Inside Einstein's Mind Hero

<p>On November 25th, 1915, Einstein published his greatest work: general relativity. The theory transformed our understanding of nature’s laws and the entire history of the cosmos, reaching back to the origin of time itself. NOVA tells the inside story of Einstein’s masterpiece. The story begins with the intuitive thought experiments that set Einstein off on his quest and traces the revolution in cosmology that is still playing out in today’s labs and observatories. Discover the simple but powerful ideas at the heart of relativity, illuminating the theory—and Einstein’s brilliance—as never before. From the first spark of an idea to the discovery of the expanding universe, the Big Bang, black holes, and dark energy, NOVA uncovers the inspired insights and brilliant breakthroughs of “the perfect theory.” (Premiered November 25, 2015)</p>

<p>Retrace the thought experiments that inspired his theory on the nature of reality.</p>

Inside Einstein's Mind

The Origami Revolution Hero

<p></p><p>The centuries-old tradition of folding two-dimensional paper into three-dimensional shapes is inspiring a scientific revolution. The rules of folding are at the heart of many natural phenomena, from how leaves blossom to how beetles fly. But now, engineers and designers are applying its principles to reshape the world around us—and even within us, designing new drugs, micro-robots, and future space missions. With this burgeoning field of origami-inspired-design, the question is: can the mathematics of origami be boiled down to one elegant algorithm—a fail-proof guidebook to make any object out of a flat surface, just by folding? And if so, what would that mean for the future of design? Explore the high-tech future of this age-old art as NOVA unfolds “The Origami Revolution.”</p>

<p>Engineers are using origami to design drugs, micro-robots, and future space missions.</p>

The Origami Revolution

Hunting the Elements Hero

<p></p><p>Where do nature&#x27;s building blocks, called the elements, come from? They&#x27;re the hidden ingredients of everything in our world, from the carbon in our bodies to the metals in our smartphones. To unlock their secrets, David Pogue, technology columnist and lively host of NOVA&#x27;s popular &quot;Making Stuff&quot; series, spins viewers through the world of weird, extreme chemistry: the strongest acids, the deadliest poisons, the universe&#x27;s most abundant elements, and the rarest of the rare—substances cooked up in atom smashers that flicker into existence for only fractions of a second.</p>

<p>A two-hour special from the producers of &quot;Making Stuff&quot;</p>

Hunting the Elements

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Physics & Math

Koch Foundation

Draper





  
      <div class="rich-text"><p>Imagine you have a pair of quantum dice. You put the dice in your cup, throw them, and they are both a “six.” You do it again, and they’re both a “three.” You do it again, and they’re both a “one.” No matter how many times you throw the dice, they are always the same number. This is a seemingly random process, but quantum entanglement ensures that these dice will always act in unison.</p><p>The thought of tackling quantum entanglement in your classroom can be intimidating. Even Albert Einstein was skeptical of the concept, calling it “spooky action at a distance,” and didn’t think it was possible. If this was a tough sell for Einstein, how can you teach this idea to middle and high school students?</p><p></p></div>
  

  
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      <div class="rich-text"><p>Quantum physics are the laws that govern subatomic particles. It can help explain the movements, interactions, and behaviors of very small things like photons and electrons. How small are particles in the subatomic world? Imagine something a million times smaller than the width of a human hair, or making a soccer ball into the size of the Earth and moving inside. This is how we can understand the scale of the world of atoms and subatomic particles.</p><p>Quantum physics is rooted in probability. An electron doesn’t have a specific location in space until it is looked for or detected. When we picture an atom, we often imagine its electrons orbiting the atom’s nucleus in clear defined paths. However, electrons are not the ever-present tiny spheres we imagine them to be. They are really a “fuzzy wave of probability,” ready to be in an infinite amount of locations around the nucleus of an atom until we look at it. The simple act of observing an electron changes the electron’s location.</p></div>
  

  
      <div class="rich-text"><p>Quantum entanglement takes this idea one step further, and is a phenomenon where two particles act in unison, no matter the distances between them. Unlike a row of dominoes that rely on the actions of each previous domino to be knocked down over time, entangled particles change instantly once one is detected, no matter how far apart they may be. For example, if a particle on Earth is entangled with a particle in the Andromeda galaxy, they will change at the exact same time once a change is made to one of the particles.</p><p></p><p>While quantum physics pertains to the smallest units in the universe, the ways in which it impacts our daily lives are immense. Quantum theory played a role in the Manhattan Project and the atom bomb and in the development of lasers and transistors. Our increasingly digital world relies on quantum entanglement to send encrypted messages and quantum computers with massive processing power to solve problems a normal computer could never accomplish.</p><p>Quantum physics impacts the technology students use every day. Use these resources from NOVA broadcasts, NOVA Digital, and <i>What the Physics!?</i> to introduce quantum concepts to your students.</p></div>
  

  
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      <div class="rich-text"><h2><b><i>Einstein’s Quantum Riddle</i></b><b> Resources</b></h2><p><a href="https://mass.pbslearningmedia.org/resource/nveqr-sci-entanglement/quantum-entanglement-einsteins-quantum-riddle/">Quantum Entanglement</a>: Conceptualize quantum entanglement, the idea that particles can instantaneously influence each other even when they are spatially separated, in this video from NOVA: <i>Einstein’s Quantum Riddle</i>.</p><p><a href="https://mass.pbslearningmedia.org/resource/nveqr-sci-electronduality/waveparticle-duality-of-electrons-einsteins-quantum-riddle/">Wave Particle Duality of Electrons:</a> Conceptualize the nonintuitive idea that electrons can behave both as a wave and a particle (wave–particle duality) in this video from NOVA: <i>Einstein’s Quantum Riddle</i>.</p><p><a href="https://mass.pbslearningmedia.org/resource/nveqr-sci-evidence/collecting-evidence-for-quantum-entanglement-einsteins-quantum-riddle/">Collecting Evidence for Quantum Entanglement</a>: Learn why different experimental designs were needed to collect evidence for quantum entanglement in this media gallery of videos from NOVA: <i>Einstein’s Quantum Riddle</i>.</p><p></p><h2><b><i>What the Physics!?</i></b><b> Resources</b></h2><p><a href="https://www.pbs.org/wgbh/nova/video/seeing-quantum-with-the-naked-eye/">Seeing Quantum with the Naked Eye</a>: How can you train yourself to be a quantum detector? You can detect quantum mechanics all over—if you know how to look for it. In this episode of <i>What the Physics!?</i> find out how simply squinting at a lamp reveals the quantum nature of light.</p><p><a href="https://www.pbs.org/wgbh/nova/video/the-biggest-puzzle-in-physics/">The Biggest Puzzle in Physics:</a> Sometimes the biggest puzzle in physics seems like the worst relationship in the universe. Quantum mechanics and general relativity are the two best theories in physics, but they have never been able to get along. Find out why in this episode of<i> What the Physics!?</i></p><p></p><h2><b>NOVA Digital Resources</b></h2><p><a href="https://mass.pbslearningmedia.org/resource/arct14.sci.nvqconf/quantum-confidential/">Quantum Confidential</a>: Watch how a technique called quantum cryptography could save a state secret from falling into enemy hands in this video from NOVA Digital.</p><p><a href="https://mass.pbslearningmedia.org/resource/nvnd-sci-voterfraud/wgbh-nova-digital-using-quantum-physics-to-prevent-voter-fraud/">Quantum Physics to Protect Votes:</a> Voters want to be assured that every election is fraud-proof and hack-free. With the help of quantum mechanics, it’s possible to do just that — encrypt and transmit a vote in ways that can’t be tampered with.</p></div>
  

  
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<p>Quantum physics impacts the technology students use every day. Use these resources from NOVA broadcasts, NOVA Digital, and <i>What the Physics!?</i> to introduce quantum concepts to your classroom.</p>

Bring "Spooky Action at a Distance" into the Classroom with NOVA Resources

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<p>Why this card trick might fool your eyes.</p>
<p>Watch a ten of clubs transform into an ace of hearts in this magic trick, which demonstrates “change blindness,” a phenomenon that causes gaps in visual.</p>
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<p>Why this card trick might fool your eyes.</p>

The Science Behind This Sleight of Hand





  
      <div class="rich-text"><p>If there’s anything more mesmerizing than iridescent swirls dancing across a soap bubble, it’s the sight of icy stars whirling around that bubble as it freezes.</p><p>So when a <a href="https://www.youtube.com/watch?v=H7pqoCJQp2I">YouTube video</a> of a bubble freezing made its way to mechanical engineer Jonathan Boreyko and his team at Virginia Tech, they weren’t just awed. They wanted to understand the physics behind the stunning display of swirling ice crystals.</p><p>“A lot of things in research are more motivated by a desire for truth or beauty,” Boreyko says, “like just trying to understand a new and mysterious thing.”</p></div>
  

  
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      <div class="rich-text"><p>The team’s <a href="https://www.nature.com/articles/s41467-019-10021-6">study</a>, published last month in the journal <i>Nature</i> <i>Communications</i>, reveals the physics of the “snow globe effect,” a phenomenon that causes hundreds of tiny ice crystals to float across a bubble’s surface and freeze simultaneously in a whimsical display.</p><div style="padding-bottom: 74.94553376906318%;" class="responsive-object">
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<p>What Boreyko and his team set out to determine was where the hundreds of small ice crystals in the snow globe effect come from. Typically, when a relatively small quantity of a liquid freezes—like when water turns into an ice cube—the freezing process begins from a single point of origin. That point creates an expanding boundary between frozen and unfrozen liquid called a freeze front. As the freeze front expands outward, it cools the remaining liquid, causing it to change phase and become ice.</p><p>But in bubbles, Boreyko and his team noticed, this process can be different. When the researchers froze some bubbles in a walk-in freezer and took photos and videos of them, they saw what looked like hundreds of freeze fronts floating simultaneously across the bubbles’ surfaces.</p></div>
  

  
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      <div class="rich-text"><p>To look more closely at the physics behind the multitude of freeze fronts, the team developed a mathematical model to simulate bubbles freezing. The modeling, Boreyko says, was the hardest part. “Once all the experiments were done, it took over a year to fully model and understand the physics behind the stuff we were seeing,” he says.</p><p>What the team discovered follows the fundamental process of freezing itself: The moment a liquid freezes, it gets slightly warmer. This is because as a liquid’s molecules rearrange and fuse into a solid, excess energy is released in the form of heat, called latent heat.</p><p>When a bubble is in a freezing environment and lands on a cold surface, the first thing to freeze is the bottom of the bubble. As this freeze front expands, it releases latent heat into the adjacent liquid surface of the bubble. This warms the water at the edge of the freeze front ever so slightly and causes it to flow toward the top of the bubble.</p><p>As more latent heat is released, the water flow grows stronger. This puts stress on the freeze front and causes extremely tiny ice crystals to break off and slide across the bubble’s surface. These crystals then begin to grow simultaneously, giving the impression that there are multiple freeze fronts forming at once.</p><p>“It actually is only one freeze front,” Boreyko says, adding that the cold surface provides a point of origin to start the growth of ice crystals.</p><p>“This paper was not about ice, really. It was more about liquid flow,” says Kenneth Libbrecht, a physicist at Caltech specializing in ice crystals and snowflake formation who was not involved in the study. The study’s unique finding, he says, is that freezing creates liquid flows on the surface of bubbles that create a feedback loop, which enhances the freezing process itself.</p><p>This new understanding of the snow globe effect could someday help experts engineer better ways to freeze things, including biological material like human tissue.</p>
            <figure class="richtext-image full-width"><img alt="Image-1-1 (1).png" class="richtext-image full-width" height="228" width="800"
            src="/wgbh/nova/media/images/Image-1-1_1.width-800.png"/><figcaption><p>The progression of the &quot;snow globe effect&quot; in three images. Image Credit: Farzad Ahmadi and Christian Kingett</p><div class="credit"><p></p></div></figcaption>
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            <p>Currently, the low-temperature freezing of human tissue, called cryonics, is mostly limited to freezing small tissue samples or single cells, says Steven Van Sciver, a professor studying cryogenics and cryonics at Florida State University who was not involved in the study. Larger samples, such as full organs, he says, become damaged during the freezing and thawing process.</p><p>“Most of what you see in Star Wars and Star Trek and Hollywood is things like freezing people and bringing them back to life,” Van Sciver says. “And most of it is a hoax.”</p><p>But, to researchers looking for better ways to freeze things, bubbles present a unique opportunity, he says. “Understanding how these crystals are formed in very thin bubbles and how they move around could be helpful in understanding biological freezing done with cryogenics.”</p><p>But Boreyko says his team didn’t have an end use in mind when they started this project, just a desire to understand what they were seeing.</p><p>“People are always thinking about applications,” Libbrecht says. “I think that’s the wrong way to think about it. In this case, the research is very inexpensive....It’s OK to spend a little bit of money trying to understand what’s going on around you.”</p></div>
  

  
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<p>Freezing soap bubbles look like snow globes. This whimsical effect could help us improve biological freezing techniques—and is incredibly fun to watch.</p>

The physics of freezing soap bubbles is cooler than you’d think





  
      <div class="rich-text"><p>At some point or another, most of us have played travel agent to a dandelion. Blowing on their tufted tops is a childhood rite of passage for many, and a simple puff of air is all it takes to send the seeds of these wayfaring weeds wafting into the breeze.</p><p>But even when our lungs are the source of the initial gust, we humans can’t take all the credit for dandelion fight. Thanks to evolution’s incessant tinkering, these seeds have become some of nature’s deftest dispersers, tumbling inches, feet, sometimes miles from their original source. Now, two <a href="https://www.nature.com/articles/s41586-018-0604-2">recent</a> <a href="https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.071901">studies</a> reveal the physics behind their fanciful flight.</p></div>
  

  
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      <div class="rich-text"><p>In the wake of their golden days of flowering, the tops of dandelion plants mature into dozens of flight-ready seeds, each tethered to its own personal parachute. But what crowns these seeds aren’t the billowing cloth contraptions we’re used to. Rather, they’re tufts of haphazard fluff, each made up of about 100 individual bristles that fan out into a sparse, delicate plume called a pappus.</p><p>To suss out how these strange little structures keep seeds aloft, a team of University of Edinburgh engineers led by <a href="https://www.eng.ed.ac.uk/about/people/dr-cathal-cummins">Cathal Cummins</a> went into the weeds. Using a tiny, vertical wind tunnel that suspended seeds at a fixed height, simulating flight, the researchers were able to observe how air interacted with the pappus’ filaments.</p><p>The trick behind the seeds’ airborne acrobatics, it turned out, was less about the bristles themselves than the gaps between them. High-speed cameras showed that, after air flowed up and around the pappus, it was quickly rerouted into the center of a swirling, elongated whirlpool called a <a href="https://www.youtube.com/watch?v=jzq5gfeHfuc">vortex ring</a> that pushed the air back down toward the top of the pappus, where it ascended once more. This fast-moving funnel was so good at recycling air that it generated an ever-present pocket of low pressure just above the seed, sucking it upward into an easy, breezy cruise—and delaying its inevitable descent.</p>
            <figure class="richtext-image full-width"><img alt="Image One Madeleine Seale, Alice Macente.png" class="richtext-image full-width" height="517" width="800"
            src="/wgbh/nova/media/images/41185693185_a07e06b42d_o.width-800.jpg"/><figcaption><p>Fun fact: Each unit of a dandelion is actually home to hundreds of individual flowers clustered together. Because dandelions can reproduce both sexually (through pollination) and asexually, every seed emerging from a dandelion’s head can have a different genetic makeup. Image Credit: Theo Crazzolara, flickr</p><div class="credit"><p></p></div></figcaption>
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            <p>Dandelions are by no means the first organisms (<a href="https://science.sciencemag.org/content/329/5990/406.long">or even the first plants</a>) that have been shown to DIY their own vortex rings to achieve liftoff. But as Cummins and his colleagues <a href="https://www.nature.com/articles/s41586-018-0604-2">reported</a> last October in the journal <i>Nature,</i> their pappuses have an especially aerodynamic structure, with bristles so thin that they take up just 10 percent of the total space in the seed’s frizzy updo. This gives the pappus a lot of porosity—a measure of its relative “emptiness,” explains study author <a href="https://www.ed.ac.uk/profile/madeleine-seale">Madeleine Seale</a>, who specializes in plant biomechanics.</p><p>And dandelion seeds, it would seem, have a knack for turning nothing into a whole lotta something. Compared to a solid, parachute-shaped structure of about the same size, the pappus is actually <i>four times</i> as efficient at creating drag, the force that counteracts gravity to keep the seed airborne, the researchers found.</p></div>
  

  
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      <div class="rich-text"><p>There was a second effect, too: By generating super-efficient drag, the pappus’ porosity also has the perk of keeping the seed’s flight stable.</p><p>When upward-bound air travels up and around a falling object, it can create a sort of wobble—a bit like a flag flapping in a gust of wind, just on a much smaller scale. But because the pappus is porous, some air flows <i>through</i> it instead, streaming between the bristles of the seed’s thin toupee. The more porous the parachute, the smoother its flight.</p><p>What wasn’t quite clear, however, was if the seeds’ stability was affected by the number of filaments in each pappus. That’s where the <a href="https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.071901">second paper</a>, published today in the journal <i>Physical Review Fluids</i>, comes in. Taking a theoretical approach, a team led by fluid dynamicist <a href="https://people.epfl.ch/francois.gallaire?lang=en">François Gallaire</a> of the Swiss Federal Institute of Technology Lausanne devised a mathematical model of the super-steady nature of dandelion vortex rings.</p><p>The results revealed a fragile balancing act between two opposing forces. The fewer filaments atop a seed, the higher its porosity, and thus stability—good news for a skyfaring seed. But stability also comes at the cost of drag, which increases as the number of bristles goes <i>up</i>. A fair compromise, the researchers found, is for the seeds to hit a sweet spot around 100 bristles per pappus. This figure matched up with what’s found on real-life dandelions, Gallaire says. There’s some wiggle room, but at lower numbers, the seed would have trouble staying afloat; too much higher, and things might start to get shaky.</p><p>“It is super cool that dandelions and this mathematical model came up with the same number,” says <a href="https://biology.williams.edu/profile/jedwards/">Joan Edwards</a>, a plant biologist at Williams College who was not involved in either study. “Adaptation is one of the hardest questions to answer in evolutionary biology...but now, we can theoretically explain why a pappus has this number of filaments, and that’s really exciting.”</p><div style="padding-bottom: 74.94553376906318%;" class="responsive-object">
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<p>But the theoretical model does more than add credence the first paper’s experimentally-driven results, Seale says. “With a model, they can explore things we can’t explore experimentally very easily...including how these structures can be used in new and different ways,” she says.</p><p>For instance, plugging different numbers into the Swiss team’s equations could aid the design of better microdelivery systems, says <a href="https://www.mcdb.ucla.edu/faculty/siobhanb">Siobhan Braybrook</a>, who studies plant form and function at the University of California, Los Angeles, but was not involved in either study. Someday, pappus-like structures could play a role in tasks like airdropping fertilizer or transporting teeny robots.</p><p>One thing that’s probably <i>not</i> in our future, though, is a dandelion-inspired parachute for people or their parcels, Braybrook adds. We humans (and most of the things we buy) are far too big and bulky for the same physical principles to apply. “For this design to be relevant...you need to talk about objects that are incredibly light or incredibly small,” she says.</p>
            <figure class="richtext-image full-width"><img alt="HaloVortexRingLiftsDandelionSeeds (1).png" class="richtext-image full-width" height="600" width="800"
            src="/wgbh/nova/media/images/HaloVortexRingLiftsDandelionSeeds_1.width-800.png"/><figcaption><p>The dandelion&#x27;s sparse, tufted pappus creates a swirling pocket of air called a vortex ring in the space above it. The pappus is mostly empty space, but the 100 or so filaments that comprise it hit a &quot;sweet spot&quot; between creating just enough drag to keep it aloft, while maintaing the seed&#x27;s stability. Image Credit: Courtesy of Cathal Cummins, Madeleine Seale, Enrico Mastropaolo, Ignazio Maria Viola, and Naomi Nakayama</p><div class="credit"><p></p></div></figcaption>
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            <p>Unless, that is, we fiddle with one pesky constraint: gravity itself. “If we were on a different planet...we might need to come up with different ways of dealing with drag,” Braybrook says. “In that kind of situation, [this model] could be incredibly relevant.”</p><p>We’re not quite ready to deploy those tactics just yet. In the meantime, there are still exciting opportunities to study some marvels of innovation right here on Earth: Many other plants spread their seed by wind; even some animals have evolved specialized structures that help them navigate through air or water.</p><p>As research on these organisms and more continues to take flight, a one-size-fits-all equation probably won’t apply. But maybe that’s part of the beauty of this dazzlingly simple system.</p><p>“Nature has optimized something so beautiful,” Braybrook says. “For us, it’s only as we start to develop [new technologies] that we start thinking about these problems...but nature’s already done the work. We have the best simulations ever in the products of evolution.”</p></div>
  

  
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<p>Two research teams went into the weeds to quantify the magic behind the flight of the dandelion seed.</p>

The uplifting science of how dandelion seeds stay aloft

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<p>See why experts are saying it&#x27;s the dawn of a new Information Age.</p>
<p>Quantum computers operate using the strange laws of quantum physics and could be used to solve complex problems traditional computers aren&#x27;t able to tackle today.</p>
<p><b>Six Ways Quantum Computers Could Change the World</b></p><p>Published: June 24, 2019</p><p></p><p><b>Onscreen</b>: A new type of supercomputer is on the horizon. Quantum computers are able to solve complex problems quickly, thanks to quantum physics.</p><p><b>Rob Schoelkopf:</b> A quantum computer is a new device for processing information that employs the unique aspects of the quantum world.</p><p><b>Onscreen</b>: Ordinary computers store information in 0s and 1s, or bits.Quantum computers store information in qubits which can exist as both 0s and 1s at once.</p><p><b>Rob Schoelkopf:</b> A quantum computer can be uniquely suited for doing certain computational tasks that are otherwise intractable today. anything where there is a needle-in-a-haystack type problem where you are searching through a very large number of combinations, a quantum computer can explore them, in a properly designed algorithm, all at the same time. “</p><p><b>Marissa Giustina:</b> I think quantum computing will change the way we do research. It will give us a different tool for asking questions about nature and that’s really exciting.</p><p><b>Onscreen</b>: To outperform traditional computers, a quantum computer needs many qubits to work together. And that’s no easy task.</p><p><b>Marissa Giustina</b>: One qubit does not a quantum computer make. There is a big difference between one qubit and a large array of qubits that all work together and can be controlled coherently. It can be that adding a few more qubits affects your system in more complicated ways that you didn’t anticipate.</p><p><b>Onscreen</b>: Here are six ways quantum computing would change the world.</p><p>1. Enhance artificially intelligent systems</p><p>Quantum computers have the potential to create really robust AI algorithms</p><p>2. Discover new materials</p><p>The search for a high temperature superconductors has been the holy grail of material science. Quantum computers could help make this a reality, and vastly improve the energy grid and transportation system.</p><p><b>Rob Schoelkopf:</b> Giving chemists for example insight new ways to synthesize molecules, or material scientists hints about how they could make a better material for photocells or better batteries – these are the things we are excited about and looking forward to in the next few years.</p><p><b>Onscreen</b>: 3. Improve roads, and travel</p><p>Quantum computers could predict high traffic hours. Leading to advances in navigation applications and traffic signal coordination.</p><p>4. Revolutionize cryptography</p><p>A method called quantum encryption has the potential to make messages exponentially more secure. But it also might make current methods of encryption obsolete.</p><p>5. Better predict weather</p><p>Better predictions could mean more time to evacuate ahead of catastrophic weather.</p><p>6. Create more effective drugs</p><p>Quantum computing could accelerate the rate of medical breakthroughs.</p><p>Quantum computing is still a very young field, but it could fundamentally change almost every industry.</p><p><b>Schoelkopf</b>: We’re on the dawn of creating a whole new industry or paradigm for information so this is very exciting.</p>
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<p>See why experts are saying it&#x27;s the dawn of a new Information Age.</p>

Six Ways Quantum Computers Could Change the World





  
      <div class="rich-text"><p>In the world of quantum computing, diamonds might be an engineer’s best friend.</p><p>That’s because a fabled, <a href="https://wired.com/story/these-perfectly-imperfect-diamonds-are-built-for-quantum-physics/">super-pure type of gem</a> mined from the Ural Mountains has quantum properties that could provide a promising model for a stable, scalable quantum computer.</p><p>For several decades, scientists have been working on applying the strange laws of quantum mechanics—which govern the subatomic world—to the field of computing. So-called quantum computers, they say, could theoretically solve many problems much faster than any classical computer could. That’s because the basic unit of quantum information (a qubit) is fundamentally different in nature from the basic unit of classical information (a bit).</p></div>
  

  
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      <div class="rich-text"><p>A qubit is sort of like a person—it contains multitudes. Whereas a bit has a definite value of 0 or 1, a qubit can exist in two states (both 0 and 1) simultaneously. Quantum particles spend their lives in a superposition of states: sometimes 0 and a hint of 1, other times possibly 0 but more likely 1, and so on. When we observe a qubit, or subject it to the influences of the macroscopic world, that mosaic of states “collapses” into a single reality—much like when you interact with or observe a friend, you’re only seeing a snapshot of her personality at any given moment. Qubits’ complexity makes them stronger. Together with lots of other qubits, they’re able to assess all possible solutions to a problem at once, yielding a vast mélange of options in just seconds.</p></div>
  

  
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      <div class="rich-text"><p>Quantum computing, then, is <a href="http://iontrap.umd.edu/wp-content/uploads/2016/06/SciAm_May2016.pdf">extremely exciting</a>. This sophisticated technology could enhance privacy and security, help build more accurate clocks, improve machine learning, and even assist in the creation of new materials. And yet, a major barrier to realizing these advances is qubits’ strength. Along with superposition, “entanglement,” which allows two particles to exert an instantaneous influence on each other, is a key element of quantum computing. But scientists haven’t figured out how to entangle a huge bundle of qubits at once, nor how to increase their coherence times (the amount of time a particle is locked in a state of superposition before collapsing into a single state). Until engineers can transcend these limitations, we likely won’t see a large-scale quantum computer available for commercial use.</p><p>“I think it’s going to be just a few years until we see quantum computers that are offering real value on the first initial [math] problem sets, which will maybe be more scientific in nature,” says Robert Schoelkopf, a professor of physics at Yale University and a director of the Yale Quantum Institute. “But then I think we’ll rapidly see an expansion of the kinds of problems these quantum computers can address as we get better and better at engineering them.”</p><p>To get there, Schoelkopf and others are trying to make qubits into Olympic athletes: strong, resilient, and cooperative in team settings. And they’re looking to the tiniest and purest objects in the universe for the most elite qubit prototypes, since any Schrödinger’s cat-like object that both <i>is</i> and <i>isn’t</i> in a particular state could be the basis for a viable qubit. Three major contenders for the gold medal in qubit-ing are nitrogen-vacancy (NV) centers in diamond lattices, trapped ions, and superconducting qubits—but they all have distinct advantages and disadvantages.</p><h2><b>Qubits need to be isolated from their surrounding environment</b></h2><p>The most amateur qubit, the isolated single atom, obeys one of the most important laws of quantum computing: that qubits need to be completely isolated from the outside world. This is the most basic form a qubit can take. When separated from the outside world in a vacuum, its energy states (sometimes called spin states) store quantum information in a way that is durable and long-lasting.</p><p>Too many interactions with the surrounding environment can deflate the integrity of the quantum system and cause it to collapse into a single reality, a process called decoherence. This is why experimentalists cool most quantum computers to very low temperatures: large copper-colored cylinders refrigerate so-called superconducting qubits (which companies like IBM and Google are investing in) so that they move more slowly and are less suited to interact with undesirable particles. Laser beams can also cool single atoms until they are nearly at rest by transferring momentum from the atom to the scattered laser light.</p><p>The problem with the isolated single atom, though, is that its neutral charge means it’s harder to entangle them because they’re not as reactive. And to build real quantum machines capable of super-powered mathematical acrobatics, engineers need to entangle lots of qubits.</p><p>“There’s a fundamental tension of trying to keep the isolation from the outside world while simultaneously controlling the quantum bits and making them talk to each other,” Schoelkopf says.</p><h2><b>Qubits need to communicate effectively with other qubits</b></h2><p>Take away one electron from a neutral atom and you have an ion—a positively charged particle. Ions interact strongly with one another, but scientists have played around with “trapping” ions in an electromagnetic field and then deep-freezing them with lasers to form a crystal of ions. Additional lasers can help nudge the crystals’ ions into a state of entanglement, and multiple crystals linked together subsequently become the building blocks of a larger quantum network.</p><p>The benefit of trapped-ion systems is that the ions are inherently going to affect one another. “When you physically shake one of them, all of the other ions feel it,” says Michael Goldman, a postdoctoral researcher at the Joint Quantum Institute in Maryland. Systems like this that are scalable (meaning engineers can make them bigger) and malleable are promising models for quantum computers—they can do very fast operations, Schoelkopf says.</p><p></p>
            <figure class="richtext-image full-width"><img alt="razoriontrap-001.jpg" class="richtext-image full-width" height="800" width="800"
            src="/wgbh/nova/media/images/razoriontrap-001.width-800.jpg"/><figcaption><p>Segmented razor blade trap used to trap ions | Photo credit: E. Edwards/Joint Quantum Institute</p><div class="credit"><p></p></div></figcaption>
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            <p></p><p>Trapped-ion qubits can do a lot. They’re easily entangled, plus scientists can turn that interactivity on and off easily so that individual qubits don’t engage with unwanted thermal fluctuations, or heat that would cause the system to decohere. And they’re becoming popular enough that companies like IonQ and Honeywell are investing in technologies that incorporate them.</p><p>“Nature makes [the ions] identical,” Goldman says. “They’re clean and have a long coherence time. As a system, they are really mature. Every system does have a problem with scaling past a certain point, but I think right now ion trapping has a viable path.”</p><h2><b>Qubits need to be cheap and future-proof</b></h2><p>Whereas the trapped-ion method requires elaborate tools—an electromagnetic field and lasers—to trap the ions, scientists are finding that Russian “magic diamonds” can hold qubits in place and thus act the same way that a trapped-ion rig does. By replacing a single carbon atom in a diamond’s atomic lattice with a nitrogen atom and leaving a neighboring lattice node empty, engineers can create what’s called a nitrogen-vacancy (NV) center. This is generally inexpensive since it’s derived from nature. The NV center is a flaw, or blemish, in an otherwise super-pure atomic structure.</p><p>“I like to think of the NV center as an inside-out atom, in a way,” Goldman says. In a typical atom, electrons surround the nucleus in orbitals; in this case, electrons occupy orbitals inside the vacancy of the NV center (they come from the valence, or outer-ring, electrons of the nitrogen atom) while the NV center’s electronic spins react with the nuclear spin of some of the carbon atoms nearby. In this case, both the NV center and the adjacent carbon atoms function as qubits, and the diamond lattice keeps them stationary and entangled.</p><p>These qubits—called solid-state spin qubits—are limited, though, since the system can only have as many qubits as there are neighboring carbon atoms (just three in the immediate vicinity). And NV centers are difficult to control, which means they might not be as scalable as other options. Nature, too, is fundamentally variable, and NV centers can be influenced by the nuclear spins of other atoms in the lattice—which means one diamond lattice is undoubtedly going to be slightly different from the next.</p><p>“In terms of being a general, perfect qubit, ions may be better suited… just because they’re cleaner,” Goldman says.</p><p>NV centers can operate at room temperature (trapped ions can, too), which is a massive bonus, depending on what scientists want to use them for. For example, we may need to experiment with types of quantum machines that aren’t large enough to maintain cool temperatures, or that need to accomplish tasks that wouldn’t be allowed in a standard ultra-cold arrangement.</p><p>Researchers at the Delft University of Technology in the Netherlands have entangled an NV center’s electronic spin with the spins of nine nearby nuclei, an impressive start to this burgeoning technology, which is being developed by a Harvard-bred start-up called Quantum Diamond Technologies.</p></div>
  

  
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      <div class="rich-text"><p>Nicole Yunger Halpern, a theoretical physicist and quantum computing expert at Harvard University, says that NV centers are promising, but that the scientific community shouldn’t rule out other uses of solid-state qubits (qubits contained in solid objects). Ultimately, a mixture of qubit types in one system could be the best way to build a scalable quantum computer.</p><p>“Over the past decade or two, there have been revolutions in the way people have been using different types of platforms to build qubits,” she says. If scientists could figure out how to transfer information from one type of qubit to another, she says, they might be able to knit together a robust fabric of top-tier qubits.</p><h2><b>Qubits need long coherence times</b></h2><p>A popular type of qubit is the superconducting qubit, which has a decent coherence time, meaning it can endure in a state of quantum superposition for a relatively long time. These qubits take the form of superconducting (that is, zero electrical resistance) circuits that maintain a state of both 0 and 1 as a photon both does and doesn’t zoom through them. Though trapped ions have a better track record when it comes to coherence time, superconducting qubits (and NV centers) are close behind.</p><p>Some scientists, like Schoelkopf and the University of Chicago’s David Schuster, are trying to build a twist into this model that will help coherence times and improve this type of system. “When you’re using superconducting qubits in a quantum computer, you’re also using light that interacts with the superconducting qubits,” Yunger Halpern says. “Some of these groups are reversing the roles of the superconducting qubits and the light.” In other words, they’re storing quantum information in the light as opposed to the superconducting qubits.</p><p>Schoelkopf says this kind of information carrier can live longer than qubits created by conventional methods by a factor of 30 or 50. “Not just the rate but the number or type of errors that it can experience are smaller,” he says.</p><h2><b>Qubits need to be flexible</b></h2><p>Above all, the most refined and athletic qubits are the ones that are going to be more flexible. The ability to operate quantum computers at room temperature, for example, is a particularly enticing possibility that would give qubits more flexibility. And the more receptive qubits are to being guided by lasers, the more amenable they’ll be to entanglement.</p><p>“You want the qubits to be docile and go where they are led,” Yunger Halpern says. “This is maybe more of a characteristic of a show dog than an Olympic athlete.”</p><p>Techniques for adding flexibility to these systems vary tremendously: From understanding the relationship between entropy and information (which could affect how engineers understand thermodynamic processes in quantum situations) to using different methods of entanglement, scientists are training qubits to reach and surpass their expected limits.</p><p></p>
            <figure class="richtext-image full-width"><img alt="Qubit2.JPG" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/Qubit2.width-800.jpg"/><figcaption><p>This cat’s name is Qubit. He may not be an Olympic athlete, but the author thinks he’s a pretty Great Qubit. | Photo courtesy Amanda Gefter and Justin Smith</p><div class="credit"><p></p></div></figcaption>
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            <p></p><p>“There are always going to be physical challenges with a quantum computer,” says Ashley Montanaro, a quantum computation researcher at the University of Bristol. “But when you scale up, as long as the noise [that the qubits] have to contend with doesn’t increase too much, you’ll be able to have a system that’s a thousand or one million qubits.”</p><p>Scientists are slowly, incrementally making their way toward that goal. And in the process, these little qubits could help solve some universal puzzles.</p><p>“The transition from truly quantum behavior to behavior that can be described as classical mechanics has been mysterious for a long time,” Yunger Halpern says. “I hope that as our quantum systems grow, we’ll be able to use them more and more to probe the crossover.”</p></div>
  



<p>At the core of quantum computing is the qubit. The best ones have a few defining traits, and scientists are looking to everything from lasers to Russian diamonds to help refine the best qubits for the next generation of quantum computing.</p>

What makes a great qubit? Diamonds and ions could hold the answer

<p>Learn about gerrymandering—the manipulation of district boundaries for political advantage—and see how geometry can be used to detect and help solve the problem in this video from NOVA.</p>

Topic: Physics & Math

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