Lifeboat Foundation

Quanta of light—photons—form the basis of quantum key distribution in modern cryptographic networks. Before the huge potential of quantum technology is fully realized, however, several challenges remain. A solution to one of these has now been found.

In a paper published in the journal Science, teams led by David Novoa, Nicolas Joly and Philip Russell report a breakthrough in frequency up-conversion of single photons, based on a hollow-core photonic crystal fiber (PCF) filled with hydrogen gas. First a spatio-temporal hologram of molecular vibrations is created in the gas by stimulated Raman scattering. This hologram is then used for highly efficient, correlation-preserving frequency conversion of single photons. The system operates at a pressure-tuneable wavelength, making it potentially interesting for quantum communications, where efficient sources of indistinguishable single-photons are unavailable at wavelengths compatible with existing fiber networks.

The approach combines quantum optics, gas-based nonlinear optics, hollow-core PCF, and the physics of molecular vibrations to form an efficient tool that can operate in any spectral band from the ultraviolet to the mid-infrared—an ultra-broad working range inaccessible to existing technologies. The findings may be used to develop fiber-based tools in technologies such as quantum communications, and quantum-enhanced imaging.

Physicists from Paderborn University have developed a novel concept for generating individual photons—tiny particles of light that make up electromagnetic radiation—with tailored properties, the controlled manipulation of which is of fundamental importance for photonic quantum technologies. The findings have now been published in the journal Nature Communications.

Professor Artur Zrenner, head of the “nanostructure optoelectronics” research group, explains how tailored desired states have so far posed a challenge: “Corresponding sources are usually based on light emissions from individual semiconductor quantum emitters, which generate the photons. Here, the properties of the emitted photons are defined by the fixed properties of the quantum emitter, and can therefore not be controlled with full flexibility.”

To get around the problem, the scientists have developed an all-optical, non-linear method to tailor and control single photon emissions. Based on this concept, they demonstrate laser-guided energy tuning and polarization control of photons (i.e., the light frequency and direction of oscillation of electromagnetic waves).

Future quantum computers are expected not only to solve particularly tricky computing tasks, but also to be connected to a network for the secure exchange of data. In principle, quantum gates could be used for these purposes. But until now, it has not been possible to realize them with sufficient efficiency. By a sophisticated combination of several techniques, researchers at the Max Planck Institute of Quantum Optics (MPQ) have now taken a major step towards overcoming this hurdle.

For decades, computers have been getting faster and more powerful with each new generation. This development makes it possible to constantly open up new applications, for example in systems with artificial intelligence. But further progress is becoming increasingly difficult to achieve with established computer technology. For this reason, researchers are now setting their sights on alternative, completely new concepts that could be used in the future for some particularly difficult computing tasks. These concepts include quantum computers.

Their function is not based on the combination of digital zeros and ones—the classical bits—as is the case with conventional, microelectronic computers. Instead, a quantum computer uses quantum bits, or qubits for short, as the basic units for encoding and processing information. They are the counterparts of bits in the quantum world—but differ from them in one crucial feature: qubits can not only assume two fixed values or states such as zero or one, but also any values in between. In principle, this offers the possibility to carry out many computing processes simultaneously instead of processing one logical operation after the other.

The digital device you are using to view this article is no doubt using the bit, which can either be 0 or 1, as its basic unit of information. However, scientists around the world are racing to develop a new kind of computer based on the use of quantum bits, or qubits, which can simultaneously be 0 and 1 and could one day solve complex problems beyond any classical supercomputers.

A research team led by scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, in close collaboration with FAMU-FSU College of Engineering Associate Professor of Mechanical Engineering Wei Guo, has announced the creation of a new qubit platform that shows great promise to be developed into future quantum computers. Their work is published in the journal Nature.

“Quantum computers could be a revolutionary tool for performing calculations that are practically impossible for classical computers, but there is still work to do to make them reality,” said Guo, a paper co-author. “With this research, we think we have a breakthrough that goes a long way toward making qubits that help realize this technology’s potential.”

Over the years, supercomputers have played a pivotal role in pushing the frontiers of science. Earlier this year, Meta launched one of the fastest AI supercomputers, the AI Research SuperCluster (RSC), to build sophisticated AI models that can learn from trillions of examples; navigate hundreds of different languages; seamlessly analyse text, images, and video together; build AR tools etc.

However, the quest for something even faster than supercomputers led to the development of quantum computers. Last year, the University of Science and Technology of China (USTC) introduced the world’s fastest programmable superconducting quantum computer; Zuchongzhi 2.1 is a million times faster than a conventional computer.

At last year’s I/O conference, Google unveiled a Quantum AI campus in Santa Barbara, California, complete with a quantum data centre, quantum hardware research labs, and quantum processor chip fab facilities. The tech giant plans to build a useful, error-corrected quantum computer within a decade.

Quantum computing operations are realized using acoustic devices, paving the way for a new type of quantum processor.

Very thin wires made of a topological insulator could enable highly stable qubits, the building blocks of future quantum computers. Scientists see a new result in topological insulator devices as an important step towards realizing the technology’s potential.

An international group of scientists have demonstrated that wires more than 100 times thinner than a human hair can act like a quantum one-way street for electrons when made of a peculiar material known as a topological insulator.

The discovery opens the pathway for new technological applications of devices made from topological insulators and demonstrates a significant step on the road to achieving so-called topological qubits, which it has been predicted can robustly encode information for a quantum computer.

Over the past decades, electronics engineers and material scientists worldwide have been investigating the potential of various materials for fabricating transistors, devices that amplify or switch electrical signals in electronic devices. Two-dimensional (2D) semiconductors have been known to be particularly promising materials for fabricating the new electronic devices.

Despite their advantages, the use of these materials in electronics greatly depends on their integration with high-quality dielectrics, insulating materials or materials that are poor conductors of electrical current. These materials, however, can be difficult to deposit on 2D semiconductor substrates.

Researchers at Nanyang Technological University, Peking University, Tsinghua University, and the Beijing Academy of Quantum Information Sciences have recently demonstrated the successful integration of single-crystal strontium titrate, a high-κ perovskite oxide, with 2D semiconductors, using van der Waals forces. Their paper, published in Nature Electronics, could open new possibilities for the development of new types of transistors and electronic components.

Some materials, like wood, are insulators that block the flow of electricity. Conductors, such as copper, allow for electricity to flow through them. Other materials—semiconductors—can be either/or depending on conditions such as applied electric field or temperature. Unlike wood or copper or silicon, though, topological insulators (TIs) are an exotic state of matter that is conductive on the surface, but not in the bulk. Such unique material properties have great scientific implications and could be of use in a range of technologies, including wireless communications, radar and quantum information processing.

Through a collaborative effort, the research labs of Aravind Nagulu, assistant professor in the Preston M. Green Department of Electrical & Systems Engineering at Washington University in St. Louis, and colleagues from Columbia University and the City University of New York’s Advanced Science Research Center have demonstrated the first implementation of an electromagnetic topological insulator on an integrated chip.

The collaborative project’s findings were published May 2 in the journal Nature Electronics.