The lab test suggests a reliable quantum internet between cities might be possible.
Category: quantum physics – Page 690
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.
Circa 2019
Researchers at Delft University of Technology have created a quantum circuit to listen to the weakest radio signal allowed by quantum mechanics. This new quantum circuit opens the door to possible future applications in areas such as radio astronomy and medicine (MRI). It also enables experiments to shed light on the interplay between quantum mechanics and gravity. The results have been published in Science.
The usual solution to a weak radio signal is to find a bigger signal, for instance, by picking a different radio station or by moving to the other side of the room. However, m what if we could just listen more carefully?
Weak radio signals are not just a challenge for people trying to find their favourite radio station, but also for magnetic resonance imaging (MRI) scanners at hospitals, as well as for the telescopes scientists use to peer into space. In a quantum leap in radio frequency detection, researchers in the group of Prof. Gary Steele in Delft demonstrated the detection of photons or quanta of energy, the weakest signals allowed by the theory of quantum mechanics.
Newly created artificial atoms on a silicon chip could become the new basis for quantum computing.
Engineers in Australia have found a way to make these artificial atoms more stable, which in turn could produce more consistent quantum bits, or qubits — the basic units of information in a quantum system.
The research builds on previous work by the team, wherein they produced the very first qubits on a silicon chip, which could process information with over 99 percent accuracy. Now, they have found a way to minimise the error rate caused by imperfections in the silicon.