Lifeboat Foundation

For the first time, researchers have demonstrated a way to map and measure large-scale photonic quantum correlation with single-photon sensitivity. The ability to measure thousands of instances of quantum correlation is critical for making photon-based quantum computing practical.

In Optica, The Optica l Society’s journal for high impact research, a multi-institutional group of researchers reports the new measurement technique, which is called correlation on spatially-mapped photon-level image (COSPLI). They also developed a way to detect signals from single photons and their correlations in tens of millions of images.

“COSPLI has the potential to become a versatile solution for performing quantum particle measurements in large-scale photonic quantum computers,” said the research team leader Xian-Min Jin, from Shanghai Jiao Tong University, China. “This unique approach would also be useful for quantum simulation, quantum communication, quantum sensing and single-photon biomedical imaging.”

Building a quantum computer requires reckoning with errors—in more than one sense. Quantum bits, or “qubits,” which can take on the logical values zero and one simultaneously, and thus carry out calculations faster, are extremely susceptible to perturbations. A possible remedy for this is quantum error correction, which means that each qubit is represented redundantly in several copies, such that errors can be detected and eventually corrected without disturbing the fragile quantum state of the qubit itself. Technically, this is very demanding. However, several years ago, an alternative proposal suggested storing information not in several redundant qubits, but rather in the many oscillatory states of a single quantum harmonic oscillator. The research group of Jonathan Home, professor at the Institute for Quantum Electronics at ETH Zurich, has now realised such a qubit encoded in an oscillator. Their results have been published in the scientific journal Nature.

Periodic oscillatory states

In Home’s laboratory, Ph.D. student Christa Flühmann and her colleagues work with electrically charged calcium atoms that are trapped by electric fields. Using appropriately chosen laser beams, these ions are cooled down to very low temperatures at which their oscillations in the electric fields, inside which the ions slosh back and forth like marbles in a bowl, are described by quantum mechanics as so-called wave functions. “At that point, things get exciting,” says Flühmann, who is first author of the Nature paper. “We can now manipulate the oscillatory states of the ions in such a way that their position and momentum uncertainties are distributed among many periodically arranged states.”

System hides cold ions from cooling laser, allowing hot ions to be selectively cooled.

The countdown to the arrival of quantum computing has already begun. Here’s how the government can get ready.

Long story short, qubits need a better immune system before they can grow up.

A new material, engineered by Purdue University researchers into a thin strip, is one step closer to “immunizing” qubits against noise, such as heat and other parts of a computer, that interferes with how well they hold information. The work appears in Physical Review Letters.

The thin strip, called a “nanoribbon,” is a version of a material that conducts electrical current on its surface but not on the inside — called a “topological insulator” — with two superconductor electrical leads to form a device called a “Josephson junction.”

Do our minds have quantum structures that give rise to consciousness? Sir Roger Penrose, one of the world’s most famous scientists, believes this and can explain how it works.

Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons in these materials have exotic, so-called topological behaviors and others behave somewhat like graphene, another material prized for its potential for new types of electronics.

Now, an international team led by researchers at Princeton University has observed that some of the electrons in these magnets behave collectively, like an almost infinitely massive electron that is strangely magnetic, rather than like individual particles. The study was published in the journal Nature Physics this week.

The team also showed that placing the kagome magnet in a high magnetic field causes the direction of magnetism to reverse. This “negative magnetism” is akin to having a compass that points south instead of north, or a refrigerator magnet that suddenly refuses to stick.

A team of Cambridge researchers have found a way to control the sea of nuclei in semiconductor quantum dots so they can operate as a quantum memory device.

Quantum dots are crystals made up of thousands of atoms, and each of these atoms interacts magnetically with the trapped electron. If left alone to its own devices, this interaction of the electron with the nuclear spins, limits the usefulness of the electron as a quantum bit—a qubit.

Led by Professor Mete Atatüre, a Fellow at St John’s College, University of Cambridge, the research group, located at the Cavendish Laboratory, exploit the laws of quantum physics and optics to investigate computing, sensing or communication applications.

Continue reading “Physicists get thousands of semiconductor nuclei to do ‘quantum dances’ in unison” »

Barely a week goes by without reports of some new mega-hack that’s exposed huge amounts of sensitive information, from people’s credit card details and health records to companies’ valuable intellectual property. The threat posed by cyberattacks is forcing governments, militaries, and businesses to explore more secure ways of transmitting information.