We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz second harmonic emission vanishes above the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, THz driving frequency that is not allowed by equilibrium symmetry. We explain the microscopic physics by a dynamical symmetry breaking principle at sub-THz-cycle by using quantum kinetic modeling of the interplay between strong THz-lightwave nonlinearity and pulse propagation. The resulting nonzero integrated pulse area inside the superconductor leads to light-induced nonlinear supercurrents due to subcycle Cooper pair acceleration, in contrast to dc-biased superconductors, which can be controlled by the band structure and THz driving field below the superconducting gap.
Category: quantum physics – Page 599
Researchers at the University of Science and Technology of China have recently introduced a new satellite-based quantum-secure time transfer (QSTT) protocol that could enable more secure communications between different satellites or other technology in space. Their protocol, presented in a paper published in Nature Physics, is based on two-way quantum key distribution in free space, a technique to encrypt communications between different devices.
“Our main idea was to realize quantum-secure time transfer in order to resolve the security issues in practical time–frequency transfer,” Feihu Xu, one of the researchers who carried out the study, told Phys.org.
Quantum key distribution (QKD) is a technique to achieve secure communication that utilize cryptographic protocols based on the laws of quantum mechanics. Quantum key distribution protocols can generate secret security keys based on quantum physics, enabling more secure data transfer between different devices by spotting attackers who are trying to intercept communications.
Essentially a quantum radar teleportation device could entangle objects anywhere in the universe.
Last year, a Long March 2D rocket took off from the Jiuquan Satellite Launch Centre in the Gobi Desert carrying a satellite called Micius, named after an ancient Chinese philosopher who died in 391 B.C. The rocket placed Micius in a Sun-synchronous orbit so that it passes over the same point on Earth at the same time each day.
Micius is a highly sensitive photon receiver that can detect the quantum states of single photons fired from the ground. That’s important because it should allow scientists to test the technological building blocks for various quantum feats such as entanglement, cryptography, and teleportation.
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Using two flat-top diamonds and a lot of pressure, scientists have forced a magnetic crystal into a spin liquid state, which may lead to insights into high-temperature superconductivity and quantum computing.
It sounds like a riddle: What do you get if you take two small diamonds, put a small magnetic crystal between them and squeeze them together very slowly?
The answer is a magnetic liquid, which seems counterintuitive. Liquids become solids under pressure, but not generally the other way around. But this unusual pivotal discovery, unveiled by a team of researchers working at the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Argonne National Laboratory, may provide scientists with new insight into high-temperature superconductivity and quantum computing.
Here’s a new chapter in the story of the miniaturization of machines: researchers in a laboratory in Singapore have shown that a single atom can function as either an engine or a fridge. Such a device could be engineered into future computers and fuel cells to control energy flows.” Think about how your computer or laptop has a lot of things inside it that heat up. Today you cool that with a fan that blows air. In nanomachines or quantum computers, small devices that do cooling could be something useful,” says Dario Poletti from the Singapore University of Technology and Design (SUTD).
This work gives new insight into the mechanics of such devices. The work is a collaboration involving researchers at the Centre for Quantum Technologies (CQT) and Department of Physics at the National University of Singapore (NUS), SUTD and at the University of Augsburg in Germany. The results were published in the peer-reviewed journal npj Quantum Information on 1 May.
Engines and refrigerators are both machines described by thermodynamics, a branch of science that tells us how energy moves within a system and how we can extract useful work. A classical engine turns energy into useful work. A refrigerator does work to transfer heat, reducing the local temperature. They are, in some sense, opposites.
Micro-combs — optical frequency combs generated by integrated micro-cavity resonators – offer the full potential of their bulk counterparts, but in an integrated footprint. They have enabled breakthroughs in many fields including spectroscopy, microwave photonics, frequency synthesis, optical ranging, quantum sources, metrology and ultrahigh capacity data transmission. Here, by using a powerful class of micro-comb called soliton crystals, we achieve ultra-high data transmission over 75 km of standard optical fibre using a single integrated chip source. We demonstrate a line rate of 44.2 Terabits s−1 using the telecommunications C-band at 1550 nm with a spectral efficiency of 10.4 bits s−1 Hz−1. Soliton crystals exhibit robust and stable generation and operation as well as a high intrinsic efficiency that, together with an extremely low soliton micro-comb spacing of 48.9 GHz enable the use of a very high coherent data modulation format (64 QAM — quadrature amplitude modulated). This work demonstrates the capability of optical micro-combs to perform in demanding and practical optical communications networks.
Education Saturday with Space Time.
This episode of space time is brought to you by the information flowing through an impossibly complex network of quantum entanglement, that just happens to mutually agree that you and I exist inside it. Oh, and Schrodinger’s cat is in here too.
In quantum world things are routinely in multiple states at once – what we call a “superposition” of states. But in the classical world of large scales, things are either this or that. The famous thought experiment is Schrodinger’s cat – in which a cat is in an opaque box with a vial of deadly poison that’s released on the radioactive decay of an atom. Quantum mechanics tells us that the atom’sfunction can be in a superposition of states – simultaneously decayed or not decayed. So is the cat’sfunction also in a superposition of both dead and alive.
If you’re interested in superlongevity and superintelligence, then I have a book to recommend., by Sonia Contera, is a book about the intersection of biotech and nanotech. Interesting and well written for the layman, the book covers some of the latest developments in nanotechnology as it applies to biological matters. Although there are many topics, I was primarily interested in the DNA nanobots, DNA origami, and the protein nanotechnology sections. My interest is piqued in these arenas due to my expectation that DNA nanobots and protein nanobots, as well as complex self-assembled custom nanostructures, are going to be key to some of the longevity technologies and some of the possible substrates for mind uploading that are key to superlongevity and superintelligence. There are also sections in the book on 3D bioprinted organs — progress and possibilities, as well as difficulties.
There is even a section that clearly was written specifically to address a discussion that has engaged my friends, Dinorah Delfin and Dan Faggella. The title is:
FUTURE DEVICES: QUANTUM PHYSICS MEETS BIOLOGY MEETS NANOTECHNOLOGY
Now, some might be tempted to consider that particular combination to be “woo woo”, however, please keep in mind the author’s credentials. Sonia Contera is a professor of biological physics in the Department of Physics at the University of Oxford.
Increasingly, scientists are gaining control over matter at the nanometer scale. Spearheaded by physical scientists operating at the interfaces of physics and biology, advances in nanoscience and technology are transforming how people think about life and treat human health.