Physicists Detect Neutrinos in Superposition Hurtling Through Spacetime

<div class="related"></div>
<p>
 Physicists have verified a central tenet of quantum mechanics—that quantum particles can occupy a so-called superposition—using neutrinos separated by 450 miles, the farthest such test to date.
</p>
<p>
 A group of physicists from MIT shot a beam consisting of one “flavor” of neutrino, a tiny subatomic particle that rarely interacts with other matter, but hundreds of miles away, they detected a different flavor of neutrino. This indicates the neutrinos were traveling in a quantum superposition, a midflight mixture of flavors, as reported last week in
 <i>
  Physical Review Letters
 </i>
 .
</p>
<p>
 The study adds credence a long-held theory that says that subatomic particles can be in superposition while hurtling through spacetime.
</p>
<p>
 Many physicists are pleased with this affirmation of quantum mechanics, but they were also tickled by the way in which it was done. Here’s Adrian Cho, reporting for Science:
</p>
<blockquote>
<p>
 “If you had told me 10 years ago that we would use neutrinos to study quantum foundations, I would have said that you’d been smoking something very exciting,” says Andrew White, a physicist at the University of Queensland, St. Lucia, in Brisbane, Australia, who was not involved in the work. “The result is utterly unsurprising and yet utterly attractive because it tells us that there’s a new system for testing quantum foundations.”
</p>
</blockquote>
<p>
 Erwin Schrödinger highlighted this sort of weirdness that’s inherent to quantum mechanics with his famous feline thought experiment. Inside of a box, he imagined, there’s a cat and a radioactive particle. The cat will die if the particle decays. After exactly the half-life of the radioactive particle, there’s a 50% chance the particle has decayed and a 50% chance it has not. So, the cat is in limbo, equally likely to be alive or dead. The cat is in a quantum superposition, both alive and dead…sort of. Just like a quantum particle, the cat is only in a superposition until it’s observed. When you open the box, the cat is either alive or dead—not both.
</p>
<div class="ad"></div>
<p>
 If multiple particles like neutrinos are in a superposition together, their states can be entangled. In Schrödinger’s experiment, if there are two cats and we open the first box, we immediately know whether the second cat is alive or dead, without observing it directly. This is true even if the cats are around the globe from each other, an effect that Einstein referred to as “spooky action at a distance.”
</p>
<p>
 Physicists demonstrated quantum mechanical these effects by firing the neutrino from the outskirts of Chicago to the northern edge of Minnesota—adding another convincing data point yet in support of the theory that that quantum superposition can happen over infinite distances.
</p>
<div class="newsletter"></div>
<p>
 Photo credit:
 <a>
  Reidar Hahn/Fermilab
 </a>
</p>

<p>Physicists have verified that neutrinos can occupy a quantum superposition while traveling hundreds of miles.</p>

Bioluminescence in fish evolved 27 different times

<p>There might be plenty of fish in the sea, but evolution seems to prefer the glowing ones.</p><p>Impressed by the diversity and pervasiveness of light-emitting sea creatures, a team of zoologists recently began to puzzle out the evolutionary origins of bioluminescence. After tracing the branches that these fish took along the evolutionary tree, the scientists determined that fish developed some type of bioluminescence in at least 27 independent evolutionary events. This repeated evolution signifies that bioluminescence are an extremely useful adaptation for fish, according to the <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0155154#pone.0155154.ref004">recent article in the journal PLoS ONE</a> .</p><p>These results are especially curious since land animals rarely evolve bioluminescent features. That the trait evolved so many different times in fish is partly due to the multitude of reasons why fish glow.</p>
<div class="related"></div>
<p>Many sea creatures use bioluminescence as locating beacons in dark or murky waters, where finding another member of your species isn’t always easy. During mating season, these fish announce their presence by luminescing steadily or flashing a special pattern.</p><p>The same glow that attracts mates can also attract prey, especially in deep sea fish. The fantastical black dragonfish—imagine a black eel with fangs and a bioluminescent barbel— uses its glow as a deep-sea flashlight to facilitate hunting.</p><p>On the defensive side, certain species use bioluminescence to confuse predators. A family of fish known as tubeshoulders shoots bioluminescent ink to evade attackers, similar to a squid or an octopus. Many fish develop lightly-colored glowing bellies to hide themselves from predators below by mimicking the diffuse lighting of the water above.</p><p>The proteins that make fish fluoresce could help scientists map the human brain.</p>
<div class="ad"></div>
<p>In the case of the myctophid lanternfish, scientists believe that their bioluminescence initially evolved for camouflage, but developed into a mechanism for intraspecies communication. Unique underwater lights and patterns give fish the ability to quickly recognize their compatriots from the many other fish in the sea, and this may have profound consequences for their evolution. With Ars Technica, Annalee Newitz writes:</p><p>Many glowing fish groups are called “species rich” because they tend to diverge into new species very quickly. Smith and his colleagues believe this is probably because they’re using species-specific light patterns to recognize mates and communicate. If a group of fish finds a nice ecological niche that works, and it has a very obvious way of communicating with its immediate group, members of that group of fish will mate only with each other and rapidly diverge from their neighbors.</p><p>In other words, bioluminescence in fish is an example of both convergent evolution—the same trait arises many different times—and divergent evolution—species which possess bioluminescence tend to differentiate into new species more rapidly—making bioluminescence a particularly useful trait to study if you’re an evolutionary biologist.</p><p><i>Explore the tree of life and get a front row seat to what some have called the greatest show on Earth.</i> <a href="http://www.pbs.org/wgbh/nova/labs/lab/evolution/"><i>Play NOVA’s Evolution Lab</i></a><i> .</i></p>
<div class="newsletter"></div>
<p>Photo credit: <a href="https://commons.wikimedia.org/wiki/File:Bufoceratias.jpg">Masaki Miya/ Wikipedia Commons (CC BY-SA)</a></p>

<p data-block-key="cobtk">This repeated evolution signifies that bioluminescence are an extremely useful adaptation for fish.</p>

There's Hope for fMRI Despite Major Software Flaws

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Over the last 25 years, fMRI has developed into a powerful technique to look at the brain. But a recent analysis of fMRI software found a bug that jeopardizes 40,000 studies which use the technique.
 </p>
<p>
  Functional magnetic resonance imaging, or fMRI, is used to highlight which portions of the brain are active during certain tasks. The brain scans they produce are so large and complex that they require statistical software to find patterns within the data. But the three most common types of software used frequently produces false-positives, according to a
  <a href="http://www.pnas.org/content/early/2016/06/27/1602413113">
   recent paper in PNAS
  </a>
  . Led by Dr. Anders Eklund, an associate professor of medical informatics at Linköping University in Sweden, the study showed that up to 70% of the time the software reported brain activity where there was none.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/fmri.width-990_zv2OvgF.jpg"/>
<figcaption>An fMRI scan showing different active areas of the brain.
        
    </figcaption>
</figure>
<p>
  Ivo Dinov, an associate professor at the University of Michigan and director of the Statistics Online Computational Resource, called the study a “Herculean task,” and he was quick to point out that “the report certainly does not invalidate the studies. I want to make it crystal-clear that it does not discredit, specifically, any of these studies.”
 </p>
<p>
  The study only addresses large scale fMRI studies—those looking to find patterns within a particular group of people. For example, scientists might compare the brain scans of people diagnosed with schizophrenia to the general population, comparing what regions of the brain respond to visual stimuli. Individual brains have a lot of natural variation, but using fMRI images from many individuals help scientists find patterns, which can indicate the neural causes of diseases like schizophrenia.
 </p>
<p>
  When an fMRI machine scans a person’s brain, it’s looking for the extra blood that flows to a firing cluster of neurons and marks it on a map of the brain. Researchers use statistical software to analyze the resulting map and determine which areas of the brain are active. It’s in this software, not the fMRI itself, where the problem lies.
 </p>
<p>
  Eklund and his team collected 499 fMRI scans of brains in a resting-state, which happens when a person isn’t performing a particular task. Collectively, the scans should look random, with each person’s brain lighting up in a different location. But the three most common types of fMRI software-—those used in up to 90% of fMRI studies—showed false patterns up to 70% of the time. Acceptable error is usually limited to 5%.
 </p>
<p>
  More specifically, the team of researchers randomly split the fMRI scans in small groups of 20. Using one group as a control and another as experimental data, the researchers compared the two groups. They repeated this process 3 million times. Since the scans are randomly drawn, they should rarely exhibit patterns, far less often than Eklund and his team observed.
 </p>
<p>
  Roughly 40,000 fMRI studies have used these flawed statistical methods, according to the recent analysis. This does not indicate the findings of these studies are wrong. But “it suggests, potentially, that some of these might not be reproducible,” Dinov said. An fMRI study, repeated ten times, might only yield the same results three or four times. This, Dinov said, “suggests caution by investigators in interpreting their results.”
 </p>
<p>
  Researchers aren’t certain what causes the software to produce false-positives, but it’s probably the result of incorrect assumptions the software is making. For example, the software makes educated guesses the size and shape of neuron clusters that light up together. It might assume they form a perfect sphere when the actual shape is lumpy and irregular. It’s a balancing act—without using any assumptions, the software wouldn’t be able to do it’s job. But with too many assumptions, it produces errors.
 </p>
<p>
  Despite these findings, fMRI remains an important imaging technique, and statistical software is needed to analyze it, Dinov said. “People should continue using it,” he said. But, he adds, they should be wary that “if you use state-of-the-art techniques blindly, then you have a high rate of identifying effects when there aren’t any.”
 </p>
</section>
<p>
 Photo credit:
 <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0133034#pone-0133034-g003">
  Karch, et al. 2015 (CC-BY)
 </a>
</p>

Why Food Date Labels Don’t Mean What You Think

<p>
 The dates printed on milk cartons are probably the six most misunderstood numbers in grocery stores.
</p>
<p>
 First, let’s clear one thing up: It’s not an expiration date. Potentially harmful bacteria are destroyed in the pasteurization process. They can’t spontaneously regenerate, so old milk stored in the fridge doesn’t present an increased risk of foodborne illness.
</p>
<p>
 So what is it? Often, the date is set for around three weeks after pasteurization, which is when the milk will begin to taste off. After reacting with oxygen and light, the fat in milk becomes rancid or stale. The distinct sour taste of aged milk is a byproduct of harmless lactic acid bacteria that feed on the sugar in milk. “It’s more of a sensory defect that we don’t like, but you’re not going to get sick on it,” says Randy Worobo, professor of food science at Cornell University.
</p>
<div class="related"></div>
<p>
 Sixteen states prescribe by law the date on milk cartons, and some go a step further, regulating what happens to milk after that date. Montana requires milk to be thrown away 12 days after pasteurization, despite a lack of scientific evidence to support this practice.
</p>
<p>
 Sometimes, the date is prefaced by the words “use by” or “best before.” Sometimes it’s a “sell by” date. Often it’s just a few cryptic numbers.
</p>
<p>
 And the trouble with date labels extends beyond the dairy case and into the rest of the grocery store aisles.
</p>
<p>
 “We do have a state of confusion in terms of date labeling,” says Donald Schaffner, professor of food science at Rutgers University. “Date labels primarily exist as a way for food manufacturers to communicate to their customers what to do or what to expect from the food product. There is not a lot of standardization.”
</p>
<p>
 Confusion over date labels is a huge contributor to food waste. Americans trash an estimated 40% of viable food—upwards of 160 billion pounds per year—and misunderstandings about food date label comprises 20% of consumer food waste, based on a British study.
</p>
<p>
 But there’s rarely reason to fret if your food is past date, says Emily Broad Leib, director of the Harvard Food Law and Policy Clinic. “There are a small handful of foods that shouldn’t be sitting in your refrigerator for such a long time—there is a safety risk. Whereas for all other foods it’s just about quality.”
</p>
<p>
 Congress is currently considering a bill that would standardize food date labels and clearly distinguish manufacturer’s quality suggestions from scientifically based safety dates. It’s a simple fix that could save billions of dollars worth of food every year, and it would require almost no action on the part of consumers. Clarifying food date labels is the most cost effective way to combat food waste in the United States.
</p>
<h2>
 “Expires On”
</h2>
<p>
 In the world of food, the difference between “best by” and “expires on” is significant. “Everybody thinks it’s an expiration date when in fact it’s a best before date. And there’s a big difference,” Worobo says. Expiration dates are about food safety. Best before dates are about taste, texture and appearance, he says.
</p>
<p>
 Only a small group of foods need expiration dates—primarily ready-to-eat foods like deli meats and prepared sandwiches, both foods which may contain bacteria like listeria and are not cooked immediately prior to consumption. Unlike other pathogenic bacteria, listeria is durable enough to grow at refrigerator temperatures. Recently cooked meats are safe from listeria—it dies at 160°F—but the expiration date on deli meats importantly reflects when listeria may have reached dangerous levels.
</p>
<div class="pullquote">
<p>
 Expiration dates are about food safety. Best before dates are about taste, texture and appearance.
</p>
</div>
<p>
 But most harmful bacteria, like
 <i>
  Salmonella
 </i>
 and
 <i>
  E. coli
 </i>
 , aren’t capable of growing on foods stored at cold temperatures or in dry conditions, like crackers in the pantry. “Microorganisms are no different than us—we need water, we need food, and we need the proper temperature to survive,” Worobo says. Depriving bacteria of their basic needs is the central philosophy of food storage.
</p>
<p>
 Provided you do your part—keep foods refrigerated, wash fruits and vegetables, cook meat thoroughly and isolate raw meat from other foods—there’s a low risk of contracting a foodborne illness. And that risk usually doesn’t increase as food ages.
</p>
<p>
 “If those lettuce leaves had no
 <i>
  Salmonella
 </i>
 at the start, then after it becomes a slimy disgusting mess, there will still be no
 <i>
  Salmonella
 </i>
 , because there’s no such thing as spontaneous generation—Louis Pasteur proved that,” Schaffner says. “
 <i>
  Salmonella
 </i>
 have to arrive from someplace—they don’t arrive from nothing. And the bacteria that turn that salad into a slimy disgusting mess, those bacteria don’t make us sick. I mean, they might turn our stomach, but they’re not infectious.”
</p>
<p>
 To be clear, he’s not telling you to eat soupy lettuce—if a food item seems gross, throw it out. But if it looks and tastes okay a few days after the date, go ahead and eat it.
</p>
<h2>
 “Best If Used By”
</h2>
<p>
 For other foods—the vast majority—date labels are simply the manufacturer’s suggestion about when a product might taste freshest. “While shelf-life dating might be important for those products, it’s probably—and that’s a big asterisk there—not that important for food safety. It’s really about delivering to the customer a product that, at the end of its shelf-life isn’t a slimy disgusting mess,” Schaffner says.
</p>
<p>
 But just because it isn’t likely to make you sick doesn’t mean the dates are arbitrary. Food ages in a staggering number of ways, making it nearly impossible to set uniform standards for shelf-life.
</p>
<div class="ad"></div>
<p>
 From the point of view of microbes, frozen pizza will never change. “From the day that it’s packaged in the manufacturer, 30 years out in your freezer, as long as it’s kept at that temperature, the microorganisms don’t grow,” Worobo says. That doesn’t mean it won’t change, though. Freezer burn is a common problem with frozen foods. It happens when water molecules, drawn to the drier environment outside the food, migrate out, only to then recrystallize on the outside, causing the burn.
</p>
<p>
 Other foods like cookies and crackers, which are stable on store and pantry shelves for long periods of time, spoil for the same reason milk does. Over time, their fat reacts with the oxygen in the package, becoming rancid. The process—called oxidative rancidity—is what makes old crackers taste funky. “If you’ve never had a snack food past its shelf-life, try one,” Schaffner says. “It’s not going to make you sick, but it’ll taste gross.”
</p>
<p>
 The texture of a cracker will probably change—it’ll lose its crispness as it draws water out of the air—but the moisture level inside an opened package “isn’t enough to support the growth of pathogens,” Worobo says. “It would never grow something that would make you sick. Unless you dunked it in contaminated water and they left it out at room temperature, then it would grow pathogens. But if you left it out on your counter—even after 30 years—it would not have pathogens growing on it.”
</p>
<p>
 Food science labs typically determine a product’s shelf-life based on a combination of taste and microbial activity. “We do a lot of product evaluation studies in our lab,” says Willis Fedio, director of the food safety laboratory at New Mexico State University. They test—and taste—everything from potato salad to salsa and cookie icing. Every month or two he buys a batch of chicken wings and hosts a hot sauce tasting panel with the members of his lab. “I bribe them with wings and they fill out the forms.”
</p>
<p>
 “We know what rancid tastes like,” Fedio says.
</p>
<h2>
 Legislating for Standardization
</h2>
<p>
 Because food labs and manufacturers use so many different criteria—bacteria levels, taste, texture—to determine a food’s shelf-life, it can be difficult to interpret what a date label means. The challenge of determining whether a date label indicates safety or quality is magnified by the many different conventions and labeling styles currently in use.
</p>
<p>
 Representative Chellie Pingree of Maine and Senator Richard Blumenthal of Connecticut recently introduced a bill in Congress to standardize food date labels. Select foods that require safety dates will be labeled “expires on.” All other food labels will read “best if used by” to emphasize that it’s a quality date.
</p>
<div class="pullquote">
<p>
 “The words ‘use by’ are probably the most confusing.”
</p>
</div>
<p>
 “There’s no way for the consumer generally to tell if the date that you see is the date it was manufactured, is the date that it ‘expires’, is the date that it’s best if you eat it by, or is a date after which you’ll get sick. Those labels become meaningless, and even if they have any basis in something, most of the time we don’t know what it is,” Pingree says.
</p>
<p>
 Broad Leib and the Harvard Food Law and Policy Clinic recently studied how consumers react to the wide array of food labels currently in use: “best by,” “use before,” “sell by,” and more. “The words ‘use by’ are probably the most confusing,” Broad Leib says. People tended to interpret that label equally as a safety date and a quality suggestion.
</p>
<p>
 “There’s going to need to be education no matter what term is used. We’ve been doing it this weird way for so long that didn’t have much meaning.” Broad Leib says. “If we suddenly want these to have meaning, we’re going to have to make that really clear to people.”
</p>
<p>
 Of all the tens of thousands of foods in grocery stores, infant formula is the only food product whose date label is currently regulated by federal law. For everything else, state laws vary tremendously, covering different products or making conflicting recommendations about the same product.
</p>
<h2>
 Mitigating Food Waste
</h2>
<p>
 Pingree and Blumenthal’s legislation is a step toward standardizing and clarifying food date recommendations. “Sometimes we joke and say, ‘This should be the Domestic Harmony Bill,’ because we’re just trying to return happiness back into households or pantries,” Pingree says.
</p>
<p>
 More than that, though, Pingree wants to address the billions of dollars Americans spend on wasted food. It’s estimated that 90% of Americans throw food away after the date for safety reasons, unsure whether it will make them sick of not.
</p>
<p>
 “The largest cause of household consumer food waste is not knowing if you should throw something away or not, and I’ve seen studies that show the most cost effective thing we could do to reduce food waste is to bring some sort of uniformity, education, sensibility, into our date labeling system,” Pingree says.
</p>
<div class="newsletter"></div>
<h2>
 A Food Giant Lumbers Forward
</h2>
<p>
 Not everyone is waiting on an act of Congress, though. Inspired by a
 <a href="https://www.nrdc.org/sites/default/files/dating-game-report.pdf">
  report
 </a>
 from the Harvard Food Law and Policy Clinic highlighting the problems with food date labels, Walmart decided to investigate their own labeling practices.
</p>
<p>
 The company surveyed how companies that made their Walmart-brand foods decided to date label the items. “We discovered that our food suppliers were date labeling them 47 different ways,” says Frank Yiannas, vice president of food safety for Walmart.
</p>
<p>
 They recently moved from 47 labels to just one. All of Walmart’s private brand food is labeled with “best if used by”. Walmart’s research—coinciding with Harvard’s independent
 <a href="http://www.chlpi.org/wp-content/uploads/2013/12/Consumer-Perceptions-on-Date-Labels_May-2016.pdf">
  further research
 </a>
 —determined the phrasing to be clearest to consumers.
</p>
<p>
 Even with standardized date labels, the reason for a “best if used by” label will change depending on the food. “I don’t think there’s a one-size fits all approach,” Schaffner says. “The problem is that all foods are different. The way that I’m going to label my bacon is going to be different than the way that I’m going to label a cookie or cracker, which is going to be different than how I label my milk.” The food’s date hints at the best time to consume it, but the date alone won’t tell you if most food is spoiled—only your tastes can.
</p>
<p>
 “For the vast majority of spoilage, it’s mostly an ick factor,” Worobo says.
</p>
<p>
 Photo credit: Kelsey Houston-Edwards
</p>

<p>Date labels can have different meanings, leading consumers to throw out perfectly good food.</p>

Olympic Athletes Are Experimenting with VR and Electric Brain Stimulation

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  The latest performance enhancement isn’t biological—it’s electric.
 </p>
<p>
  Athletes, desperate to get an edge on the competition, are escalating their mental preparation with technologies like virtual reality glasses and headphones that send an electric current into the brain. Manufactured by Halo Neuroscience, the over-the-ear headphones stimulate the motor cortex, the area of the brain responsible for coordinating movement. Despite a lack of support from neuroscience research, the headphones are being tested by five athletes training for the upcoming Olympics in Rio.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/sprinters.width-990_aM2CyQt.jpg"/>
<figcaption>Small margins can make a big difference in sprint competitions.
        
    </figcaption>
</figure>
<p>
  Here’s Mike Orcutt, reporting for MIT Technology Review:
 </p>
<blockquote>
<p>
   The stimulation technique, called transcranial direct current stimulation, is a very popular subject of neuroscience research at the moment. Scientists have shown that delivering a small amount of electrical current can make neurons more or less likely to fire. And in the past 15 years a flurry of studies have suggested that the approach can be used for many things, from improving cognition to helping stroke patients regain movement.
  </p>
<p>
   Most of the studies have been small, though, and for many potential applications there is not yet enough data to tell if the stimulation actually works. Halo chose to target the motor cortex because it’s the area where there’s the most evidence that the technique does improve learning, says Chao [co-founder and CEO of Halo Neuroscience].
  </p>
</blockquote>
<p>
  Halo’s website refers to the electrical stimulation as “a preworkout for the brain.”
 </p>
<p>
  In another quirky take on performance enhancement is using virtual reality and 360˚ viewing technology. It’s a high-tech remake of the old-school advice to visualize the finish line. The company VR-Vantage is producing video for athletes in sailing, canoe slalom and sailing.
 </p>
<p>
<a href="http://www.theengineer.co.uk/road-to-rio-virtual-reality-puts-athletes-on-the-right-track/">
   The Engineer reports:
  </a>
</p>
<blockquote>
<p>
   The video playback can be viewed on smartphones and headsets, giving athletes a fully immersive experience and allowing them to feel familiar in the environments in which they’ll be competing as well as understanding the characteristics of a course layout ahead of competition.
  </p>
</blockquote>
<p>
  Olympic races are often won by a fraction of a second and athletes are willing to gamble on new technology for a slight edge. Over the next few weeks, we’ll see what pays off.
 </p>
</section>
<p>
 Photo credit:
 <a href="https://pixabay.com/p-652493/?no_redirect">
  skeeze / Pixabay (CC0 Public Domain)
 </a>
</p>

Quantum Computer Simulates Quantum Particle Interactions for the First Time

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  In a first, a quantum computer has simulated a high-energy particle physics experiment.
 </p>
<p>
  Physicists have long hoped to create computer models of these experiments. This would allow them to simply press “play” on a quantum computer and watch the experiment play out in real-time, a vision of Richard Feynman’s from 1982. High-energy particle physics experiments—like those being performed at the Large Hadron Collider at CERN—are expensive and can provide limited information.
 </p>
<p>
  Now, a team of Austrian physicists
  <a href="http://www.nature.com/nature/journal/v534/n7608/full/nature18318.html">
   announced in Nature
  </a>
  that they have taken a step in that direction, simulating the process by which a positron-electron pair are spontaneously created using a small quantum computer.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/particlecollision2.width-990_i1RO398.jpg"/>
<figcaption>A proton-antiproton collision—an example of the kind of particle interaction physicists hope to simulate on quantum computers.
        
    </figcaption>
</figure>
<p>
  Elementary particles, such as electrons and positrons, are difficult to simulate because they are governed by quantum mechanics. Any simulation of their interactions needs to encode the complicated phenomenon of quantum entanglement, which describes the way all of the particles in a system interact collectively. It ends up being too much information for a standard computer—but not for a quantum computer.
 </p>
<p>
  The difference lies in the basic building blocks of the two machines. Classical computers process information as a series of bits, which are either 0 or 1. But quantum computers use qubits—a shortening of ‘quantum bit’—which can be in a so-called superposition. Just as Schrödinger’s cat can be alive, dead, or somewhere in between, a qubit can be in 0, 1, or somewhere in between—a superposition. This flexibility allows for vastly more computation power.
 </p>
<p>
  Today, quantum computers are largely a theoretical construct. Scientists pretty much understand how a quantum computer should work, but can’t quite overcome the engineering challenges to build a full-scale one. The most advanced quantum computers are still fairly small and rudimentary.
 </p>
<p>
  Esteban Martinez and Christine Muschik, the pair of physicists who led the recent experiments, used one of these basic quantum computers to simulate the mechanism by which energy is converted into two antiparticles, in this case, an electron and positron.
 </p>
<p>
  Here’s Davide Castelvecchi, writing for Nature News:
 </p>
<blockquote>
<p>
   The team used a tried-and-tested type of quantum computer in which an electromagnetic field traps four ions in a row, each one encoding a qubit, in a vacuum. They manipulated the ions’ spins — their magnetic orientations — using laser beams. This coaxed the ions to perform logic operations, the basic steps in any computer calculation.
  </p>
<p>
   After sequences of about 100 steps, each lasting a few milliseconds, the team looked at the state of the ions using a digital camera. Each of the four ions represented a location, two for particles and two for antiparticles, and the orientation of the ion revealed whether or not a particle or an antiparticle had been created at that location.
  </p>
</blockquote>
<p>
  The small-scale experiment was successful, but questions remain about whether the technique will scale up. It would take a larger quantum computer—the kind scientists don’t yet know how to build—to simulate more complicated particle interactions. But Martinez and his team have provided proof of concept, a valuable step toward realizing Feynman’s vision.
 </p>
<p>
  Scientists could learn a lot by simulating elementary particle interactions on a quantum computer, but it’s unlikely to ever replace the genuine discovery of experimentation. For now, the Large Hadron Collider’s job is safe.
 </p>
</section>
<p>
 Photo credit:
 <a href="http://cds.cern.ch/record/39466">
  CERN PhotoLab
 </a>
</p>

Wave of the Future?

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<div class="add-container clearfix" id="add-block-placer">
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<p>
  Two years ago, in a hospital in Paris, a 38-year-old man lay dying from a golf ball-sized brain tumor. Doctors pumped chemotherapy into his bloodstream through an IV.
 </p>
<p>
  Under normal circumstances, it would have been a pointless treatment. The drugs never would have reached their target. Large-molecule drugs like chemotherapies are barred by the blood-brain barrier, a vascular sealant that isolates the brain from the blood vessels that wind through it. Its purpose is to keep dangerous substances—like chemotherapy, bacteria, and viruses—away from the delicate brain.
 </p>
<p>
  But this man’s blood-brain barrier had been pushed wide open.
 </p>
<p>
  Inside his skull, researchers had implanted a button-sized device which emitted a pulsing beam of ultrasound focused on the tissue in and around his tumor. Next, they injected tons of tiny bubbles into his bloodstream that vibrate in the beam. The animated bubbles burrow through the blood-brain barrier, leaving a hole for the chemotherapy drugs to infiltrate.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/ultrasound-therapy_1.width-990_ukOQXMu.png"/>
<figcaption>Ultrasound waves vibrate bubbles injected into the bloodstream, prying open the blood-brain barrier so chemotherapy drugs can enter.
        
    </figcaption>
</figure>
<p>
  The 38-year-old patient was the first to be treated in a series of clinical trials led by Dr. Alexandre Carpentier, a neurosurgeon at the Pitié-Salpêtrière Hospital in Paris. He and his team began treating patients with low levels of ultrasound and slowly ramped up the power as they grew more confident in the procedure’s safety. “We found the optimal ultrasound intensity and sequence to repeatedly open the blood-brain barrier,” Dr. Carpentier said of the results, published recently in the journal
  <em>
   Science Translational Medicine
  </em>
  .
 </p>
<p>
  For decades, doctors have been experimenting with therapeutic ultrasound, or the use of ultrasound to treat diseases and injuries as opposed to the more prosaic use for imaging babies and gallbladders. It’s not the first time that the technology has been heralded as a breakthrough. But the current applications might be the most promising.
 </p>
<p>
  Today, scientists are experimenting with using ultrasound to do everything from cure Alzheimer’s to treat fibroid pain. The recent experiments in France, says Dr. Neal Kassell, chairman of the Focused Ultrasound Foundation, are “just the tip of the iceberg.”
 </p>
<h2>
  The Case of the Prostate
 </h2>
<p>
  Thirteen years ago, Dr. George Suarez attended a meeting of the European Urological Association that transformed the way he treats prostate cancer. At the meeting, Dr. Suarez, a urologist based out of Miami, Florida, learned how doctors in Europe were using focused ultrasound to essentially cook tumors in their place. In ultrasound, he saw the future of medicine—an incarnation of Star Trek’s fantastical bloodless surgery.
 </p>
<p>
  But at the time, focused ultrasound had not been approved for use in the United States. So Dr. Suarez opened a clinic in the Dominican Republic. For the next eleven years, men with prostate cancer would fly to the Caribbean, perhaps spend a few days on the beach, and then receive this promising new treatment.
 </p>
<p>
  Had these men been treated in the United States instead, they likely would have had either radiation therapy or a prostatectomy, where the prostate is removed surgically. Both treatments are well-studied and highly effective at eliminating the cancer—most men never have a recurrence. However, erectile dysfunction and urinary incontinence are common side-effects, prevalent enough to discourage some men from getting treated and drive others to experiment with high-intensity focused ultrasound abroad. HIFU, as it’s known, uses the energy of ultrasound waves to heat tumors, destroying the cancerous cells.
 </p>
<aside class="pulledquote">
  At least in some men with specific cases, it appears to be a promising cancer treatment.
 </aside>
<p>
  Dr. Suarez is unabashed in his enthusiasm for the technology. He sees HIFU as a “total game changer in treating prostate cancer,” an effective treatment with far fewer side-effects than surgery or radiation, he says.
 </p>
<p>
  But not all urologists share in his excitement, and many express skepticism whether the benefits outweigh the risks. Dr. Peter Scardino, a urologist and chair of the Department of Surgery at Memorial Sloan Kettering Cancer Center, is one of them. “When I look at the results of HIFU for prostate cancer—which has been used in Europe for the last 15 years—what I see is cancer control rates that are no better than radiation therapy of the past, and that’s not very good. And complication rates that are comparable to surgery,” he says. “It seems to me that it’s the worst of both worlds.”
 </p>
<p>
  The FDA partially agrees with Dr. Scardino’s assessment. In October 2015, after a decade of clinical trials and investigations, it approved the use of HIFU as part of a treatment regimen for prostate cancer—with a major caveat. The FDA panel noted that there was insufficient evidence to suggest that HIFU could serve as a cancer treatment; instead, they said it was capable of safely destroying prostate tissue. It’s a subtle but significant distinction, one that suggested the FDA was not confident in answering whether HIFU can effectively treat cancer.
 </p>
<p>
  Even skeptics like Dr. Scardino think that ultrasound probably has some role in treating prostate cancer, but maybe only for men with a specific form of the cancer. Dr. Scardino is glad HIFU was approved by the FDA because now doctors have room to explore its use and find the best candidates for HIFU treatment. For example, men with medium-level cancer—those who are too advanced to simply monitor, but who might not require the full strength of surgical or radiological treatment—might stand to benefit from HIFU.
 </p>
<p>
  Still, many questions about focused ultrasound treatment remain unanswered. Currently, there’s not a lot of data on the long-term risk of recurrence after the treatment, and doctors don’t know what size and location of tumor is best treated by HIFU. But at least in some men with specific cases, it appears to be a promising, and arguably better, cancer treatment.
 </p>
<h2>
  Tumors Elsewhere
 </h2>
<p>
  At a technical level, high-intensity focused ultrasound is appealingly blunt. Faced with an offending lump of tissue, you blast it with a wall of ultrasound, melting it. Ablating prostate tissue is perhaps the most widely implemented use of focused ultrasound, but doctors are also testing it to treat liver, kidney, and pancreas cancers. Dr. Pejman Ghanouni, an assistant professor of radiology at Stanford University Medical Center, is currently using focused ultrasound to treat an array of ailments, from soft tissue tumors and bone metastasis to uterine fibroids.
 </p>
<p>
  Focused ultrasound can even be used to ablate tissue in the brain, though it’s not as straightforward as elsewhere in the body. “In the brain, the challenge is the skull. The bone is really highly absorbing of ultrasound, so it heats up very easily,” says Nathan McDannold, an associate professor of radiology at Brigham and Women’s Hospital. Because the brain is surrounded by thick skull bone, focused ultrasound can only be directed at tissue in the center of the brain, far from skull.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/bloodbrainbarrier_151105_252-2.width-990_ewdaFoJ.jpg"/>
<figcaption>Early trials have used networks of ultrasound emitters to treat brain tumors.
        
    </figcaption>
</figure>
<p>
  The device that delivers focused ultrasound to the central brain resembles “those old-style hairdryers in a woman’s hair salon, the kind of hemispherical thing,” Dr. Ghanouni says. Instead of hot air, the nodes along the cap emit ultrasound beams, each pointing at the target in the center of the brain. The pressure from each individual beam is low enough to not damage the skull, but at their focused intersection, they heat and destroy tissue.
 </p>
<p>
  While researchers have refined the technique, directly ablating tumors in the brain remains  complicated, and clinical trials of the technique are still in their early phases. The consequences of one misstep are grave, and scientists are proceeding cautiously.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/ultrasound-therapy_2.width-990_DnmS5i4.png"/>
<figcaption>Powerful ultrasound beams tend to heat the skull rather than the targeted tumor, so doctors use a network of less powerful beams that converge on the tumor to ablate cancer cells.
        
    </figcaption>
</figure>
<h2>
  Opening the Blood-Brain Barrier
 </h2>
<p>
  Many drugs which might be useful in the treatment of brain diseases—from cancer to Parkinson’s—can’t get from the bloodstream into the brain. They are simply too large to squeeze through the blood-brain barrier.
 </p>
<p>
  The blood-brain barrier is a complex collection of cells that function as a sheath around the blood vessels that wind through the brain. “Just like a mainframe computer needs a very constant environment, the brain, which is an electric organ, needs a very constant environment,” says Dr. Edward Neuwelt, director of the Blood Brain Barrier Program at Oregon Health and Science University.
 </p>
<p>
  In the late 1800s, Nobel Prize winning scientist Paul Ehrlich first observed the effects of the blood-brain barrier. When Ehrlich injected dye into an animal’s bloodstream, it colored all of the organs except the brain. Shortly after, his student observed the opposite—dye injected into the brain doesn’t flow to the rest of the body. The mystery remained unsolved for another half century, when scientists could finally explain what Ehrlich observed, the blood-brain barrier.
 </p>
<p>
  Last year, a team of scientists at Sunnybrook Hospital in Toronto opened the blood-brain barrier with ultrasound for the first time. Where the French researchers implanted the ultrasound device inside the skull—allowing them easily and repeatedly open the blood-brain barrier in a fixed region around the implant—the Canadian researchers used external ultrasound beams, which are guided by magnetic resonance imaging and can be focused to a particular region of the brain. “They are very complementary techniques,” Carpentier says. External ultrasound works best when the tumor is located in the center of the brain, whereas ultrasound emitted from an internal implant works best for tumors located in the outer layers of the brain.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/bloodbrainbarrier_151105_542.width-990_h5Uy7RV.jpg"/>
<figcaption>Doctors are experimenting with ultrasound to ablate tumors deep in the brain.
        
    </figcaption>
</figure>
<p>
  Both share some of the same risks, though. The blood-brain barrier is an key part of our body’s natural defense system, and it’s possible that microbes—harmlessly floating through the bloodstream—could leak through an open barrier and into the brain where they can wreak havoc.
 </p>
<p>
  But in these and other clinical trials, scientists have not observed any adverse effects from either the ultrasound or from repeatedly opening the blood-brain barrier. The opening created by the ultrasound closes within six hours, quickly enough that no one has observed any damage to the brain.
 </p>
<h2>
  Future Potential
 </h2>
<p>
  If focused ultrasound really does provide a temporary, non-invasive way to open the blood-brain barrier and allow any drug to enter the brain, its potential applications reach far beyond brain cancer. It could enable unprecedented access to the brain and inspire new lines of research and medication in the treatment of Alzheimer’s, Parkinson’s, and more.
 </p>
<p>
  Immune sensitization is another application of focused ultrasound that’s on the horizon. When cancer cells are cooled or heated, they release a protein which stimulates the body’s natural immune response, making it more sensitive to immunotherapy drugs. Earlier, scientists tried to elicit the response using cryotherapy, the freezing of tissue. Similar to HIFU, cryotherapy offered a way to destroy cancerous tissue while also prompting an immune response.
 </p>
<p>
  It was approved as a treatment for prostate cancer over thirty years ago. “There was a wave of enthusiasm for it, and then it cooled off when people really looked at the results and said, ‘You know, the chances of curing the cancer weren’t that great, and the side-effects were significant,’” Dr. Scardino says. “It just didn’t have a good risk-benefit ratio, and I think HIFU is going to be the same.”
 </p>
<p>
  For now, McDannold says, “I think the drug delivery has a lot more potential.”
 </p>
</section>
<p>
 Image credits: Sunnybrook/Doug Nicholson/Media Source, Alicia DeWitt
</p>

A powerful form of ultrasound could give doctors a new way to treat cancer. 

Kelsey Houston-Edwards

Articles