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Category: particle physics – Page 488

Four-charm tetraquark has been spotted at CERN

The first tetraquark comprising all charm quarks and antiquarks may have been spotted by physicists working on the LHCb experiment on the Large Hadron Collider (LHC) at CERN. The exotic hadron was discovered as it decayed into two J/ψ mesons, each of which is made from a charm quark and charm antiquark. The particle appears to be the first known tetraquark to be made entirely of “heavy quarks”, which are the charm and beauty quarks (but not the top quark, which is the heaviest quark but does not form hadrons).

“Particles made up of four quarks are already exotic, and the one we have just discovered is the first to be made up of four heavy quarks of the same type, specifically two charm quarks and two charm antiquarks,” explains Giovanni Passaleva, who is just stepping down as spokesperson for LHCb. “Up until now, the LHCb and other experiments had only observed tetraquarks with two heavy quarks at most and none with more than two quarks of the same type.”

The new tetraquark is dubbed X(6900), with the number referring to its mass of 6900 MeV/c2 (6.9 GeV/c2). The X denotes the fact that LHCb physicists are not yet certain about key properties of the particle including its spin, parity and quark content.

‘Hybrid’ Quantum Networking Demonstrated for First Time

In a world’s first, researchers in France and the U.S. have performed a pioneering experiment demonstrating “hybrid” quantum networking. The approach, which unites two distinct methods of encoding information in particles of light called photons, could eventually allow for more capable and robust communications and computing.

Similar to how classical electronics can represent information as digital or analog signals, quantum systems can encode information as either discrete variables (DVs) in particles or continuous variables (CVs) in waves. Researchers have historically used one approach or the other—but not both—in any given system.

“DV and CV encoding have distinct advantages and drawbacks,” says Hugues de Riedmatten of the Institute of Photonic Sciences in Barcelona, who was not a part of the research. CV systems encode information in the varying intensity, or phasing, of light waves. They tend to be more efficient than DV approaches but are also more delicate, exhibiting stronger sensitivity to signal losses. Systems using DVs, which transmit information by the counting of photons, are harder to pair with conventional information technologies than CV techniques. They are also less error-prone and more fault-tolerant, however. Combining the two, de Riedmatten says, could offer “the best of both worlds.”

A scheme to enhance how swarm robots search for multiple targets

Over the past decade or so, researchers have been trying to develop techniques that could enable effective collaborative strategies among teams of robots. One of the tasks that teams of robots could complete better than individual robots is simultaneously searching for several targets or objects in their surrounding environment.

The ability of a team of robots to collectively seek and identify numerous targets at once could be useful for a wide range of applications. For instance, it could aid surveillance applications and help to better track individuals or vehicles.

Researchers at Tongji University and University of Stuttgart have recently devised a systematic framework for enabling more effective multiple target search in swarm robots. This framework, presented in a paper published in IEEE Access, is based on the use of a mechanical particle swarm optimization method and artificial potential fields.

Atom-by-atom assembly makes for cheap, tuneable graphene nanoribbons

The wonder material graphene can take many forms for many different purposes, from transparent films that repel mosquitoes to crumpled balls that could boost the safety of batteries. One that has scientists particularly excited is nanoribbons for applications in energy storage and computing, but producing these ultra-thin strips of graphene has proven a difficult undertaking. Scientists are claiming a breakthrough in this area, devising a method that has enabled them to efficiently produce graphene nanoribbons directly on the surface of semiconductors for the first time.

As opposed to the sheets of carbon atoms arranged in honeycomb patterns that make up traditional graphene, graphene nanoribbons consist of thin strips just a handful of atoms wide. This material has great potential as a cheaper and smaller alternative to silicon transistors that would also run faster and use less power, or as electrodes for batteries that can charge in as little as five minutes.

“This is why many research groups around the world are focusing their efforts on graphene nanoribbons,” explains study author and chemist, Professor Konstantin Amsharov from Germany’s Martin Luther University of Halle-Wittenberg (MLU).

Mathematical Breakthrough Makes It Easier to Explore Quantum Entanglement

Updated mathematical techniques that can distinguish between two types of ‘non-Gaussian curve’ could make it easier for researchers to study the nature of quantum entanglement.

Quantum entanglement is perhaps one of the most intriguing phenomena known to physics. It describes how the fates of multiple particles can become entwined, even when separated by vast distances. Importantly, the probability distributions needed to define the quantum states of these particles deviate from the bell-shaped, or ‘Gaussian’ curves which underly many natural processes. Non-Gaussian curves don’t apply to quantum systems alone, however. They can also be composed of mixtures of regular Gaussian curves, producing difficulties for physicists studying quantum entanglement. In new research published in EPJ D, Shao-Hua Xiang and colleagues at Huaihua University in China propose a solution to this problem. They suggest an updated set of equations that allows physicists to easily check whether or not a non-Gaussian state is genuinely quantum.

As physicists make more discoveries about the nature of quantum entanglement, they are rapidly making progress towards advanced applications in the fields of quantum communication and computation. The approach taken in this study could prove to speed up the pace of these advances. Xiang and colleagues acknowledge that while all previous efforts to distinguish between both types of non-Gaussian curve have had some success, their choices of Gaussian curves as a starting point have so far meant that no one approach has yet proven to be completely effective. Based on the argument that there can’t be any truly reliable Gaussian reference for any genuinely quantum non-Gaussian state, the researchers present a new theoretical framework.