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Category: particle physics

Researchers with the University of Cambridge say they have the first real evidence of a new state of matter, some 40 years after it was first theorized.

Known as “quantum spin liquid,” the matter states causes normally unbreakable electrons to fracture into pieces, called “Majorana fermions.” These fermions are an important discovery: Physicists believe the material is crucial to further develop quantum computing. Computers employing Majorana fermions would be able to carry out calculations beyond the scope of modern computers quickly, they say.

Quantum spin liquid explains some of the odd behaviors inside magnetic materials. In these materials, the electrons should behave like small bar magnets, all aligning towards magnetic north when a material is cooled. But not all magnetic materials do this — if the material contains quantum spin liquid, the electrons don’t all line up and become entangled.

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Researchers have just discovered evidence of a mysterious new state of matter in a real material. The state is known as ‘quantum spin liquid’ and it causes electrons — one of the fundamental, indivisible building blocks of matter — to break down into smaller quasiparticles.

Scientists had first predicted the existence of this state of matter in certain magnetic materials 40 years ago, but despite multiple hints of its existence, they’ve never been able to detect evidence of it in nature. So it’s pretty exciting that they’ve now caught a glimpse of quantum spin liquid, and the bizarre fermions that accompany it, in a two-dimensional, graphene-like material.

“This is a new quantum state of matter, which has been predicted but hasn’t been seen before,” said one of the researchers, Johannes Knolle, from the University of Cambridge in the UK.

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The main benefit of an interstellar mission is to carry out in-situ measurements within a target star system. To allow for extended in-situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technologys shortcomings: A magnetic sail is more effective at higher velocities than the electric sail and vice versa. It is demonstrated that using both sails sequentially outperforms using only the magnetic or electric sail for various mission scenarios and velocity ranges, at a constant total spacecraft mass. For example, for decelerating from 5% c, to interplanetary velocities, a spacecraft with both sails needs about 29 years, whereas the electric sail alone would take 35 years and the magnetic sail about 40 years with a total spacecraft mass of 8250 kg. Furthermore, it is assessed how the combined deceleration system affects the optimal overall mission architecture for different spacecraft masses and cruising speeds. Future work would investigate how operating both systems in parallel instead of sequentially would affect its performance. Moreover, uncertainties in the density of interstellar matter and sail properties need to be explored.

The Msail (Magnetic Sail) consists of a superconducting coil and support tethers which connect it to the spacecraft and transfer the forces onto the main structure. The current through the coil produces a magnetic field. When the spacecraft has a non-zero velocity, the stationary ions of the interstellar medium are moving towards the sail in its own reference frame. The interaction of ions with the magnetosphere of the coil leads to a momentum exchange and a force on the sail, along the direction of the incoming charged particles.

According to Zubrin, the current densities of superconductors can reach up to jmax = 2 · 1010A/m2 and this is the value used in the analysis. For the material of the sail, the density of common superconductors like copper oxide (CuO) and YBCO was used, with ρMsail = 6000 kg/m3.

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Game theory is a branch of mathematics that looks at how groups solve complex problems. The Schrödinger equation is the foundational equation of quantum mechanics — the area of physics focused on the smallest particles in the Universe. There’s no reason to expect one to have anything to do with the other.

But according to a team of French physicists, it’s possible to translate a huge number of problems in game theory into the language of quantum mechanics. In a new paper, they show that electrons and fish follow the exact same mathematics.

Schrödinger is famous in popular culture for his weird cat, but he’s famous to physicists for being the first to write down an equation that fully describes the weird things that happen when you try to do experiments on the fundamental constituents of matter. He realised that you can’t describe electrons or atoms or any of the other smallest pieces of the Universe as billiard balls that will be exactly where you expect them to be exactly when you expect them to be there.

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An international team of researchers have found evidence of a mysterious new state of matter, first predicted 40 years ago, in a real material. This state, known as a quantum spin liquid, causes electrons — thought to be indivisible building blocks of nature — to break into pieces.

The researchers, including physicists from the University of Cambridge, measured the first signatures of these fractional particles, known as Majorana fermions, in a two-dimensional material with a structure similar to graphene. Their experimental results successfully matched with one of the main theoretical models for a , known as a Kitaev model. The results are reported in the journal Nature Materials.

Quantum spin liquids are mysterious states of matter which are thought to be hiding in certain magnetic materials, but had not been conclusively sighted in nature.

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One of the main principles of quantum physics is the superposition of states. Systems are simultaneously in different states, i.e. “alive and dead” at the same time such as Schrödinger’s cat, until someone measures them and the system opts for one of the possibilities. As long as the superposition lasts the system is said to be in a coherent state. In real systems, sets of diverse elemental particles or atoms existing in a state of superposition, for example, in different positions simultaneously, with different levels of energy, or with two opposite spin orientations, have weak coherence: the superposition is broken easily by the vibrations associated with temperature and the interactions with the environment.

In the scientific article, researchers from the Universitat Autònoma de Barcelona Department of Physics Andreas Winter and Dong Yang propose a groundbreaking method with which to measure the degree of coherence in any given quantum state. The researchers created simple formulas to calculate how much “pure coherence” is contained in a given quantum state, by answering two fundamental questions: How efficiently can one transform the state into “pure coherence”? And how efficient is the reverse process?

“At first the quantum state must be distilled. We must see how much coherence can be extracted from it,” explains Andreas Winter, to later “once again form a noisy state in which the coherence is diluted.” The distillation and dilution process allows measuring the strength of coherence of the initial state of superposition with experiments which can be tailored to each particular case. This is an outstanding contribution to the study of quantum physics given that “traditionally, to measure the degree of coherence of a superposition it was necessary to be able to measure the visibility of interference fringes, linked to standardised experiments,” Winter highlights. “With our approach, in contrast, the experiment can be adapted to every state in order to make the quantum coherence manifest itself better.”

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Researchers of CWI, University of Gdansk, Gdansk University of Technology, Adam Mickiewicz University and the University of Cambridge have proven that quantum communication is based on nonlocality. They show that whenever quantum communication is more efficient than classical communication, it must be possible find a nonlocal correlation somewhere. Their paper ‘Quantum communication complexity advantage implies violation of a Bell inequality’, appeared in this month’s issue of the influential journal PNAS.

It has long been known that predicts counterintuitive effects such as instantaneous interaction at a distance between entangled particles. This teleportation effect, which Albert Einstein famously called ‘spooky action at a distance,’ was long thought to show that the theory of quantum mechanics was incomplete. However, in 1964, physicist J.S. Bell proved that no theory involving the principle of locality can ever reproduce all predictions of quantum mechanics. In other words, it is impossible to find classical explanations for quantum correlations. This evidence for the existence of nonlocality became known as Bell’s inequality.

For a long time, the existence of was merely of interest to philosophically minded physicists, and was considered an exotic peculiarity rather than a useful resource for practical problems in physics or computer science. This has changed dramatically in recent years. Quantum correlation proved to be very useful in information processing. In several communication tasks, using quantum effects substantially reduced the communication complexity: the minimum number of steps necessary to complete a certain task between two parties. In such cases, there is a so-called quantum advantage in communication complexity.

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A University of Oklahoma-led team of physicists believes chip-based atomic physics holds promise to make the second quantum revolution—the engineering of quantum matter with arbitrary precision—a reality. With recent technological advances in fabrication and trapping, hybrid quantum systems are emerging as ideal platforms for a diverse range of studies in quantum control, quantum simulation and computing.

James P. Shaffer, professor in the Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and Sciences; Jon Sedlacek, OU graduate student; and a team from the University of Nevada, Western Washington University, The United States Naval Academy, Sandia National Laboratories and Harvard-Smithsonian Center for Astrophysics, have published research important for integrating Rydberg atoms into hybrid quantum systems and the fundamental study of atom– interactions, as well as applications for electrons bound to a 2D surface.

“A convenient surface for application in hybrid quantum systems is quartz because of its extensive use in the semiconductor and optics industries,” Sedlacek said. “The surface has been the subject of recent interest as a result of it stability and low surface energy. Mitigating electric fields near ‘trapping’ surfaces is the holy grail for realizing hybrid ,” added Hossein Sadeghpour, director of the Institute for Theoretical Atomic Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics.

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Dark matter is one of the greatest revelations in modern physics. Even though it hasn’t been directly detected yet, we know that it makes up around five-sixths of the total matter in the universe, binding much of it together in dramatic ways. It is this matter that stops galaxies from being torn apart as they spin.

As a new study published in the journal Physics of the Dark Universe notes, dark matter can also be destroyed. A signature of dark matter’s annihilation could potentially reveal what it was composed of in the first place, and this team of researchers from Harvard University think they’ve found one right in the heart of our own Milky Way.

Scientists are still debating what dark matter may actually be composed of, and one recent suggestion implies the particles are so dense that they are on the verge of becoming miniature black holes. Whatever they turn out to be, many astrophysicists think that these particles share a property with “ordinary” matter: they come in two flavors, matter and antimatter. When matter encounters antimatter, both are destroyed in a powerful blast that emits high-energy radiation.

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