Physicists have reported what could be the first incontrovertible evidence for the existence of unusual particle-like objects called anyons, which were first proposed more than 40 years ago. Anyons are the latest addition to a growing family of phenomena called quasiparticles, which are not elementary particles, but are instead collective excitations of many electrons in solid devices. Their discovery—made using a 2D electronic device—could represent the first steps towards making anyons the basis of future quantum computers.
“This does look like a very big deal,” says Steven Simon, a theoretical physicist at the University of Oxford, UK. The results, which have not yet been peer-reviewed, were posted on the arXiv preprint repository last week.
Known quasiparticles display a range of exotic behaviours. For example, magnetic monopole quasiparticles have only one magnetic pole—unlike all ordinary magnets, which always have a north and a south. Another example is Majorana quasiparticles, which are their own antiparticles.
Anyons are even more strange. All elementary particles fall into one of two possible categories—fermions and bosons. Anyons are neither. The defining property of fermions (which include electrons) is Fermi statistics: when two identical fermions switch spatial positions, their quantum-mechanical wave—the wavefunction—is rotated by 180º. When bosons exchange places, their wave doesn’t change. Switching two anyons should produce a rotation by some intermediate angle, an effect called fractional statistics that cannot occur in 3D space, but only as collective states of electrons confined to move in two dimensions.
Fractional statistics is the defining property of anyons, and the latest work—led by Michael Manfra, an experimental physicist at Purdue University in West Lafayette, Indiana—is the first time it has been measured so conclusively.
The quasiparticles’ unusual behaviour when switching places means that if one moves in a full circle around another—equivalent to the two particles switching positions twice—it will retain a memory of that motion in its quantum state. That memory is one of the telltale signs of fractional statistics that experimentalists have been looking for.
Manfra and his team manufactured a structure consisting of thin layers of gallium arsenide and aluminium gallium arsenide. This confines electrons to move in two dimensions, while shielding them from stray electric charges in the rest of the device. The researchers then cooled it to 10,000ths of a degree above absolute zero and added a strong magnetic field. This produced a state of matter in the device called a ‘fractional quantum Hall’ (FQH) insulator, which has the peculiarity that no electric current can run in the interior of the 2D device, but can run along the edge. FQH insulators can host quasiparticles whose electric charge is not a multiple of the electron charge, but instead is one-third of it: these quasiparticles have long been suspected to be anyons.
To prove that they were indeed anyons, the team etched the device so that it could carry currents from one electrode to another along two possible edge paths. They tweaked the conditions by varying the magnetic field and adding an electric field. These tweaks were expected to create or destroy anyon states stuck in the interior, and also to produce anyons running between the electrodes. Because moving anyons had two possible paths, each producing a different twist in their quantum-mechanical waves, when the anyons reached the end point, their quantum-mechanical waves produced an interference pattern called pyjama stripes.
This pattern shows how the relative amount of rotation between the two paths varies in response to changes in the voltage and the magnetic-field strength. But the interference also displayed jumps, which were the smoking gun for the appearance or disappearance of anyons in the bulk of the material.
“As far as I can tell, it is an extremely solid observation of anyons—directly observing their defining property: that they accumulate a fractional phase when one anyon travels around another,” Simon says.
It is not the first time that researchers have reported evidence of fractional statistics. Robert Willett, a physicist at Nokia Bell Labs in Murray Hill, New Jersey, says that his team saw “strong evidence” for fractional statistics in 2013.
And other teams have probed a different property that makes anyons an intermediate between fermions and bosons. Fermions obey the Pauli exclusion principle: no two fermions can occupy exactly the same quantum state. But bosons have no such restrictions. Anyons are in the middle—they do bunch, but not as much as bosons do, as an experiment described in April in Science reported. “It is strikingly different from the fermionic behaviour that we can also probe in the same set-up,” says Gwendal Fève, an experimentalist at the Sorbonne University in Paris who led that effort.
But some theoretical physicists say that the evidence in these and other experiments, although striking, was not conclusive. “In many cases, there are several ways of explaining an experiment,” says Bernd Rosenow, a condensed-matter theorist at the University of Leipzig in Germany. But the evidence reported by Manfra’s team, if confirmed, is unequivocal, Rosenow says. “I’m not aware of an explanation of this experiment which is plausible and does not involve fractional statistics.”
The results potentially lay the groundwork for applications for anyons. Simon and others have developed elaborate theories that use anyons as the platform for quantum computers. Pairs of the quasiparticle could encode information in their memory of how they have circled around one another. And because the fractional statistics is ‘topological’—it depends on the number of times one anyon went around another, and not on slight changes to its path—it is unaffected by tiny perturbations. This robustness could make topological quantum computers easier to scale up than are current quantum-computing technologies, which are error-prone. Microsoft (which employs Manfra as a consultant) has been alone in pursuing the topology path for quantum computing, whereas other large companies, including IBM, Intel, Google and Honeywell, have invested in alternative approaches.
Topological quantum computing will require more-sophisticated anyons than those Manfra and colleagues have demonstrated; his team is now redesigning its device to do just that. Still, anyon applications are some way off, researchers warn. “Even with this new result, it is very hard to see [fractional quantum-Hall] anyons as a strong contender for quantum computing,” Simon says.
But the quasiparticles’ unique physics is worth exploring: “To me, as a condensed-matter theorist, they are at least as fascinating and exotic as the Higgs particle,” says Rosenow.
This article is reproduced with permission and was first published on July 3 2020.
“The citizens of Buffalo, N.Y., were treated to a remarkable mirage between 10 and 11 o’clock on the morning of August 16. It was the city of Toronto, with its harbor and small island to the south of the city. Toronto is ﬁfty-six miles from Buffalo, but the church spires could be counted with the greatest ease. This mirage is what is known as a mirage of the third order. That is, the object looms up far above the real level and not inverted, as is the case with mirages of the ﬁrst and second class, but appearing like a perfect landscape far away in the sky.”
—Scientific American, August 1894
More gems from Scientific American’s first 175 years can be found on our anniversary archive page.
Can philosophy give us Truth? Probably not, but I still enjoy it. At its best, philosophy knocks my perceptions off kilter and helps me see the world anew. Sometimes, it makes me smile. And that brings me to philosopher Eric Schwitzgebel. I first encountered his work in 2015, after I posted a critique of integrated information theory, a theory of consciousness with crazy implications. Someone pointed me toward a position that Schwitzgebel calls “crazyism,” which holds that a theory of consciousness is likely to sound, well, crazy. A year later, at an N.Y.U. conference on “The Ethics of AI,” I heard Schwitzgebel give a witty talk on whether artificial intelligences should be designed to be “cheerfully suicidal.” I have also enjoyed, and cited (here and here), Schwitzgebel’s investigations into whether moral philosophers are more moral than other folk. In short, I’m a Schwitzgebel fan. Looking for respite from the world’s troubles, I e-mailed him some questions.– John Horgan
Horgan: Why philosophy? Any regrets?
Schwitzgebel: No regrets yet!
Here’s why I love philosophy: For all X, you can do philosophy of X, just by diving down deep and long into the most fundamental questions about that topic. That’s what I enjoy, and I’ll do it for any topic that catches my attention—whether it’s the nature of jerkitude, garden snail cognition, robot rights or the moral behavior of ethics professors. What could be more fun?
Horgan: Why do you write fiction? Doesn’t that mean philosophy isn’t really that fulfilling for you?
Schwitzgebel: Wait, writing fiction can’t be a way of doing philosophy? Sartre, Rousseau, Zhuangzi, Voltaire, Nietzsche and Borges might disagree! Is anyone currently doing better work on the ethics of technology than the TV series Black Mirror?
For instance, weirdly implemented group minds feature both in my science fiction stories and in my expository philosophy. Under what conditions could there be real thought and consciousness at a group level? In an expository essay, I’ve argued that most philosophical theories of consciousness imply that the United States, as it currently exists, literally has a stream of conscious experience over and above the conscious experiences of its citizens and residents. (It has, for example, abundant complex information processing, self-monitoring, and strategic reactivity to its environment.) In a series of fictions, I’ve explored possibilities of group consciousness and cognition hypothetically, imagining cases of group cognition via hypnotic memory induction, via millions of monkeys trading gold foil, and via evolutionary processes among an infinitude of randomly constituted computers.
Think of it this way. A philosophical thought experiment is a mini-fiction. As a fiction, it engages the imagination and emotions better than purely abstract propositions do. It meets the human mind where it’s strongest. Should we act on a maxim that we can will to be a universal law? Should we try to maximize good consequences? Who knows? We can barely solve simple logic puzzles like the Wason Selection Task when they’re presented abstractly. We need to sink our teeth into specific examples. We need to imagine scenarios, work out cases, engage our social and emotional cognition. A fully developed fiction simply carries the thought experiment further, making it richer, more immersive, more engaging—and potentially more illuminating for those reasons.
Horgan: Is having a strong sense of humor, and irony, a liability for a truth-seeker?
Schwitzgebel: I’ve never really understood humor or irony. I simply say what’s on my mind in all sincerity and for some reason people think I’m joking. [See Postscript.]
Horgan: Nietzsche said all great philosophy consists of “involuntary and unconscious autobiography.” Was he right?
Schwitzgebel: The better the philosopher, the more so.
Horgan: Marianne Moore suggested that if you read poetry with “perfect contempt,” you might find something “genuine” in it. True of philosophy, too?
Schwitzgebel: Great philosophical work shines with something genuine—a personality, a worldview you’re invited to, a characteristic spirit and angle of approach. Immerse yourself in a great philosopher for a while and you learn to see the world through a different lens. By doing so, maybe you can, as Moore suggests, get a real toad from an imaginary garden. But I doubt contempt is a helpful first step.
Horgan: I’ve argued that philosophy’s chief value consists in “countering our terrible tendency toward certitude.” Comment?
Schwitzgebel: Ah, John, now I feel certain why you’ve chosen to interview me, among the many wonderful philosophers you might have selected! We have a similar perspective on this, and much of my work is directed toward exactly that end (sometimes covertly).
Here’s a way of expanding that thought. At its best, philosophy opens you to seeing things differently. It reveals possible ways the world could be, possible ways of living or valuing things or organizing society, even possible general structures of the cosmos, that might otherwise never have crossed your mind. To achieve this, it needn’t provide definitive answers. For me, the greatest philosophical rush comes from realizing that something I’d long taken for granted might not be true. The world opens up into new spaces of weirdness and complexity.
Horgan: Has moral philosophy gotten anywhere over the past 2,500 years?
Schwitzgebel: Aggressive warfare, slavery and bigotry are bad. It’s kind of amazing to me how few historical philosophers fully appreciated this. It seems so obvious now!
Some ethical disputes might forever elude resolution by the human mind, but that doesn’t mean we can’t make some progress.
Horgan: Why aren’t modern philosophers—especially Americans, who live in the most warlike nation on earth—more concerned with the moral problems posed by war?
Schwitzgebel: Academic philosophy, like most academic disciplines, favors the nerd. A nerd, as I’ve defined it, is someone who loves an intellectual topic, for its own sake, to an unreasonable degree. It’s hard to write a successful dissertation unless you’re the kind of weirdo (and I intend that word as a compliment) who for some inexplicable reason genuinely wants to spend a full three years puzzling out one tiny corner of, for example, what Kant says in part two of the Groundwork of the Metaphysics of Morals. When you think about it, that’s a really strange thing to want to do!
Consider a nerd who loves the original Star Trek series. You can tell her that there are more useful ways to spend her time than watching Shatner and Nimoy do their thing over and over. But this is not news. She knows that already. Consider a nerd who loves 19th-century trains. You can remind him that people suffer across the world while he studies the history and politics of the narrow gauge. All of that intellectual energy, you might urge him, could be going instead toward something useful, like advocating world peace. Yes, he is perfectly aware of that. But maybe he wouldn’t be so good at advocating world peace? And those old trains are so beautiful! Hopefully, he thinks, someone else can take care of the world peace thing….
Consider also the demand side. It’s not like Donald Trump and Vladimir Putin are begging academic philosophers to share their thoughts on the ethics of war.
This isn’t to excuse U.S. philosophers, exactly, for our relative neglect of the ethics of war. But in philosophy as in science there’s a kind of beautiful nerdiness in the passionate commitment to what captures your heart, regardless of its application.
Horgan: You’ve written a lot about jerks. Do you worry that you are one? If you worry you’re a jerk, does that mean you’re probably not one? And vice versa?
Schwitzgebel: I’ve defined a jerk as someone who culpably fails to appreciate the intellectual and emotional perspectives of the people around him. The picture-perfect jerk sees himself as surrounded by fools whose interests he can ignore and whose opinions don’t concern him—the pompous ass at the staff meeting who’s sure he’s right and doesn’t give a hoot about others’ projects, or the guy who cuts to the front of the line not for any good reason but just because he can get away with it and he sees the other shoppers as faceless nonentities.
I think we all have a bit of the jerk in us, sometimes. I include myself. My essays on the inner life of the jerk are based partly in my own experience of that inner life.
But here’s the twist: As soon as you genuinely worry that you might be acting like a jerk, you become less of one. Worrying about how you are treating others is exactly what the jerk doesn’t do. That sting of self-disapprobation when you confront your jerkitude is a moral treasure, because that very sting is what makes it less so.
Horgan: Owen Flanagan told me that philosophers are “more ill-formed than your average person.” Do you agree?
Schwitzgebel: I’d suggest this instead: Academic philosophers are no better formed—no wiser and no more ethically astute in their personal lives—than others of similar social background. On average, they’re about average.
Already, though, this should be disappointing. We philosophers read and think about ethics and the meaning of life. We study the great wisdom traditions of the world. Shouldn’t we be at least somewhat improved by that? Somewhat wiser? Somewhat more ethically insightful? I regard philosophers’ personal and ethical mediocrity as one of the greatest puzzles in all of moral philosophy and moral cognition.
Admittedly, most people don’t seem to be as puzzled by this as I am. There’s a kind of easy cynicism that is tempting here. However, I would recommend trying to resist that easy cynicism.
Horgan: Christof Koch has proposed building a device that can detect and measure consciousness in humans and other things. Do you think a “consciousness-meter” is possible? If not, isn’t it pointless to debate whether smart phones or snails are conscious?
Schwitzgebel: Philosophical, psychological and neuroscientific theories of consciousness span the entire range from panpsychism, according to which consciousness is ubiquitous in the universe, even in very simple systems, to highly restrictive theories on which consciousness requires such sophisticated cognition or such specific biological processes that it’s reasonable to doubt whether even apes and dogs have conscious experiences. Unless the range of defensible possibilities soon narrows radically, and I see no reason to think it will, any purported consciousness-meter will be regarded as a failure by the majority of well-informed researchers. It will be too theory-specific.
But it’s still worth thinking about the question of whether garden snails are conscious! Garden snails are fascinatingly bizarre. Their brains are mostly clumps of ganglia in a ring around their esophagus, and they’ve got these huge neurons that resemble our neurons in some ways and differ in other ways; and they have far more neurons in their tentacles than in their brains; and despite their limited central nervous system, they have these fascinatingly complicated mating dances. Nifty theories of consciousness come crashing down around your toes when you try to apply them in a principled way to the case of the garden snail.
Earlier, you suggested that philosophy’s chief value is countering our certitude. Of course we don’t need the right theory for that. What works better is showing how weird, wondrous, complicated and incomprehensible even ordinary things, like garden snails, can be. Maybe garden snails are conscious. Maybe they’re not. There’s a mystery of the universe, right there in your own garden, eating the daisies!
Horgan: I’ve argued that our inability to find a single, universal solution to the mind-body problem gives us more freedom to explore many possible ways of being human. Comment?
Schwitzgebel: There are so many ways the world could be, and there are so many ways we could fit into it. This is true not only of the mind-body problem but also of ethics and basic cosmology. We are like fleas on the back of a dog, watching a hair grow and saying, “Ah, so that’s the nature of the universe!”
We needn’t be disheartened by our failure to converge on final, correct answers to the biggest philosophical questions. Instead of being disheartened we can be awed and inspired by the mystery, and we can celebrate the diverse ways still open to us of viewing and confronting the world.
Horgan: Do you believe in God? Why/why not?
Schwitzgebel: My credence in the existence of a god or gods fluctuates from about 1 percent [to] 10 percent, depending on my mood and depending on what I’ve been reading and thinking about recently. I don’t think we know very well what the origins of the universe are or how we fit into it. Here’s one vision of a god: He’s a sadistic teenager running the universe as a giant computer simulation for his entertainment, and you’re just a little AI who exists primarily to provide an amusing reaction when he releases disasters. Or were you thinking of a more benevolent entity?
Horgan: What’s your utopia?
Schwitzgebel: Imagine a planet on the other side of the galaxy—one we will never see and never interact with. What might we hope for on that planet?
Would we hope that it’s a sterile rock? I wouldn’t. I’d hope for a planet with life. Moreover, I’d hope for interesting life—not just bacteria (although bacteria can be interesting in their way), but something richer and more complex than that. I’d hope for all kinds of animals and plants, in strange and wild forms, doing complex and intriguing things. I’d hope for intelligence, and social relationships, and art, and philosophy, and science, and sports competitions, and passionate lovers. I’d want heroes and tragedies, and great things, and terrible things—and manifold interests and conflicts and catastrophes and triumphs, diverse kinds at diverse scales, with a generally improving trajectory over time. That’s the world I’d hope for over there, even more so than I’d hope for a bland world of happy angels.
The tragedies and catastrophes are harder to hope for here, though. Wouldn’t I rather that we and our descendants have only the good with as little as possible of the bad, even if the result is bland?
I’m still trying to figure that one out. When I’m ready, if ever I’m ready, I’ll write it both as an essay and as a story.
Postscript: I asked Schwitzgebel if he was joking when he said, “I’ve never really understood humor or irony…,” and he replied with the “backstory” of his response: Eating lunch after one of my talks, a fellow philosopher expressed envy that I was able to put so much humor in my talks. I was surprised by this remark, since in fact I rarely put humor intentionally in my talks (though I do enjoy finding cute and clever ways of saying things sometimes), and I didn’t think that the talk I’d given had a single humorous part. However, on reflection, I did recall that the audience had sometimes chuckled. So I told him what I told you, that I just say what’s on my mind in complete sincerity and people think I’m joking. I said that completely sincerely. Predictably enough, he thought I was joking. So when you asked a similar question, I went to the same answer. On reflection, I think the answer is in fact, in this particular context, partly joking and partly ironic—though maybe less so than it seems.
Is Self-Knowledge Overrated?
What Is Philosophy’s Point?, Part 1 (Hint: It’s Not Discovering Truth)
See Q&As with Scott Aaronson, David Albert, David Chalmers, Noam Chomsky, Richard Dawkins, David Deutsch, George Ellis, Marcelo Gleiser, Robin Hanson, Nick Herbert, Jim Holt,
“A Cosmic Crisis,” by Richard Panek, discusses possible reasons why the two methods used to measure the universe’s rate of expansion find conflicting values—a discrepancy known as the Hubble tension. I am puzzled that the article does not mention forces from outside our universe acting on it. Can’t we expect that there are other universes with mass like ours that will have gravitational, and possibly other, effects on us? I don’t mean quantum parallel stuff but other big bang results beyond our own. We live in a galaxy that is part of a cluster of galaxies in a universe. Why not a cluster of universes? How do we know we are not in collision with one that is pulling our universe in ways that massively mess with our measurements?
The spines of a cactus, the proboscis of a mosquito, the quills of a porcupine: straight, pointed objects serve a plethora of functions in nature. Yet no matter the size, from bacteriophages’ nanometer-scale tail fibers to narwhals’ two- or three-meter-long tusk, these structures tend to be long and slender cones whose base diameter is much smaller than their length. Now researchers have used physics to explain why this narrow shape is optimal for stingers and other piercing objects—including human-made tools such as hypodermic needles.
A stingerlike object’s dimensions are limited by two opposing constraints. To puncture its target, it must apply a force large enough to overcome the pressure created by friction. At the same time, this force must be smaller than the “critical load,” the maximum force that the structure can support without bending or breaking. A large range of geometries, from long and narrow to short and wide, satisfy both constraints. Yet living organisms do not exhibit all the possible variability. Instead nature seems to prefer narrow designs with a base-diameter-to-length ratio of around 0.06.
Porcupine quills. Credit: Chris Ainslie Getty Images
That apparent predilection arises because another factor is at play: Nature tends to “live on the cheap,” says Kaare Jensen, a physicist at the Technical University of Denmark. Organisms are under evolutionary pressure to economize by using as little biological matter as possible to accomplish a given task. Wider stingers are more stable but require more material. This consideration suggests evolution would select for the narrowest designs possible: those that are barely sturdy enough to pierce their target without bending. In a paper published in June in Nature Physics, Jensen’s team showed that this design principle accurately predicts the shapes of stingers and similar structures.
Jensen and his graduate student Anneline Christensen devised a simple theoretical model for a solid conical stinger at the edge of stability. Their calculations predicted that the optimal base diameter depended on only three factors: the object’s length, the stiffness of its material and the friction from the pressure of the target tissue. The dependence on stiffness and pressure was weak: doubling the stiffness would allow the base diameter to decrease by only 21 percent, for instance. It was primarily the relationship between diameter and length that intrigued the duo.
In a major study of similar structures in the early 1980s, researchers using a different friction model proposed that the base diameter of the cone scales with its length to the power of ⅔ : thus, if the length doubled, the base diameter would need to increase by 59 percent. Jensen and Christensen’s equation, in contrast, predicted that the two should be directly proportional. In that case, doubling one would require doubling the other as well.
A narwhal tusk. Credit: Getty Images
To see if a linear relationship held in the natural world, Jensen’s team compiled the dimensions of nearly 140 stingers, spikes and spines in living organisms. Vertebrates and invertebrates, land and sea creatures, and plants, algae and viruses all had structures that matched the new model. Almost 100 human-made “stingers” such as needles, nails and arrows also aligned with the researchers’ predictions. “It’s always nice when you do some kind of theoretical work, and then you see it applies to something in real life,” Christensen says. “It’s not just an equation on a piece of paper.”
The team did “a really nice job of tackling a pretty common design problem from a really simple mechanics perspective,” says Douglas Holmes, an engineer at Boston University, who peer-reviewed the study but was not directly involved in the research. “It was a really creative approach to the problem.” Holmes, who investigates the stability of thin structures, notes that the result has applications beyond nature. Understanding the physics of this kind of object “gives you a nice design principle for designing anything sharp,” including hypodermic needles, he says. In fact, Jensen is already using what he learned to develop more break-resistant needles for unrelated research on plant cells.
Although Jensen and Christensen’s equation describes the shape of a multitude of stingerlike structures, others have complexities not considered in the model. Some plant “stingers” are hollow or contain liquids, and some wasps intentionally bend their stinger during insertion. In both cases, the equation overestimates the base diameter. Jensen hopes to build on his research to understand the physics governing curved teeth, claws and other sharp objects in the natural world. This work could, in turn, inspire a new wave of engineering innovations, he says: “There’s quite substantial potential for learning from nature on how to design these things.”
A new color-changing ink could aid in health and environment monitoring—for example, allowing clothing that switches hues when exposed to sweat or a tapestry that shifts colors if carbon monoxide enters a room. The formulation could be printed on anything from a T-shirt to a tent.
Wearable sensing devices such as smartwatches and patches use electronics to monitor heart rate, blood glucose, and more. Now researchers at Tufts University’s Silklab say their new silk-based inks can respond to, and quantify, the presence of chemicals on or around the body. Silk’s ability to “act like a protective ‘cocoon’ for biological materials” means the necessary sensing and color-changing materials can be added to the ink without losing their function, says Fiorenzo Omenetto, a biomedical engineer at Silklab and senior author of a new paper on the technology.
Illustration of how pH-sensitive ink changes based on exposure. Credit: Silk Lab, Tufts University
The researchers had created an earlier version of the material that inkjet printers could spray on fabric, turning small items, such as patches or gloves, into sensors. For the recent study, published online in May in Advanced Materials, they thickened the ink with the chemical sodium alginate to make it work in screen printing and then added various reactive substances. With the new ink, they can now “easily print a large number of reactive elements onto large surfaces,” Omenetto says.
The team made silk ink by breaking down raw fibers into constituent proteins, which the researchers suspended in water. Next they mixed in reactive molecules (such as pH-sensitive indicators and lactate oxidase) and analyzed how the resulting products changed color when exposed to alterations in their environment. When printed on fabric and worn, pH indicators could lend insight into skin health or dehydration; lactate oxidase could measure a wearer’s fatigue levels. The changes are visible to the naked eye, but the researchers also used a camera-imaging analysis to continuously monitor the color variations and create a database of values.
“In the case of a T-shirt, the wearer ‘paints’ the shirt [through] exercise—with colors correlating to the acidity distribution of their sweat,” Omenetto says. He envisions using the ink to help monitor such activity. It could also be adapted to track environmental changes in a room, he says—or to respond to bacteria and follow disease progression.
Mechanical engineer Tyler Ray of the University of Hawaii at Manoa, who was not involved with the study, notes that most of today’s wearable monitors are rigid, wired and relatively bulky. The new ink technology has “the potential to transform consumer wearables from recreational novelty devices into body-worn, clinical-grade physiological measurement tools that yield physician-actionable information,” he says. But “one of the challenges with any colorimetric approach is the effect various environmental conditions have on accuracy, such as lighting … or the camera used.” Future studies would need to address these issues.
In a world’s first, researchers in France and the U.S. have performed a pioneering experiment demonstrating “hybrid” quantum networking. The approach, which unites two distinct methods of encoding information in particles of light called photons, could eventually allow for more capable and robust communications and computing.
Similar to how classical electronics can represent information as digital or analog signals, quantum systems can encode information as either discrete variables (DVs) in particles or continuous variables (CVs) in waves. Researchers have historically used one approach or the other—but not both—in any given system.
“DV and CV encoding have distinct advantages and drawbacks,” says Hugues de Riedmatten of the Institute of Photonic Sciences in Barcelona, who was not a part of the research. CV systems encode information in the varying intensity, or phasing, of light waves. They tend to be more efficient than DV approaches but are also more delicate, exhibiting stronger sensitivity to signal losses. Systems using DVs, which transmit information by the counting of photons, are harder to pair with conventional information technologies than CV techniques. They are also less error-prone and more fault-tolerant, however. Combining the two, de Riedmatten says, could offer “the best of both worlds.”
In quantum networks, information is created, stored and transferred based on the tenets of quantum mechanics. Doing so theoretically allows for levels of security and computational power that surpass anything possible with classical systems.
For instance, classical bits encode information in values of either 0 or 1. Quantum networks can instead use quantum bits, or qubits, which exploit quantum effects to embody 0 and 1 at the same time. To distribute data, such networks also often rely on another effect called quantum entanglement. Famously described by Albert Einstein as “spooky action at a distance,” entanglement is generated between particles, such as photons, after they interact closely. Einstein and others considered it “spooky” because, against all intuition, even after being separated over arbitrarily long distances, entangled particles continue to influence each other’s behavior. Any change in the state of one of the particles triggers a simultaneous change in the state of the other. Computer scientists long ago realized this effect could enable ultrasecure telecommunications, in which any attempt at eavesdropping would disrupt the entanglement, making the surveillance transparently obvious.
Systems leveraging these quantum effects can take many forms, but they generally follow either a DV or CV architecture. Now scientists at the Kastler Brossel Laboratory in Paris and the U.S. National Institute of Standards and Technology have successfully united both techniques by establishing and distributing entanglement between DV- and CV-encoded states of light within a single quantum network.
Using a complicated assembly of optical components, the team successfully produced photons in two highly entangled states. One of them arose from splitting a single photon between two different paths. The other—a so-called hybrid-entangled state—emerged from entangling a DV optical qubit with a CV qubit, which was held in a superposition of two different phases of light. “By using a special procedure called Bell-state measurement between these two separately entangled states, the entanglement was transferred or ‘teleported’ to the two systems, [which] never interacted with each other,” says Julien Laurat, a professor at Sorbonne University in Paris and senior author of the study. This transference allowed the conversion of the qubits’ quantum information from one encoding method to the other, paving the way for incorporating both DV and CV approaches into a single, scalable quantum network.
From Workbench to Workhorse
For Marco Bellini of the National Institute of Optics in Italy, who was not part of the study, what makes it novel and significant is that the researchers successfully swapped entanglement between two light beams carrying two distinct varieties of encoded quantum information. Linking disparate systems together remains a major challenge. But “this experiment has demonstrated what could become an important ingredient of future networks versatile enough to connect memories and processors based on different physical quantum platforms—and faithfully carry a broad range of quantum states, including the DV and CV ones,” he says.
Much more work remains to be done before a practical hybrid quantum network is achieved, however, Bellini adds. The current experimental method is extremely inefficient: on average, it generates hybrid entanglement just three times per minute across a distance between a CV qubit and a DV one. “While this rate is still sufficient to accumulate enough data for a proof-of-principle demonstration, it is orders of magnitude too low for any practical application,” Bellini concludes.
Further breakthroughs may be imminent. Around the world, other groups are racing to develop and demonstrate additional new quantum-networking protocols—and to close the gap between such preliminary laboratory demonstrations and practical real-world devices.
One such team, led by Bellini, is also working on using the hybrid technique to manipulate entanglement by adding and subtracting single photons to and from classical light fields. Groups in Japan, Russia, Denmark and the Czech Republic are also researching the optical hybrid approach for quantum information. Sooner or later, such hybrid-entanglement experiments should become more compact and efficient, breaking free of the workbench to become workhorses that are compatible with telecoms’ existing fiber-optic networks.
Recently, NASA has been working to erase all hints of gender bias lingering from previous generations. The agency even converted the phrase “manned mission” to “crewed mission,” and stood by the change for the recent SpaceX launch, despite the fact that both members of the crew possessed their very own Y chromosomes. Casual English speech is riddled with gender-specific terms like “manned” that we now use without deliberate bias or sexism but that sometimes carry inadvertent shadows of past decades’ antiquated stereotypes. Many of them leave me scratching my head to figure out why we need to mention gender at all.
Unsurprisingly, the swap to the neutral “crewed” caused some petulant foot-stamping in internet comments sections, because traditional male-specific phrases seem to stick most insistently in fields that are still perceived as male-dominated. Nobody ever protests that an elementary school should be described as “manned” instead of “staffed,” but dare to suggest a “men at work” sign could just as easily read “workers present” and you might spark a kerfuffle. However, the growing number of women who fill these allegedly macho jobs are starting to speak up, and to push for gender neutrality in language. It’s possible the phrase “giant leap for mankind” would now reference “humanity” instead, because of socially aware modern-day NASA professionals.
But in many cases women are still subtly identified as outsiders. For fields stereotyped as male, like science, medicine or firefighting, we often create special two-noun phrases to describe the women storming the ivory towers of manliness: woman scientist, woman doctor, woman firefighter. To begin with, these peculiar two-noun phrases are grammatically incorrect. The right way to modify the nouns scientist, doctor and firefighter is with an adjective, for example the word “female,” as in female doctor. Unless, of course, we mean that a “woman scientist” is somehow an entirely different creature than a normal scientist. Some protest that the word “female” sounds clinical, but notably the grammatical mistake never occurs in reverse, even for men in traditionally female roles; we always manage correctly to apply the adjective “male,” as in “a male nurse” rather than “a man nurse.”
A search of the online database Newspapers.com shows that prior to the turn of the century the phrase “woman scientist” was used a sparse 40 times in total, peppered throughout multiple decades. The highest concentration was a light smattering of articles about one Jennie A. Estes, who showed up and existed at a scientific meeting in 1897.
But then, enter Marie Curie. The trailblazing genius and her husband were awarded the Nobel Prize, the first time the award had ever been given to a woman, and by 1906, when she became a professor with a lab, she could no longer be ignored. Immediately, the term “woman scientist” exploded into the media, going from a bare trickle of women discussed as curiosities to a sudden flood of articles, with nearly a thousand uses over the next decade.
Some of the articles were supportive, describing Curie as an exotic but admirable specimen. The majority of journalists, however, wondered if woman scientists could possibly have “any manners” at all; attributed their work to male partners; or quipped that women in science were “as rare as the dodo,” which as you’ll recall is a bird famous for its extinction. Many articles had cautionary titles seemingly designed to scare off women inspired by Curie, such as “Intellectual Powers Could Not Compensate for Loss of Suitor.” To me, the subtext seems clear: “woman scientists” are less than, as both women and as scientists.
After this, such phrases began to bloom in other conventionally masculine fields, with newspaper stories about the fashion choices of “woman pilots” who dared to wear pants, and “woman firefighters” who somehow would be physically capable of operating engines. The increasing genesis of two-noun woman phrases correlated with a growing presence in the papers of another gender-shaking, world-altering word: suffrage. After women were granted the right to vote in 1920, the woman phrases dipped in popularity before a resurgence with post–World War II feminism.
The field of aviation is unique in that the women themselves have embraced their two-noun term—to a degree. Pilot and historian Katherine Sharp Landdeck, author of The Women with Silver Wings, a book about the Women Airforce Service Pilots (WASPs) of WWII, says she belongs to the group Women Military Aviators and used to read Woman Pilot magazine. She doesn’t think the trend traces directly to the legendary WASPs, though, who were named in part because co-founder Jackie Cochran wanted to be clear the women were not trying to replace the “normal” pilots. Rather, Landdeck thinks the term “woman pilot” originated outside the influence of the early female aviators themselves, and is reflective of the more general linguistic trend of outside observers applying two-noun phrases to trailblazing women. However, she does note that many women in aviation are willing to use the phrase as part of an ongoing effort to encourage more equality in a world where a mere 7 percent of participants are female.
And Landdeck has a point. As she says, “if you can’t see it, you can’t be it.” She’s never heard a woman introduce herself as “a woman pilot,” just as I’ve never heard a scientific colleague introduce herself as “a woman scientist,” but our very existence makes us stand out nonetheless. I’ve been called two-noun woman phrases too, by people pointing out my rarity, as my doctorate in blast trauma often renders me a gender oddity in my profession as well as a social oddity at cocktail parties. Recently the phrase “woman scientist” even eked itself without my permission into library catalog descriptions of my book In the Waves, which is about blast science and the Civil War submarine H. L. Hunley, and which contains not one discussion of gender.
In fields where women remain the few, the odd ducks, the anomalous outliers who constantly have to justify to others our passions for our “manly” fields, I will admit there is sometimes value in pointing out our existence to younger generations when it is relevant to do so. Perhaps it will help one or two young women feel more normal about their inherent love of math or airplanes. But maybe, as society slowly edges toward equality, we can at least start to be more equal in our language too, like NASA, and dispose of the grammatically incorrect two-noun woman phrases. Grammarian Mignon Fogarty recommends a simple test: ask yourself if you would phrase the sentence the same way if your subject were a man. If you would use “male” instead of “man,” then use “female” instead of “woman.” If you would omit his gender altogether, then consider whether mentioning her gender is necessary. It certainly wouldn’t be a giant leap for mankind, but it might be a tiny nudge for humanity.