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A new unified theory for heat transport accurately describes a wide range of materials – from crystals and polycrystalline solids to alloys and glasses – and allows them to be treated in the same way for the first time. The methodology, which is based on the Green-Kubo theory of linear response and concepts from lattice dynamics, naturally accounts for quantum mechanical effects and thus allows for the predictive modelling of heat transport in glasses at low temperature – a feat never achieved before, say the researchers who developed it. It will be important for better understanding and designing heat transporting devices in a host of applications, from heat management in high-power electronics, batteries and photovoltaics to thermoelectric energy harvesting and solid-state cooling. It might even help describe heat flow in planetary systems.

“Heat transport is the fundamental mechanism though which thermal equilibrium is reached,” explains Stefano Baroni of the Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Trieste, Italy, who led this research effort. “It can also be thought of as the most fundamental manifestation of irreversibility in nature – as heat flows from warm areas in the same system to cooler ones as time flows from the past to the future (the ‘arrow of time’). What is more, many modern technologies rely on our ability to control heat transport.”

However, despite its importance, heat transport is still poorly understood and it is difficult to simulate the heat transport of materials because of this lack of understanding. To overcome this knowledge gap, researchers employ various simulation techniques based on diverse physical assumptions and approximations for different classes of material – crystals on one hand and disordered solids and liquids on the other.

A handful of spins in diamond have shone new light on one of the most enduring mysteries in physics – how the objective reality of classical physics emerges from the murky, probabilistic quantum world. Physicists in Germany and the US have used nitrogen-vacancy (NV) centres in diamond to demonstrate “quantum Darwinism”, whereby the “fittest” states of a system survive and proliferate in the transition between the quantum and classical worlds.

In the past, physicists tended to view the classical and quantum worlds as being divided by an abrupt barrier that makes a fundamental distinction between the familiar macroscopic (classical) and the unfamiliar microscopic (quantum) realms. But in recent decades that view has changed. Many experts now think that the transition is gradual, and that the definite classical states we measure come from probabilistic quantum states progressively (although very quickly) losing their coherence as they become ever more entangled with their environment.

Quantum Darwinism, put forward by Wojciech Zurek of Los Alamos National Laboratory in New Mexico, argues that the classical states we perceive are robust quantum states that can survive entanglement during decoherence. His theoretical framework posits that the information about these states will be duplicated many times and disseminated throughout the environment. Just as natural selection tells us that the fittest individuals in a species must survive to reproduce in great numbers and so go on to shape evolution, the fittest quantum states will be copied and appear classical. This redundancy means that many individual observers will measure any given state as having the same value, so ensuring objective reality.

Time has a fundamentally different character in quantum mechanics and when in general relativity. In quantum theory, events develop in a fixed order while in general relativity temporal order is affected by the distribution of matter.

Now, a team of international scientists has discovered a new kind of quantum time order. Through this study, scientists sought to determine: what happens when an object massive enough to influence the flow of time is placed in a quantum state?

The disclosure emerged from a test the group intended to bring together elements of the two significant physics theories developed in the past century.

A team of researchers has just demonstrated quantum enhancement in an actual X-ray machine, achieving the desirable goal of eliminating background noise for precision detection.

The relationships between photon pairs on quantum scales can be exploited to create sharper, higher-resolution images than classical optics. This emerging field is called quantum imaging, and it has some really impressive potential — particularly since, using optical light, it can be used to show objects that can’t usually be seen, like bones and organs.

Quantum correlation describes a number of different relationships between photon pairs. Entanglement is one of these, and is applied in optical quantum imaging.

The quantum internet promises absolutely tap-proof communication and powerful distributed sensor networks for new science and technology. However, because quantum information cannot be copied, it is not possible to send this information over a classical network. Quantum information must be transmitted by quantum particles, and special interfaces are required for this. The Innsbruck-based experimental physicist Ben Lanyon, who was awarded the Austrian START Prize in 2015 for his research, is investigating these important intersections of a future quantum Internet.

Now his team at the Department of Experimental Physics at the University of Innsbruck and at the Institute of Quantum Optics and Quantum Information of the Austrian Academy of Sciences has achieved a record for the transfer of quantum entanglement between matter and light. For the first time, a distance of 50 kilometers was covered using fiber optic cables. “This is two orders of magnitude further than was previously possible and is a practical distance to start building inter-city quantum networks,” says Ben Lanyon.

This week a collaborative effort among computer scientists and academics to safeguard data is winning attention and it has quantum computing written all over it.

The Netherlands’ Centrum Wiskunde & Informatica (CWI), national research institute for mathematics and computer science, had the story: IBM Research developed “quantum-safe algorithms” for securing data. They have done so by working with international partners including CWI and Radboud University in the Netherlands.

IBM and partners share concerns that data protected by current encryption methods may become insecure within the next 10 to 30 years.

Ultra-low-loss metal films with high-quality single crystals are in demand as the perfect surface for nanophotonics and quantum information processing applications. Silver is by far the most preferred material due to low-loss at optical and near infrared (near-IR) frequencies. In a recent study now published on Scientific Reports, Ilya A. Rodionov and an interdisciplinary research team in Germany and Russia reported a two-step approach for electronic beam evaporation of atomically smooth single crystalline metal films. They proposed a method to establish thermodynamic control of the film growth kinetics at the atomic level in order to deposit state-of-the-art metal films.

The researchers deposited 35 to 100 nm thick, single-crystalline silver films with sub-100 picometer (pm) surface roughness with theoretically limited optical losses to form ultrahigh-Q nanophotonic devices. They experimentally estimated the contribution of material purity, material grain boundaries, surface roughness and crystallinity to the optical properties of metal films. The team demonstrated a fundamental two-step approach for single-crystalline growth of silver, gold and aluminum films to open new possibilities in nanophotonics, biotechnology and superconductive quantum technologies. The research team intends to adopt the method to synthesize other extremely low-loss single-crystalline metal films.

Optoelectronic devices with plasmonic effects for near-field manipulation, amplification and sub-wavelength integration can open new frontiers in nanophotonics, quantum optics and in quantum information. Yet, the ohmic losses associated in metals are a considerable challenge to develop a variety of useful plasmonic devices. Materials scientists have devoted research efforts to clarify the influence of metal film properties to develop high performance material platforms. Single-crystalline platforms and nanoscale structural alterations can prevent this problem by eliminating material-induced scattering losses. While silver is one of the best known plasmonic metals at optical and near-IR frequencies, the metal can be challenging for single-crystalline film growth.

If you’ve ever been wakened by the roar of a freight train – or waited at a level crossing for one to trundle by – you’ll be glad to know that these noisy vehicles have a new and potentially life-saving purpose: predicting earthquakes. As Hamish Johnston explains on this week’s podcast, freight trains generate surprisingly strong seismic waves, and changes in the velocity of these waves is an early sign of hazardous earthquake activity. Researchers in France, Belgium and the US studied the rumblings of freight trains running through California’s Coachella Valley and found that they could, in principle, be used to monitor the nearby San Jacinto fault.

Next on the podcast is Chris Monroe, an atomic physicist and quantum technologist whose start-up firm, Ion Q, is developing a quantum computer that uses trapped ions as qubits. In an interview with Physics World’s industry editor Margaret Harris, Monroe explains how Ion Q’s technology differs from classical computers, and describes how trapped ions execute quantum gates.

The third segment of the podcast focuses on the persistent lack of diversity in physics. In an interview, Jess Wade, a physicist at Imperial College London, discusses the scientific impact of this poor diversity and suggests ways to make the field more welcoming to members of underrepresented groups. Afterwards, our features editor Sarah Tesh, who commissioned Wade and Maryam Zarainghalam to write about this topic in the August issue of Physics World, talks about the portraits of white male scientists that adorn walls in many physics departments. These so-called “dude walls” honour important historical figures, but they also send out subtle signals about what a “great” physicist looks like.

Light and sound waves are at the basis of energy and signal transport and fundamental to some of our most basic technologies—from cell phones to engines. Scientists, however, have yet to devise a method that allows them to store a wave intact for an indefinite period of time and then direct it toward a desired location on demand. Such a development would greatly facilitate the ability to manipulate waves for a variety of desired uses, including energy harvesting, quantum computing, structural-integrity monitoring, information storage, and more.

In a newly published paper in Science Advances, a group of researchers led by Andrea Alù, founding director of the Photonics Initiative at the Advanced Science Research Center (ASRC) at The Graduate Center, CUNY, and by Massimo Ruzzene, professor of Aeronautics Engineering at Georgia Tech, have experimentally shown that it is possible to efficiently capture and store a wave intact then guide it towards a specific location.

“Our experiment proves that unconventional forms of excitation open new opportunities to gain control over wave propagation and scattering,” said Alù. “By carefully tailoring the time dependence of the excitation, it is possible to trick the wave to be efficiently stored in a cavity, and then release it on demand towards the desired direction.”