String theory is widely considered beyond empirical investigation. But we could conceivably test it thanks to ancient particles called moduli, which might appear in astronomical observations, says theorist Joseph Conlon.
Category: quantum physics – Page 298
Scientists closer to solving mysteries of universe after measuring gravity in quantum world
Scientists are a step closer to unravelling the mysterious forces of the universe after working out how to measure gravity on a microscopic level.
Experts have never fully understood how the force which was discovered by Isaac Newton works in the tiny quantum world.
Even Einstein was baffled by quantum gravity and, in his theory of general relativity, said there is no realistic experiment which could show a quantum version of gravity.
Surface Acoustic Wave Cavity Optomechanics with Atomically Thin $h$-BN and mathrmWSe_2$ Single-Photon Emitters
In pursuing quantum networking technologies, single-photon emitters in acoustic cavities are a promising pathway that enables the conversion and transfer of quantum information across multiple platforms. The recent discovery of single-photon emitters within two-dimensional (2D) materials, such as WSe and hexagonal boron nitride (h-BN), opens new avenues in exploring such quantum optomechanical phenomena in lower dimensional systems. In this work, we demonstrate the integration of 2D-based single-photon emitters with surface acoustic wave optomechanical cavities and illustrate their potential for radio-frequency electronic control of quantum light emission.
Using simple exfoliation techniques, WSe and h-BN layers are transferred onto surface acoustic wave cavities patterned on lithium niobate—a highly piezoelectric host material. Using electro-optical measurements, we confirm high-quality resonators and cavity-phonon modes that couple to the 2D quantum emitters. Remarkably, the interaction between the 2D emitters and acoustic waves is exceptionally strong owing to the ultrathin nature of the 2D materials and their proximity to the surface waves, verified through quantum spectroscopy measurements. In addition to the radio-frequency acoustic modulation of the emitters in these materials, new physics emerges from the emitter-phonon coupling that leads to new mechanisms for high-speed manipulation of quantum emitters, opening avenues for the generation of entangled-photon pairs.
These advancements set the stage for the exploration of cavity optomechanics with 2D materials. In future experiments, higher frequency resonators will enable studies of the interplay and dynamics between single photons and phonons deep in the quantum regime, a key technology for quantum networking.
The Dual-Laser Revolution: A New Design for Quantum Computers
Creating a quantum computer powerful enough to tackle problems we cannot solve with current computers remains a big challenge for quantum physicists. A well-functioning quantum simulator – a specific type of quantum computer – could lead to new discoveries about how the world works at the smallest scales. Quantum scientist Natalia Chepiga from Delft University of Technology has developed a guide on how to upgrade these machines so that they can simulate even more complex quantum systems. The study is now published in Physical Review Letters.
“Creating useful quantum computers and quantum simulators is one of the most important and debated topics in quantum science today, with the potential to revolutionize society,” says researcher Natalia Chepiga. Quantum simulators are a type of quantum computer, Chepiga explains: “Quantum simulators are meant to address open problems of quantum physics to further push our understanding of nature. Quantum computers will have wide applications in various areas of social life, for example in finances, encryption, and data storage.”
Steering Wheel
Quantum Breakthrough in High-Temperature Superconductivity
An international team of scientists has made a new discovery that may help to unlock the microscopic mystery of high-temperature superconductivity and address the world’s energy problems.
In a paper published in the journal Nature, Swinburne University of Technology’s Associate Professor Hui Hu collaborated with researchers at the University of Science and Technology of China (USTC) in a new experimental observation quantifying the pseudogap pairing in a strongly attractive interacting cloud of fermionic lithium atoms.
A single atom could drive a piston in a quantum engine
In a quantum engine, a single atom can emit radiation that bounces around a reflective cavity and creates enough pressure to push down a piston.
Microscopic Origin of the Entropy of Black Holes in General Relativity
In the 1970s, physicists Bekenstein and Hawking used general relativity and quantum mechanics in curved spacetime to propose that black holes behave as thermodynamic objects. They found that black holes carry an entropy described by a remarkable formula that applies for any mass, charge, angular momentum, or spacetime dimension. Here, we use new results at the interface of quantum information theory and quantum gravity to address an outstanding challenge: how to explain the microscopic origin of this formula.
In quantum mechanics, entropy measures the logarithm of the dimension of the space of microstates consistent with the macroscopic description of a system. We show that, in any theory of gravity that reduces to general relativity with matter at low energies, there are infinite families of states that have geometries identical to the black hole outside the horizon but different structures inside. We show that these states overlap quantum mechanically because of gravitational wormholes. The overlaps have a dramatic consequence: The microstates span a space whose dimension equals the exponential of the Bekenstein-Hawking entropy formula.
This explanation of black-hole entropy does not require new forms of matter and involves a novel description of all black-hole microstates as quantum superpositions of objects having geometric semiclassical descriptions. Our results also imply a macroscopic manifestation of quantum mechanics in cosmic settings: We show that one can understand long Einstein-Rosen bridges between universes as quantum superpositions of short bridges.
Scientists discover exotic quantum interference effect in a topological insulator device
In a novel experiment, physicists have observed long range quantum coherence effects due to Aharonov-Bohm interference in a topological insulator-based device. This finding opens up a new realm of possibilities for the future development of topological quantum physics and engineering.
This finding could also affect the development of spin-based electronics, which may potentially replace some current electronic systems for higher energy efficiency and may provide new platforms to explore quantum information science.
The research, published in the February 20 issue of Nature Physics, is the culmination of more than 15 years of work at Princeton. It came about when Princeton scientists developed a quantum device —called a bismuth bromide (α-Bi4Br4) topological insulator—only a few nanometers thick and used it to investigate quantum coherence.