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Category: quantum physics – Page 779

Entangled photons can see through translucent materials

Quantum twist on optical coherence tomography offers million-fold improvement in imaging.

Entangled pairs of photons have been used by physicists in Germany and Austria to image structures beneath the surfaces of materials that scatter light. The research was led by Aron Vanselow and Sven Ramelow at Humboldt University of Berlin and achieved high-resolution images of the samples using “ultra-broadband” photon pairs with very different wavelengths. One photon probed the sample, while the other read out image information. Their compact, low-cost and non-destructive system could be put to work inspecting advanced ceramics and mixing in fluids.

Optical coherence tomography (OCT) is a powerful tool for imaging structures beneath the surfaces of translucent materials and has a number of applications including the 3D scanning of biological tissues. The technique uses interferometry to reject the majority of light that has scattered many times in an object, focussing instead on the rare instances when light only scatters once from a feature of interest. This usually involves probing the material with visible or near-infrared light, which can be easily produced and detected. Yet in some materials such as ceramics, paints, and micro-porous samples, visible and near-infrared light is strongly scattered – which limits the use of OCT. Mid-infrared light, however, can penetrate deeper into these samples without scattering – but this light is far more difficult to produce and detect.

Vanselow, Ramelow and colleagues circumvented this problem by using pairs of quantum-mechanically entangled photons in which one photon is mid-infrared and the other is either visible or near-infrared. The entangled pairs are generated by firing a “pump” laser beam at a specialized nonlinear crystal developed by the team. This creates entangled pairs of photons – one mid-infrared “idler” photon and one visible/near-infrared “signal” photon.

Quantum Experiment Reveals Particles Can Form Collectives Out of Almost Nothing

How many particles do you need before individual atoms start behaving collectively? According to new research, the number is incredibly low. As few as six atoms will start transitioning into a macroscopic system, under the right conditions.

Using a specially designed ultra-cold laser trap, physicists observed the quantum precursor of the transition from a normal to a superfluid phase – offering a way to study the emergence of collective atomic behaviour and the limits of macroscopic systems.

Many-body physics is the field that seeks to describe and understand the collective behaviour of large numbers of particles: a bucket of water, for example, or a canister of gas. We can describe these substances in terms of their density, or their temperature – the way the substance is acting as a whole.

Quantum Entanglement of Electrons Using Heat

Quantum entanglement is key for next-generation computing and communications technology, Aalto researchers can now produce it using temperature differences.

A joint group of scientists from Finland, Russia, China, and the USA have demonstrated that temperature difference can be used to entangle pairs of electrons in superconducting structures. The experimental discovery, published in Nature Communications, promises powerful applications in quantum devices, bringing us one step closer towards applications of the second quantum revolution.

The team, led by Professor Pertti Hakonen from Aalto University, has shown that the thermoelectric effect provides a new method for producing entangled electrons in a new device. “Quantum entanglement is the cornerstone of the novel quantum technologies. This concept, however, has puzzled many physicists over the years, including Albert Einstein who worried a lot about the spooky interaction at a distance that it causes,” says Prof. Hakonen.

Energy transmission using recyclable quantum entanglement

Circa 2016

It is known that faster-than-light (FTL) transmission of energy could be achieved if the transmission were considered in the framework of non-relativistic classical mechanics. Here we show that FTL transmission of energy could also be achieved if the transmission were considered in the framework of non-relativistic quantum mechanics. In our transmission protocol a two-spin Heisenberg model is considered and the energy is transmitted by two successive local unitary operations on the initially entangled spins. Our protocol does not mean that FTL transmission can be achieved in reality when the theory of relativity is considered, but it shows that quantum entanglement can be used in a recyclable way in energy transmission.

Using the SYK model to examine the fast-charging process of quantum batteries

The Sachdev-Ye-Kitaev (SYK) model, an exactly solvable model devised by Subir Sachdev and Jinwu Ye, has recently proved useful for understanding the characteristics of different types of matter. As it describes quantum matter without quasiparticles and is simultaneously a holographic version of a quantum black hole, it has so far been adopted by both condensed matter and high-energy physicists.

Researchers at University of Pisa and the Italian Institute of Technology (IIT) have recently used the SYK model to examine the charging protocols of quantum batteries. Their paper, published in Physical Review Letters, offers evidence of the potential of quantum mechanical resources for boosting the charging process of batteries.

“Previous theoretical studies laid down the idea that entanglement can be used to greatly speed up the charging process of a quantum battery,” Davide Rossini and Gian Marcello Andolina, two of the researchers who carried out the study, told Phys.org, via email. “However, a concrete solid-state model displaying such fast charging was missing, until now.”

Researchers realize efficient generation of high-dimensional quantum teleportation

In a study published in Physical Review Letters, a team led by academician Guo Guangcan from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) has made progress in high dimensional quantum teleportation. The researchers demonstrated the teleportation of high-dimensional states in a three-dimensional six-photon system.

To transmit unknown quantum states from one location to another, quantum teleportation is one of the key technologies to realize long-distance transmission.

Compared with two-dimensional systems, high-dimensional system quantum networks have the advantages of higher channel capacity and better security. In recent years more and more researchers of the quantum information field have been working on generating efficient generation of high-dimensional quantum teleportation to achieve efficient high-dimensional quantum networks.

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