Researchers Kazuaki Takasan and Kyogo Kawaguchi of the University of Tokyo with Kyosuke Adachi of RIKEN, Japan, have demonstrated that ferromagnetism, an ordered state of atoms, can be induced by increasing particle motility and that repulsive forces between atoms are sufficient to maintain it.

The discovery not only extends the concept of active matter to quantum systems but also contributes to the development of novel technologies that rely on the magnetic properties of particles, such as magnetic memory and quantum computing. The findings were published in the journal Physical Review Research.

Flocking birds, swarming bacteria, cellular flows. These are all examples of active matter, a state in which individual agents, such as birds, bacteria, or cells, self-organize. The agents change from a disordered to an ordered state in what is called a “phase transition.” As a result, they move together in an organized fashion without an external controller.

An international collaboration of researchers, led by Philip Walther at University of Vienna, have achieved a significant breakthrough in quantum technology, with the successful demonstration of quantum interference among several single photons using a novel resource-efficient platform. The work published in the prestigious journal Science Advances represents a notable advancement in optical quantum computing that paves the way for more scalable quantum technologies.

Interference among photons, a fundamental phenomenon in quantum optics, serves as a cornerstone of optical quantum computing. It involves harnessing the properties of light, such as its wave-particle duality, to induce interference patterns, enabling the encoding and processing of quantum information.

In traditional multi-photon experiments, spatial encoding is commonly employed, wherein photons are manipulated in different spatial paths to induce interference. These experiments require intricate setups with numerous components, making them resource-intensive and challenging to scale.

Entanglement is a form of correlation between quantum objects, such as particles at the atomic scale. The laws of classical physics cannot explain this uniquely quantum phenomenon, yet it is one of the properties that explain the macroscopic behavior of quantum systems.

Because entanglement is central to the way quantum systems work, understanding it better could give scientists a deeper sense of how information is stored and processed efficiently in such systems.

Qubits, or quantum bits, are the building blocks of a quantum computer. However, it is extremely difficult to make specific entangled states in many-qubit systems, let alone investigate them. There are also a variety of entangled states, and telling them apart can be challenging.

Photonic quantum computers are computational tools that leverage quantum physics and utilize particles of light (i.e., photons) as units of information processing. These computers could eventually outperform conventional quantum computers in terms of speed, while also transmitting information across longer distances.

Despite their promise, photonic quantum computers have not yet reached the desired results, partly due to the inherently weak interactions between individual photons. In a paper published in Physical Review Letters, researchers at University of Science and Technology of China demonstrated a large cluster state that could facilitate quantum computation in a photonic system, namely three-photon entanglement.

“Photonic quantum computing holds promise due to its operational advantages at room temperature and minimal decoherence,” Hui Wang, co-author of the paper, told Phys.org.