Quantum dots are semiconductor particles measuring just a few nanometres across, which are now widely studied for their intriguing electrical and optical properties.
Through new research published in EPJ B (“Third-order nonlinear susceptibility in CdS/Cdx1Zn 1-x1 S/ZnS multilayer spherical quantum dot,”), Kobra Hasanirokh at Azarbaijan Shahid Madani University in Iran, together with Luay Hashem Abbud at Al-Mustaqbal University College, Iraq, show how quantum dots containing spherical defects can significantly enhance their nonlinear optical properties.
By fine-tuning these defects, researchers could tightly control the frequency and brightness of the light emitted by quantum dots.
A team led by Professor Andrea Morello has just demonstrated the operation of a new type of quantum bit, called ‘flip-flop’ qubit, which combines the exquisite quantum properties of single atoms, with easy controllability using electric signals, just as those used in ordinary computer chips.
“Sometimes new qubits, or new modes of operations, are discovered by lucky accident. But this one was completely by design,” says Prof. Morello. “Our group has had excellent qubits for a decade, but we wanted something that could be controlled electrically, for maximum ease of operation. So we had to invent something completely new.”
Prof. Morello’s group was the first in the world to demonstrate that using the spin of an electron as well as the nuclear spin of a single phosphorus atom in silicon could be used as ‘qubits’ – units of information that are used to make quantum computing calculations. He explains that while both qubits perform exceptionally well on their own, they require oscillating magnetic fields for their operation.
Stephen Hawking was one of the greatest scientific and analytical minds of our time, says NASA’s Michelle Thaller. She posits that Hawking might be one of the parents of an entirely new school of physics because he was working on some incredible stuff—concerning quantum entaglement— right before he died. He was even humble enough to go back to his old work about black holes and rethink his hypotheses based on new information. Not many great minds would do that, she says, relaying just one of the reasons Stephen Hawking will be so deeply missed. You can follow Michelle Thaller on Twitter at @mlthaller.
MICHELLE THALLER: Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory’s (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA’s Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit NASA.
TRANSCRIPT: Michelle Thaller: Yes Jeremy, a lot of us were really sad with the passing of Stephen Hawking. He was definitely an inspiration. He was one of the most brilliant theoretical physicists in the world, and of course, he overcame this incredible disability, his life was very difficult and very dramatic and I for one am really going to miss having him around. And I certainly miss him as a scientist too. He made some incredible contributions. Now, Stephen Hawking was something that we call a theoretical physicist, and what that means is that people use the mathematics of physics to explore areas of the universe that we can’t get to very easily. For example, conditions right after the Big Bang, the beginning of the universe, what were things like when the universe was a fraction of a second old? That’s not something we can create very easily in a laboratory or any place we can go to, but we can use our mathematics to predict what that would have been like and then test our assumptions based on how the universe changed over time. And one of the places that is also very difficult to go to is, could we explore a black hole? And this is what Stephen Hawking was best known for. Now, black holes are massive objects they’re made from collapsed dead stars, and the nearest black hole to us is about 3,000 light years away. That one is not particularly large, it’s only a couple times the mass of the sun. The biggest black hole that’s in our galaxy is about four million times the mass of the sun and that actually sits right in the heart of the Milky Way Galaxy. And right now you and I are actually orbiting that giant black hole at half a million miles an hour. These are incredibly exotic objects. The reason we call them black holes is that the gravity is so intense it can suck in everything, including light. Not even light, going through space freely at the speed of light, can escape a black hole, so talk about dramatic exotic objects that are difficult to do experiments on. Stephen Hawking laid down some of our basic understanding of how a black hole works. And one of the things he actually did was he even predicted that black holes can die. You would think that a collapsed star that forms a bottomless pit of gravity would exist forever, but Stephen Hawking used the laws of quantum mechanics and something called thermodynamics, how heat behaves in the universe, to prove that maybe black holes can evaporate over time. And of course, that’s a hugely significant thing. One of the reasons I think it’s very unfortunate he died is we’re actually right on the cusp of being able to do actual experiments with black holes. And I know that sounds like a strange thing to say, but there are some particle accelerators, I mean specifically the Large Hadron Collider, which is in Europe, that are about to get to high enough energies they’re going to smash particles together so hard that so much energy is generated they might be able to make tiny little black holes. Read full transcript on: https://bigthink.com/videos/michelle-thaller-ask-a-nasa-astr…-the-world
In quantum mechanics, the unitary nature of time evolution makes it intrinsically reversible, given control over the system in question. Remarkably, there have been several recent demonstrations of protocols for reverting unknown unitaries in scenarios where even the interactions with the target system are unknown. These protocols are limited by their probabilistic nature, raising the fundamental question of whether time-reversal could be performed deterministically. Here we show that quantum physics indeed allows for this by exploiting the non-commuting nature of quantum operators, and demonstrate a recursive protocol for two-level quantum systems with an arbitrarily high probability of success. Using a photonic platform, we achieve an average rewinding fidelity of over 95%. Our protocol, requiring no knowledge of the quantum process to be rewound, is optimal in its running time, and brings quantum rewinding into a regime of practical relevance.
Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
CAMBRDIGE, United Kingdom — “Quantum light” may sound like something out of a Marvel movie, but scientists say it may hold the real-world key to revolutionizing science as we know it. An international team says generating this high-energy light and controlling it can unlock a whole new realm in quantum computing.
Researchers from the University of Cambridge, as well as scientists in the United States, Israel, and Austria, have come up with a theory describing this new state of light. They say it has controllable quantum properties and a wide range of frequencies which reach X-ray levels. Harnessing this power could lead to advances in microscopy — or the ability to see incredibly small things normally invisible to the naked eye.
Life looks completely different at the atomic level.
Quantum mechanics is simultaneously beautiful and frustrating.
Its explanatory power is unmatched. Armed with the machinery of quantum theory, we have unlocked the secrets of atomic power, divined the inner workings of chemistry, built sophisticated electronics, discovered the power of entanglement, and so much more. According to some estimates, roughly a quarter of our world’s GDP relies on quantum mechanics.
Yet despite its overwhelming success as a framework for understanding what nature does, quantum mechanics tells us very little about how nature works. Quantum mechanics provides a powerful set of tools for successfully making predictions about what subatomic particles will do, but the theory itself is relatively silent about how those subatomic particles actually go about their lives.
QuEra Computing, maker of the world’s first and only publicly accessible neutral-atom quantum computer—Aquila—today announces its research team has uncovered a method to perform a wider set of optimization calculations than previously known to be possible using neutral-atom machines.
The findings are the work of QuEra researchers and collaborators from Harvard and Innsbruck Universities: Minh-Thi Nguyen, Jin-Guo Liu, Jonathan Wurtz, Mikhail D. Lukin, Sheng-Tao Wang, and Hannes Pichler.
“There is no question that today’s news helps QuEra deliver value to more partners, sooner. It helps bring us closer to our objectives, and marks an important milestone for the industry as well,” said Alex Keesling, CEO at QuEra Computing. “This opens the door to working with more corporate partners who may have needs in logistics, from transport and retail to robotics and other high-tech sectors, and we are very excited about cultivating those opportunities.”
If life is common in our Universe, and we have every reason to suspect it is, why do we not see evidence of it everywhere? This is the essence of the Fermi Paradox, a question that has plagued astronomers and cosmologists almost since the birth of modern astronomy.
It is also the reasoning behind the Hart-Tipler Conjecture, one of the many (many!) proposed resolutions, which asserts that if advanced life had emerged in our galaxy sometime in the past, we would see signs of their activity everywhere we looked. Possible indications include self-replicating probes, megastructures, and other Type III-like activity.
On the other hand, several proposed resolutions challenge the notion that advanced life would operate on such massive scales. Others suggest that advanced extraterrestrial civilizations would be engaged in activities and locales that would make them less noticeable.
