The pursuit of creating reliable, efficient, and cost-effective quantum dot sources has taken a significant leap forward with the latest discovery by an international research team. Led by Vikas Remesh from the University of Innsbruck’s Photonics Group, this breakthrough sidesteps limitations in previous approaches that relied on expensive and customized electro-optic modulators.

Visualize a microscopic quantum dot emitting multiple photons with different polarization states, demonstrating the power of stimulated two-photon excitation. The image should convey the elegance of this technique, which moves complexity from electronic components to optical excitation stage, making it more practical for real-world applications.

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The researchers’ innovative approach utilizes stimulated two-photon excitation to generate streams of photons in different polarization states directly from a quantum dot without requiring any active switching components. This method works by exciting the quantum dot with precisely timed laser pulses to create a biexciton state, followed by polarization-controlled stimulation pulses that deterministically trigger photon emission in the desired polarization.

The team’s demonstration of high-quality two-photon states with excellent single-photon properties marks a significant step forward in making quantum dot sources more practical for real-world applications. The technique has immediate implications for secure quantum key distribution protocols and multi-photon interference experiments, which are essential to testing fundamental principles of quantum mechanics.

As noted by Gregor Weihs, head of the photonics research group in Innsbruck, “The study has immediate applications in secure quantum key distribution protocols, where multiple independent photon streams can enable simultaneous secure communication with different parties, and in multi-photon interference experiments which are very important to test even the fundamental principles of quantum mechanics.”

The research represents a collaborative effort involving expertise in quantum optics, semiconductor physics, and photonic engineering. It was supported by the Austrian Science Fund (FWF), the Austrian Research Promotion Agency (FFG), and the European Union’s research programs.

This breakthrough has the potential to revolutionize photonic quantum computing, making it more efficient, cost-effective, and practical for real-world applications. The researchers envision extending this technique to generate photons with arbitrary linear polarization states using specially engineered quantum dots.

As researchers from Penn State and Colorado State have demonstrated, tiny gold “super atoms” could revolutionize the field of quantum computing. These clusters, which have a core of gold surrounded by other molecules called ligands, can mimic the properties of trapped atomic ions in a gas, allowing scientists to take advantage of these spin properties in a system that can be easily scaled up.

The researchers found that gold clusters can exhibit spin polarization, a property that is usually fixed in a material. This means that electrons in the cluster can be aligned with each other, making it possible to maintain their correlation for a longer time and remain accurate for much longer periods. The current state-of-the-art system for high accuracy and low error in quantum information systems involve trapped atomic ions — atoms with an electric charge — in a gaseous state.

The gold clusters, which can be synthesized relatively large amounts at one time, have the key properties needed to carry out spin-based operations. They can mimic the super-positions that are done in the trapped, gas-phase dilute ions, and have been identified as having 19 distinguishable and unique Rydberg-like spin-polarized states.

The researchers determined the spin polarization of the gold clusters using a similar method used with traditional atoms. While one type of gold cluster had 7% spin polarization, a cluster with different ligands approached 40% spin polarization, which is competitive with some of the leading two-dimensional quantum materials.

This research has opened up new possibilities for chemists to use their synthesis skills to design materials with tunable results, and could lead to breakthroughs in quantum computing and other fields. The researchers plan to explore how different structures within the ligands impact spin polarization and how they could be manipulated to fine tune spin properties.

In conclusion, tiny gold “super atoms” have the potential to revolutionize the field of quantum computing and could lead to breakthroughs in various fields.

As scientists continue to push the boundaries of what is possible, they stumble upon unexpected discoveries that challenge our understanding of the world. A recent breakthrough at the SLAC National Accelerator Laboratory has revealed the secret chemistry of gold, a metal once thought to be unreactive and boring. Researchers have successfully formed solid binary gold hydride, a compound made exclusively of gold and hydrogen atoms, under extreme conditions.

The team led by Mungo Frost, staff scientist at SLAC, was studying how hydrocarbons form diamonds under high pressure and heat. In their experiments at the European XFEL in Germany, they embedded gold foil into the samples to absorb X-rays and heat the weakly absorbing hydrocarbons. To their surprise, they not only observed the formation of diamonds but also discovered the formation of gold hydride.

“It was unexpected because gold is typically chemically very boring and unreactive — that’s why we use it as an X-ray absorber in these experiments,” said Mungo Frost. “These results suggest there’s potentially a lot of new chemistry to be discovered at extreme conditions where the effects of temperature and pressure start competing with conventional chemistry, and you can form these exotic compounds.”

The research team used a diamond anvil cell to squeeze hydrocarbon samples to pressures greater than those within Earth’s mantle and then heated them to over 3,500 degrees Fahrenheit using X-ray pulses from the European XFEL. This allowed them to resolve the structural transformations within the samples and observe how the gold lattice scattered X-rays.

The team found that under these extreme conditions, hydrogen was in a dense, superionic state, flowing freely through the gold’s rigid atomic lattice and increasing its conductivity. This phenomenon is not directly accessible through other experimental means, but studying it could provide new insights into nuclear fusion processes inside stars like our sun and help develop technology to harness fusion energy on Earth.

The discovery of gold hydride also opens up new avenues for exploring chemistry at extreme conditions. Gold, once thought to be unreactive, was found to form a stable compound with hydrogen under high pressure and temperature. This suggests that more research is needed to understand the properties of materials under these extreme conditions.

In addition to their findings on gold hydride, the team also developed simulation tools that could model other exotic material properties in extreme conditions. These tools have the potential to be applied beyond this specific study, offering new opportunities for researchers to explore and understand complex phenomena.

The research was conducted by an international team of scientists from SLAC National Accelerator Laboratory, European XFEL, DESY, Rostock University, Frankfurt University, Bayreuth University, Carnegie Institution for Science, Stanford University, and the Stanford Institute for Materials and Energy Sciences (SIMES). The work was supported by the DOE Office of Science.