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New sensor could allow MRIs to see molecular-level changes
You’ve seen people sliding into the tube of a magnetic resonance imaging (MRI) machine on your favorite medical drama, or maybe you’ve been inside one yourself, waiting as the noisy scanner makes images of your brain, heart, bones, or other structures, which doctors use to identify injury or disease.
Since the 1970s, MRIs have been important diagnostic tools, combining a magnetic field and radio waves to produce snapshots of the body’s interior without using ionizing radiation, which can create health risks at higher doses. An MRI can typically capture changes in anatomy, but the molecular-level changes that could further aid understanding of disease have been beyond its reach.
Now, in a new article in Science Advances, University of California, Santa Barbara researchers report the invention of a modular, genetically encoded, protein-based sensor that enables MRI machines to visualize molecular activity inside cells—a development that could transform how scientists study cancer, neurodegeneration, and inflammation.
Scientists just found DNA “supergenes” that speed up evolution
Hidden within fish DNA are powerful genetic twists that may explain one of nature’s biggest mysteries: how new species form so quickly. In Lake Malawi, hundreds of cichlid fish species evolved at lightning speed, and scientists now think “flipped” sections of DNA—called chromosomal inversions—are the secret. These inversions lock together useful gene combinations, creating “supergenes” that help fish rapidly adapt to different environments, from deep waters to sandy shores.
Extending the Adiabatic Theorem
Jerk the support from which a swinging pendulum hangs, and you will change the pendulum’s motion. But move the support very gradually, and the system will adapt so that the pendulum’s motion relative to its support remains unchanged. A similar principle holds true for quantum systems. The quantum adiabatic theorem says that a system, when perturbed sufficiently slowly, remains in its instantaneous ground state. Sarah Damerow and Stefan Kehrein of the University of Göttingen in Germany now show that aspects of this principle remain true even for the opposite limit: The ground state remains the single most likely state even for a quantum system subjected to an instantaneous perturbation [1].
Formally, the quantum adiabatic theorem describes how a perturbed system’s Hamiltonian evolves in time. It shows that, for a slow perturbation, the system transitions from its initial ground state to the time-evolved Hamiltonian’s ground state with a probability greater than the combined probabilities of all the excited states.
Damerow and Kehrein used analytical and numerical tools to examine a quantum system undergoing rapid perturbation. They considered a quantum Ising model—a lattice of interacting magnetic spins—subjected to a rapidly changing external field. They found that the system was more likely to evolve from its initial ground state to the time-evolved Hamiltonian’s ground state than to any given excited state—provided that the lattice was in the same magnetic phase (paramagnetic or ferromagnetic) in both ground states.
Building desktop particle accelerators to unlock new realms of research
Using high-intensity lasers, researchers have taken an important step toward miniaturization of particle accelerators by demonstrating free-electron laser amplification at extreme ultraviolet wavelengths (27–50 nm), with an acceleration length of only a few millimeters. By generating high-quality, monoenergetic electron beams (i.e. beams where all the electrons have nearly the same energy), they have achieved a key milestone toward compact accelerator technologies.
The work is published in the journal Physical Review Research.
The research team led by The University of Osaka’s Institute of Scientific and Industrial Research (SANKEN) in collaboration with Kansai Institute for Photon Science (KPSI), National Institutes for Quantum Science and Technology (QST), RIKEN SPring-8 Center (RSC), High Energy Accelerator Research Organization (KEK), used a technique called laser wakefield acceleration to create plasma waves that generate extremely strong accelerating electric fields, thanks to waves within the plasma that travel at almost the speed of light.
Helical liquid crystals can flip light’s chirality under ultralow electric fields
The direction in which the electromagnetic field of circularly polarized light rotates can be easily reversed by applying a voltage, RIKEN researchers have demonstrated. This could enable a new generation of optical devices based on circularly polarized light. The work is published in two papers in the journal Advanced Materials.
Polarized sunglasses produce light that is polarized along a single direction. But some special devices can generate light with a polarization that rotates as the light propagates. Such circularly polarized light is useful for many applications, including spectroscopy, satellite communications, stereoscopy and microscopy.
For some applications, it would be useful to switch between clockwise and anticlockwise circularly polarized light. However, this handedness is locked into the molecular structure. Known as the material’s chirality, it is used to produce the circularly polarized light. And reversing that requires a lot of energy.
Useful quantum computers could be built with as few as 10,000 qubits, team finds
Quantum computers of the future may be closer to reality thanks to new research from Caltech and Oratomic, a Caltech-linked start-up company. Theorists and experimentalists teamed up to develop a new approach for reducing the errors that riddle today’s rudimentary quantum computers. Whereas these machines were previously thought to require millions of qubits to work properly (qubits being the quantum equivalent to 1’s and 0’s in classical computers), the new results indicate that a fully realized quantum computer could be built with as few as 10,000 to 20,000 qubits. The need for fewer qubits means that quantum computers could, in theory, be operational by the end of the decade.
The team proposes a new quantum error-correction architecture that is significantly more efficient than previous approaches. Quantum error correction is a process by which extra, redundant qubits are introduced to correct errors, or faults, enabling the ultimate goal in the field: fault-tolerant quantum computing.
The results exploit special properties of quantum computing platforms built out of neutral atoms, which serve as the qubits. Alternative platforms in development include superconducting circuits and trapped ions (ions are charged whereas neutral atoms are not). In a neutral atom system, laser beams known as optical tweezers are used to arrange atoms into qubit arrays. Manuel Endres, a professor of physics at Caltech, and his colleagues recently created the largest qubit array ever assembled, containing 6,100 trapped neutral atoms.
Ultrafast quantum light pulses measured for the first time
Researchers at the Technion—Israel Institute of Technology have, for the first time, measured the temporal duration of individual pulses of an extraordinary form of quantum light known as bright squeezed vacuum (BSV). Their findings are published in Optica.
Bright squeezed vacuum is a unique quantum state of light. Although it is formally considered the “vacuum state” and the electric field of this light is zero on average, it exhibits enormous quantum fluctuations of its electric field due to the squeezing effect.
This is in stark contrast to typical light produced by intense lasers, known as coherent-state light, that exhibit only extremely weak quantum fluctuations. However, for BSV, the fluctuations can lead to extremely intense light pulses, containing up to one trillion (10¹²) photons in a single pulse, hence the term bright squeezed vacuum. Until now, no one had measured the temporal duration of single BSV pulses.