Andreas heinrich director of the IBS center for quantum nanoscience and distinguished professor at ewha womans university
Category: quantum physics – Page 625
A team of researchers affiliated with several institutions in China has succeeded in sending entangled quantum memories over a 50-kilometer coiled fiber cable. In their paper published in the journal Nature, the group describes several experiments they conducted involving entangling quantum memory over long distances, the challenges they overcame, and problems still to be addressed.
Over the past several years, scientists have been working toward the development of a quantum internet—one very much the same as the present-day network, but with much stronger security. One such approach is based on the development of quantum keys that would allow parties to a private conversation to know that an interloper is eavesdropping, because doing so would change the state of the keys. But in such systems, measurements of the quantum state of the keys is required, which can be impacted by environmental conditions, making the approach nearly impractical.
Another approach involves using entangled particles to form a network—but this has proven to be difficult to implement because of the sensitivity of such particles and their short lifespan. But progress is being made. In this new effort, the researchers in China succeeded in entangling quantum memory between buildings 20 kilometers apart and across 50 kilometers of coiled cable in their lab.
Quantum cascade lasers are compact, electrically pumped light sources in the technologically important mid-infrared and terahertz region of the electromagnetic spectrum1,2. Recently, the concept of topology3 has been expanded from condensed matter physics into photonics4, giving rise to a new type of lasing5,6,7,8 using topologically protected photonic modes that can efficiently bypass corners and defects4. Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime5,6,7,8. Here we demonstrate an electrically pumped terahertz quantum cascade laser based on topologically protected valley edge states9,10,11. Unlike topological lasers that rely on large-scale features to impart topological protection, our compact design makes use of the valley degree of freedom in photonic crystals10,11, analogous to two-dimensional gapped valleytronic materials12. Lasing with regularly spaced emission peaks occurs in a sharp-cornered triangular cavity, even if perturbations are introduced into the underlying structure, owing to the existence of topologically protected valley edge states that circulate around the cavity without experiencing localization. We probe the properties of the topological lasing modes by adding different outcouplers to the topological cavity. The laser based on valley edge states may open routes to the practical use of topological protection in electrically driven laser sources.
Researchers were able to demonstrate ‘spooky’ process happening at much bigger distances than ever before.
Brillouin scattering has applications ranging from signal processing1,2, sensing3 and microscopy4 to quantum information5 and fundamental science6,7. Most of these applications rely on the electrostrictive interaction between light and phonons3,7,8. Here we show that in liquids optically induced surface deformations can provide an alternative and far stronger interaction. This allows the demonstration of ultralow-threshold Brillouin lasing and strong phonon-mediated optical coupling. This form of strong coupling is a key capability for Brillouin-reconfigurable optical switches and circuits9,10, for photonic quantum interfaces11 and to generate synthetic electromagnetic fields12,13. While applicable to liquids quite generally, our demonstration uses superfluid helium. Configured as a Brillouin gyroscope14 this provides the prospect of measuring superfluid circulation with unprecedented precision, and exploring the rich physics of quantum fluid dynamics, from quantized vorticity to quantum turbulence15,16.
A basic rule of quantum physics is that knowing too much about an experiment will break quantum interference, but now physicists have discovered a way to bend that rule.
“The discovery of dark energy has greatly changed how we think about the laws of nature,” said Edward Witten, creator of string theory and one of the world’s leading theoretical physicist at the Institute for Advanced Study in Princeton, N.J. who has been compared to Newton and Einstein.
One of the great known unknowns of the universe is the nature of dark energy, a force field making the universe expand faster. Current theories range from end-of-the universe scenarios to dark energy as the manifestation of advanced alien life.
A new, controversial theory suggests that this dark energy might be getting stronger and denser, leading to a future in which atoms are torn asunder and time ends.
O.o.
New research has exploded the space of problems that quantum computers can efficiently verify, simultaneously knocking down milestone problems in quantum physics and math.