The physics of Light and Sound: Examining the Quantum Nature of Nanostructures – Putting Quantum Scientists in the Driver’s Seat

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An electron beam (teal) hits a nanodiamond, exciting plasmons and vibrations in the nanodiamond that interact with the sample’s nitrogen vacancy center defects. Correlated (yellow) photons are emitted from the nanodiamond, while uncorrelated (yellow) photons are emitted by a nearby diamond excited by surface plasmons (red).
Credit: Raphael Pooser/Oak Ridge National Laboratory, US Department of Energy

Scientists at the Department of Energy’s Oak Ridge National Laboratory are conducting fundamental physics research that will lead to more control over mercurial quantum systems and materials. Their studies will enable advancements in quantum computing, sensing, simulation, and materials development.

The researchers’ experimental results were recently published in Physical Review B Rapid Communication and Optics Letters.

Quantum information is considered fragile because it can be lost when the system in which it is encoded interacts with its environment, a process called dissipation. Scientists with ORNL’s Computing and Computational Sciences and Physical Sciences directorates and Vanderbilt University have collaborated to develop methods that will help them control — or drive — the “leaky,” dissipative behavior inherent in quantum systems.

“Our goal is to develop experimental platforms that allow us to probe and control quantum coherent dynamics in materials,” said Benjamin Lawrie, a research scientist in the Quantum Sensing Team in ORNL’s Quantum Information Science Group. “To do that, you often have to be able to understand what’s going on at the nanoscale.”

Bringing perspectives from quantum information science, nanoscience and electron microscopy, the scientists exploit existing knowledge of matter and the physics of light and sound to examine the quantum nature of nanostructures — structures that measure about one-billionth of a meter.

One project focused on driving nitrogen vacancy center defects in nanodiamonds with plasmons. The naturally occurring defects are created when a nitrogen atom forms in place of the typical carbon atom, adjacent to an atomless vacancy. The defects are being investigated for use in tests of entanglement, a state that will allow substantially more information to be encoded in a quantum system than can be accomplished with classical computing.

Electrons generate an electric field. When an electron beam is applied to a material, the material’s electrons are spurred to motion — a state called excitation — creating a magnetic field that can then be detected as light. Working with plasmons, electron excitations that couple easily with light, allows scientists to examine electromagnetic fields at the nanoscale.

Matthew Feldman, a Vanderbilt University graduate student conducting doctoral research at ORNL through the National Defense Science and Engineering Graduate Fellowship program and a member of the Quantum Sensing Team, used a high-energy electron beam to excite nitrogen vacancy centers in diamond nanoparticles, causing them to emit light. He then used a cathodoluminescence microscope owned by ORNL’s Materials Science and Technology Division, which measures the visible-spectrum luminescence in irradiated materials, to collect the emitted photons and characterize high-speed interactions among nitrogen vacancy centers, plasmons and vibrations within the nanodiamond.

In other research, Jordan Hachtel, a postdoctoral fellow with ORNL’s Center for Nanophase Materials Sciences, used the cathodoluminescence microscope to excite plasmons in gold nanospirals. He explored how the geometry of the spirals could be harnessed to focus energy in nanoscale systems. Andy Lupini served the project as a microscopy consultant, providing expertise regarding equipment optimization and troubleshooting.

Precise control over nanoscale energy transfer is required to enable long-lived entanglement in a model explored by Eugene Dumitrescu, a research scientist in ORNL’s Quantum Information Science Group. Dumitrescu’s research, published in Physical Review A in late 2017, showed that the photon statistics Feldman collected could be used in calculations to show entanglement.

“This work advances our knowledge of how to control light-matter interactions, providing experimental proof of a phenomenon that had previously been described by simulations,” Lawrie said.

Closed systems, in which quantum information can be kept away from its surroundings, theoretically can prevent dissipation, but real-world quantum systems are open to numerous influences that result in information leakage.

“The elephant in the room in discussions of quantum systems is decoherence,” Feldman said. “If we can model an environment to influence how a quantum system works, we can enable entanglement.”

Dumitrescu agreed. “We know quantum systems will be leaky. One remedy is to drive them,” he said. “The driving mechanisms we’re exploring cancel out the effects of dissipation.”

Dumitrescu used the analogy of a musical instrument to explain the researchers’ attempts to control quantum systems. “If you pluck a violin string, you get the sound, but it begins to dissipate through the environment, the air,” he said. “But if you slowly draw the bow across the string, you get a more stable, longer-lasting sound. You’ve brought control to the system.”

Feldman thinks these are fascinating times for quantum physicists because the field of quantum computing is at the same phase classical computing was in the mid-20th century. “What excites me most is how current research could change our understanding of quantum systems and materials,” he said.

Story Source:

Materials provided by DOE/Oak Ridge National LaboratoryNote: Content may be edited for style and length.

Journal Reference:

  1. Matthew A. Feldman, Eugene F. Dumitrescu, Denzel Bridges, Matthew F. Chisholm, Roderick B. Davidson, Philip G. Evans, Jordan A. Hachtel, Anming Hu, Raphael C. Pooser, Richard F. Haglund, Benjamin J. Lawrie. Colossal photon bunching in quasiparticle-mediated nanodiamond cathodoluminescencePhysical Review B, 2018; 97 (8) DOI: 10.1103/PhysRevB.97.081404

“Your Heart (Organ) on-a-chip” ~ mimics heart’s biomechanical properties (w/video)

Posted: Feb 23, 2017

The human heart beats more than 2.5 billion times in an average lifetime. Now scientists at Vanderbilt University have created a three-dimensional organ-on-a-chip that can mimic the heart’s amazing biomechanical properties.

“We created the I-Wire Heart-on-a-Chip so that we can understand why cardiac cells behave the way they do by asking the cells questions, instead of just watching them,” said Gordon A. Cain University Professor John Wikswo, who heads up the project. 

“We believe it could prove invaluable in studying cardiac diseases, drug screening and drug development, and, in the future, in personalized medicine by identifying the cells taken from patients that can be used to patch damaged hearts effectively.”

The device and the results of initial experiments demonstrating that it faithfully reproduces the response of cardiac cells to two different drugs that affect heart function in humans are described in an article published last month in the journal Acta Biomaterialia ~

(“I-Wire Heart-on-a-Chip I: Three-dimensional cardiac tissue constructs for physiology and pharmacology”). 

A companion article in the same issue presents a biomechanical analysis of the I-Wire platform that can be used for characterizing biomaterials for cardiac regenerative medicine.

I-Wire device with cardiac fiber shown in magnification window. (Image: VIIBRE / Vanderbilt)

The unique aspect of the new device, which represents about two millionths of a human heart, is that it controls the mechanical force applied to cardiac cells. 

This allows the researchers to reproduce the mechanical conditions of the living heart, which is continually stretching and contracting, in addition to its electrical and biochemical environment.

“Heart tissue, along with muscle, skeletal and vascular tissue, represents a special class of mechanically active biomaterials,” said Wikswo. “Mechanical activity is an intrinsic property of these tissues so you can’t fully understand how they function and how they fail without taking this factor into account.”

“Currently, we don’t have many models for studying how the heart responds to stress. Without them, it is very difficult to develop new drugs that specifically address what goes wrong in these conditions,” commented Charles Hong, associate professor of cardiovascular medicine at Vanderbilt’s School of Medicine, who didn’t participate in the research but is familiar with it. 

“This provides us with a really amazing model for studying how hearts fail.”

The I-Wire device consists of a thin thread of human cardiac cells 0.014 inches thick (about the size of 20-pound monofilament fishing line) stretched between two perpendicular wire anchors. 

The amount of tension on the fiber can be varied by moving the anchors in and out, and the tension is measured with a flexible probe that pushes against the side of the fiber.

The fiber is supported by wires and a frame in an optically clear well that is filled with liquid medium like that which surrounds cardiac cells in the body. The apparatus is mounted on the stage of a powerful optical microscope that records the fiber’s physical changes. 
The microscope also acts as a spectroscope that can provide information about the chemical changes taking place in the fiber. 
A floating microelectrode also measures the cells’ electrical activity.

According to the researchers, the I-Wire system can be used to characterize how cardiac cells respond to electrical stimulation and mechanical loads and can be implemented at low cost, small size and low fluid volumes, which make it suitable for screening drugs and toxins. Because of its potential applications, Vanderbilt University has patented the device.

Video taken through a microscope shows I-Wire heart fiber. left, beating at different frequencies. The black circle, right, is the flexible cantilever that measures the force of the fiber’s contractions. (Veniamin Sidorov / VIIBRE /Vanderbilt)

Unlike other heart-on-a-chip designs, I-Wire allows the researchers to grow cardiac cells under controlled, time-varying tension similar to what they experience in living hearts. 

As a consequence, the heart cells in the fiber align themselves in alternating dark and light bands, called sarcomeres, which are characteristic of human muscle tissue. The cardiac cells in most other heart-on-a-chip designs do not exhibit this natural organization.

In addition, the researchers have determined that their heart-on-a-chip obeys the Frank-Starling law of the heart. The law, which was discovered by two physiologists in 1918, describes the relationship between the volume of blood filling the heart and the force with which cardiac cells contract. The I-Wire is one of the first heart-on-a-chip devices to do so.

To demonstrate the I-Wire’s value in determining the effects that different drugs have on the heart, the scientists tested its response with two drugs known to affect heart function in humans: isoproterenol and blebbistatin. Isoproterenol is a medication used to treat bradycardia (slow heart rate) and heart block (obstruction of the heart’s natural pacemaker). Blebbistatin inhibits contractions in all types of muscle tissue, including the heart.

According to Veniamin Sidorov, the research assistant professor at the Vanderbilt Institute for Integrative Biosystems Research and Education (VIIBRE) who led its development, the device faithfully reproduces the response of cardiac cells in a living heart.

“Cardiac tissue has two basic elements: an active, contractile element and a passive, elastic element,” said Sidorov. “By separating these two elements with blebbistatin, we successfully characterized the elasticity of the artificial tissue. By exposing it to isoproterenol, we tested its response to adrenergic stimulation, which is one of the main systems responsible for regulation of heart contractions. 
We found that the relationship between these two elements in the cardiac fiber is consistent with that seen in natural tissue. 

This confirms that our heart-on-a-chip model provides us with a new way to study the elastic response of cardiac muscle, which is extremely complicated and is implicated in heart failure, hypertension, cardiac hypertrophy and cardiomyopathy.”

Source: Vanderbilt University

2 for 1: Turning Smokestack Emissions into Carbon Nanotube-Based Batteries = Clean Emissions + Clean Renewable Energy: Vanderbilt & George Washington Universities

Smokestack Emissions Nano Carbon Capture id42759

“Our climate change solution is two fold: To transform the greenhouse gas carbon dioxide into valuable products and to provide greenhouse gas emission-free alternatives to today’s industrial and transportation fossil fuel processes,” Stuart Licht, professor of chemistry at George Washington University

An interdisciplinary team of scientists has worked out a way to make electric vehicles that are not only carbon neutral, but carbon negative, capable of actually reducing the amount of atmospheric carbon dioxide as they operate. They have done so by demonstrating how the graphite electrodes used in the lithium-ion batteries that power electric automobiles can be replaced with carbon material recovered from the atmosphere. The recipe for converting carbon dioxide gas into batteries is described in a paper published in the March 2 issue of the journal ACS Central Science (“Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes”).

Converting Carbon Dioxide into BatteriesThe Solar Thermal Electrochemical Process (STEP) converts atmospheric carbon dioxide into carbon nanotubes that can be used in advanced batteries. (Image: Julie Turner, Vanderbilt University)

“Our climate change solution is two fold: To transform the greenhouse gas carbon dioxide into valuable products and to provide greenhouse gas emission-free alternatives to today’s industrial and transportation fossil fuel processes,” Stuart Licht, professor of chemistry at George Washington University said.

“In addition to better batteries other applications for the carbon nanotubes include carbon composites for strong, lightweight construction materials, sports equipment and car, truck and airplane bodies.” The unusual pairing of carbon dioxide conversion and advanced battery technology is the result of a collaboration between Dr. Licht, and the laboratory of assistant professor of mechanical engineering Cary Pint at Vanderbilt University. Licht adapted the lab’s solar thermal electrochemical process (STEP) so that it produces carbon nanotubes from carbon dioxide and with Pint by incorporating them into both lithium-ion batteries like those used in electric vehicles and electronic devices and low-cost sodium-ion batteries under development for large-scale applications, such as the electric grid. In lithium-ion batteries, the nanotubes replace the carbon anode used in commercial batteries.

The team demonstrated that the carbon nanotubes gave a small boost to the performance, which was amplified when the battery was charged quickly. In sodium-ion batteries, the researchers found that small defects in the carbon, which can be tuned by STEP, can unlock stable storage performance over 3.5 times above that of sodium-ion batteries with graphite electrodes. Most importantly, both carbon-nanotube batteries were exposed to about 2.5 months of continuous charging and discharging and showed no sign of fatigue.

Published on Feb 25, 2016: Video interview with Cary Pint explaining this research.

Scientists from Vanderbilt and George Washington universities have worked out a way to make electric vehicles not just carbon neutral but carbon negative by demonstrating how the graphite electrodes used in the lithium-ion batteries can be replaced with carbon recovered from the atmosphere.

“This trailblazing research has achieved yet another amazing milestone with the incorporation of the carbon nanotubes produced by Stuart Licht’s STEP reduction of carbon dioxide process into batteries for electric vehicles and large scale storage,” said Michael King, chair of GW’s Department of Chemistry. “We are thrilled by this translation of basic research into potentially useful consumer products while mitigating atmospheric carbon dioxide buildup. This is a win-win for everyone!”
The researchers estimate that with a battery cost of $325 per kWh (the average cost of lithium-ion batteries reported by the Department of Energy in 2013), a kilogram of carbon dioxide has a value of about $18 as a battery material – six times more than when it is converted to methanol – a number that only increases when moving from large batteries used in electric vehicles to the smaller batteries used in electronics.

And unlike methanol, combining batteries with solar cells provides renewable power with zero greenhouse emissions, which is needed to put an end to the current carbon cycle that threatens future global sustainability.


Licht also proposes a modified flue system for combustion plants that incorporates this process could be self-sustaining, as exemplified by a new natural gas power plant with zero carbon dioxide emissions. That’s because the side product of the process is pure oxygen, which plants could then use for further combustion. The calculated total cost per metric tonne of CNTs would be much less expensive than current synthetic methods.


“This approach not only produces better batteries but it also establishes a value for carbon dioxide recovered from the atmosphere that is associated with the end-user battery cost unlike most efforts to reuse CO2 that are aimed at low-valued fuels, like methanol, that cannot justify the cost required to produce them,” said Pint.
Source: Vanderbilt University

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Rice and Sandia National Labs Discover Unique NanoTube Photodetector


Project with Sandia National Laboratories leads to promising optoelectronic device

HOUSTON – (Feb. 27, 2013) – Researchers at Rice University and Sandia National Laboratories have made a nanotube-based photodetector that gathers light in and beyond visible wavelengths. It promises to make possible a unique set of optoelectronic devices, solar cells and perhaps even specialized cameras.

A traditional camera is a light detector that captures a record, in chemicals, of what it sees. Modern digital cameras replaced film with semiconductor-based detectors.

But the Rice detector, the focus of a paper that appeared today in the online Nature journal Scientific Reports, is based on extra-long carbon nanotubes. At 300 micrometers, the nanotubes are still only about 100th of an inch long, but each tube is thousands of times longer than it is wide.

That boots the broadband detector into what Rice physicist Junichiro Kono considers a macroscopic device, easily attached to electrodes for testing. The nanotubes are grown as a very thin “carpet” by the lab of Rice chemist Robert Hauge and pressed horizontally to turn them into a thin sheet of hundreds of thousands of well-aligned tubes.

They’re all the same length, Kono said, but the nanotubes have different widths and are a mix of conductors and semiconductors, each of which is sensitive to different wavelengths of light. “Earlier devices were either a single nanotube, which are sensitive to only limited wavelengths,” he said. “Or they were random networks of nanotubes that worked, but it was very difficult to understand why.”

“Our device combines the two techniques,” said Sébastien Nanot, a former postdoctoral researcher in Kono’s group and first author of the paper. “It’s simple in the sense that each nanotube is connected to both electrodes, like in the single-nanotube experiments. But we have many nanotubes, which gives us the quality of a macroscopic device.”

With so many nanotubes of so many types, the array can detect light from the infrared (IR) to the ultraviolet, and all the visible wavelengths in between. That it can absorb light across the spectrum should make the detector of great interest for solar energy, and its IR capabilities may make it suitable for military imaging applications, Kono said. “In the visible range, there are many good detectors already,” he said. “But in the IR, only low-temperature detectors exist and they are not convenient for military purposes. Our detector works at room temperature and doesn’t need to operate in a special vacuum.”

The detector is also sensitive to polarized light and absorbs light that hits it parallel to the nanotubes, but not if the device is turned 90 degrees.

The work is the first successful outcome of a collaboration between Rice and Sandia under Sandia’s National Institute for Nano Engineering program funded by the Department of Energy. François Léonard’s group at Sandia developed a novel theoretical model that correctly and quantitatively explained all characteristics of the nanotube photodetector. “Understanding the fundamental principles that govern these photodetectors is important to optimize their design and performance,” Léonard said.

Kono expects many more papers to spring from the collaboration. The initial device, according to Léonard, merely demonstrates the potential for nanotube photodetectors. They plan to build new configurations that extend their range to the terahertz and to test their abilities as imaging devices. “There is potential here to make real and useful devices from this fundamental research,” Kono said.

Co-authors are Aron Cummings, a postdoctoral fellow in Léonard’s Nanoelectronics and Nanophotonics Group at Sandia; Rice alumnus Cary Pint, an assistant professor of mechanical engineering at Vanderbilt University; Kazuhisa Sueoka, a professor at Hokkaido University; and Akira Ikeuchi and Takafumi Akiho, Hokkaido University graduate students who worked in Kono’s lab as part of Rice’s NanoJapan program. Hauge is a distinguished faculty fellow in chemistry. Kono is a professor of electrical and computer engineering and of physics and astronomy.

The U.S. Department of Energy, the National Institute for Nano Engineering at Sandia National Laboratories, the Lockheed Martin Advanced Nanotechnology Center of Excellence at Rice University, the National Science Foundation and the Robert A. Welch Foundation supported the research.