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Category: particle physics – Page 370

Pink Noise as a Probe of Quantum Transport

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Noise in an electronic circuit is a nuisance that can scramble information or reduce a detector’s sensitivity. But noise also offers a way to learn about the microscopic quantum mechanisms at play in a material or device. By measuring a circuit’s “shot noise,” a form of white noise, researchers have previously shed light on conduction in quantum Hall and spintronic systems, for instance. Now, a collaboration led by Oren Tal at the Weizmann Institute of Science, Israel, and by Dvira Segal at the University of Toronto, Canada, has shown that an easier-to-measure form of noise, called “flicker noise,” can also be a powerful probe of quantum effects [1].

Flicker noise is a type of pink noise, whose spectrum is dominated by low frequencies—the kind of noise associated with light rainfall. Flicker noise also appears in electrical circuits, but its connection to microscopic transport channels remains poorly understood. To investigate this connection, the team studied an atomic-scale junction between two wires. They modeled the electrons passing through the junction as coherent quantum-mechanical waves that scatter off fluctuating defects located near the junction. These fluctuations can represent the trapping and releasing of electrons by static defects, the movement of charged impurities between lattice sites, and the fluctuations of atoms and molecules adsorbed on surfaces.

By comparing calculations with experiments on junctions with different parameters, the team showed that flicker noise can be connected to the number of quantum conduction channels and to the contributions of the individual channels to the overall conduction, providing similar information to shot noise. Since flicker-noise measurements are widely used, they could now be applied to shed light on quantum and many-body effects in a broad range of nanoscale electronic devices, the researchers say.

New Class of Atom Cooled to Near Absolute Zero

Researchers have cooled indium atoms to a temperature close to 1 mK, making indium the first group-III atom to be made ultracold.

At temperatures near to absolute zero, atoms move slower than a three-toed sloth, allowing physicists to gain unprecedented experimental control over these systems. New phases of matter can form when atoms become ultracold and quirky quantum properties can emerge, yet much of the periodic table remains unexplored in the ultracold regime. Now, Travis Nicholson of the National University of Singapore and colleagues have successfully cooled indium to close to 1 mK [1]. Indium is the first “main group-III” atom—a specific group of transition metals on the periodic table—to be cooled to such a low temperature. The demonstration opens the door to studying systems with properties previously unexplored by ultracold physicists.

For their experiments, Nicholson and colleagues used a magneto-optical trap—a standard tool for trapping and cooling atoms. But because this was the first attempt at making indium atoms ultracold, the team had to make their own version of the apparatus rather than using one designed to cool other atoms. “The systems used for this research are highly customized to specific atoms,” Nicholson says. So every part of the setup from designing the laser systems to picking the screws had to be “hashed out by us.” With their custom setup, the group loaded 500,000,000 indium atoms into the trap using a laser beam and then cooled them.

Eternal matter waves

Imagining our everyday life without lasers is difficult. We use lasers in printers, CD players, pointers, measuring devices, etc. What makes lasers so special is that they use coherent waves of light: all the light inside a laser vibrates completely in sync.

Meanwhile, quantum mechanics tells us that particles like atoms should also be considered waves. As a result, we can build ‘atom lasers’ containing coherent waves of matter. But can we make these matter waves last so they may be used in applications? In research that was published in Nature, a team of Amsterdam physicists shows that the answer to this question is affirmative.

Decoding a key part of the cell, atom

Whatever you are doing, whether it is driving a car, going for a jog, or even at your laziest, eating chips and watching TV on the couch, there is an entire suite of molecular machinery inside each of your cells hard at work. That machinery, far too small to see with the naked eye or even with many microscopes, creates energy for the cell, manufactures its proteins, makes copies of its DNA, and much more.

Among those pieces of machinery, and one of the most complex, is something known as the nuclear pore complex (NPC). The NPC, which is made of more than 1,000 individual proteins, is an incredibly discriminating gatekeeper for the cell’s nucleus, the membrane-bound region inside a cell that holds that cell’s genetic material. Anything going in or out of the nucleus has to pass through the NPC on its way.

Nuclear pores stud the surface of the cell’s nucleus, controlling what flows in and out of it. (Image: Valerie Altounian)

Graphene charge-injection photodetectors with a broader detection bandwidth

Photodetectors, sensors that can detect light or other forms of electromagnetic radiation, are essential components of imaging tools, communication systems, and various other technologies on the market. These sensors work by converting photons (i.e., light particles) into electrical current.

Researchers at Zhejiang University have recently developed a new photodetector that could detect light within a broader bandwidth. Their device, presented in a paper published in Nature Electronics, could be used to develop new and more advanced imaging technologies.

“Our recent project is based on traditional charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) imaging technologies,” Prof. Yang Xu, one of the researchers who carried out the study, told TechXplore. “Our novel imaging devices combining CCD’s MOS photogate for and CMOS’s independent pixel structure can significantly benefit monolithic integration, performance, and readout.”

Scientists discovered a never-before-seen particle and it could be dark matter

Extremely interested to hear some of your opinions on this. Published in the journal Nature.

Scientists have discovered a new, mysterious particle. Of course, making new discoveries is exciting. But, perhaps the most exciting thing about this particle is that it could be a candidate for dark matter.

Incredibly, the never-before-seen particle was discovered using an experiment small enough to fit on a kitchen counter.

“When my student showed me the data I thought she must be wrong,” Boston College professor and lead researcher Kenneth Burch told Live Science. “It’s not every day you find a new particle sitting on your tabletop.”

How Can a Quantum Computer Catch its Own Errors in Calculations?

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A collection of 16 qubits has been organized in such a way that they may be able to operate any computation without error. It is an important step toward constructing quantum computers that outperform standard ones.

When completing any task, a quantum computer consisting of charged atoms can detect its own faults. Because conventional computers constantly detect and rectify their own flaws, quantum computers will need to do the same in order to fully outperform them. Nevertheless, quantum effects can cause errors to propagate rapidly through the qubits, or quantum bits, that comprise these devices.

Lukas Postler and his team from the Austria’s University of Innsbruck have created a quantum computer that can perform any calculation without error.