent years. By inviting artists and scientists to have a dialogue in the Laboratory, the programme shows how the two fields impact one another. I am proud to announce new opportunities for participation, and to welcome artists-in-residence this autumn,” says Mónica Bello, head of Arts at CERN.

For the sixth Collide Geneva residency, Arts at CERN, the Republic and Canton of Geneva and the City of Geneva have joined forces. The three-month fully funded residency award will be granted to a Geneva-based artist or artist collective working in the field of dance. The winner will have the opportunity to carry out their research at CERN and work together with particle physicists, engineers and IT professionals. Collide Geneva/Dance encourages applications from dance artists inspired by scientific ideas or technological concepts, with innovative approaches in their artistic expression.

For the first time, physicists in the US have confirmed a decades-old theory regarding the breaking of time-reversal symmetry in gauge fields. Marin Soljacic at the Massachusetts Institute of Technology and an international team of researchers have made this first demonstration of the “non-Abelian Aharonov-Bohm effect” in two optics experiments. With improvements, their techniques could find use in optoelectronics and fault-tolerant quantum computers.

First emerging in Maxwell’s famous equations for classical electrodynamics, a gauge theory is a description of the physics of fields. Gauge theories have since become an important part of physicists’ descriptions of the dynamics of elementary particles – notably the theory of quantum electrodynamics.

A salient feature of a gauge theory is that the physics it describes does not change when certain transformations are made to the underlying equations describing the system. An example is the addition of a constant scalar potential or a “curl-free” vector potential to Maxwell’s equations. Mathematically, this does not change the electric and magnetic fields that act on a charged particle such as an electron – and therefore the behaviour of the electron – so Maxwell’s theory is gauge invariant.

Albert Einstein received the Nobel Prize for explaining the photoelectric effect: in its most intuitive form, a single atom is irradiated with light. According to Einstein, light consists of particles (photons) that transfer only quantised energy to the electron of the atom. If the photon’s energy is sufficient, it knocks the electrons out of the atom. But what happens to the photon’s momentum in this process? Physicists at Goethe University are now able to answer this question. To do so, they developed and constructed a new spectrometer with previously unattainable resolution.

Doctoral student Alexander Hartung became a father twice during the construction of the apparatus. The device, which is three meters long and 2.5 meters high, contains approximately as many parts as an automobile. It sits in the experiment hall of the Physics building on Riedberg Campus, surrounded by an opaque, black tent inside which is an extremely high performing laser. Its photons collide with individual argon atoms in the apparatus, and thereby remove one electron from each of the atoms. The momentum of these electrons at the time of their appearance is measured with extreme precision in a long tube of the apparatus.

The device is a further development of the COLTRIMS principle that was invented in Frankfurt and has meanwhile spread across the world: it consists of ionising individual atoms, or breaking up molecules, and then precisely determining the momentum of the particles. However, the transfer of the photon momentum to electrons predicted by theoretic calculations is so tiny that it was previously not possible to measure it. And this is why Hartung built the “super COLTRIMS.”

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of “Your Place in the Universe.” Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.

Is it a wave, or is it a particle? This seems like a very simple question. Waves are very distinct phenomena in our universe, as are particles. And we have different sets of mathematics to describe each of them. So, if we want to go about describing the entire universe, this appears to be a very handy classification scheme — except when it isn’t. And it isn’t in one of the most important aspects of our universe: the subatomic world.

Continue reading “Is It a Wave or a Particle? It’s Both, Sort Of” »

In years to come, quantum computers and quantum networks might be able to tackle tasks that are inaccessible to traditional computer systems. For instance, they could be used to simulate complex matter or enable fundamentally secure communications.

The elementary building blocks of quantum information systems are known as qubits. For quantum technology to become a tangible reality, researchers will need to identify strategies to control many qubits with very high precision rates.

Spins of individual particles in solids, such as electrons and nuclei have recently shown great promise for the development of quantum networks. While some researchers were able to demonstrate an elementary control of these qubits, so far, no one has reported entangled quantum states containing more than three spins.

A team of researchers from the U.K., China and Spain has found that graphene exhibits mechanical properties that are similar to those of graphite. In their paper published in the journal Physical Review Letters, the group describes testing flakes of graphene in a unique way, and what they found.

Graphene is a sheet of carbon atoms just a single atom thick, sometimes called a two-dimensional material. In this new effort, the researchers questioned whether it truly is a two-dimensional material by testing it to see if it has 3D mechanical properties.

Prior research has shown that graphene does behave as a 2-D material when looking at its electronic properties. It also behaves like a 2-D material when testing its thermal properties. But until now, its mechanical properties had not been tested. The reason fis that graphene falls apart nearly instantly when not supported by a substrate, presenting difficulties in testing its mechanical properties without also including those of the substrate. To get around this problem, the researchers tested one of graphene’s mechanical properties by suspending graphene flakes in a viscous liquid, thereby preventing phonons from shaking it apart. The liquid also prevented the flakes from bonding and forming graphite. The team then carried out a common 3D test—applying high pressure, in this case, using a diamond anvil cell. Doing so showed (via Raman spectroscopy) that the energy shift that resulted from its phonons was closer to that exhibited by a 3D material (graphite) than a 2-D material.

The foundational theory of particle physics, the Standard Model, predicts…

The KATRIN experiment has turned up a new, more-precise-than-ever measurement for the barely-detectable neutrino mass.