Tag Archives: quantum mechanics

Light-captured energetics (harvesting light for optoelectronics)

Comparing graphene to a tiger is unusual but that’s what researcher Sanfeng Wu does—eventually—in a May 13, 2016 University of Washington news release (also on EurekAlert) about his work,

In the quest to harvest light for electronics, the focal point is the moment when photons — light particles — encounter electrons, those negatively-charged subatomic particles that form the basis of our modern electronic lives. If conditions are right when electrons and photons meet, an exchange of energy can occur. Maximizing that transfer of energy is the key to making efficient light-captured energetics possible.

“This is the ideal, but finding high efficiency is very difficult,” said University of Washington physics doctoral student Sanfeng Wu. “Researchers have been looking for materials that will let them do this — one way is to make each absorbed photon transfer all of its energy to many electrons, instead of just one electron in traditional devices.”

In traditional light-harvesting methods, energy from one photon only excites one electron or none depending on the absorber’s energy gap, transferring just a small portion of light energy into electricity. The remaining energy is lost as heat. But in a paper released May 13 in Science Advances, Wu, UW associate professor Xiaodong Xu and colleagues at four other institutions describe one promising approach to coax photons into stimulating multiple electrons. Their method exploits some surprising quantum-level interactions to give one photon multiple potential electron partners. Wu and Xu, who has appointments in the UW’s Department of Materials Science & Engineering and the Department of Physics, made this surprising discovery using graphene.

There has been intense research on graphene’s electrical properties but the researchers’ discovery adds a new property to be investigated (from the news release),

“Graphene is a substance with many exciting properties,” said Wu, the paper’s lead author. “For our purposes, it shows a very efficient interaction with light.”

Graphene is a two-dimensional hexagonal lattice of carbon atoms bonded to one another, and electrons are able to move easily within graphene. The researchers took a single layer of graphene — just one sheet of carbon atoms thick — and sandwiched it between two thin layers of a material called boron-nitride.

Boron-nitride is a material that has excited a great deal of interest in the last 12 to 18 months (from the news release),

“Boron-nitride has a lattice structure that is very similar to graphene, but has very different chemical properties,” said Wu. “Electrons do not flow easily within boron-nitride; it essentially acts as an insulator.”

Xu and Wu discovered that when the graphene layer’s lattice is aligned with the layers of boron-nitride, a type of “superlattice” is created with properties allowing efficient optoelectronics that researchers had sought. These properties rely on quantum mechanics, the occasionally baffling rules that govern interactions between all known particles of matter. Wu and Xu detected unique quantum regions within the superlattice known as Van Hove singularities.

Here’s an animated .gif illustrating the superlattice in action,

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The news release goes on to describe the Van Hove singularities within the superlattice and to mention the ‘tiger’,

“These are regions of huge electron density of states, and they were not accessed in either the graphene or boron-nitride alone,” said Wu. “We only created these high electron density regions in an accessible way when both layers were aligned together.”

When Xu and Wu directed energetic photons toward the superlattice, they discovered that those Van Hove singularities were sites where one energized photon could transfer its energy to multiple electrons that are subsequently collected by electrodes— not just one electron or none with the remaining energy lost as heat. By a conservative estimate, Xu and Wu report that within this superlattice one photon could “kick” as many as five electrons to flow as current.

With the discovery of collecting multiple electrons upon the absorption of one photon, researchers may be able to create highly efficient devices that could harvest light with a large energy profit. Future work would need to uncover how to organize the excited electrons into electrical current for optimizing the energy-converting efficiency and remove some of the more cumbersome properties of their superlattice, such as the need for a magnetic field. But they believe this efficient process between photons and electrons represents major progress.

“Graphene is a tiger with great potential for optoelectronics, but locked in a cage,” said Wu. “The singularities in this superlattice are a key to unlocking that cage and releasing graphene’s potential for light harvesting application.”

H/t to a May 13, 2016 news item on phys.org.

Here’s a link to and a citation for the paper,

Multiple hot-carrier collection in photo-excited graphene Moiré superlattices by Sanfeng Wu, Lei Wang, You Lai, Wen-Yu Shan, Grant Aivazian, Xian Zhang, Takashi Taniguchi, Kenji Watanabe, Di Xiao, Cory Dean, James Hone, Zhiqiang Li, and Xiaodong Xu. Science Advances 13 May 2016: Vol. 2, no. 5, e1600002 DOI: 10.1126/sciadv.1600002

This paper is open access.

A new state for water molecules

ORNL researchers discovered that water in beryl displays some unique and unexpected characteristics. (Photo by Jeff Scovil)

ORNL researchers discovered that water in beryl displays some unique and unexpected characteristics. (Photo by Jeff Scovil)

That striking image from the Oak Ridge National Laboratory (ORNL; US) depicting a new state for water molecules looks like mixed media: photography and drawing/illustration. Thankfully, an April 22, 2016 news item on ScienceDaily provides a text description,

Neutron scattering and computational modeling have revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid or solid states.

In a paper published in Physical Review Letters, researchers at the Department of Energy’s Oak Ridge National Laboratory [ORNL] describe a new tunneling state of water molecules confined in hexagonal ultra-small channels — 5 angstrom across — of the mineral beryl. An angstrom is 1/10-billionth of a meter, and individual atoms are typically about 1 angstrom in diameter.

The discovery, made possible with experiments at ORNL’s Spallation Neutron Source and the Rutherford Appleton Laboratory in the United Kingdom, demonstrates features of water under ultra confinement in rocks, soil and cell walls, which scientists predict will be of interest across many disciplines.

An April 22, 2016 ORNL news release (also on EurekAlert), which originated the news item, offers more detail,

“At low temperatures, this tunneling water exhibits quantum motion through the separating potential walls, which is forbidden in the classical world,” said lead author Alexander Kolesnikov of ORNL’s Chemical and Engineering Materials Division. “This means that the oxygen and hydrogen atoms of the water molecule are ‘delocalized’ and therefore simultaneously present in all six symmetrically equivalent positions in the channel at the same time. It’s one of those phenomena that only occur in quantum mechanics and has no parallel in our everyday experience.”

The existence of the tunneling state of water shown in ORNL’s study should help scientists better describe the thermodynamic properties and behavior of water in highly confined environments such as water diffusion and transport in the channels of cell membranes, in carbon nanotubes and along grain boundaries and at mineral interfaces in a host of geological environments.

ORNL co-author Lawrence Anovitz noted that the discovery is apt to spark discussions among materials, biological, geological and computational scientists as they attempt to explain the mechanism behind this phenomenon and understand how it applies to their materials.

“This discovery represents a new fundamental understanding of the behavior of water and the way water utilizes energy,” Anovitz said. “It’s also interesting to think that those water molecules in your aquamarine or emerald ring – blue and green varieties of beryl – are undergoing the same quantum tunneling we’ve seen in our experiments.”

While previous studies have observed tunneling of atomic hydrogen in other systems, the ORNL discovery that water exhibits such tunneling behavior is unprecedented. The neutron scattering and computational chemistry experiments showed that, in the tunneling state, the water molecules are delocalized around a ring so the water molecule assumes an unusual double top-like shape.

“The average kinetic energy of the water protons directly obtained from the neutron experiment is a measure of their motion at almost absolute zero temperature and is about 30 percent less than it is in bulk liquid or solid water,” Kolesnikov said. “This is in complete disagreement with accepted models based on the energies of its vibrational modes.”

Here’s a link to and a citation for the paper,

Quantum Tunneling of Water in Beryl: A New State of the Water Molecule by Alexander I. Kolesnikov, George F. Reiter, Narayani Choudhury, Timothy R. Prisk, Eugene Mamontov, Andrey Podlesnyak, George Ehlers, Andrew G. Seel, David J. Wesolowski, and Lawrence M. Anovitz.
Phys. Rev. Lett. 116, 167802 – Published 22 April 2016

This paper is behind a paywall.

An atom without properties?

There’s rather intriguing Swiss research into atoms and so-called Bell Correlations according to an April 21, 2016 news item on ScienceDaily,

The microscopic world is governed by the rules of quantum mechanics, where the properties of a particle can be completely undetermined and yet strongly correlated with those of other particles. Physicists from the University of Basel have observed these so-called Bell correlations for the first time between hundreds of atoms. Their findings are published in the scientific journal Science.

Everyday objects possess properties independently of each other and regardless of whether we observe them or not. Einstein famously asked whether the moon still exists if no one is there to look at it; we answer with a resounding yes. This apparent certainty does not exist in the realm of small particles. The location, speed or magnetic moment of an atom can be entirely indeterminate and yet still depend greatly on the measurements of other distant atoms.

An April 21, 2016 University of Basel (Switzerland) press release (also on EurekAlert), which originated the news item, provides further explanation,

With the (false) assumption that atoms possess their properties independently of measurements and independently of each other, a so-called Bell inequality can be derived. If it is violated by the results of an experiment, it follows that the properties of the atoms must be interdependent. This is described as Bell correlations between atoms, which also imply that each atom takes on its properties only at the moment of the measurement. Before the measurement, these properties are not only unknown – they do not even exist.

A team of researchers led by professors Nicolas Sangouard and Philipp Treutlein from the University of Basel, along with colleagues from Singapore, have now observed these Bell correlations for the first time in a relatively large system, specifically among 480 atoms in a Bose-Einstein condensate. Earlier experiments showed Bell correlations with a maximum of four light particles or 14 atoms. The results mean that these peculiar quantum effects may also play a role in larger systems.

Large number of interacting particles

In order to observe Bell correlations in systems consisting of many particles, the researchers first had to develop a new method that does not require measuring each particle individually – which would require a level of control beyond what is currently possible. The team succeeded in this task with the help of a Bell inequality that was only recently discovered. The Basel researchers tested their method in the lab with small clouds of ultracold atoms cooled with laser light down to a few billionths of a degree above absolute zero. The atoms in the cloud constantly collide, causing their magnetic moments to become slowly entangled. When this entanglement reaches a certain magnitude, Bell correlations can be detected. Author Roman Schmied explains: “One would expect that random collisions simply cause disorder. Instead, the quantum-mechanical properties become entangled so strongly that they violate classical statistics.”

More specifically, each atom is first brought into a quantum superposition of two states. After the atoms have become entangled through collisions, researchers count how many of the atoms are actually in each of the two states. This division varies randomly between trials. If these variations fall below a certain threshold, it appears as if the atoms have ‘agreed’ on their measurement results; this agreement describes precisely the Bell correlations.

New scientific territory

The work presented, which was funded by the National Centre of Competence in Research Quantum Science and Technology (NCCR QSIT), may open up new possibilities in quantum technology; for example, for generating random numbers or for quantum-secure data transmission. New prospects in basic research open up as well: “Bell correlations in many-particle systems are a largely unexplored field with many open questions – we are entering uncharted territory with our experiments,” says Philipp Treutlein.

Here’s a link to and a citation for the paper,

Bell correlations in a Bose-Einstein condensate by Roman Schmied, Jean-Daniel Bancal, Baptiste Allard, Matteo Fadel, Valerio Scarani, Philipp Treutlein, Nicolas Sangouard. Science  22 Apr 2016: Vol. 352, Issue 6284, pp. 441-444 DOI: 10.1126/science.aad8665

This paper is behind a paywall.

Prime Minister Trudeau, the quantum physicist

Prime Minister Justin Trudeau’s apparently extemporaneous response to a joking (non)question about quantum computing by a journalist during an April 15, 2016 press conference at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada has created a buzz online, made international news, and caused Canadians to sit taller.

For anyone who missed the moment, here’s a video clip from the Canadian Broadcasting Corporation (CBC),

Aaron Hutchins in an April 15, 2016 article for Maclean’s magazine digs deeper to find out more about Trudeau and quantum physics (Note: A link has been removed),

Raymond Laflamme knows the drill when politicians visit the Perimeter Institute. A photo op here, a few handshakes there and a tour with “really basic, basic, basic facts” about the field of quantum mechanics.

But when the self-described “geek” Justin Trudeau showed up for a funding announcement on Friday [April 15, 2016], the co-founder and director of the Institute for Quantum Computing at the University of Waterloo wasn’t met with simple nods of the Prime Minister pretending to understand. Trudeau immediately started talking about things being waves and particles at the same time, like cats being dead and alive at the same time. It wasn’t just nonsense—Trudeau was referencing the famous thought experiment of the late legendary physicist Erwin Schrödinger.

“I don’t know where he learned all that stuff, but we were all surprised,” Laflamme says. Soon afterwards, as Trudeau met with one student talking about superconductivity, the Prime Minister asked her, “Why don’t we have high-temperature superconducting systems?” something Laflamme describes as the institute’s “Holy Grail” quest.

“I was flabbergasted,” Laflamme says. “I don’t know how he does in other subjects, but in quantum physics, he knows the basic pieces and the important questions.”

Strangely, Laflamme was not nearly as excited (tongue in cheek) when I demonstrated my understanding of quantum physics during our interview (see my May 11, 2015 posting; scroll down about 40% of the way to the Ramond Laflamme subhead).

As Jon Butterworth comments in his April 16, 2016 posting on the Guardian science blog, the response says something about our expectations regarding politicians,

This seems to have enhanced Trudeau’s reputation no end, and quite right too. But it is worth thinking a bit about why.

The explanation he gives is clear, brief, and understandable to a non-specialist. It is the kind of thing any sufficiently engaged politician could pick up from a decent briefing, given expert help. …

Butterworth also goes on to mention journalists’ expectations,

The reporter asked the question in a joking fashion, not unkindly as far as I can tell, but not expecting an answer either. If this had been an announcement about almost any other government investment, wouldn’t the reporter have expected a brief explanation of the basic ideas behind it? …

As for the announcement being made by Trudeau, there is this April 15, 2016 Perimeter Institute press release (Note: Links have been removed),

Prime Minister Justin Trudeau says the work being done at Perimeter and in Canada’s “Quantum Valley” [emphasis mine] is vital to the future of the country and the world.

Prime Minister Justin Trudeau became both teacher and student when he visited Perimeter Institute today to officially announce the federal government’s commitment to support fundamental scientific research at Perimeter.

Joined by Minister of Science Kirsty Duncan and Small Business and Tourism Minister Bardish Chagger, the self-described “geek prime minister” listened intensely as he received brief overviews of Perimeter research in areas spanning from quantum science to condensed matter physics and cosmology.

“You don’t have to be a geek like me to appreciate how important this work is,” he then told a packed audience of scientists, students, and community leaders in Perimeter’s atrium.

The Prime Minister was also welcomed by 200 teenagers attending the Institute’s annual Inspiring Future Women in Science conference, and via video greetings from cosmologist Stephen Hawking [he was Laflamme’s PhD supervisor], who is a Perimeter Distinguished Visiting Research Chair. The Prime Minister said he was “incredibly overwhelmed” by Hawking’s message.

“Canada is a wonderful, huge country, full of people with big hearts and forward-looking minds,” Hawking said in his message. “It’s an ideal place for an institute dedicated to the frontiers of physics. In supporting Perimeter, Canada sets an example for the world.”

The visit reiterated the Government of Canada’s pledge of $50 million over five years announced in last month’s [March 2016] budget [emphasis mine] to support Perimeter research, training, and outreach.

It was the Prime Minister’s second trip to the Region of Waterloo this year. In January [2016], he toured the region’s tech sector and universities, and praised the area’s innovation ecosystem.

This time, the focus was on the first link of the innovation chain: fundamental science that could unlock important discoveries, advance human understanding, and underpin the groundbreaking technologies of tomorrow.

As for the “quantum valley’ in Ontario, I think there might be some competition here in British Columbia with D-Wave Systems (first commercially available quantum computing, of a sort; my Dec. 16, 2015 post is the most recent one featuring the company) and the University of British Columbia’s Stewart Blusson Quantum Matter Institute.

Getting back to Trudeau, it’s exciting to have someone who seems so interested in at least some aspects of science that he can talk about it with a degree of understanding. I knew he had an interest in literature but there is also this (from his Wikipedia entry; Note: Links have been removed),

Trudeau has a bachelor of arts degree in literature from McGill University and a bachelor of education degree from the University of British Columbia…. After graduation, he stayed in Vancouver and he found substitute work at several local schools and permanent work as a French and math teacher at the private West Point Grey Academy … . From 2002 to 2004, he studied engineering at the École Polytechnique de Montréal, a part of the Université de Montréal.[67] He also started a master’s degree in environmental geography at McGill University, before suspending his program to seek public office.[68] [emphases mine]

Trudeau is not the only political leader to have a strong interest in science. In our neighbour to the south, there’s President Barack Obama who has done much to promote science since he was elected in 2008. David Bruggeman in an April 15, 2016  post (Obama hosts DNews segments for Science Channel week of April 11-15, 2016) and an April 17, 2016 post (Obama hosts White House Science Fair) describes two of Obama’s most recent efforts.

ETA April 19, 2016: I’ve found confirmation that this Q&A was somewhat staged as I hinted in the opening with “Prime Minister Justin Trudeau’s apparently extemporaneous response … .” Will Oremus’s April 19, 2016 article for Slate.com breaks the whole news cycle down and points out (Note: A link has been removed),

Over the weekend, even as latecomers continued to dine on the story’s rapidly decaying scraps, a somewhat different picture began to emerge. A Canadian blogger pointed out that Trudeau himself had suggested to reporters at the event that they lob him a question about quantum computing so that he could knock it out of the park with the newfound knowledge he had gleaned on his tour.

The Canadian blogger who tracked this down is J. J. McCullough (Jim McCullough) and you can read his Oct. 16, 2016 posting on the affair here. McCullough has a rather harsh view of the media response to Trudeau’s lecture. Oremus is a bit more measured,

… Monday brought the countertake parade—smaller and less pompous, if no less righteous—led by Gawker with the headline, “Justin Trudeau’s Quantum Computing Explanation Was Likely Staged for Publicity.”

But few of us in the media today are immune to the forces that incentivize timeliness and catchiness over subtlety, and even Gawker’s valuable corrective ended up meriting a corrective of its own. Author J.K. Trotter soon updated his post with comments from Trudeau’s press secretary, who maintained (rather convincingly, I think) that nothing in the episode was “staged”—at least, not in the sinister way that the word implies. Rather, Trudeau had joked that he was looking forward to someone asking him about quantum computing; a reporter at the press conference jokingly complied, without really expecting a response (he quickly moved on to his real question before Trudeau could answer); Trudeau responded anyway, because he really did want to show off his knowledge.

Trotter deserves credit, regardless, for following up and getting a fuller picture of what transpired. He did what those who initially jumped on the story did not, which was to contact the principals for context and comment.

But my point here is not to criticize any particular writer or publication. The too-tidy Trudeau narrative was not the deliberate work of any bad actor or fabricator. Rather, it was the inevitable product of today’s inexorable social-media machine, in which shareable content fuels the traffic-referral engines that pay online media’s bills.

I suggest reading both McCullough’s and Oremus’s posts in their entirety should you find debates about the role of media compelling.

Handling massive digital datasets the quantum way

A Jan. 25, 2016 news item on phys.org describes a new approach to analyzing and managing huge datasets,

From gene mapping to space exploration, humanity continues to generate ever-larger sets of data—far more information than people can actually process, manage, or understand.

Machine learning systems can help researchers deal with this ever-growing flood of information. Some of the most powerful of these analytical tools are based on a strange branch of geometry called topology, which deals with properties that stay the same even when something is bent and stretched every which way.

Such topological systems are especially useful for analyzing the connections in complex networks, such as the internal wiring of the brain, the U.S. power grid, or the global interconnections of the Internet. But even with the most powerful modern supercomputers, such problems remain daunting and impractical to solve. Now, a new approach that would use quantum computers to streamline these problems has been developed by researchers at [Massachusetts Institute of Technology] MIT, the University of Waterloo, and the University of Southern California [USC}.

A Jan. 25, 2016 MIT news release (*also on EurekAlert*), which originated the news item, describes the theory in more detail,

… Seth Lloyd, the paper’s lead author and the Nam P. Suh Professor of Mechanical Engineering, explains that algebraic topology is key to the new method. This approach, he says, helps to reduce the impact of the inevitable distortions that arise every time someone collects data about the real world.

In a topological description, basic features of the data (How many holes does it have? How are the different parts connected?) are considered the same no matter how much they are stretched, compressed, or distorted. Lloyd [ explains that it is often these fundamental topological attributes “that are important in trying to reconstruct the underlying patterns in the real world that the data are supposed to represent.”

It doesn’t matter what kind of dataset is being analyzed, he says. The topological approach to looking for connections and holes “works whether it’s an actual physical hole, or the data represents a logical argument and there’s a hole in the argument. This will find both kinds of holes.”

Using conventional computers, that approach is too demanding for all but the simplest situations. Topological analysis “represents a crucial way of getting at the significant features of the data, but it’s computationally very expensive,” Lloyd says. “This is where quantum mechanics kicks in.” The new quantum-based approach, he says, could exponentially speed up such calculations.

Lloyd offers an example to illustrate that potential speedup: If you have a dataset with 300 points, a conventional approach to analyzing all the topological features in that system would require “a computer the size of the universe,” he says. That is, it would take 2300 (two to the 300th power) processing units — approximately the number of all the particles in the universe. In other words, the problem is simply not solvable in that way.

“That’s where our algorithm kicks in,” he says. Solving the same problem with the new system, using a quantum computer, would require just 300 quantum bits — and a device this size may be achieved in the next few years, according to Lloyd.

“Our algorithm shows that you don’t need a big quantum computer to kick some serious topological butt,” he says.

There are many important kinds of huge datasets where the quantum-topological approach could be useful, Lloyd says, for example understanding interconnections in the brain. “By applying topological analysis to datasets gleaned by electroencephalography or functional MRI, you can reveal the complex connectivity and topology of the sequences of firing neurons that underlie our thought processes,” he says.

The same approach could be used for analyzing many other kinds of information. “You could apply it to the world’s economy, or to social networks, or almost any system that involves long-range transport of goods or information,” says Lloyd, who holds a joint appointment as a professor of physics. But the limits of classical computation have prevented such approaches from being applied before.

While this work is theoretical, “experimentalists have already contacted us about trying prototypes,” he says. “You could find the topology of simple structures on a very simple quantum computer. People are trying proof-of-concept experiments.”

Ignacio Cirac, a professor at the Max Planck Institute of Quantum Optics in Munich, Germany, who was not involved in this research, calls it “a very original idea, and I think that it has a great potential.” He adds “I guess that it has to be further developed and adapted to particular problems. In any case, I think that this is top-quality research.”

Here’s a link to and a citation for the paper,

Quantum algorithms for topological and geometric analysis of data by Seth Lloyd, Silvano Garnerone, & Paolo Zanardi. Nature Communications 7, Article number: 10138 doi:10.1038/ncomms10138 Published 25 January 2016

This paper is open access.

ETA Jan. 25, 2016 1245 hours PST,

Shown here are the connections between different regions of the brain in a control subject (left) and a subject under the influence of the psychedelic compound psilocybin (right). This demonstrates a dramatic increase in connectivity, which explains some of the drug’s effects (such as “hearing” colors or “seeing” smells). Such an analysis, involving billions of brain cells, would be too complex for conventional techniques, but could be handled easily by the new quantum approach, the researchers say. Courtesy of the researchers

Shown here are the connections between different regions of the brain in a control subject (left) and a subject under the influence of the psychedelic compound psilocybin (right). This demonstrates a dramatic increase in connectivity, which explains some of the drug’s effects (such as “hearing” colors or “seeing” smells). Such an analysis, involving billions of brain cells, would be too complex for conventional techniques, but could be handled easily by the new quantum approach, the researchers say. Courtesy of the researchers

*’also on EurekAlert’ text and link added Jan. 26, 2016.

100 percent efficiency transporting the energy of sunlight from receptors to reaction centers

Genetic engineering has been combined with elements of quantum physics to find a better way of transferring the energy derived from sunlight from the receptors to the reaction centers (i.e., photosynthesis). From an Oct. 15, 2015 news item on Nanowerk,

Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100 percent efficiency in transporting the energy of sunlight from receptors to reaction centers where it can be harnessed — a performance vastly better than even the best solar cells.

One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics — effects sometimes known as “quantum weirdness.” These effects, which include the ability of a particle to exist in more than one place at a time [superposition], have now been used by engineers at MIT to achieve a significant efficiency boost in a light-harvesting system.

Surprisingly, the MIT [Massachusetts Institute of Technology] researchers achieved this new approach to solar energy not with high-tech materials or microchips — but by using genetically engineered viruses.

An Oct. 15, 2015 MIT news release (also on EurekAlert), which originated the news item, recounts an exciting tale of interdisciplinary work and an international collaboration,

This achievement in coupling quantum research and genetic manipulation, described this week in the journal Nature Materials, was the work of MIT professors Angela Belcher, an expert on engineering viruses to carry out energy-related tasks, and Seth Lloyd, an expert on quantum theory and its potential applications; research associate Heechul Park; and 14 collaborators at MIT and in Italy.

Lloyd, a professor of mechanical engineering, explains that in photosynthesis, a photon hits a receptor called a chromophore, which in turn produces an exciton — a quantum particle of energy. This exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life.

But the hopping pathway is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle.

This efficient movement of excitons has one key requirement: The chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the “Quantum Goldilocks Effect.”

That’s where the virus comes in. By engineering a virus that Belcher has worked with for years, the team was able to get it to bond with multiple synthetic chromophores — or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.

In the end, they were able to more than double excitons’ speed, increasing the distance they traveled before dissipating — a significant improvement in the efficiency of the process.

The project started from a chance meeting at a conference in Italy. Lloyd and Belcher, a professor of biological engineering, were reporting on different projects they had worked on, and began discussing the possibility of a project encompassing their very different expertise. Lloyd, whose work is mostly theoretical, pointed out that the viruses Belcher works with have the right length scales to potentially support quantum effects.

In 2008, Lloyd had published a paper demonstrating that photosynthetic organisms transmit light energy efficiently because of these quantum effects. When he saw Belcher’s report on her work with engineered viruses, he wondered if that might provide a way to artificially induce a similar effect, in an effort to approach nature’s efficiency.

“I had been talking about potential systems you could use to demonstrate this effect, and Angela said, ‘We’re already making those,'” Lloyd recalls. Eventually, after much analysis, “We came up with design principles to redesign how the virus is capturing light, and get it to this quantum regime.”

Within two weeks, Belcher’s team had created their first test version of the engineered virus. Many months of work then went into perfecting the receptors and the spacings.

Once the team engineered the viruses, they were able to use laser spectroscopy and dynamical modeling to watch the light-harvesting process in action, and to demonstrate that the new viruses were indeed making use of quantum coherence to enhance the transport of excitons.

“It was really fun,” Belcher says. “A group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That’s why I’m so excited by this.”

While this initial result is essentially a proof of concept rather than a practical system, it points the way toward an approach that could lead to inexpensive and efficient solar cells or light-driven catalysis, the team says. So far, the engineered viruses collect and transport energy from incoming light, but do not yet harness it to produce power (as in solar cells) or molecules (as in photosynthesis). But this could be done by adding a reaction center, where such processing takes place, to the end of the virus where the excitons end up.

MIT has produced a video explanation of the work,

Here’s a link to and a citation for the paper,

Enhanced energy transport in genetically engineered excitonic networks by Heechul Park, Nimrod Heldman, Patrick Rebentrost, Luigi Abbondanza, Alessandro Iagatti, Andrea Alessi, Barbara Patrizi, Mario Salvalaggio, Laura Bussotti, Masoud Mohseni, Filippo Caruso, Hannah C. Johnsen, Roberto Fusco, Paolo Foggi, Petra F. Scudo, Seth Lloyd, & Angela M. Belcher. Nature Materials (2015) doi:10.1038/nmat4448 Published online 12 October 2015

This paper is behind a paywall.

Access (virtual) to a quantum lab for everybody

I love the idea behind this project “find a way to make research equipment available to everyone” and that’s what the researchers at the University of Vienna (Austria) hope they have achieved according to a Sept. 16, 2015 University of Vienna press release (also on EurekAlert),

Topical research experiments are often too expensive or too complex to be rebuilt and incorporated in teaching. How can one, nevertheless, make modern science accessible to the public? This challenge was tackled in the research group Quantum Nanophysics led by Markus Arndt at the University of Vienna. For the first time, two research laboratories were created as complete, photorealistic computer simulations allowing university and high-school students as well as the general public to virtually access unique instruments. “One could describe it as a flight simulator of quantum physics”, says Mathias Tomandl who designed and implemented the essential elements of the simulation in the course of his PhD studies.

The press release goes on to describe the process for using the laboratory and some real life events promoting the lab,

A learning path guides the visitors of the virtual quantum lab through the world of delocalized complex molecules. A series of lab tasks and essential background information on the experiments enable the visitors to gradually immerse into the quantum world. The engaging software was developed together with university and high-school students and was fine-tuned by periodic didactic input. The teaching concept and the accompanying studies have now been published in the renowned scientific journal Scientific Reports.

Wave-particle dualism with large molecules

The virtual laboratories provide an insight into the fundamental understanding and into the applications of quantum mechanics with macromolecules and nanoparticles. In recent years, the real-life versions of the experiments verified the wave-particle dualism with the most complex molecules to date. Now, everyone can conduct these experiments in the virtual lab for the first time.

The quantum lab on tour through Austria

Currrently, a light version of the virtual lab can be experienced as an interactive exhibit in the special exhibition “Das Wissen der Dinge” in the Natural History Museum Vienna. In the travelling exhibition “Wirkungswechsel” of the Science-Center-Netzwerk the exhibit will be available at various locations throughout Austria.

Here’s a video produced by the researchers to demonstrate their virtual quantum lab,

For more information about the exhibitions,

Special exhibition “Das Wissen der Dinge”: http://www.nhm-wien.ac.at/ausstellung/sonderausstellungen/das_wissen_der_dinge_1

Travelling exhibition “Wirkungswechsel”: http://www.wirkungswechsel.at/

Here’s a link to and a citation for the paper,

Simulated Interactive Research Experiments as Educational Tools for Advanced Science by Mathias Tomandl, Thomas Mieling, Christiane M. Losert-Valiente Kroon, Martin Hopf, & Markus Arndt. Scientific Reports 5, Article number: 14108 (2015) doi:10.1038/srep14108 Published online: 15 September 2015

This paper is open access.

Complex networks to provide ‘grand unified theory’

Trying to mesh classical physics and quantum physics together in one theory which accounts for behaviour on the macro and quantum scales has occupied scientists for decades and it seems that mathematicians have discovered a clue so solving the mystery. A Sept. 13, 2015 news item on Nanotechnology Now describes the findings,

Mathematicians investigating one of science’s great questions — how to unite the physics of the very big with that of the very small — have discovered that when the understanding of complex networks such as the brain or the Internet is applied to geometry the results match up with quantum behavior.

A Sept. 9, 2015 Queen Mary University of London press release, which originated the news item, describes the collaboration between Queen Mary and Karlsruhe Institute of Technology mathematicians,

The findings, published today (Thursday) in Scientific Reports, by researchers from Queen Mary University of London and Karlsruhe Institute of Technology, could explain one of the great problems in modern physics.

Currently ideas of gravity, developed by Einstein and Newton, explain how physics operates on a very large scale, but do not work at the sub-atomic level. Conversely, quantum mechanics works on the very small scale but does not explain the interactions of larger objects like stars. Scientists are looking for a so called ‘grand unified theory’ that joins the two, known as quantum gravity.

Several models have been proposed for how different quantum spaces are linked but most assume that the links between quantum spaces are fairly uniform, with little deviation from the average number of links between each space. The new model, which applies ideas from the theory of complex networks, has found that some quantum spaces might actually include hubs, i.e. nodes with significantly more links than others, like a particularly popular Facebook user.

Calculations run with this model show that these spaces are described by well-known quantum Fermi-Dirac, and Bose-Einstein statistics, used in quantum mechanics, indicating that they could be useful to physicists working on quantum gravity.

Dr Ginestra Bianconi, from Queen Mary University of London, and lead author of the paper, said:

“We hope that by applying our understanding of complex networks to one of the fundamental questions in physics we might be able to help explain how discrete quantum spaces emerge.

“What we can see is that space-time at the quantum-scale might be networked in a very similar way to things we are starting to understand very well like biological networks in cells, our brains and online social networks.”

Here’s a link to and a citation for the paper,

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free by Ginestra Bianconi & Christoph Rahmede. Scientific Reports 5, Article number: 13979 (2015) doi:10.1038/srep13979 Published online: 10 September 2015

This is an open access paper.

Nano (?) diamonds used in mechanical system to control quantum states

We do end up back in the world of spin but, first, there are the nano (I think) diamonds in an Aug. 3, 2015 news item on Nanotechnology Now,

Scientists at the Swiss Nanoscience Institute at the University of Basel have used resonators made from single-crystalline diamonds to develop a novel device in which a quantum system is integrated into a mechanical oscillating system. For the first time, the researchers were able to show that this mechanical system can be used to coherently manipulate an electron spin embedded in the resonator – without external antennas or complex microelectronic structures. …

A July 16, 2014 University of Basel press release (also on EurekAlert), which originated the news item, provides more detail about the work,

In previous publications, the research team led by Georg H. Endress Professor Patrick Maletinsky described how resonators made from single-crystalline diamonds with individually embedded electrons are highly suited to addressing the spin of these electrons. These diamond resonators were modified in multiple instances so that a carbon atom from the diamond lattice was replaced with a nitrogen atom in their crystal lattices with a missing atom directly adjacent. In these “nitrogen-vacancy centers,” individual electrons are trapped. Their “spin” or intrinsic angular momentum is examined in this research.

When the resonator now begins to oscillate, strain develops in the diamond’s crystal structure. This, in turn, influences the spin of the electrons, which can indicate two possible directions (“up” or “down”) when measured. The direction of the spin can be detected with the aid of fluorescence spectroscopy.

Extremely fast spin oscillation

In this latest publication, the scientists have shaken the resonators in a way that allows them to induce a coherent oscillation of the coupled spin for the first time. This means that the spin of the electrons switches from up to down and vice versa in a controlled and rapid rhythm and that the scientists can control the spin status at any time. This spin oscillation is fast compared with the frequency of the resonator. It also protects the spin against harmful decoherence mechanisms.

It is conceivable that this diamond resonator could be applied to sensors – potentially in a highly sensitive way – because the oscillation of the resonator can be recorded via the altered spin. These new findings also allow the spin to be coherently rotated over a very long period of close to 100 microseconds, making the measurement more precise. Nitrogen-vacancy centers could potentially also be used to develop a quantum computer. In this case, the quick manipulation of its quantum states demonstrated in this work would be a decisive advantage.

Unfortunately, the researchers do not indicate the measurement scale for the diamonds so I’m guessing, given the descriptions, that these were nanoscale diamonds being used in the research.

In any event, here’s a link to and a citation for the paper,

Strong mechanical driving of a single electron spin by A. Barfuss, J. Teissier, E. Neu, A. Nunnenkamp, & P. Maletinsky. Nature Physics (2015)  doi:10.1038/nphys3411 Published online 03 August 2015

This paper is behind a paywall.

TRIUMF accelerator used by US researchers to visualize properties of nanoscale materials

The US researchers are at the University of California at Los Angeles (UCLA) and while it’s not explicitly stated I’m assuming the accelerator they mention at TRIUMF (Canada’s national laboratory for particle and nuclear physics) has something special as there are accelerators in California and other parts of the US.

A July 15, 2015 news item on Nanotechnology Now announces the latest on visualizing the properties of nanoscale materials,

Scientists trying to improve the semiconductors that power our electronic devices have focused on a technology called spintronics as one especially promising area of research. Unlike conventional devices that use electrons’ charge to create power, spintronic devices use electrons’ spin. The technology is already used in computer hard drives and many other applications — and scientists believe it could eventually be used for quantum computers, a new generation of machines that use quantum mechanics to solve complex problems with extraordinary speed.

A July 15, 2015 UCLA news release, which originated the news item, expands on the theme and briefly mentions TRIUMF’s accelerator (Note: A link has been removed),

Emerging research has shown that one key to greatly improving performance in spintronics could be a class of materials called topological insulators. Unlike ordinary materials that are either insulators or conductors, topological insulators function as both simultaneously — on the inside, they are insulators but on their exteriors, they conduct electricity.

But topological insulators have certain defects that have so far limited their use in practical applications, and because they are so tiny, scientists have so far been unable to fully understand how the defects impact their functionality.

The UCLA researchers have overcome that challenge with a new method to visualize topological insulators at the nanoscale. An article highlighting the research, which was which led by Louis Bouchard, assistant professor of chemistry and biochemistry, and Dimitrios Koumoulis, a UCLA postdoctoral scholar, was published online in the Proceedings of the National Academy of Sciences.

The new method is the first use of beta‑detected nuclear magnetic resonance to study the effects of these defects on the properties of topological insulators.

The technique involves aiming a highly focused stream of ions at the topological insulator. To generate that beam of ions, the researchers used a large particle accelerator called a cyclotron, which accelerates protons through a spiral path inside the machine and forces them to collide with a target made of the chemical element tantalum. This collision produces lithium-8 atoms, which are ionized and slowed down to a desired energy level before they are implanted in the topological insulators.

In beta‑detected nuclear magnetic resonance, ions (in this case, the ionized lithium-8 atoms) of various energies are implanted in the material of interest (the topological insulator) to generate signals from the material’s layers of interest.

Bouchard said the method is particularly well suited for probing regions near the surfaces and interfaces of different materials.

In the UCLA research, the high sensitivity of the beta‑detected nuclear magnetic resonance technique and its ability to probe materials allowed the scientists to “see” the impacts of the defects in the topological insulators by viewing the electronic and magnetic properties beneath the surface of the material.

The researchers used the large TRIUMF cyclotron in Vancouver, British Columbia.

According to the UCLA news release, there were also researchers from the University of British Columbia, the University of Texas at Austin and Northwestern University *were* involved with the work.

Here’s a link to and a citation for the paper,

Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators by Dimitrios Koumoulis, Gerald D. Morris, Liang He, Xufeng Kou, Danny King, Dong Wang, Masrur D. Hossain, Kang L. Wang, Gregory A. Fiete, Mercouri G. Kanatzidis, and Louis-S. Bouchard. PNAS July 14, 2015 vol. 112 no. 28 doi: 10.1073/pnas.1502330112

This paper is behind a paywall.

*’were’ added Jan. 20, 2016.