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Quantum Physics in Proteins

2021/11/042021/11/16

Artificial intelligence affords unprecedented insights into how biomolecules work

A new analytical technique is able to provide hitherto unattainable insights into the extremely rapid dynamics of biomolecules. The team of developers, led by Abbas Ourmazd from the University of Wisconsin–Milwaukee and Robin Santra from DESY, is presenting its clever combination of quantum physics and molecular biology in the scientific journal Nature. The scientists used the technique to track the way in which the photoactive yellow protein (PYP) undergoes changes in its structure in less than a trillionth of a second after being excited by light.

“In order to precisely understand biochemical processes in nature, such as photosynthesis in certain bacteria, it is important to know the detailed sequence of events,” Santra explains their underlying motivation. “When light strikes photoactive proteins, their spatial structure is altered, and this structural change determines what role a protein takes on in nature.” Until now, however, it has been almost impossible to track the exact sequence in which structural changes occur. Only the initial and final states of a molecule before and after a reaction can be determined and interpreted in theoretical terms. “But we don’t know exactly how the energy and shape changes in between the two,” says Santra. “It’s like seeing that someone has folded their hands, but you can’t see them interlacing their fingers to do so.”

Creating the best TV screen yet

2020/08/192020/08/19

Breakthrough in blue quantum dot technology

There are many things quantum dots could do, but the most obvious place they could change our lives is to make the colours on our TVs and screens more pristine. Research using the Canadian Light Source (CLS) at the University of Saskatchewan is helping to bring this technology closer to our living rooms.

Quantum dots are nanocrystals that glow, a property that scientists have been working with to develop next-generation LEDs. When a quantum dot glows, it creates very pure light in a precise wavelength of red, blue or green. Conventional LEDs, found in our TV screens today, produce white light that is filtered to achieve desired colours, a process that leads to less bright and muddier colours.

Until now, blue-glowing quantum dots, which are crucial for creating a full range of colour, have proved particularly challenging for researchers to develop. However, University of Toronto (U of T) researcher Dr. Yitong Dong and collaborators have made a huge leap in blue quantum dot fluorescence, results they recently published in Nature Nanotechnology.

Read more on the Canadian Light Source website

Image: The blue quantum dot solution glows in a vial in a laboratory.

Breaking the link between a quantum material’s spin and orbital states

2020/05/152020/05/19

The advance opens a path toward a new generation of logic and memory devices that could be 10,000 times faster than today’s.

In designing electronic devices, scientists look for ways to manipulate and control three basic properties of electrons: their charge; their spin states, which give rise to magnetism; and the shapes of the fuzzy clouds they form around the nuclei of atoms, which are known as orbitals.

Until now, electron spins and orbitals were thought to go hand in hand in a class of materials that’s the cornerstone of modern information technology; you couldn’t quickly change one without changing the other. But a study at the Department of Energy’s SLAC National Accelerator Laboratory shows that a pulse of laser light can dramatically change the spin state of one important class of materials while leaving its orbital state intact.

>Read more on the LCLS at SLAC website

Image: These balloon-and-disk shapes represent an electron orbital – a fuzzy electron cloud around an atom’s nucleus – in two different orientations. Scientists hope to someday use variations in the orientations of orbitals as the 0s and 1s needed to make computations and store information in computer memories, a system known as orbitronics. A SLAC study shows it’s possible to separate these orbital orientations from electron spin patterns, a key step for independently controlling them in a class of materials that’s the cornerstone of modern information technology.

Credit: Greg Stewart/SLAC National Accelerator Laboratory

Brookhaven Lab and University of Delaware begin joint initiative

2019/08/122019/08/15

Through this partnership, scientists from both institutions will conduct collaborative research on rice soil chemistry and quantum materials.

The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and the University of Delaware (UD) have begun a two-year joint initiative to promote collaborative research in new areas of complementary strength and strategic importance. Though Brookhaven Lab and UD already have a tradition of collaboration, especially in catalysis, this initiative encourages partnerships in strategic areas where that tradition does not yet exist. After considering several potential areas, a committee from Brookhaven and UD selected two projects—one on rice soil chemistry and the other on quantum materials—for the new initiative. For each project, one graduate student based at Brookhaven and one graduate student from UD will work with and be supervised by a principal investigator from each respective institution. The research, to start in October 2019, is funded separately by the two institutions. Brookhaven funding is provided through its Laboratory-Directed Research and Development program, which promotes highly innovative and exploratory research that supports the Lab’s mission and areas for growth.

Image: Principal investigators from Brookhaven Lab and the University of Delaware (UD) will collaborate on two different research projects through a new joint initiative. Brookhaven’s Peter Johnson (left) and UD’s Stephanie Law (second from left) will measure the energy level spectrum of a topological insulator, a new type of material that behaves as an insulator internally but as a conductor on the surface; Brookhaven’s Ryan Tappero (second from the right) and UD’s Angelia Seyfferth (right) will study how toxic and nutrient metals are distributed in rice grain.

New method for imaging electronic orbitals in solids

2019/04/022019/04/04

Orbital states are quantum mechanical constructions that describe the probability to find an electron in an atom, molecule or solid. We know from atomic physics that an s-orbital is spherical or that a p-orbital is dumbbell-shaped, but how do the complicated distributions of the electrons that contribute to chemical bonds in solids look like? Knowledge of these orbital states or electron distributions is the basis for our understanding of chemical bonds and related physical properties, which is a crucial step towards tailoring materials with specific characteristics. Here X-ray spectroscopy has contributed tremendously, however, the interpretation of the spectra is not easy and is often based on some assumptions for the analysis of the data. Hence it would be very important to have an experimental method that gives a direct image of the local electron density.

Image: (a) (b) Integrated intensities of the M₁ transition 3s→3d in the Fig. above plotted on the respective projections of the ³A₂ 3d(x^2-y2/3z²-r²) orbital of Ni²⁺. (c) The three dimensional plot of the ³A₂ 3d(x²-y²/3z²-r²) orbital (more specific: the hole density) with the projections as in (a) and (b), respectively.
Credit: © MPI CPfS

How virtual photons alter atomic X-ray spectra

2019/03/292019/04/04

Control out of the vacuum, virtually

Certain X-ray optical properties of metal atoms can be controlled with the help of virtual photons. This has been demonstrated for the first time by a DESY research team at PETRA III, by using the highly brilliant radiation from this X-ray light source at DESY. In the journal Physical Review Letters they report on how the X-ray spectra of metal atoms can be controlled by virtual photons. This opens up new possibilities for specifically modifying the X-ray optical properties of materials.
So-called virtual photons play an important role in the interaction of light and matter. This is quite remarkable because they do not exist in the classical sense. Virtual photons are created in the vacuum out of nothing and then disappear again after an extremely short time. If these photons interact during their short existence with the electrons of an atom, the binding energies of the electrons shift ever so slightly.

Image: Experimental setup to measure the collective Lamb shift at tantalum.
Credit: DESY, Haber et al.

Classic double-slit experiment in a new light

2019/02/012019/02/12

An international research team led by physicists from Collaborative Research Centre 1238, ‘Control and Dynamics of Quantum Materials’ at the University of Cologne has implemented a new variant of the basic double-slit experiment using resonant inelastic X-ray scattering at the European Synchrotron ESRF in Grenoble. This new variant offers a deeper understanding of the electronic structure of solids. Writing in Science Advances, the research group have now presented their results under the title ‘Resonant inelastic x-ray incarnation of Young’s double-slit experiment’.

The double-slit experiment is of fundamental importance in physics. More than 200 years ago, Thomas Young diffracted light at two adjacent slits, thus generating interference patterns (images based on superposition) behind this double slit. That way, he demonstrated the wave character of light. In the 20th century, scientists have shown that electrons or molecules scattered on a double slit show the same interference pattern, which contradicts the classical expectation of particle behaviour, but can be explained in quantum-mechanical wave-particle dualism. In contrast, the researchers in Cologne investigated an iridium oxide crystal (Ba3CeIr2O9) by means of resonant inelastic X-ray scattering (RIXS).

Image: Beamline ID20, where the experiments took place.
Credit: P. Jayet.

Photocathodes with high quantum efficiency at bERLinPro

2018/12/072018/12/18

A team at the HZB has improved the manufacturing process of photocathodes and can now provide photocathodes with high quantum efficiency for bERLinPro.

Teams from the accelerator physics and the SRF groups at HZB are developing a superconducting linear accelerator featuring energy recovery (Energy Recovery Linac) as part of the bERLinPro project. It accelerates an intense electron beam that can then be used for various applications – such as generating brilliant synchrotron radiation. After use, the electron bunches are directed back to the superconducting linear accelerator, where they release almost all their remaining energy. This energy is then available for accelerating new electron bunches.

Electron source: photocathode

A crucial component of the design is the electron source. Electrons are generated by illuminating a photocathode with a green laser beam. The quantum efficiency, as it is referred to, indicates how many electrons the photocathode material emits when illuminated at a certain laser wavelength and power. Bialkali antimonides exhibit particularly high quantum efficiency in the region of visible light. However, thin films of these materials are highly reactive and therefore very sensitive, so they only work at ultra-high vacuum.

Image: Photocathode after its production in the preparatory system.
Credit: J. Kühn/HZB

Scientists have a new way to gauge the growth of nanowires

2018/03/192018/03/27

In a new study, researchers from the U.S. Department of Energy’s Argonne and Brookhaven National Laboratories observed the formation of two kinds of defects in individual nanowires, which are smaller in diameter than a human hair.

These nanowires, made of indium gallium arsenide, could be useful for a wide range of applications in a field scientists have termed optoelectronics, which encompasses devices that work by converting light energy into electrical impulses. Fiber optic relays are a good example.

The effectiveness of these devices, however, can be affected by tiny defects in their components. These defects, which can change both the optical and electronic properties of these materials, interest scientists who seek to tailor them to boost the functionality of future optoelectronics, including materials that will be able to manipulate quantum information.

>Read more on the NSLS-II website and the Advanced Photon Source website

Image: Argonne and Brookhaven researchers observed two kinds of defects forming in individual nanowires, depicted here. These nanowires are smaller in diameter than a human hair.
Credit: Megan Hill/Northwestern University

Scientists measure accelerated emission

2017/12/292018/01/16

Grazing light for rapid events

An international team, including scientists from DESY, has verified a prediction about the quantum-mechanical behaviour of resonant systems made more than 50 years ago. In experiments at SACLA, the Japanese X-ray laser, and at the European Synchrotron Radiation Facility ESRF in France, the group led by Aleksandr Chumakov from ESRF could show a dramatic reduction in the time to emit the first X-ray photon from an ensemble of excited nuclei when the number of X-rays for the excitation was increased. This behaviour is in good agreement with one limit of a superradiant system, predicted by the US physicist Robert Dicke in 1954, as the scientists report in the journal Nature Physics.

One of the broad challenges of science is to understand the behaviour of groups of atoms based on the response of a single atom in isolation, which is usually much simpler. A facet of this is understanding the behaviour of a group of identical oscillators. An analogy is a collection of bells that all have the same tone: one can easily imagine the sound of a single bell struck once – a clear tone ringing out with a volume that decays away over time.

But what happens if one gently taps all the bells in a large collection? Will the tone be the same as a single one? What about the volume? What about the direction – does it matter where you are standing when you listen to the sound? Does it matter if you tap them all at the same time?

>Read more on the FLASH website

Watching a Quantum Material Lose Its Stripes

2017/11/292017/12/07

Berkeley Lab study uses terahertz laser pulses to reveal ultrafast coupling of atomic-scale patterns

Stripes can be found everywhere, from zebras roaming in the wild to the latest fashion statement. In the world of microscopic physics, periodic stripe patterns can be formed by electrons within so-called quantum materials.

Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have now disentangled the intriguing dynamics of how such atomic-scale stripes melt and form, providing fundamental insights that could be useful in the development of novel energy materials.

>Read more on the ALS website

Image: Illustration of an ultrashort laser light striking a lanthanum strontium nickel oxide crystal, triggering the melting of atomic-scale stripes. The charges (yellow) quickly become mobile while the crystal distortions react only with delay, exposing the underlying interactions.
Credit: Robert Kaindl/Berkeley Lab

Precise test of quantum physical tunnel effect at DESY’s X-ray laser FLASH

2016/10/042017/12/04

Partnership at a distance: deep-frozen helium molecules

Helium atoms are loners. Only when you cool them to very low temperatures do they form extremely weakly bonded molecules. Yet even in this state, they are able to maintain an extremely large separation from each other thanks to quantum tunnelling. With the help of DESY’s free-electron laser FLASH, Frankfurt nuclear physicists have been able to confirm that the atoms spend more than 75 percent of their time so far apart from each other that their bond can only be explained by means of quantum tunnelling. The scientists have presented their findings in the US journal “Proceedings of the National Academy of Sciences” (PNAS).

The binding energy of a helium molecule is approximately one billionth of the binding energy of everyday molecules like oxygen or nitrogen. On top of this, the molecule is so huge that small viruses or soot particles could actually pass between the atoms. Physicists explain this in terms of quantum tunnelling. They visualise the bond in a classical molecule as a potential well, in which atoms cannot get further apart from each other than by going to opposite “walls”. However, quantum theory also allows atoms to tunnel inside these walls. “It is as if each of them were to dig a shaft without an exit,” explains Reinhard Dörner, a professor at the Institute of Nuclear Physics at the Goethe University in Frankfurt.

>Read more on the FLASH website

Cartoon: “When two loners are forced to share a bed, they move well beyond its edges to get away from each other.”
Credit: Peter Evers