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Category: quantum physics – Page 240

Quantum communications have rapidly progressed toward practical, large-scale networks based on quantum key distributions that spearhead the process. Quantum key distribution systems typically include a sender “Alice,” a receiver “Bob,” who generate a shared secret from quantum measurements for secure communication. Although fiber-based systems are well-suited for metropolitan scale, a suitable fiber infrastructure might not always be in place.

In a new report in npj Quantum Information, Andrej Kržič and a team of scientists developed an entanglement-based, free-space quantum . The platform offered a practical and efficient alternative for metropolitan applications. The team introduced a free-space quantum key distribution system to demonstrate its use in realistic applications in anticipation of the work to establish free-space networks as a viable solution for metropolitan applications in the future global quantum internet.

Quantum communication typically aims to distribute quantum information between two or more parties. A series of revolutionary applications of quantum networks have provided a roadmap towards engineering a full-blown quantum internet. The proposed invention provides a heterogeneous network of special purpose sub-networks with diverse links and interconnects. The concept of quantum key distribution networks have driven this development to pave the way for other distributed processing methods to benchmark the technological maturity of quantum networks in general.

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A research team led by Prof. Yossi Paltiel at the Hebrew University of Jerusalem with groups from HUJI, Weizmann, and IST Austria recently conducted a study unveiling the significant influence of nuclear spin on biological activities. This discovery challenges long-held assumptions and opens up exciting possibilities for advancements in biotechnology and quantum biology.

Scientists have long believed that nuclear spin had no impact on biological processes. However, recent research has shown that certain isotopes behave differently due to their nuclear spin. The team focused on stable oxygen isotopes (16O, 17O, 18O) and found that nuclear spin significantly affects oxygen dynamics in chiral environments, particularly in its transport.

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Researcher show that n-bit integers can be factorized by independently running a quantum circuit with orders of magnitude fewer qubits many times. It then use polynomial-time classical post-processing. The correctness of the algorithm relies on a number-theoretic heuristic assumption reminiscent of those used in subexponential classical factorization algorithms. It is currently not clear if the algorithm can lead to improved physical implementations in practice.

Shor’s celebrated algorithm allows to factorize n-bit integers using a quantum circuit of size O(n^2). For factoring to be feasible in practice, however, it is desirable to reduce this number further. Indeed, all else being equal, the fewer quantum gates there are in a circuit, the likelier it is that it can be implemented without noise and decoherence destroying the quantum effects.

The new algorithm can be thought of as a multidimensional analogue of Shor’s algorithm. At the core of the algorithm is a quantum procedure.

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A team of researchers has found a way to speed up the creation of quantum entanglement, a mystifying property of quantum mechanics that Albert Einstein once described as “spooky action at a distance.”

The researchers behind the discovery include Kater Murch, the Charles M. Hohenberg Professor of Physics; Weijian Chen, a postdoctoral research associate in the Department of Physics; and Maryam Abbasi, a postdoctoral research associate in the Department of Chemistry. Their paper was featured on the cover of Physical Review Letters.

Entanglement has baffled researchers—and nearly everyone who has ever read about —since Einstein and colleagues first proposed it in the 1930s.

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“Using the new quantum ruler to study how the circular orbits vary with magnetic field, we hope to reveal the subtle magnetic properties of these moiré quantum materials”

Graphene, a single-atom-thick sheet of carbon, is renowned for its exceptional electrical conductivity and mechanical strength.

However, when two or more layers of graphene are stacked with a slight misalignment, they become moiré quantum matter, opening the door to a world of exotic possibilities. Depending on the angle of twist, these materials can generate magnetic fields, become superconductors with zero electrical resistance, or transform into perfect insulators.

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To listen to more of John Wheeler’s stories, go to the playlist: https://www.youtube.com/playlist?list=PLVV0r6CmEsFzVlqiUh95Q881umWUPjQbB

American physicist, John Wheeler (1911−2008), made seminal contributions to the theories of quantum gravity and nuclear fission, but is best known for coining the term ‘black holes’. A keen teacher and mentor, he was also a key figure in the Manhattan Project. [Listener: Ken Ford]

TRANSCRIPT: I knew the stories about Gödel being concerned always about his health. I knew from his friend Oscar Morgenstern how Gödel would never take a pills prescription from his doctor without getting out a big medical book and studying up on that pill himself to make sure that it was okay. But I didn’t realize how far his dreams went, because I had failed to resonate to a talk he gave in 1945 at the symposium held in honor of Einstein’s birthday. In that talk Gödel had described what he called a Rotating Universe, a universe where all the galaxies turn the same way, and where the geometry is such that you keep on going living your life and you come round and come back and can live it over again; ‘Closed Time-like Line’ was the magic phrase to describe it. So you didn’t have to worry about the pill because you come back and live your life all over again. Well, after I’d introduced the two I said “Professor Gödel, we’d like to know what the relation is between the great Heisenberg Principle of Uncertainty or Indeterminism; and your famous proof that every significant mathematical system contains theorems which cannot be proven, your theorem of Unprovable Propositions.” Well, he didn’t want to talk about that. It turned out that later that he had walked and talked enough with Einstein to dismiss quantum theory. He didn’t believe quantum[theory]. All he wanted to know is what we were going to say in our book about the rotating universe that he had described. Well actually, we weren’t saying anything. Well, this bothered him and he wanted to know what the evidence is today, at that moment, about whether galaxies do rotate in the same way. We said we hadn’t studied it. Well it turned out that he himself had taken out the great Hubble atlas of the galaxies and page after page had opened it up and looked at each galaxy, determined the direction of its axis. He made a statistics of these numbers and found there was no preferred direction of rotation, so they couldn’t all be rotating in the same way.

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In a schematic view, an engine uses a thermodynamic change to produce work. For example, when a gas is ignited, it expands and so pushes a piston. Now, researchers have been able to develop a similar kind of engine but instead of using the relationship between temperature, pressure, and volume, the new device uses quantum mechanics.

The quantum engine employs a gas that can turn from a fermion gas to a boson gas. Fermions and bosons are a way to divide all particles into two categories. Their difference comes from a property called spin, an intrinsic angular momentum. Fermions have a fractional value (1÷2, 3/2) while bosons have integer spin (0, 1, 2, …).

There is another difference that matters in the engine too: the Pauli exclusion principle. And this only applies to fermions.

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The method is still at its basic stage but multiple such microscopes could be pooled up to build a larger quantum computer.

Researchers at the IBS Center for Quantum Nanoscience (QNS) in Seoul, South Korea, have successfully demonstrated using a scanning tunneling microscope (STM) to perform quantum computation using electrons as qubits, a press release said.

Quantum computing is usually associated with terms such as atom traps or superconductors that aid in isolating quantum states or qubits that serve as a basic unit of information. In many ways, everything in nature is quantum and can be used to perform quantum computations as long as we can isolate its quantum states.

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