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Category: quantum physics

As transistors are made ever tinier to fit more computing power into a smaller footprint, they bump up against a big problem: quantum mechanics. Electrons get jumpy in small devices and leak out, which wastes energy while degrading performance. Now a team of researchers is showing that it doesn’t have to be that way. With careful engineering, it’s possible to turn electrons’ quantum behavior into an advantage.

A team of English, Canadian, and Italian researchers have developed a single-molecule transistor that harnesses quantum effects. At low temperatures, the single-molecule device shows a strong change in current with only a small change in gate voltage, nearing a physical limit known as the sub-threshhold swing. Getting near or beyond this limit will allow transistors to be switched with lower voltages, making them more efficient and generating less waste heat. The research team, including physicists at Queen Mary University of London, achieved this by taking advantage of how quantum interference alters the flow of current in single molecules.

“We’ve demonstrated, in principle, that you can use destructive quantum interference for something useful.” —Jan Mol, Queen Mary University of London.

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Iron screws and other so-called ferromagnetic materials are made up of atoms with electrons that act like little magnets. Normally, the orientations of the magnets are aligned within one region of the material but are not aligned from one region to the next. Think of packs of tourists in Times Square pointing to different billboards all around them. But when a magnetic field is applied, the orientations of the magnets, or spins, in the different regions line up and the material becomes fully magnetized. This would be like the packs of tourists all turning to point at the same sign.

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A new study by Hebrew University has made a significant breakthrough by successfully incorporating single-photon sources into small chips that operate at room temperature. This development marks a crucial progress in the field of quantum photonics, opening up possibilities for its use in quantum computing and cryptography. It represents a key achievement in creating usable quantum photonic devices, signaling an optimistic outlook for the complete realization of quantum technologies, including computing, communication, and sensing.

A recent study, spearheaded by Boaz Lubotzky during his Ph.D. research, along with Prof. Ronen Rapaport from the Racah Institute of Physics at The Hebrew University of Jerusalem, in collaboration with teams from Los Alamos National Laboratory (LANL) in the USA and from Ulm University in Germany, unveiled a significant advancement toward the on-chip integration of single-photon sources at room temperature. This achievement represents a significant step forward in the field of quantum photonics and holds promise for various applications including quantum computing, cryptography, and sensing.

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To understand the relationship between the science fiction genre and the Many-Worlds Interpretation, let’s turn to two men – a scientist and a writer. The scientist is Hugh Everett III (1930−1982), a physicist who developed the notion of parallel universes based on an original interpretation of quantum mechanics. He proposed that a pre-formulated theory should be the basis of scientific measurement, quite the opposite of the traditional scientific process in which measurement preceded and determined the theory. But quantum particles do not behave normally, so quantum phenomena and their atomic dynamics cannot be measured by the Newtonian mechanics traditionally applied to the universe.

When Hugh Everett published “Relative State Formulation of Quantum Mechanics” in the Reviews of Modern Physics scientific journal (Volume 29, Issue 3, July — September 1957), his theory that there are many worlds existing in parallel at the same space and time as our own sounded like fantasy fiction to a skeptical scientific world.

While scientists scoffed for more than a decade after Everett published his theory, someone else entered the scene. His name was Philip K. Dick, a scruffy beatnik writer who tramped around Berkeley (California) looking for ways to describe this alternative reality – the one hiding behind our visible reality.

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As transistors get smaller, they become increasingly inefficient and susceptible to errors, as electrons can leak through the device even when it is supposed to be switched off, by a process known as quantum tunneling. Researchers are exploring new types of switching mechanisms that can be used with different materials to remove this effect.

In the nanoscale structures that Professor Jan Mol, Dr. James Thomas, and their group study at Queen Mary’s School of Physical and Chemical Sciences, quantum mechanical effects dominate, and electrons behave as waves rather than particles. Taking advantage of these quantum effects, the researchers built a new transistor.

The transistor’s conductive channel is a single zinc porphyrin, a molecule that can conduct electricity. The porphyrin is sandwiched between two graphene electrodes, and when a voltage is applied to the electrodes, electron flow through the molecule can be controlled using .

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