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Category: quantum physics – Page 749

One of the secrets to making tiny laser devices such as opthalmic surgery scalpels work even more efficiently is the use of tiny semiconductor particles, called quantum dots. In new research at Los Alamos National Laboratory’s Nanotech Team, the ~nanometer-sized dots are being doctored, or “doped,” with additional electrons, a treatment that nudges the dots ever closer to producing the desired laser light with less stimulation and energy loss.

“When we properly tailor the compositional profile within the particles during their fabrication, and then inject two or more electrons in each dot, they become more able to emit . Importantly, they require considerably less power to initiate the lasing action,” said Victor Klimov, leader of the Nanotech team.

In order to force a material to emit light one has to work toward a “population inversion,” that is, making the number of electrons in a higher-energy electronic state exceed the number that are in a lower-energy state. To achieve this condition normally, one applies an external stimulus (optical or electrical) of a certain power, which should exceed a critical value termed the “optical-gain threshold.” In a recent paradigm-changing advance, Los Alamos researchers demonstrated that by adding extra electrons into their specially designed quantum dots, they can reduce this threshold to virtually zero.

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In a classical thermodynamic system, heat current flows from the hotter body to the colder one, or electricity from the higher voltage to the lower one. The same thing happens in quantum systems, but this state can be changed, and the flow of energy and particles can be reversed if a quantum observer is inserted into the system.

This is the main result obtained by the group led by Professor Ángel Rubio of the UPV/EHU and of the Max Planck Institute PMSD, together with collaborators at the BCCMS centre in Bremen. Their study has been published in npj Quantum Materials.

In macroscopic objects such as a current of water, observing the current does not affect the flow of the water and, in accordance with the laws of classical thermodynamics, this flow would take place from the upper to the lower part of the system. However, in , “the process of observation changes the state of the system, and this makes it more likely that the current will be made to flow in one or another,” says Ángel Rubio, a professor with the Hamburg-based Max Planck Institute for the Structure and Dynamics of Matter.

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Quantum theory predicts that a vast number of atoms can be entangled and intertwined by a very strong quantum relationship, even in a macroscopic structure. Until now, however, experimental evidence has been mostly lacking, although recent advances have shown the entanglement of 2,900 atoms. Scientists at the University of Geneva (UNIGE), Switzerland, recently reengineered their data processing, demonstrating that 16 million atoms were entangled in a one-centimetre crystal. They have published their results in Nature Communications.

The laws of allow immediately detecting when emitted signals are intercepted by a third party. This property is crucial for data protection, especially in the encryption industry, which can now guarantee that customers will be aware of any interception of their messages. These signals also need to be able to travel long distances using special relay devices known as quantum repeaters—crystals enriched with rare earth and cooled to 270 degrees below zero (barely three degrees above absolute zero), whose atoms are entangled and unified by a very strong quantum relationship. When a photon penetrates this small crystal block, is created between the billions of atoms it traverses. This is explicitly predicted by the theory, and it is exactly what happens as the crystal re-emits a single photon without reading the information it has received.

It is relatively easy to entangle two particles: Splitting a photon, for example, generates two that have identical properties and behaviours. Florian Fröwis, a researcher in the applied group in UNIGE’s science faculty, says, “But it’s impossible to directly observe the process of entanglement between several million atoms since the mass of data you need to collect and analyse is so huge.”

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Intel’s quantum computing efforts have yielded a new 17-qubit chip, which the company has just delivered to its partner in that field, QuTech in the Netherlands. It’s not a major advance in the actual computing power or applications — those are still in very early days — but it’s a step toward production systems that can be ordered and delivered to spec rather than experimental ones that live in a physics lab somewhere.

Intel’s celebration of this particular chip is a bit arbitrary; 17 isn’t some magic number in the quantum world, nor does this chip do any special tricks other quantum computer systems can’t. Intel is just happy that its history and undeniable expertise in designing and fabricating chips and architectures is paying off in a new phase of computing.

I chatted with Intel’s director of quantum hardware, Jim Clarke, about the new system.

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Intel says it is shipping an experimental quantum computing chip to research partners in The Netherlands today. The company hopes to demonstrate that its packaging and integration skills give it an edge in the race to produce practical quantum computers.

The chip contains 17 superconducting qubits—the quantum computer’s fundamental component. According to Jim Clarke, Intel’s director of quantum hardware, the company chose 17 qubits because it’s the minimum needed to perform surface code error correction, an algorithm thought to be necessary to scaling up quantum computers to useful sizes.

Intel’s research partners, at the TU Delft and TNO research center Qutech, will be testing the individual qubits’ abilities as well as performing surface code error correction and other algorithms.

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Ever since the EM drive first made headlines, science lovers have puzzled over how the propulsion system seems to produce thrust, despite the fact it’s ‘impossible’ according to one of the most fundamental laws of physics — Newton’s third law of motion.

Now a team of physicists have put forward an alternative explanation — it turns out the EM drive could actually work without breaking any scientific laws, if we factor in a weird and often overlooked idea in quantum physics — pilot wave theory.

For those who need a refresher, the crux of the problem here is that the EM, or electromagnetic, drive appears to produce thrust without any fuel or propellant.

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At its Ignite developer conference yesterday, Microsoft announced that it has developed a new programming language designed to not only run on current computers but on the most advanced machines of the future: quantum computers. Ignite is running from Sept. 25–29 in Orlando.

Like many other of the world’s largest tech companies, Microsoft has been working to develop quantum computers that could handle massively complex problems in minutes or seconds. Unlike today’s conventional devices that use the digital bits “0” and “1,” quantum computers use qubits that can act as 0s, 1s or both simultaneously.

Microsoft said its new quantum computing language, which has yet to be named, is “deeply integrated” into its Visual Basic development environment and does many of the things other standard programming languages do. However, it is specifically designed to allow programmers to create apps that will eventually run on true quantum computers.

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Intelligent Machines

Google reveals blueprint for quantum supremacy.

The ability of quantum machines to outperform classical computers is called quantum supremacy. Now Google says it has this goal firmly in its sights.

Continue reading “Google has unveiled plans to build quantum machines that are vastly superior to classical computers” | >

There’s a lot we don’t know about the actinides. On the periodic table, this series of heavy, radioactive elements hangs at the bottom, and includes a host of mysterious substances that don’t naturally occur on Earth.

Among this cast of unknowns, berkelium looks to be even stranger than we realised. New experiments with this incredibly rare synthetic element have shown that its electrons don’t behave the way they should, defying quantum mechanics.

“It’s almost like being in an alternate universe because you’re seeing chemistry you simply don’t see in everyday elements,” says chemist Thomas Albrecht-Schmitt from Florida State University.

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