At the annual APS Division of Atomic, Molecular and Optical Physics meeting, physicists made the case for a new way of modeling a universe.
Category: quantum physics – Page 395
How splitting sound might lead to a new kind of quantum computer
When you turn on a lamp to brighten a room, you are experiencing light energy transmitted as photons, which are small, discrete quantum packets of energy. These photons must obey the sometimes strange laws of quantum mechanics, which, for instance, dictate that photons are indivisible, but at the same time, allow a photon to be in two places at once.
Similar to the photons that make up beams of light, indivisible quantum particles called phonons make up a beam of sound. These particles emerge from the collective motion of quadrillions of atoms, much as a “stadium wave” in a sports arena is due to the motion of thousands of individual fans. When you listen to a song, you’re hearing a stream of these very small quantum particles.
Quantum Leap: Scientists Develop Promising Building Blocks for Photonic Quantum Simulators
Scientists at the Niels Bohr Institute, in cooperation with the University of Münster and Ruhr-Universität Bochum, developed new technology capable of processing the enormous amounts of information quantum systems generate. They’ve successfully linked deterministic single-photon.
A photon is a particle of light. It is the basic unit of light and other electromagnetic radiation, and is responsible for the electromagnetic force, one of the four fundamental forces of nature. Photons have no mass, but they do have energy and momentum. They travel at the speed of light in a vacuum, and can have different wavelengths, which correspond to different colors of light. Photons can also have different energies, which correspond to different frequencies of light.
A new type of quantum bit in semiconductor nanostructures
Researchers have created a quantum superposition state in a semiconductor nanostructure that might serve as a basis for quantum computing. The trick: two optical laser pulses that act as a single terahertz laser pulse.
A German-Chinese research team has successfully created a quantum bit in a semiconductor nanostructure. Using a special energy transition, the researchers created a superposition state in a quantum dot—a tiny area of the semiconductor—in which an electron hole simultaneously possessed two different energy levels. Such superposition states are fundamental for quantum computing.
However, excitation of the state would require a large-scale free-electron laser that can emit light in the terahertz range. Additionally, this wavelength is too long to focus the beam on the tiny quantum dot. The German-Chinese team has now achieved the excitation with two finely tuned short-wavelength optical laser pulses.
‘Quantum avalanche’ explains how nonconductors turn into conductors
Looking only at their subatomic particles, most materials can be placed into one of two categories.
Metals—like copper and iron—have free-flowing electrons that allow them to conduct electricity, while insulators —like glass and rubbe r— keep their electrons tightly bound and therefore do not conduct electricity.
Insulators can turn into metals when hit with an intense electric field, offering tantalizing possibilities for microelectronics and supercomputing, but the physics behind this phenomenon called resistive switching is not well understood.
Record-Breaking Quantum Contextuality Observed in Single System
A team of scientists studied the single-system version of multipartite Bell nonlocality, and observed the highest degree of quantum contextuality in a single system. Their work was published in Physical Review Letters.
Physical Review Letters (PRL) is a peer-reviewed scientific journal published by the American Physical Society. It is one of the most prestigious and influential journals in physics, with a high impact factor and a reputation for publishing groundbreaking research in all areas of physics, from particle physics to condensed matter physics and beyond. PRL is known for its rigorous standards and short article format, with a maximum length of four pages, making it an important venue for rapid communication of new findings and ideas in the physics community.
Error Rate Reduced for Scalable Quantum Technology
A scalable system for controlling quantum bits demonstrates a very low error rate, which is essential for making practical devices.
A major obstacle to the development of practical quantum computers is the difficulty of scaling up—making a device with large numbers of quantum bits (qubits) that also gives accurate results in the presence of environmental noise. Now researchers report a significant improvement in the accuracy of a technology that is already known to be much easier to scale up than conventional techniques [1]. This alternative technology uses units of magnetic flux called flux quanta to control conventional superconducting qubits. The reduction in the error rate came from physically separating the control circuits from the qubits. With further refinement, the flux-quanta technology could provide a superior pathway to practical quantum computation.
Many current efforts to carry out quantum logic operations—the basic units of computation—use short microwave pulses to control the qubits. Currently, however, this technology is difficult to scale up beyond 1,000 qubits. But the presence of environmental noise requires error-correction methods that rely on large numbers of qubits, perhaps a million or more, for an effective error-correcting system that performs useful computations, according to some estimates.
Researchers observe strongest quantum contextuality in single system
A team led by Prof. Li Chuanfeng and Prof. Xu Jinshi from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), collaborating with Prof. Chen Jingling from Nankai University and Prof. Adán Cabello from the University of Seville, studied the single-system version of multipartite Bell nonlocality, and observed the highest degree of quantum contextuality in single system. Their work was published in Physical Review Letters.
Quantum contextuality refers to the phenomenon that the measurements of quantum observables cannot be simply considered as revealing preexisting properties. It is a distinctive feature in quantum mechanics and a crucial resource for quantum computation. Contextuality defies noncontextuality hidden-variable theories and is closely linked to quantum nonlocality.
In multipartite systems, quantum nonlocality arises as the result of the contradiction between quantum contextuality and noncontextuality hidden-variable theories. The extent of nonlocality can be measured by the violation of Bell inequality and previous researches showed that the violation increases exponentially with the number of quantum bits involved. However, while single-particle high-dimensional system offers more possibilities for measurements compared to multipartite systems, the quest to enhance contextual correlation’s robustness remains an ongoing challenge.