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A photodetector converts light into an electrical signal, causing the light to be lost. Researchers led by Tracy Northup at the University of Innsbruck have now built a quantum sensor that can measure light particles non-destructively. It can be used to further investigate the quantum properties of light.

Physicist Tracy Northup is currently researching the development of quantum internet at the University of Innsbruck. The American citizen builds interfaces with which quantum information can be transferred from matter to light and vice versa. Over such interfaces, it is anticipated that quantum computers all over the world will be able to communicate with each other via fiber optic lines in the future. In their research, Northup and her team at the Department of Experimental Physics have now demonstrated a method with which visible light can be measured non-destructively. The development follows the work of Serge Haroche, who characterized the quantum properties of microwave fields with the help of neutral atoms in the 1990s and was awarded the Nobel Prize in Physics in 2012.

In work led by postdoc Moonjoo Lee and Ph.D. student Konstantin Friebe, the researchers place an ionized calcium atom between two hollow mirrors through which visible laser light is guided. “The ion has only a weak influence on the light,” explains Tracy Northup. “Quantum measurements of the ion allow us to make statistical predictions about the number of light particles in the chamber.” The physicists were supported in their interpretation of the measurement results by the research group led by Helmut Ritsch, a Innsbruck quantum optician from the Department of Theoretical Physics. “One can speak in this context of a quantum sensor for light particles”, sums up Northup, who has held an Ingeborg Hochmair professorship at the University of Innsbruck since 2017. One application of the new method would be to generate special tailored light fields by feeding the measurement results back into the system via a feedback loop, thus establishing the desired states.

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Quantum communication is a strange beast, but one of the weirdest proposed forms of it is called counterfactual communication — a type of quantum communication where no particles travel between two recipients.

Theoretical physicists have long proposed that such a form of communication would be possible, but in 2017, for the first time, researchers were able to experimentally achieve it — transferring a black and white bitmap image from one location to another without sending any physical particles.

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Quantum physicist Paul Kwiat reveals what it takes do well in LabEscape, his science-themed escape room.

Circa 2016

Entanglement is an extremely strong correlation that can exist between quantum systems. These correlations are so strong that two or more entangled particles have to be described with reference to each other, even though the individual objects may be spatially separated.

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Like memory in conventional computers, quantum memory components are essential for quantum computers—a new generation of data processors that exploit quantum mechanics and can overcome the limitations of classical computers. With their potent computational power, quantum computers may push the boundaries of fundamental science to create new drugs, explain cosmological mysteries, or enhance accuracy of forecasts and optimization plans. Quantum computers are expected to be much faster and more powerful than their traditional counterparts as information is calculated in qubits, which, unlike the bits used in classical computers, can represent both zero and one in a simultaneous superstate.

Photonic quantum memory allows for the storage and retrieval of flying single-photon quantum states. However, production of such highly efficient quantum memory remains a major challenge as it requires a perfectly matched photon-matter quantum interface. Meanwhile, the energy of a single photon is too weak and can be easily lost into the noisy sea of stray light background. For a long time, these problems suppressed quantum memory efficiencies to below 50 percent—a threshold value crucial for practical applications.

Now, for the first time, a joint research team led by Prof. Du Shengwang from HKUST, Prof. Zhang Shanchao from SCNU, Prof. Yan Hui from SCNU and Prof. Zhu Shi-Liang from SCNU and Nanjing University has found a way to boost the efficiency of photonic quantum memory to over 85 percent with a fidelity of over 99 percent.

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The future of VPNs may be fighting quanta with quanta.

For the first time, physicists at the University of Basel have succeeded in measuring the magnetic properties of atomically thin van der Waals materials on the nanoscale. They used diamond quantum sensors to determine the strength of the magnetization of individual atomic layers of the material chromium triiodide. In addition, they found a long-sought explanation for the unusual magnetic properties of the material. The journal Science has published the findings.

The use of atomically thin, two-dimensional van der Waals materials promises innovations in numerous fields in science and technology. Scientists around the world are constantly exploring new ways to stack different single atomic layers and thus engineer new materials with unique, emerging properties.

These super-thin composite materials are held together by van der Waals forces and often behave differently to bulk crystals of the same material. Atomically thin van der Waals materials include insulators, semiconductors, superconductors and a few materials with magnetic properties. Their use in spintronics or ultra-compact magnetic memory media is highly promising.

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Scientists find surprising way to affect information storage properties in metal alloy.

Sometimes scientific discoveries can be found along well-trodden paths. That proved the case for a cobalt-iron alloy material commonly found in hard disk drives.

As reported in a recent issue of Physical Review Letters, researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, along with Oakland University in Michigan and Fudan University in China, have found a surprising quantum effect in this alloy.

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And why Einstein’s quest for unification was doomed from the start.