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Category: particle physics – Page 271

Light-pulse matter-wave interferometers exploit the quantized momentum kick given to atoms during absorption and emission of light to split atomic wave packets so that they traverse distinct spatial paths at the same time. Additional momentum kicks then return the atoms to the same point in space to interfere the two matter-wave wave packets. The key to the precision of these devices is the encoding of information in the phase ϕ that appears in the superposition of the two quantum trajectories within the interferometer. This phase must be estimated from quantum measurements to extract the desired information. For N atoms, the phase estimation is fundamentally limited by the independent quantum collapse of each atom to an r.m.s. angular uncertainty \(\Delta {\theta }_{{\rm{SQL}}}=1/\sqrt{N}\) rad, known as the standard quantum limit (SQL)2.

Here we demonstrate a matter-wave interferometer31,32 with a directly observed interferometric phase noise below the SQL, a result that combines two of the most striking features of quantum mechanics: the concept that a particle can appear to be in two places at once and entanglement between distinct particles. This work is also a harbinger of future quantum many-body simulations with cavities26,27,28,29 that will explore beyond mean-field physics by directly modifying and probing quantum fluctuations or in which the quantum measurement process induces a phase transition30.

Quantum entanglement between the atoms allows the atoms to conspire together to reduce their total quantum noise relative to their total signal1,3. Such entanglement has been generated between atoms using direct collisional33,34,35,36,37,38,39 or Coulomb40,41 interactions, including relative atom number squeezing between matter waves in spatially separated traps33,35,39 and mapping of internal entanglement onto the relative atom number in different momentum states42. A trapped matter-wave interferometer with relative number squeezing was realized in ref. 35, but the interferometer’s phase was antisqueezed and thus the phase resolution was above the SQL.

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Physicists have created the first Bose-Einstein condensate—the mysterious fifth state of matter—made from quasiparticles, entities that do not count as elementary particles but that can still have elementary-particle properties like charge and spin. For decades, it was unknown whether they could undergo Bose-Einstein condensation in the same way as real particles, and it now appears that they can. The finding is set to have a significant impact on the development of quantum technologies including quantum computing.

A paper describing the process of creation of the substance, achieved at temperatures a hair’s breadth from absolute zero, was published in the journal Nature Communications.

Bose-Einstein condensates are sometimes described as the fifth state of matter, alongside solids, liquids, gases and plasmas. Theoretically predicted in the early 20th century, Bose-Einstein condensates, or BECs, were only created in a lab as recently as 1995. They are also perhaps the oddest state of matter, with a great deal about them remaining unknown to science.

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A type of aurora briefly tore a 400 km wide hole in Earth’s ozone layer.

An international team of researchers showed that a certain type of aurora called the “Isolated proton aurora” depletes our atmosphere’s ozone layer. They discovered a nearly 250-mile-wide (400 kilometers) hole in the ozone layer right above where an aurora occurred. Before now, the influence of these particles was only vaguely known. The study is published in Scientific reports.

What causes the auroras?

Solar storms on the sun’s surface give out huge clouds of electrically charged particles. These particles can travel millions of miles, and some may eventually collide with the Earth. Most of these particles are deflected away, but some become captured in the Earth’s magnetic field. When they are entrapped, their charge ionizes the atmosphere and produces nitrogen oxides and hydrogen oxides. Both compounds contribute to ozone loss.

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Astronomers have discovered a mysterious neutron star that’s far lighter than previously thought possible, undermining our understanding of the physics and evolution of stars. And fascinatingly, it may be composed largely of quarks.

As detailed in a new paper published in the journal Nature Astronomy this week, the neutron star has a radius of just 6.2 miles and only the mass of 77 percent of the Sun.

That makes it much lighter than other previously studied neutron stars, which usually have a mass of 1.4 times the mass of the Sun at the same radius.

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The engineering of so-called Floquet states leads to almost-perfect atom-optics elements for matter-wave interferometers—which could boost these devices’ ability to probe new physics.

Since Michelson and Morley’s famous experiment to detect the “luminiferous aether,” optical interferometry has offered valuable tools for studying fundamental physics. Nowadays, cutting-edge applications of the technique include its use as a high-precision ruler for detecting gravitational waves (see Focus: The Moon as a Gravitational-Wave Detector) and as a platform for quantum computing (see Viewpoint: Quantum Leap for Quantum Primacy). But as methods for cooling and controlling atoms have advanced, a new kind of interferometer has become available, in which light waves are replaced by matter waves [1]. Such devices can measure inertial forces with a sensitivity even greater than that of optical interferometers [2] and could reveal new physics beyond the standard model.

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A multiwavelength laser source known as a frequency comb provides a new technique for atom interferometry, potentially leading to new tests of fundamental physics.

In atom interferometry, researchers use the interference of quantum waves of matter, often for high-precision experiments testing fundamental physics principles. A research team has now demonstrated a new way to produce matter-wave interference by using a frequency-comb laser—a comb-like set of spectral lines at regularly spaced frequencies [1]. The comb allowed the team to generate interference in a cloud of cold atoms. The method might ultimately be used to investigate differences between matter and antimatter.

According to the weak equivalence principle, gravity must cause both matter and antimatter to fall at the same rate (see the graphical explanation, The Equivalence Principle under a MICROSCOPE). Deviations from this principle could point to explanations for the hitherto mysterious imbalance in the amounts of matter and antimatter in the Universe. Atom interferometry could provide a test of weak equivalence through precise measurements of the free fall of antihydrogen. So far, light-based control of atom interferometry has used continuous-wave (cw) lasers [2], which can’t easily be extended to the short wavelengths in the extreme ultraviolet (XUV) that are needed for such studies of antihydrogen.

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Just in time for Halloween’s spooky season, a quantum sensor now has double the spookiness by combining entanglement between atoms and delocalization of atoms.

Future quantum sensors will be able to provide more precise navigation, explore for needed natural resources, more precisely determine fundamental constants, look more precisely for dark matter, or maybe someday discover gravitational waves thanks to a team of researchers led by Fellow James K. Thompson from the Joint Institute for Laboratory Astrophysics (JILA) and the National Institute of Standards and Technology (NIST).

Thompson and his team have for the first time successfully combined two of the “spookiest” features of quantum mechanics: entanglement between atoms and delocalization of atoms. By doubling down on these “spooky” features, better quantum sensors can be made.

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Put horror movies and games aside for a few minutes to listen to something truly unsettling this Halloween season. The has released audio of what our planet’s magnetic field sounds like. While it protects us from cosmic radiation and charged particles from solar winds, it turns out that the magnetic field has an unnerving rumble.

You can’t exactly point a microphone at the sky and hear the magnetic field (nor can we see it). Scientists from the Technical University of Denmark collected by the ESA’s three Swarm satellites into sound, representing both the magnetic field and a solar storm.

The ethereal audio reminds me of wooden wind chimes rattling as a mass of land shifts, perhaps during an earthquake. It brings to mind the cracking sounds of a moving glacier as well. You might get something different out of the five-minute clip.

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