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Category: quantum physics – Page 215

In this weeks continuation article of Dark Energy and what it is, we will be looking at Quintessence: which could be what dark matter is made of.

Quintessence. It is a “time-evolving and spatially dependent form of energy with negative pressure sufficient to drive the accelerating expansion” (Cladwell R.R. and Steinhardt P.J., 2000a, para 41).

Since it has negative pressure, it also has negative gravity. This negative gravity could explain the expansion of the universe. There are many models to describe quintessence, the simplest being, the fact that quintessence might be a quantum field with very long wavelength stretching across the universe. Negative gravity arises in this field by the negative pressure, and we can calculate the pressure by subtracting the Kinetic and Potential energies of the rate of oscillations in the field strength. This model is also successful, because it explains how the density of Dark Energy, or quintessence, changed over time, and fits in with the idea that dark energy must have been insignificant during the early universe to allow the large scale structures to form.

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A future quantum network of optical fibers will likely maintain communication between distant quantum computers. Sending quantum information rapidly across long distances has proved difficult, in part because most photons don’t survive the trip. Now Viktor Krutyanskiy of the University of Innsbruck, Austria, and his colleagues have more than doubled the success rate for sending photons that are quantum mechanically entangled with atoms to a distant site [1]. Instead of the previous approach of sending photons one at a time and waiting to see if each one arrives successfully, the researchers sent photons in groups of three. They believe that sending photons in larger numbers should be feasible in the future, allowing much faster transmission of quantum information.

Quantum networks require entanglement distribution, which involves sending a photon entangled with a local qubit to a distant location. The distribution system must check for the arrival and for the entanglement of each photon at the remote site before another attempt can be made, which can be time consuming. For a 100-km-long fiber, the light travel time combined with losses in the fiber and other inefficiencies limit the rate for this process to about one successful photon transfer per second using state-of-the-art equipment.

For faster distribution, Krutyanskiy and his colleagues trapped three calcium ions (qubits) in an optical cavity and performed repeated rounds of their protocol: in rapid sequence, each ion was triggered to emit an entangled photon that was sent down a 101-km-long, spooled optical fiber. In one experiment, the team performed nearly 900,000 of these “attempts,” detecting entangled photons at the far end 1906 times. The effective success rate came out to 2.9 per second. The team’s single-ion success rate was 1.2 per second.

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Electrons—the infinitesimally small particles that are known to zip around atoms—continue to amaze scientists despite the more than a century that scientists have studied them. Now, physicists at Princeton University have pushed the boundaries of our understanding of these minute particles by visualizing, for the first time, direct evidence for what is known as the Wigner crystal—a strange kind of matter that is made entirely of electrons.

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For more than a decade, scientists have used bismuth (Bi)-based topological insulators to demonstrate and explore exotic quantum effects in bulk solids mostly by manufacturing compound materials, like mixing Bi with selenium (Se), for example. However, this experiment is the first time topological effects have been discovered in crystals made of the element As.

“The search and discovery of novel topological properties of matter have emerged as one of the most sought-after treasures in modern physics, both from a fundamental physics point of view and for finding potential applications in next-generation quantum science and engineering,” said Hasan. “The discovery of this new topological state made in an elemental solid was enabled by multiple innovative experimental advances and instrumentations in our lab at Princeton.”

An elemental solid serves as an invaluable experimental platform for testing various concepts of topology. Up until now, bismuth has been the only element that hosts a rich tapestry of topology, leading to two decades of intensive research activities. This is partly attributed to the material’s cleanliness and the ease of synthesis. However, the current discovery of even richer topological phenomena in arsenic will potentially pave the way for new and sustained research directions.

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An international research team from Innsbruck and Geneva has, for the first time, probed the dimensional crossover for ultracold quantum matter. In the regime between one and two dimensions, the quantum particles perceive their world as being 1D or 2D depending on the length scale on which they are probed: For short distances, their world is 1D, but it is 2D for long distances.

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A NEW study of quantum mechanics has argued that a real-life multiverse could be much bigger than ever previously imagined.

Just like the fictional multiverse depicted in sci-fi movies and the Marvel superhero universe, we too could be living in a world where multiple realities are possible.

That’s according to a study published on the academic site Arxiv.

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The technology can also be used to devise a range of advanced sensors for everyday use and to advance science. Twamley’s lab uses levitating materials to build oscillators, which can be used to develop ultra-sensitive sensors. Making these oscillators work without using external energy sources can make them easier to deploy, and this is what the research team at OIST set out to do. What they faced was a series of challenges.

The device that OIST researchers aimed for was a ‘frictionless’ platform. However, the system would lose energy over time without an external power source. This is known as ‘eddy damping’ since external forces make an oscillating system lose energy.

The other hurdle to overcome would be minimizing the system’s kinetic energy. This is necessary since it can help improve the system’s sensitivity if it were to be used as a sensor. If the kinetic motion can be further cooled to the quantum realm, it could also open up possibilities of more precision measurements.

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Nothing makes a mess of quantum physics quite like those space-warping, matter-gulping abominations known as black holes. If you want to turn Schrodinger’s eggs into an information omelet, just find an event horizon and let ‘em drop.

According to theoretical physicists and chemists from Rice University and the University of Illinois Urbana-Champaign in the US, basic chemistry is capable of scrambling quantum information almost as effectively.

The team used a mathematical tool developed more than half a century ago to bridge a gap between known semiclassical physics and quantum effects in superconductivity. They found the delicate quantum states of reacting particles become scrambled with surprising speed and efficiency that comes close to matching the might of a black hole.

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A research team consisting of Professor Kyoung-Duck Park and Hyeongwoo Lee, an integrated PhD student, from the Department of Physics at Pohang University of Science and Technology (POSTECH) has pioneered an innovative technique in ultra-high-resolution spectroscopy. Their breakthrough marks the world’s first instance of electrically controlling polaritons – hybridized light-matter particles – at room temperature.

This research has been published in Physical Review Letters (“Electrically Tunable Single Polaritonic Quantum Dot at Room Temperature”).

Image depicting the control of polariton particles using electric-field tip-enhanced strong coupling spectroscopy. (Image: POSTECH)

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