About Nicole Yunger Halpern

I’m a theoretical physicist at the Joint Center for Quantum Information and Computer Science in Maryland. My research group re-envisions 19th-century thermodynamics for the 21st century, using the mathematical toolkit of quantum information theory. We then apply quantum thermodynamics as a lens through which to view the rest of science. I call this research “quantum steampunk,” after the steampunk genre of art and literature that juxtaposes Victorian settings (à la thermodynamics) with futuristic technologies (à la quantum information). For more information, check out my upcoming book Quantum Steampunk: The Physics of Yesterday’s Tomorrow. I earned my PhD at Caltech under John Preskill’s auspices; one of my life goals is to be the subject of one of his famous (if not Pullitzer-worthy) poems. Follow me on Twitter @nicoleyh11.

How Captain Okoli got his name

About two years ago, I dreamt up a character called Captain Okoli. He features in the imaginary steampunk novel from which I drew snippets to begin the chapters of my otherwise nonfiction book. Captain Okoli is innovative, daring, and kind; he helps the imaginary novel’s heroine, Audrey, on her globe-spanning quest. 

Captain Okoli inherited his name from Chiamaka Okoli, who was a classmate and roommate of mine while we pursued our master’s degrees at the Perimeter Institute for Theoretical Physics. Unfortunately, an illness took Chiamaka’s life shortly after she completed her PhD. Captain Okoli is my tribute to her memory, but my book lacked the space for an explanation of who Chiamaka was or how Captain Okoli got his name. The Perimeter Institute offered a platform in its publication Inside the Perimeter. You can find the article—a story about an innovative, daring, and kind woman—here.

These are a few of my favorite steampunk books

As a physicist, one grows used to answering audience questions at the end of a talk one presents. As a quantum physicist, one grows used to answering questions about futuristic technologies. As a quantum-steampunk physicist, one grows used to the question “Which are your favorite steampunk books?”

Literary Hub has now published my answer.

According to its website, “Literary Hub is an organizing principle in the service of literary culture, a single, trusted, daily source for all the news, ideas and richness of contemporary literary life. There is more great literary content online than ever before, but it is scattered, easily lost—with the help of its editorial partners, Lit Hub is a site readers can rely on for smart, engaged, entertaining writing about all things books.”

My article, “Five best books about the romance of Victorian science,” appeared there last week. You’ll find fiction, nonfiction as imaginative as fiction, and crossings of the border between the two. 

My contribution to literature about the romance of Victorian science—my (mostly) nonfiction book, Quantum Steampunk: The Physics Of Yesterday’s Tomorrow—was  published two weeks ago. Where’s a hot-air-balloon emoji when you need one?

One equation to rule them all?

In lieu of composing a blog post this month, I’m publishing an article in Quanta Magazine. The article provides an introduction to fluctuation relations, souped-up variations on the second law of thermodynamics, which helps us understand why time flows in only one direction. The earliest fluctuation relations described classical systems, such as single strands of DNA. Many quantum versions have been proved since. Their proliferation contrasts with the stereotype of physicists as obsessed with unification—with slimming down a cadre of equations into one über-equation. Will one quantum fluctuation relation emerge to rule them all? Maybe, and maybe not. Maybe the multiplicity of quantum fluctuation relations reflects the richness of quantum thermodynamics.

You can read more in Quanta Magazine here and yet more in chapter 9 of my book. For recent advances in fluctuation relations, as opposed to the broad introduction there, check out earlier Quantum Frontiers posts here, here, here, here, and here.

The power of being able to say “I can explain that”

Caltech condensed-matter theorist Gil Refael explained his scientific raison dê’tre early in my grad-school career: “What really gets me going is seeing a plot [of experimental data] and being able to say, ‘I can explain that.’” The quote has stuck with me almost word for word. When I heard it, I was working deep in abstract quantum information theory and thermodynamics, proving theorems about thought experiments. Embedding myself in pure ideas has always held an aura of romance for me, so I nodded along without seconding Gil’s view.

Roughly nine years later, I concede his point.

The revelation walloped me last month, as I was polishing a paper with experimental collaborators. Members of the Institute for Quantum Optics and Quantum Information (IQOQI) in Innsbruck, Austria—Florian Kranzl, Manoj Joshi, and Christian Roos—had performed an experiment in trapped-ion guru Rainer Blatt’s lab. Their work realized an experimental proposal that I’d designed with fellow theorists near the beginning of my postdoc stint. We aimed to observe signatures of particularly quantum thermalization

Throughout the universe, small systems exchange stuff with their environments. For instance, the Earth exchanges heat and light with the rest of the solar system. After exchanging stuff for long enough, the small system equilibrates with the environment: Large-scale properties of the small system (such as its volume and energy) remain fairly constant; and as much stuff enters the small system as leaves, on average. The Earth remains far from equilibrium, which is why we aren’t dead yet

Far from equilibrium and proud of it

In many cases, in equilibrium, the small system shares properties of the environment, such as the environment’s temperature. In these cases, we say that the small system has thermalized and, if it’s quantum, has reached a thermal state.

The stuff exchanged can consist of energy, particles, electric charge, and more. Unlike classical planets, quantum systems can exchange things that participate in quantum uncertainty relations (experts: that fail to commute). Quantum uncertainty mucks up derivations of the thermal state’s mathematical form. Some of us quantum thermodynamicists discovered the mucking up—and identified exchanges of quantum-uncertain things as particularly nonclassical thermodynamics—only a few years ago. We reworked conventional thermodynamic arguments to accommodate this quantum uncertainty. The small system, we concluded, likely equilibrates to near a thermal state whose mathematical form depends on the quantum-uncertain stuff—what we termed a non-Abelian thermal state. I wanted to see this equilibration in the lab. So I proposed an experiment with theory collaborators; and Manoj, Florian, and Christian took a risk on us.

The experimentalists arrayed between six and fifteen ions in a line. Two ions formed the small system, and the rest formed the quantum environment. The ions exchanged the x-, y-, and z-components of their spin angular momentum—stuff that participates in quantum uncertainty relations. The ions began with a fairly well-defined amount of each spin component, as described in another blog post. The ions exchanged stuff for a while, and then the experimentalists measured the small system’s quantum state.

The small system equilibrated to near the non-Abelian thermal state, we found. No conventional thermal state modeled the results as accurately. Score!

My postdoc and numerical-simulation wizard Aleks Lasek modeled the experiment on his computer. The small system, he found, remained farther from the non-Abelian thermal state in his simulation than in the experiment. Aleks plotted the small system’s distance to the non-Abelian thermal state against the ion chain’s length. The points produced experimentally sat lower down than the points produced numerically. Why?

I think I can explain that, I said. The two ions exchange stuff with the rest of the ions, which serve as a quantum environment. But the two ions exchange stuff also with the wider world, such as stray electromagnetic fields. The latter exchanges may push the small system farther toward equilibrium than the extra ions alone do.

Fortunately for the development of my explanatory skills, collaborators prodded me to hone my argument. The wider world, they pointed out, effectively has a very high temperature—an infinite temperature.1 Equilibrating with that environment, the two ions would acquire an infinite temperature themselves. The two ions would approach an infinite-temperature thermal state, which differs from the non-Abelian thermal state we aimed to observe.

Fair, I said. But the extra ions probably have a fairly high temperature themselves. So the non-Abelian thermal state is probably close to the infinite-temperature thermal state. Analogously, if someone cooks goulash similarly to his father, and the father cooks goulash similarly to his grandfather, then the youngest chef cooks goulash similarly to his grandfather. If the wider world pushes the two ions to equilibrate to infinite temperature, then, because the infinite-temperature state lies near the non-Abelian thermal state, the wider world pushes the two ions to equilibrate to near the non-Abelian thermal state.

Tasty, tasty thermodynamicis

I plugged numbers into a few equations to check that the extra ions do have a high temperature. (Perhaps I should have done so before proposing the argument above, but my collaborators were kind enough not to call me out.) 

Aleks hammered the nail into the problem’s coffin by incorporating into his simulations the two ions’ interaction with an infinite-temperature wider world. His numerical data points dropped to near the experimental data points. The new plot supported my story.

I can explain that! Aleks’s results buoyed me the whole next day; I found myself smiling at random times throughout the afternoon. Not that I’d explained a grand mystery, like the unexpected hiss heard by Arno Penzias and Robert Wilson when they turned on a powerful antenna in 1964. The hiss turned out to come from the cosmic microwave background (CMB), a collection of photons that fill the visible universe. The CMB provided evidence for the then-controversial Big Bang theory of the universe’s origin. Discovering the CMB earned Penzias and Wilson a Nobel Prize. If the noise caused by the CMB was music to cosmologists’ ears, the noise in our experiment is the quiet wailing of a shy banshee. But it’s our experiment’s noise, and we understand it now.

The experience hasn’t weaned me off the romance of proving theorems about thought experiments. Theorems about thermodynamic quantum uncertainty inspired the experiment that yielded the plot that confused us. But I now second Gil’s sentiment. In the throes of an experiment, “I can explain that” can feel like a battle cry.

1Experts: The wider world effectively has an infinite temperature because (i) the dominant decoherence is dephasing relative to the \sigma_z product eigenbasis and (ii) the experimentalists rotate their qubits often, to simulate a rotationally invariant Hamiltonian evolution. So the qubits effectively undergo dephasing relative to the \sigma_x, \sigma_y, and \sigma_z eigenbases.

Space-time and the city

I felt like a gum ball trying to squeeze my way out of a gum-ball machine. 

I was one of 50-ish physicists crammed into the lobby—and in the doorway, down the stairs, and onto the sidewalk—of a Manhattan hotel last December. Everyone had received a COVID vaccine, and the omicron variant hadn’t yet begun chewing up North America. Everyone had arrived on the same bus that evening, feeding on the neon-bright views of Fifth Avenue through dinnertime. Everyone wanted to check in and offload suitcases before experiencing firsthand the reason for the nickname “the city that never sleeps.” So everyone was jumbled together in what passed for a line.

We’d just passed the halfway point of the week during which I was pretending to be a string theorist. I do that whenever my research butts up against black holes, chaos, quantum gravity (the attempt to unify quantum physics with Einstein’s general theory of relativity), and alternative space-times. These topics fall under the heading “It from Qubit,” which calls for understanding puzzling physics (“It”) by analyzing how quantum systems process information (“Qubit”). The “It from Qubit” crowd convenes for one week each December, to share progress and collaborate.1 The group spends Monday through Wednesday at Princeton’s Institute for Advanced Study (IAS), dogged by photographs of Einstein, busts of Einstein, and roads named after Einstein. A bus ride later, the group spends Thursday and Friday at the Simons Foundation in New York City.

I don’t usually attend “It from Qubit” gatherings, as I’m actually a quantum information theorist and quantum thermodynamicist. Having admitted as much during the talk I presented at the IAS, I failed at pretending to be a string theorist. Happily, I adore being the most ignorant person in a roomful of experts, as the experience teaches me oodles. At lunch and dinner, I’d plunk down next to people I hadn’t spoken to and ask what they see as trending in the “It from Qubit” community. 

One buzzword, I’d first picked up on shortly before the pandemic had begun (replicas). Having lived a frenetic life, that trend seemed to be declining. Rising buzzwords (factorization and islands), I hadn’t heard in black-hole contexts before. People were still tossing around terms from when I’d first forayed into “It from Qubit” (scrambling and out-of-time-ordered correlator), but differently from then. Five years ago, the terms identified the latest craze. Now, they sounded entrenched, as though everyone expected everyone else to know and accept their significance.

One buzzword labeled my excuse for joining the workshops: complexity. Complexity wears as many meanings as the stereotypical New Yorker wears items of black clothing. Last month, guest blogger Logan Hillberry wrote about complexity that emerges in networks such as brains and social media. To “It from Qubit,” complexity quantifies the difficulty of preparing a quantum system in a desired state. Physicists have conjectured that a certain quantum state’s complexity parallels properties of gravitational systems, such as the length of a wormhole that connects two black holes. The wormhole’s length grows steadily for a time exponentially large in the gravitational system’s size. So, to support the conjecture, researchers have been trying to prove that complexity typically grows similarly. Collaborators and I proved that it does, as I explained in my talk and as I’ll explain in a future blog post. Other speakers discussed experimental complexities, as well as the relationship between complexity and a simplified version of Einstein’s equations for general relativity.

Inside the Simons Foundation on Fifth Avenue in Manhattan

I learned a bushel of physics, moonlighting as a string theorist that week. The gum-ball-machine lobby, though, retaught me something I’d learned long before the pandemic. Around the time I squeezed inside the hotel, a postdoc struck up a conversation with the others of us who were clogging the doorway. We had a decent fraction of an hour to fill; so we chatted about quantum thermodynamics, grant applications, and black holes. I asked what the postdoc was working on, he explained a property of black holes, and it reminded me of a property of thermodynamics. I’d nearly reached the front desk when I realized that, out of the sheer pleasure of jawing about physics with physicists in person, I no longer wanted to reach the front desk. The moment dangles in my memory like a crystal ornament from the lobby’s tree—pendant from the pandemic, a few inches from the vaccines suspended on one side and from omicron on the other. For that moment, in a lobby buoyed by holiday lights, wrapped in enough warmth that I’d forgotten the December chill outside, I belonged to the “It from Qubit” community as I hadn’t belonged to any community in 22 months.

Happy new year.

Presenting at the IAS was a blast. Photo credit: Jonathan Oppenheim.

1In person or virtually, pandemic-dependently.

Thanks to the organizers of the IAS workshop—Ahmed Almheiri, Adam Bouland, Brian Swingle—for the invitation to present and to the organizers of the Simons Foundation workshop—Patrick Hayden and Matt Headrick—for the invitation to attend.

A quantum-steampunk photo shoot

Shortly after becoming a Fellow of QuICS, the Joint Center for Quantum Information and Computer Science, I received an email from a university communications office. The office wanted to take professional photos of my students and postdocs and me. You’ve probably seen similar photos, in which theoretical physicists are writing equations, pointing at whiteboards, and thinking deep thoughts. No surprise there. 

A big surprise followed: Tom Ventsias, the director of communications at the University of Maryland Institute for Advanced Computer Studies (UMIACS), added, “I wanted to hear your thoughts about possibly doing a dual photo shoot for you—one more ‘traditional,’ one ‘quantum steampunk’ style.”

Steampunk, as Quantum Frontiers regulars know, is a genre of science fiction. It combines futuristic technologies, such as time machines and automata, with Victorian settings. I call my research “quantum steampunk,” as it combines the cutting-edge technology of quantum information science with the thermodynamics—the science of energy—developed during the 1800s. I’ve written a thesis called “Quantum steampunk”; authored a trade nonfiction book with the same title; and presented enough talks about quantum steampunk that, strung together, they’d give one laryngitis. But I don’t own goggles, hoop skirts, or petticoats. The most steampunk garb I’d ever donned before this autumn, I wore for a few minutes at age six or so, for dress-up photos at a theme park. I don’t even like costumes.

But I earned my PhD under the auspices of fellow Quantum Frontiers blogger John Preskill,1 whose career suggests a principle to live by: While unravelling the universe’s nature and helping to shape humanity’s intellectual future, you mustn’t take yourself too seriously. This blog has exhibited a photo of John sitting in Caltech’s information-sciences building, exuding all the gravitas of a Princeton degree, a Harvard degree, and world-impacting career—sporting a baseball glove you’d find in a high-school gym class, as though it were a Tag Heuer watch. John adores baseball, and the photographer who documented Caltech’s Institute for Quantum Information and Matter brought out the touch of whimsy like the ghost of a smile.

Let’s try it, I told Tom.

One rust-colored November afternoon, I climbed to the top of UMIACS headquarters—the Iribe Center—whose panoramic view of campus begs for photographs. Two students were talking in front of a whiteboard, and others were lunching on the sandwiches, fruit salad, and cheesecake ordered by Tom’s team. We took turns brandishing markers, gesturing meaningfully, and looking contemplative.

Then, the rest of my team dispersed, and the clock rewound 150 years.

The professionalism and creativity of Tom’s team impressed me. First, they’d purchased a steampunk hat, complete with goggles and silver wires. Recalling the baseball-glove photo, I suggested that I wear the hat while sitting at a table, writing calculations as I ordinarily would.

What hat? Quit bothering me while I’m working.

Then, the team upped the stakes. Earlier that week, Maria Herd, a member of the communications office, had driven me to the University of Maryland performing-arts center. We’d sifted through the costume repository until finding skirts, vests, and a poofy white shirt reminiscent of the 1800s. I swapped clothes near the photo-shoot area, while the communications team beamed a London street in from the past. Not really, but they nearly did: They’d found a backdrop suitable for the 2020 Victorian-era Netflix hit Enola Holmes and projected the backdrop onto a screen. I stood in front of the screen, and a sheet of glass stood in front of me. I wrote equations on the glass while the photographer, John Consoli, snapped away.

The final setup, I would never have dreamed of. Days earlier, the communications team had located an elevator lined, inside, with metal links. They’d brought colorful, neon-lit rods into the elevator and experimented with creating futuristic backdrops. On photo-shoot day, they positioned me in the back of the elevator and held the light-saber-like rods up. 

But we couldn’t stop anyone from calling the elevator. We’d ride up to the third or fourth floor, and the door would open. A student would begin to step in; halt; and stare my floor-length skirt, the neon lights, and the photographer’s back.

“Feel free to get in.” John’s assistant, Gail Marie Rupert, would wave them inside. The student would shuffle inside—in most cases—and the door would close.

“What floor?” John would ask.


John would twist around, press the appropriate button, and then turn back to his camera.

Once, when the door opened, the woman who entered complimented me on my outfit. Another time, the student asked if he was really in the Iribe Center. I regard that question as evidence of success.

John Consoli took 654 photos. I found the process fascinating, as a physicist. I have a domain of expertise; and I know the feeling of searching for—working toward—pushing for—a theorem or a conceptual understanding that satisfies me, in that domain. John’s area of expertise differs from mine, so I couldn’t say what he was searching for. But I recognized his intent and concentration, as Gail warned him that time had run out and he then made an irritated noise, inched sideways, and stole a few more snapshots. I felt like I was seeing myself in a reflection—not in the glass I was writing on, but in another sphere of the creative life.

The communications team’s eagerness to engage in quantum steampunk—to experiment with it, to introduce it into photography, to make it their own—bowled me over. Quantum steampunk isn’t just a stack of papers by one research group; it’s a movement. Seeing a team invest its time, energy, and imagination in that movement felt like receiving a deep bow or curtsy. Thanks to the UMIACS communications office for bringing quantum steampunk to life.

The Quantum-Steampunk Lab. Not pictured: Shayan Majidy.

1Who hasn’t blogged in a while. How about it, John?

I wish you a Charles River

Three-and-a-quarter years ago, I was on a subway train juddering along the tracks. I gripped my suitcase tightly and—knowing myself—likely gripped a physics paper, too, so that I could read during the trip. I was moving, for my postdoctoral fellowship, to Cambridge from Pasadena, where I’d completed my PhD.

The Charles River separates Cambridge from Boston, at whose Logan Airport I’d arrived with a suitcase just under the societal size limit and ideas that I hoped weren’t. But as the metro car juddered onto the Longfellow Bridge, all physics papers vanished from my mind. So did concerns about how I’d find my new apartment, how much I had to accomplish before night fell (buy breakfast ingredients, retrieve boxes I’d shipped, unpack, …), and how strongly I smelled like airplane fuel.

The Charles stretched below us, sparkling with silver threads embroidered in blue, a carpet too grand for a king. On the river bobbed boats that resembled toys, their sails smaller than my paper. Boston’s skyline framed the river’s right-hand side, and Cambridge’s skyline framed the left. And what skylines they were—filled with glass and red brick; with rectangles, trapezoids, hemispheres, and turrets. I felt blessed for such a welcome to a new Cantab.

I vowed that afternoon that, every time I crossed the Charles via metro in the next three years, I’d stop reading my paper, or drafting my email, or planning my next talk. I’d look up through a window, recall the river’s beauty, and feel grateful—grateful for the privilege of living nearby and in an intellectual hub that echoes across centuries; for the freedom to pursue the ideas I dream up; and for the ability to perceive the beauty before me.

Humans have a knack for accustoming themselves to gifts. One day, we’re reveling over an acceptance letter or the latest Apple product; a year later, we’re chasing the next acceptance or cursing technology’s slowness. But an “attitude of gratitude,” as my high-school physics teacher put it, enhances our relationships, our health, and our satisfaction with life. I’m grateful for the nudge that, whenever I traveled to or from home throughout the past three years, reminded me to feel grateful.

I wish you a Charles River, this season and every season.

Quantum estuary

Tourism websites proclaim, “There’s beautiful…and then there’s Santa Barbara.” I can’t accuse them of hyperbole, after living in Santa Barbara for several months. Santa Barbara’s beauty manifests in its whitewashed buildings, capped with red tiles; in the glint of sunlight on ocean wave; and in the pockets of tranquility enfolded in meadows and copses. An example lies about an hour’s walk from the Kavli Institute for Theoretical Physics (KITP), where I spent the late summer and early fall: an estuary. According to National Geographic, “[a]n estuary is an area where a freshwater river or stream meets the ocean.” The meeting of freshwater and saltwater echoed the meeting of disciplines at the KITP.

The KITP fosters science as a nature reserve fosters an ecosystem. Every year, the institute hosts several programs, each centered on one scientific topic. A program lasts a few weeks or months, during which scientists visit from across the world. We present our perspectives on the program topic, identify intersections of interests, collaborate, and exclaim over the ocean views afforded by our offices.

Not a bad office view, eh?

From August to October, the KITP hosted two programs about energy and information. The first program was called “Energy and Information Transport in Non-Equilibrium Quantum Systems,” or “Information,” for short. The second program was called “Non-Equilibrium Universality: From Classical to Quantum and Back,” or “Universality.” The programs’ topics and participant lists overlapped, so the KITP merged “Information” and “Universality” to form “Infoversality.” Don’t ask me which program served as the saltwater and which as the fresh.

But the mingling of minds ran deeper. Much of “Information” centered on quantum many-body physics, the study of behaviors emergent in collections of quantum particles. But the program introduced many-body quantum physicists to quantum thermodynamics and vice versa. (Quantum thermodynamicists re-envision thermodynamics, the Victorian science of energy, for quantum, small, information-processing, and far-from-equilibrium systems.) Furthermore, quantum thermodynamicists co-led the program and presented research at it. Months ago, someone advertised the program in the quantum-thermodynamics Facebook group as an activity geared toward group members. 

The ocean of many-body physics was to meet the river of quantum thermodynamics, and I was thrilled as a trout swimming near a hiker who’s discovered cracker crumbs in her pocket. 

A few of us live in this estuary, marrying quantum thermodynamics and many-body physics. I waded into the waters in 2016, by codesigning an engine (the star of Victorian thermodynamics) formed from a quantum material (studied in many-body physics). We can use tools from one field to solve problems in the other, draw inspiration from one to design questions in the other, and otherwise do what the United States Food and Drug Administration recently announced that we can do with COVID19 vaccines: mix and match.

It isn’t easy being interdisciplinary, so I wondered how this estuary would fare when semi-institutionalized in a program. I collected observations like seashells—some elegantly molded, some liable to cut a pedestrian’s foot, and some both.

Across the street from the KITP.

A sand dollar washed up early in the program, as I ate lunch with a handful of many-body physicists. An experimentalist had just presented a virtual talk about nanoscale clocks, which grew from studies of autonomous quantum clocks. The latter run on their own, without needing any external system to wind or otherwise control them. You’d want such clocks if building quantum engines, computers, or drones that operate remotely. Clocks measure time, time complements energy mathematically in physics, and thermodynamics is the study of energy; so autonomous quantum clocks have taken root in quantum thermodynamics. So I found myself explaining autonomous quantum clocks over sandwiches. My fellow diners expressed interest alongside confusion.

A scallop shell, sporting multiple edges, washed up later in the program: Many-body physicists requested an introduction to quantum thermodynamics. I complied one afternoon, at a chalkboard in the KITP’s outdoor courtyard. The discussion lasted for an hour, whereas most such conversations lasted for two. But three participants peppered me with questions over the coming weeks.

A conch shell surfaced, whispering when held to an ear. One program participant, a member of one community, had believed the advertising that had portrayed the program as intended for his cohort. The portrayal didn’t match reality, to him, and he’d have preferred to dive more deeply into his own field.

I dove into a collaboration with other KITPists—a many-body project inspired by quantum thermodynamics. Keep an eye out for a paper and a dedicated blog post.

A conference talk served as a polished shell, reflecting light almost as a mirror. The talk centered on erasure, a process that unites thermodynamics with information processing: Imagine performing computations in math class. You need blank paper (or the neurological equivalent) on which to scribble. Upon computing a great deal, you have to erase the paper—to reset it to a clean state. Erasing calls for rubbing an eraser across the paper and so for expending energy. This conclusion extends beyond math class and paper: To compute—or otherwise process information—for a long time, we have to erase information-storage systems and so to expend energy. This conclusion renders erasure sacred to us thermodynamicists who study information processing. Erasure litters our papers, conferences, and conversations.

Erasure’s energy cost trades off with time: The more time you can spend on erasure, the less energy you need.1 The conference talk explored this tradeoff, absorbing the quantum thermodynamicist in me. A many-body physicist asked, at the end of the talk, why we were discussing erasure. What quantum thermodynamicists took for granted, he hadn’t heard of. He reflected back at our community an image of ourselves from an outsider’s perspective. The truest mirror might not be the flattest and least clouded.

The author, wearing a KITP hat, not far from either estuary—natural or quantum.

Plants and crustaceans, mammals and birds, grow in estuaries. Call me a bent-nosed clam, but I prefer a quantum estuary to all other environments. Congratulations to the scientists who helped create a quantum estuary this summer and fall, and I look forward to the harvest.

1The least amount of energy that erasure can cost, on average over trials, is called Landauer’s bound. You’d pay this bound’s worth of energy if you erased infinitely slowly.

My 100th anniversary with Quantum Frontiers

Queen Elizabeth II celebrated the 60th year of her reign in 2012. I was working as a research assistant at Lancaster University, in northern England. The university threw a tea party, which I attended with a friend. She wrangled me into donning a party hat decorated with the Union Jack. Sixtieth anniversaries, I learned that year, are associated with diamond.

I had trouble finding what 100th anniversaries are associated with—I presume because few queens and couples reach their centennials. But I dug up an answer (all hail the Internet): bone. This post marks my bone anniversary with Quantum Frontiers—my 100th article.

To everyone who’s journeyed with me since article number one, or joined me partway through, or tolerating my writing for the first time now: Thank you. The opportunity to connect with so many people, from undergraduates to art teachers to quantum-information experts to librarians, has been a blessing. I’ve been surprised at, and grateful for, your sharing of what this blog means to you. You’ve reached out during campus visits, at American Physical Society conferences, in emails, and on Twitter. Thank you for enriching my writing life.

A virtual meetup coordinated by Quantum Frontiers readers

The journey began in mid-May 2013, when I signed my soul to Caltech’s PhD program. Fellow blogger John Preskill1 agreed to supervise me for five years. My first blog post said, “For five years, I will haunt this blog. (Spiros [the creator and gatekeeper of Quantum Frontiers] will haunt me if I don’t haunt it.) I’ll try to post one article per month.” I’ve posted one article per month since then. 

Since then, much has transpired. Career-wise, I finished a Master’s degree; earned a PhD; completed a postdoctoral fellowship at the Harvard-Smithsonian Institute for Theoretical Atomic, Molecular, and Optical Physics; committed to doing physics at the National Institute for Science and Technology; stumbled over several acronyms; and founded a research group. Outside of work, I married off my best friend, fell in love and got married myself, lost two grandmothers, and wrote a book. I found myself in more countries than I can count on one hand, in more US states than countries, and jet-lagged for more hours than I care to recall. Quantum Frontiers has served as a diary and a taskmaster, challenging me to find and crystallize meaning in my experiences.

After presenting a toast at my best friend’s wedding—which, because my best friend married a former scientist, almost doubled as a conference

Although professional and personal affairs have had cameos, learning and research have starred in these 100 articles. My research has evolved over the past eight years, not only as recorded on, but also partially thanks to, this blog. Physicists lionize imagination, but some imaginings have no place even in physics papers. This blog serves as a home for the poetry, the puns, the evocative typos, and the far-fetched connections that Physical Review wouldn’t publish. But nurturing whimsy that Physical Review wouldn’t publish fosters whimsy that Physical Review would. Blogging, I’ve found, promotes creativity that enhances research.

My research dwelled in Abstract-Theory Land in 2013—pure quantum-information-theoretic thermodynamics. Caltech bridged my research to the real physical world: condensed matter; atomic molecular, and optical physics; and chemistry. The transformation continued during my postdoc, producing two experimental papers and initiating three more. I don’t think that the metamorphosis will progress, and I keep a foot in abstract theory. But if I awake one morning from troubled dreams, finding myself changed into an experimentalist or an engineer, you’ll be among the first to know. 

I’ve come to know you a little over the past eight years. Many of you like listicles, according to WordPress statistics. You like former Quantum Frontiers blogger Shaun Maguire more than you like me; his most popular article has logged about 142,000 views, whereas mine has logged about 18,000. That’s ok; I’ve never been the popular kid, and I’m a Shaun Maguire fan, too. But, beyond Shaun and listicles, what draws you has surprised Spiros, John, and me. John anticipated that the article “Theoretical physics has not gone to the dogs” would stir up conversation (Do you think it’ll offend anyone? I asked. I hope so, he replied), but other articles have taken off on Twitter unexpectedly. Maybe we’ll understand you better another 100 articles down the line.

Blogging offered me the freedom to recognize and celebrate the steampunk aesthetic of quantum thermodynamics, my field of research. My first PhD student gifted me this adorable steampunk owl sculpture for my birthday this year.

My first blog post contained a quote from Goethe’s Faust. The play opens with a poet reminiscing about his earlier years: “Nothing I had; and yet, enough for youth—/ delight in fiction, and the thirst for truth.” I still delight in fiction, as attested to by a 2020 post about the magical realist Gabriel García Marquez. I’d better thirst for truth no less, now that experimental collaborators are grounding me in reality. Partnering truth with fiction, so that each enhances the other, delights me most—and encapsulates what I aim for on Quantum Frontiers. As I wrote in May 2013, invoking the thirst for truth: Drink with me. I’ll drink a cup of tea to another 100 blog posts.

1Who hasn’t blogged much recently. How about it, John? 

How a liberal-arts education has enhanced my physics research

I attended a liberal-arts college, and I reveled in the curriculum’s breadth. My coursework included art history, psychology, biology, economics, computer science, German literature, archaeology, and chemistry. My major sat halfway between the physics major and the create-your-own major; the requirements consisted mostly of physics but included math, philosophy, and history. By the end of college, I’d determined to dive into physics. So I undertook a physics research assistantship, enlisted in a Master’s program and then a PhD program, and became a theoretical physicist. I’m now building a physics research group that spans a government institute and the University of Maryland. One might think that I became a physicist despite my art history and archaeology. 

My liberal-arts education did mortify me a little as I pursued my Master’s degree. Most of my peers had focused on physics, mathematics, and computer science while I’d been reading Aristotle. They seemed to breeze through coursework that I clawed my way through. I still sigh wistfully over math courses, such as complex analysis, that I’ve never taken. Meanwhile, a debate about the liberal arts has been raging across the nation. Debt is weighing down recent graduates, and high-school students are loading up on STEMM courses. Colleges are cutting liberal-arts departments, and educational organizations are broadcasting the value of liberal-arts educations.

I’m not an expert in public policy or school systems; I’m a physicist. As a physicist, I’m grateful for my liberal-arts education. It’s enhanced my physics research in at least five ways.

(1) I learned to seek out, and take advantage of, context. Early in my first German-literature course, I’d just completed my first reading assignment. My professor told my class to fetch out our books and open them to the beginning. A few rustles later, we held our books open to page one of the main text. 

No, no, said my professor. Open your books to the beginning. Did anyone even look at the title page?

We hadn’t, we admitted. We’d missed a wealth of information, as the book contained a reproduction of an old title page. Publishers, fonts, and advertisement styles have varied across the centuries and the globe. They, together with printing and reprinting dates, tell stories about the book’s origin, popularity, role in society, and purposes. Furthermore, a frontispiece is worth a thousand words, all related before the main text begins. When my class turned to the main text, much later in the lecture, we saw it in a new light. Context deepens and broadens our understanding.

When I read a physics paper, I start at the beginning—the true beginning. I note the publication date, the authors, their institutions and countries, and the journal. X’s lab performed the experiment reported on? X was the world’s expert in Y back then but nursed a bias against Z, a bias later proved to be unjustified. So I should aim to learn from the paper about Y but should take statements about Z with a grain of salt. Seeking and processing context improves my use of physics papers, thanks to a German-literature course.

(2) I learned argumentation. Doing physics involves building, analyzing, criticizing, and repairing arguments. I argue that mathematical X models physical system Y accurately, that an experiment I’ve proposed is feasible with today’s technology, and that observation Z supports a conjecture of mine. Physicists also prove mathematical statements deductively. I received proof-writing lessons in a math course, halfway through college. One of the most competent teachers I’ve ever encountered taught the course. But I learned about classes of arguments and about properties of arguments in a philosophy course, Informal Logic. 

There, I learned to distinguish deduction from inference and an argument’s validity and soundness from an argument’s strength and cogency. I learned strategies for proving arguments and learned fallacies to criticize. I came to respect the difference between “any” and “every,” which I see interchanged in many physics papers. This philosophical framework helps me formulate, process, dissect, criticize, and correct physics arguments. 

For instance, I often parse long, dense, technical proofs of mathematical statements. First, I identify whether the proof strategy is reductio ad absurdum, proof by counterexample, or another strategy. Upon identifying the overarching structure, I can fill my understanding with details. Additionally, I check proofs by students, and I respond to criticisms of my papers by journal referees. I could say, upon reading an argument, “Something feels a bit off, and it’s sort of like the thing that felt a bit off in that paper I read last Tuesday.” But I’d rather group the argument I’m given together with arguments I know how to tackle. I’d rather be able to say, “They’re straw-manning my argument” or “That argument begs the question.” Doing so, I put my finger on the problem and take a step toward solving it.

(3) I learned to analyze materials to bits, then extract meaning from the analysis. English and German courses trained me to wring from literature every drop of meaning that I could discover. I used to write one to three pages about a few-line quotation. The analysis would proceed from diction and punctuation to literary devices; allusions; characters’ relationships with each other, themselves, and nature; and the quotation’s role in the monograph. Everything from minutia to grand themes required scrutiny, according to the dissection technique I trained in. Every pincer probe lifted another skein of skin or drew aside another tendon, offering deeper insights into the literary work. I learned to find the skeins to lift, lift them in the right direction, pinpoint the insights revealed, and integrate the insights into a coherent takeaway.

This training has helped me assess and interpret mathematics. Physicists pick a physical system to study, model the system with equations, and solve the equations. The next two steps are intertwined: evaluating whether one solved the equations correctly and translating the solution into the physical system’s behavior. These two steps necessitate a dissection of everything from minutia to grand themes: Why should this exponent be 4/5, rather than any other number? Should I have expected this energy to depend on that length in this way? Is the physical material aging quickly or resisting change? These questions’ answers inform more-important questions: Who cares? Do my observations shed light worth anyone’s time, or did I waste a week solving equations no one should care about?

To answer all these questions, I draw on my literary training: I dissect content, pinpoint insights, and extract meaning. Having performed this analysis in literature courses facilitates an arguably deeper analysis than my physics training did: In literature courses, I had to organize my thoughts and articulate them in essays. This process revealed holes in my argumentation, as well as connections that I’d overlooked. In contrast, a couple of lines in my physics homework earned full marks. The critical analysis of literature has deepened my assessment of solutions’ correctness, physical interpretation of mathematics, and extraction of meaning from solutions. 

(4) I learned what makes a physicist a physicist. In college, I had a friend who was studying applied mathematics and economics. Over dinner, he described a problem he’d encountered in his studies. I replied, almost without thinking, “From a physics perspective, I’d approach the problem like this.” I described my view, which my friend said he wouldn’t have thought of. I hadn’t thought of myself, and of the tools I was obtaining in the physics department, the way I did after our conversation. 

Physics involves a unique toolkit,1 set of goals, and philosophy. Physicists identify problems, model them, solve them, and analyze the results in certain ways. Students see examples of these techniques in lectures and practice these techniques for homework. But, as a student, I rarely heard articulations of the general principles that underlay the examples scattered across my courses like a handful of marbles across a kitchen floor. Example principles include, if you don’t understand an abstract idea, construct a simple example. Once you’ve finished a calculation, check whether your answer makes sense in the most extreme scenarios possible. After solving an equation, interpret the solution in terms of physical systems—of how particles and waves move and interact. 

I was learning these techniques, in college, without realizing that I was learning them. I became conscious of the techniques by comparing the approach natural to me with the approach taken in another discipline. Becoming conscious of my toolkit enabled me to wield it more effectively; one can best fry eggs when aware that one owns a spatula. The other disciplines at my liberal-arts college served as a foil for physics. Seeing other disciplines, I saw what makes physics physics—and improved my ability to apply my physics toolkit.

(5) I learned to draw connections between diverse ideas. Senior year of high school, my courses extended from physics to English literature. One might expect such a curriculum to feel higgledy-piggledy, but I found threads that ran through all my courses. For instance, I practiced public speaking in Reasoning, Research, and Rhetoric. Because I studied rhetoric, my philosophy teacher turned to me for input when introducing the triumvirate “thesis, antithesis, synthesis.”2 The philosophy curriculum included the feminist essay “If Men Could Menstruate,” which complemented the feminist book Wide Sargasso Sea in my English-literature course. In English literature, I learned that Baldassare Castiglione codified how Renaissance noblemen should behave, in The Book of the Courtier. The author’s name was the answer to the first question on my AP Modern European History exam. My history course covered Isaac Newton and Gottfried Wilhelm Leibniz, who invented calculus during the 17th century. I leveraged their discoveries in my calculus course, which I applied in my physics course. My physics teacher hoped that his students would solve the world’s energy problems—perhaps averting the global thermonuclear war that graced every debate in my rhetoric course (“If you don’t accept my team’s policy, then X will happen, leading to Y, leading to Z, which will cause a global thermonuclear war”). 

Threads linked everything across my liberal-arts education; every discipline featured an idea that paralleled an idea in another discipline. Finding those parallels grew into a game for me, a game that challenged my creativity. Cultivating that creativity paid off when I began doing physics research. Much of my research has resulted from finding, in one field, a concept that resembles a concept in another field. I smash the ideas together to gain insight into each discipline from the other discipline’s perspective. For example, during my PhD studies, I found a thread connecting the physics of DNA strands to the physics of black holes. That thread initiated a research program of mine that’s yielded nine papers, garnered 19 collaborators, and spawned two experiments. Studying diverse subjects trained me to draw creative connections, which underlie much physics research.

I haven’t detailed all the benefits that a liberal-arts education can accrue to a physics career. For instance, the liberal arts enhance one’s communication skills, key to collaborating on research and to conveying one’s research. Without conveying one’s research adroitly, one likely won’t impact a field much. Also, a liberal-arts education can help one connect with researchers from across the globe on a personal level.3 Personal connections enhance science, which scientists—humans—undertake.

As I began building my research group, I sought advice from an MIT professor who’d attended MIT as an undergraduate. He advised me to seek students who have unusual backgrounds, including liberal-arts educations. Don’t get me wrong; I respect and cherish the colleagues and friends of mine who attended MIT, Caltech, and other tech schools as undergraduates. Still, I wouldn’t trade my German literature and economics. The liberal arts have enriched my physics research no less than they’ve enriched the rest of my life.

1A toolkit that overlaps partially with other disciplines’ toolkits, as explained in (3).

2I didn’t help much. When asked to guess the last concept in the triumvirate, I tried “debate.”

3I once met a Ukrainian physicist who referred to Ilya Muromets in a conversation. Ilya Muromets is a bogatyr, a knight featured in Slavic epics set in the Middle Ages. I happened to have taken a Slavic-folklore course the previous year. So I responded with a reference to Muromets’s pals, Dobrynya Nikitich and Alyosha Popovich. The physicist and I hit it off, and he taught me much about condensed matter over the following months.