Hong–Ou–Mandel experiments on a quantum photonic chip demonstrate on-chip quantum interference of indistinguishable single photons with visibilities exceeding 0.97 for two molecules separately coupled to two waveguides.
Category: computing – Page 9
Two independent quantum networks successfully fused into one
Many quantum researchers are working toward building technologies that allow for the existence of a global quantum internet, in which any two users on Earth would be able to conduct large-scale quantum computing and communicate securely with the help of quantum entanglement. Although this requires many more technological advancements, a team of researchers at Shanghai Jiao Tong University in China have managed to merge two independent networks, bringing the world a bit closer to realizing a quantum internet.
A true global quantum internet will require interconnectivity between many networks, and this has proven to be a much more difficult task for quantum networks than it is for classical networks. While researchers have demonstrated the ability to connect quantum computers within the same network, multi-user fusion remains a major challenge. Fully connected networks using dense wavelength division multiplexing (DWDM) have been achieved, but have scalability and complexity issues.
However, the research team involved in the new study, published in Nature Photonics, has merged two independent networks with 18 different users. All 18 users can communicate securely using entanglement-based protocols using this method. This represents the most complex multi-user quantum network to date.
Ultra-thin 3D display delivers wide-angle, highly-detailed images
Researchers have developed an ultra-thin 3D display with a wide viewing angle, clear image quality and vivid display depth. By overcoming tradeoffs that typically limit glasses-free 3D displays, the advance could open new possibilities for highly detailed interactive experiences in health care, education and entertainment.
“The new display is just 28 mm thick, dramatically slimmer than conventional directional backlight systems, which typically exceed 500 mm,” said research team leader Xu Liu, from Zhejiang University in China. “This level of compactness, combined with the substantial boost in resolution we achieved, represents an important step toward making the technology practical for real-world products.”
In Optica, the researchers demonstrate an ultra-slim 32-inch directional backlight-based prototype based on the new display design. The prototype is roughly the size of a large computer monitor, has a wide viewing angle of over 120° and a large 3D display volume of 28 × 16 × 39 inches.
Scientists reveal it is feasible to send quantum signals from Earth to a satellite
Quantum satellites currently beam entangled particles of light from space down to different ground stations for ultra-secure communications. New research shows it is also possible to send these signals upward, from Earth to a satellite; something once thought unfeasible.
This breakthrough overcomes significant barriers to current quantum satellite communications. Ground station transmitters can access more power, are easier to maintain and could generate far stronger signals, enabling future quantum computer networks using satellite relays.
The study, “Quantum entanglement distribution via uplink satellite channels”, by Professor Simon Devitt, Professor Alexander Solntsev and a research team from the University of Technology Sydney (UTS), is published in the journal Physical Review Research.
Stellar Giants Forged the Chemical Diversity of Ancient Clusters
“Extremely massive stars may have played a key role in the formation of the first galaxies,” said Dr. Paolo Padoan.
How did the extremely massive stars (EMS) in the early universe help form the oldest star clusters? This is what a recent study published in the Monthly Notices of the Royal Astronomical Society hopes to address as an international team of scientists investigated the role that EMS played in not only forming globular clusters (GCs), but how the latter were responsible for forming the first black holes. This study has the potential to help scientists better understand the conditions of the early universe and what this could mean to better understanding our existence.
For the study, the researchers presented a new computational model to help explain how EMS contributed to GC formation with bodies celestial objects being between 1,000 to 10,000 times as massive as our Sun and containing hundreds of thousands to millions of stars, respectively. Given the massive sizes and short lifetimes of EMS, they go supernova when they die, and the new model postulates they become black holes while releasing massive amounts of chemical and hydrogen that mixes with surrounding gas and dust, resulting in the formation of GCs. Additionally, data obtained from NASA’s James Webb Space Telescope (JWST) discovered nitrogen-rich galaxies had chemical signatures obtained from GCs.
Women perceive sleek and shiny hair as healthier and more youthful, study finds
Straight-aligned hair paired with higher shine evokes the appearance of greater youth, health, and attractiveness, according to researchers at The Procter & Gamble Company, which owns several brands of hair care products, including ones designed to make hair shinier.
Studies on appearance often center on facial shape and skin condition. Previous studies also note that skin topography and coloration can influence judgments of age, health, and attractiveness across populations. Facial studies often remove hair cues to avoid biasing feature focused framing of perception.
Hair holds social cues that observers can read quickly. Work with computer-rendered hair has tied diameter, density, style, and color to shifts in perceived age, health, and attractiveness, and some studies previously associated healthier-looking hair with the appearance of better reproductive health.
Light can reshape atom-thin semiconductors for next-generation optical devices
Rice University researchers studying a class of atom-thin semiconductors known as transition metal dichalcogenides (TMDs) have discovered that light can trigger a physical shift in their atomic lattice, creating a tunable way to adjust the materials’ behavior and properties.
The effect, observed in a TMD subtype named after the two-faced Roman god of transitions, Janus, could advance technologies that use light instead of electricity, from faster and cooler computer chips to ultrasensitive sensors and flexible optoelectronic devices.
“In nonlinear optics, light can be reshaped to create new colors, faster pulses or optical switches that turn signals on and off,” said Kunyan Zhang, a Rice doctoral alumna who is a first author on a study documenting the effect. “Two-dimensional materials, which are only a few atoms thick, make it possible to build these optical tools on a very small scale.”
Optimizing avalanche photodiode design for photodetection in the ultraviolet wavelength
Geiger-mode avalanche photodiodes (GM-APDs) are highly sensitive light detectors, capable of detecting single photons. Photons of certain wavelengths, when absorbed by photodiodes, generate electron-hole pairs in a process called impact ionization which can result in a multiplication of charges when occurring in an electric field.
An avalanche photodiode is biased above its “breakdown voltage,” at which point impact ionizations reach a self-sustaining rate, resulting in a distinct electrical pulse that is readily detectable. To detect single photons in the presence of other mechanisms that generate impact ionization, the avalanche diode must simultaneously have a high probability to absorb incident photons of the desired wavelength, known as the unity-gain quantum efficiency (QE). Both being able to support high fields and having good QE at the desired wavelength are critical factors in determining the device’s sensitivity.
Certain GM-APDs based on 4H-silicon carbide (4H-SiC) have high single-photon detection efficiency in the deep-ultraviolet (DUV) wavelengths around 280 nanometers. To reliably detect photons at higher wavelengths where absorption is weaker, SiC GM-APDs need to improve their baseline photon capture efficiency, as indicated by its unity-gain QE. To accomplish this, researchers often employ APDs with much thicker absorber layers. However, this can often lead to design challenges.