Quantum

Quantum Lessons Learned at the Port of Los Angeles

dougfinke — Sun, 27 Nov 2022 00:45:56 +0000

Picture of Pier 300 at the Port of Los Angeles Showing Ships Unloading and Containers in the Storage Yard. Credit: Google Earth Earlier this year, we reported on an logistics optimization program at Pier 300 at the Port of Los Angeles accomplished by a team from SavantX and Fenix Marine Services to optimize the logistics [...]

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Can Reskilling Help Satisfy Quantum’s Workforce Requirements?

dougfinke — Fri, 25 Nov 2022 22:45:51 +0000

The layoff situation has been brutal in the classical computing industry lately. Recent tech layoffs announced have included Meta with 11,000 workers, Amazon with 10,000 workers, Cisco with 4100, Twitter with 3700, Uber with 3700, and the list goes on. As of November 2022, the website Layoff.fyi has estimated that in 2022 so far 859 [...]

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Horizon Quantum Computing is Opening a New Office in Dublin, Ireland

dougfinke — Thu, 24 Nov 2022 21:24:59 +0000

Horizon Quantum Computing, a quantum software startup headquartered in Singapore, has decided to open up a second office in Dublin, Ireland to advance development of their new generation of quantum programming tools that are intended to make the power of quantum computing accessible to every software developer. The company currently has 13 employees but is [...]

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Quantum Computing Inc. Introduces Software that Translates QUBO Problems to a Hamiltonian for Solving on their Dirac 1 Processor

dougfinke — Thu, 24 Nov 2022 00:17:23 +0000

In order to make it easier for customers to try out Quantum Computing Inc.'s (QCI) recently introduced Dirac 1 Entropy Quantum Computer, the company has announced a free software translator that can take problems expressed as an Quadratic Unconstrained Binary Optimization (QUBO) format and convert to a Hamiltonian that can be an input to the [...]

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Achieving a quantum fiber

Wed, 23 Nov 2022 16:38:41 +0000

Researchers have successfully demonstrated the transport of two-photon quantum states of light through a phase-separated Anderson localization optical fiber.

Dismantling Quantum Hype with Tim Nguyen

Scott — Wed, 23 Nov 2022 04:12:34 +0000

Happy Thanksgiving to my American readers! While I enjoy a family holiday-week vacation in exotic Dallas—and yes, I will follow up on my old JFK post by visiting Dealey Plaza—please enjoy the following Thanksgiving victuals:

I recently recorded a 3-hour (!) YouTube video with Timothy Nguyen, host of the Cartesian Cafe. Our episode is entitled Quantum Computing: Dismantling the Hype. In it, I teach a sort of extremely compressed version of my undergraduate Intro to Quantum Information Science course, unburdening myself about whatever Tim prompts me to explain: the basic rules of quantum information, quantum circuits, the quantum black-box model, the Deutsch-Jozsa algorithm, BQP and its relationship to classical complexity classes, and sampling-based quantum supremacy experiments. This is a lot more technical than an average podcast, a lot less technical than an actual course, and hopefully just right for some nonempty subset of readers.

Outside of his podcasting career, some of you might recognize Nguyen as the coauthor, with Theo Polya, of a rebuttal of “Geometric Unity.” This latter is the proposal by the financier, podcaster, and leading “Intellectual Dark Web” figure Eric Weinstein for a unified theory of particle physics. Now, I slightly know Weinstein, and have even found him fascinating, eloquent, and correct about various issues. So, in an addendum to the main video, Nguyen chats with me about his experience critiquing Weinstein’s theory, and also about something where my knowledge is far greater: namely, my 2002 rebuttal of some of the central claims in Stephen Wolfram’s A New Kind of Science, and whether there are any updates to that story twenty years later.

Enjoy!

Investigating the impact of a laser’s noise property on qubits

Amisha Kaur — Wed, 23 Nov 2022 00:00:00 +0000

Wednesday, November 23, 2022

When Institute for Quantum Computing (IQC) Research Associate Matthew Day had his lab temporarily closed during the COVID-19 pandemic, the experimentalist found himself at some loose ends. What’s an experimentalist to do without his equipment? For Day, it was a chance for him to ask questions he’d been thinking about for a while. Specifically, Day wanted to know: how does equipment in the lab affect experiments?

Classiq and Q-CTRL Partner to Offer an Integrated Tool that Provides the Best Features of Each Company’s Offerings in One Package

dougfinke — Tue, 22 Nov 2022 22:13:11 +0000

Although both Classiq and Q-CTRL are quantum software startups, they have been focusing on completely different areas of the quantum stack. Classiq offers a software package that allows users to specify their program using high-level functional models and then automatically compiles them into lower level quantum gates. While Q-CTRL provides quantum control infrastructure software that [...]

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Rigetti Computing Reports Q3 Financial Results

dougfinke — Tue, 22 Nov 2022 20:38:58 +0000

Rigetti Computing reported Q3 revenues of $2.8 million compared with revenues of $2.1 million in the previous quarter. Gross profit was $2.0 million versus $1.3 million in the previous quarter and net GAAP loss was $18.8 million versus $10 million in Q2. The company ended the quarter with cash and cash equivalents of $161 million. [...]

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Quantum algorithms save time in the calculation of electron dynamics

Tue, 22 Nov 2022 20:28:07 +0000

Quantum computers promise significantly shorter computing times for complex problems. But there are still only a few quantum computers worldwide with a limited number of so-called qubits. However, quantum computer algorithms can already run on conventional servers that simulate a quantum computer. A team has succeeded in calculating the electron orbitals and their dynamic development using an example of a small molecule after a laser pulse excitation. In principle, the method is also suitable for investigating larger molecules that cannot be calculated using conventional methods.

Microlaser chip adds new dimensions to quantum communication

Tue, 22 Nov 2022 02:58:09 +0000

With only two levels of superposition, the qubits used in today's quantum communication technologies have limited storage space and low tolerance for interference. Engineering's hyperdimensional microlaser generates 'qudits,' photons with four simultaneous levels of information. The increase in dimension makes for robust quantum communication technology better suited for real-world applications.

Podcast with Professor Peter Kogge from Notre Dame, Professor Gerardo Ortiz from Indiana University and Dr. David Stewart from Purdue about the new Center for Quantum Technologies

dougfinke — Mon, 21 Nov 2022 18:41:49 +0000

Professor Peter Kogge from Notre Dame, Professor Gerardo Ortiz from Indiana University and Dr. David Stewart, managing director of the Purdue quantum science and engineering institute are interviewed by Yuval Boger. They talk about the new Center for Quantum Technologies, a multi-site NSF-funded research center, which commercial sponsors are participating in the center and what [...]

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New quantum tool developed in groundbreaking experimental achievement

Kelsey Stoddart — Mon, 21 Nov 2022 00:00:00 +0000

Monday, November 21, 2022

En français

Scientists recreate properties of light in neutral fundamental particles called neutrons for the first time in experimental history.

SandboxAQ Wins Phase 1 SBIR from the U.S. Air Force to Determine the Feasibility of Its Quantum-Resistant Security Solutions

dougfinke — Sun, 20 Nov 2022 22:13:24 +0000

SandboxAQ, a quantum software startup spun off from Alphabet Inc. earlier this year, has won a Phase 1 SBIR for the U.S. Air Force to investigate who its suite of software solutions can protect the Air Force and Space Force data networks from quantum attacks. Phase 1 SBIR awards have typical amounts of about $225,000 [...]

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Reform AI Alignment

Scott — Sun, 20 Nov 2022 20:44:33 +0000

Update (Nov. 22): Theoretical computer scientist and longtime friend-of-the-blog Boaz Barak writes to tell me that, coincidentally, he and Ben Edelman just released a big essay advocating a version of “Reform AI Alignment” on Boaz’s Windows on Theory blog, as well as on LessWrong. (I warned Boaz that, having taken the momentous step of posting to LessWrong, in 6 months he should expect to find himself living in a rationalist group house in Oakland…) Needless to say, I don’t necessarily endorse their every word or vice versa, but there’s a striking amount of convergence. They also have a much more detailed discussion of (e.g.) which kinds of optimization processes they consider relatively safe.

Nearly halfway into my year at OpenAI, still reeling from the FTX collapse, I feel like it’s finally time to start blogging my AI safety thoughts—starting with a little appetizer course today, more substantial fare to come.

Many people claim that AI alignment is little more a modern eschatological religion—with prophets, an end-times prophecy, sacred scriptures, and even a god (albeit, one who doesn’t exist quite yet). The obvious response to that claim is that, while there’s some truth to it, “religions” based around technology are a little different from the old kind, because technological progress actually happens regardless of whether you believe in it.

I mean, the Internet is sort of like the old concept of the collective unconscious, except that it actually exists and you’re using it right now. Airplanes and spacecraft are kind of like the ancient dream of Icarus—except, again, for the actually existing part. Today GPT-3 and DALL-E2 and LaMDA and AlphaTensor exist, as they didn’t two years ago, and one has to try to project forward to what their vastly-larger successors will be doing a decade from now. Though some of my colleagues are still in denial about it, I regard the fact that such systems will have transformative effects on civilization, comparable to or greater than those of the Internet itself, as “already baked in”—as just the mainstream position, not even a question anymore. That doesn’t mean that future AIs are going to convert the earth into paperclips, or give us eternal life in a simulated utopia. But their story will be a central part of the story of this century.

Which brings me to a second response. If AI alignment is a religion, it’s now large and established enough to have a thriving “Reform” branch, in addition to the original “Orthodox” branch epitomized by Eliezer Yudkowsky and MIRI. As far as I can tell, this Reform branch now counts among its members a large fraction of the AI safety researchers now working in academia and industry. (I’ll leave the formation of a Conservative branch of AI alignment, which reacts against the Reform branch by moving slightly back in the direction of the Orthodox branch, as a problem for the future — to say nothing of Reconstructionist or Marxist branches.)

Here’s an incomplete but hopefully representative list of the differences in doctrine between Orthodox and Reform AI Risk:

(1) Orthodox AI-riskers tend to believe that humanity will survive or be destroyed based on the actions of a few elite engineers over the next decade or two. Everything else—climate change, droughts, the future of US democracy, war over Ukraine and maybe Taiwan—fades into insignificance except insofar as it affects those engineers.

We Reform AI-riskers, by contrast, believe that AI might well pose civilizational risks in the coming century, but so does all the other stuff, and it’s all tied together. An invasion of Taiwan might change which world power gets access to TSMC GPUs. Almost everything affects which entities pursue the AI scaling frontier and whether they’re cooperating or competing to be first.

(2) Orthodox AI-riskers believe that public outreach has limited value: most people can’t understand this issue anyway, and will need to be saved from AI despite themselves.

We Reform AI-riskers believe that trying to get a broad swath of the public on board with one’s preferred AI policy is something close to a deontological imperative.

(3) Orthodox AI-riskers worry almost entirely about an agentic, misaligned AI that deceives humans while it works to destroy them, along the way to maximizing its strange utility function.

We Reform AI-riskers entertain that possibility, but we worry at least as much about powerful AIs that are weaponized by bad humans, which we expect to pose existential risks much earlier in any case.

(4) Orthodox AI-riskers have limited interest in AI safety research applicable to actually-existing systems (LaMDA, GPT-3, DALL-E2, etc.), seeing the dangers posed by those systems as basically trivial compared to the looming danger of a misaligned agentic AI.

We Reform AI-riskers see research on actually-existing systems as one of the only ways to get feedback from the world about which AI safety ideas are or aren’t promising.

(5) Orthodox AI-riskers worry most about the “FOOM” scenario, where some AI might cross a threshold from innocuous-looking to plotting to kill all humans in the space of hours or days.

We Reform AI-riskers worry most about the “slow-moving trainwreck” scenario, where (just like with climate change) well-informed people can see the writing on the wall decades ahead, but just can’t line up everyone’s incentives to prevent it.

(6) Orthodox AI-riskers talk a lot about a “pivotal act” to prevent a misaligned AI from ever being developed, which might involve (e.g.) using an aligned AI to impose a worldwide surveillance regime.

We Reform AI-riskers worry more about such an act causing the very calamity that it was intended to prevent.

(7) Orthodox AI-riskers feel a strong need to repudiate the norms of mainstream science, seeing them as too slow-moving to react in time to the existential danger of AI.

We Reform AI-riskers feel a strong need to get mainstream science on board with the AI safety program.

(8) Orthodox AI-riskers are maximalists about the power of pure, unaided superintelligence to just figure out how to commandeer whatever physical resources it needs to take over the world (for example, by messaging some lab over the Internet, and tricking it into manufacturing nanobots that will do the superintelligence’s bidding).

We Reform AI-riskers believe that, here just like in high school, there are limits to the power of pure intelligence to achieve one’s goals. We’d expect even an agentic, misaligned AI, if such existed, to need a stable power source, robust interfaces to the physical world, and probably allied humans before it posed much of an existential threat.

What have I missed?

Pasqal and Eni Are Collaborating to Explore Quantum Computing Solutions for the Energy Sector

dougfinke — Sat, 19 Nov 2022 23:19:51 +0000

Pasqal, a quantum startup company developing neutral atom based quantum processors with headquarters near Paris France, has announced it is collaborating with Italian energy giant Eni to explore potential quantum solutions for a number of applications across its value chain including what they call the upstream, downstream, chemicals and renewables. Eni already operates one of [...]

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WINNERS of the Scott Aaronson Grant for Advanced Precollege STEM Education!

Scott — Fri, 18 Nov 2022 08:01:17 +0000

I’m thrilled to be able to interrupt your regular depressing programming for 100% happy news.

Some readers will remember that, back in September, I announced that an unnamed charitable foundation had asked my advice on how best to donate $250,000 for advanced precollege STEM education. So, just like the previous time I got such a request, from Jaan Tallinn’s Survival and Flourishing Fund, I decided to do a call for proposals on Shtetl-Optimized before passing along my recommendations.

I can now reveal that the generous foundation, this time around, was the Packard Foundation. Indeed, the idea and initial inquiries to me came directly from Dave Orr: the chair of the foundation, grandson of Hewlett-Packard cofounder David Packard, and (so I learned) longtime Shtetl-Optimized reader.

I can also now reveal the results. I was honored to get more than a dozen excellent applications. After carefully considering all of them, I passed along four finalists to the Packard Foundation, which preferred to award the entire allotment to a single program if possible. After more discussion and research, the Foundation then actually decided on two winners:

$225,000 for general support to PROMYS: the long-running, world-renowned summer math camp for high-school students, which (among other things) is in the process of launching a new branch in India. While I ended up at Canada/USA Mathcamp (which I supported in my first grant round) rather than PROMYS, I knew all about and admired PROMYS even back when I was the right age to attend it. I’m thrilled to be able to play a small role in its expansion.

$30,000 for general support to AddisCoder: the phenomenal program that introduces Ethiopian high-schoolers to programming and algorithms. AddisCoder was founded by UC Berkeley theoretical computer science professor and longtime friend-of-the-blog Jelani Nelson, and also received $30,000 in my first grant round. Jelani and his co-organizers will be pressing ahead with AddisCoder despite political conflict in Ethiopia including a recently-concluded civil war. I’m humbled if I can make even the tiniest difference.

Thanks so much to the Packard Foundation, and to Packard’s talented program officers, directors, and associates—especially Laura Sullivan, Jean Ries, and Prithi Trivedi—for their hard work to make this happen. Thanks so much also to everyone who applied. While I wish we could’ve funded everyone, I’ve learned a lot about programs to which I’d like to steer future support (other prospective benefactors: please email me!!), and to which I’d like to steer kids: my own, once they’re old enough, and other kids of my acquaintance.

I feel good that, in the tiny, underfunded world of accelerated STEM education, the $255,000 that Packard is donating will already make a difference. But of course, $255,000 is only a thousandth of $255 million, which is a thousandth of $255 billion. Perhaps I could earn the latter sort of sums, to donate to STEM education or any other cause, by (for example) starting my own cryptocurrency exchange. I hope my readers will forgive me for not having chosen that route, expected-utility-maximization arguments be damned.

Algorithmiq Launches Aurora, a Drug Discovery Platform and Will Work with IBM on Drug Discovery Applications

dougfinke — Fri, 18 Nov 2022 00:57:51 +0000

Development of a new drug often takes over 10 years and requires an investment exceeding $1 billion. Part of the reason for this is that classical computers cannot accurately simulate the binding of drug molecules to certain proteins in our body that are responsible for a given disease. Many are working on using a quantum [...]

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New exotic two-dimensional magnet may hold promise for quantum computing

Kelsey Stoddart — Fri, 18 Nov 2022 00:00:00 +0000

Friday, November 18, 2022

En français

The magnetic properties of an exotic material in the atomically thin two-dimensional limit may lead to future applications in quantum information processing.

Grid of quantum islands could reveal secrets for powerful technologies

Thu, 17 Nov 2022 23:42:11 +0000

Researchers have created grids of tiny clumps of atoms known as quantum dots and studied what happens when electrons dive into these archipelagos of atomic islands. Measuring the behavior of electrons in these relatively simple setups promises deep insights into how electrons behave in complex real-world materials and could help researchers engineer devices that make possible powerful quantum computers and other innovative technologies.

Sneerers

Scott — Thu, 17 Nov 2022 01:48:08 +0000

In the past few weeks, I’ve learned two ways to think about online sneerers that have been helping me tremendously, and that I wanted to share in case they’re helpful to others:

First, they’re like a train in a movie that’s barreling directly towards the camera. If you haven’t yet internalized how the medium works, absolutely terrifying! Run from the theater! If you have internalized it, though, you can sit and watch without even flinching.

Second, the sneerers are like alligators—and about as likely to be moved by your appeals to reason and empathy. But if, like me, you’re lucky enough to have a loving family, friends, colleagues, and a nigh-uncancellable career, then it’s as though you’re standing on a bridge high above, looking down at the gators as they snap their jaws at you uselessly. There’s really no moral or intellectual obligation to go down to the swamp to wrestle them. If they mean to attack you, let them at least come up to the bridge.

Quandela Announces a European Quantum Cloud Service

dougfinke — Thu, 17 Nov 2022 00:15:14 +0000

In what it says is the first quantum cloud service in Europe, Quandela has announced that it has now made available an initial system with 5 photonic qubits for experimentation. The system can be programmed with Quandela's Percival development toolkit which also supports Quandela's photonic simulator allowing a user to simulate a program before running [...]

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Using disorder to find new magnetic transition pathways

Elizabeth Kleisath — Thu, 17 Nov 2022 00:00:00 +0000

Thursday, November 17, 2022

En français

A team of researchers at the Institute for Quantum Computing (IQC) have found a new tunable pathway to manipulate nanoscale magnetic structures known as skyrmions.

Light-matter interactions on sub-nanometer scales unlocked, leading to 'picophotonics'

Wed, 16 Nov 2022 21:49:30 +0000

Researchers have discovered new waves with picometer-scale spatial variations of electromagnetic fields which can propagate in semiconductors like silicon.

News

dougfinke — Wed, 16 Nov 2022 20:40:38 +0000

Recent news items published within the last 6 months on quantum computing developments are listed below. Click on the hyperlinked item to go to the press release or news article for more details. For older news items published in 2021 click here, for 2020 click here, for 2019 click here, for 2018 click here, and [...]

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Sam Bankman-Fried and the geometry of conscience

Scott — Sun, 13 Nov 2022 08:55:25 +0000

Several readers have asked me for updated thoughts on AI safety, now that I’m 5 months into my year at OpenAI—and I promise, I’ll share them soon! The thing is, until last week I’d entertained the idea of writing up some of those thoughts for an essay competition run by the FTX Future Fund, which (I was vaguely aware) was founded by the cryptocurrency billionaire Sam Bankman-Fried, henceforth SBF.

Alas, unless you’ve been tucked away on some Caribbean island—or perhaps, especially if you have been—you’ll know that the FTX Future Fund has ceased to exist. In the course of 2-3 days last week, SBF’s estimated net worth went from ~$15 billion to a negative number, possibly the fastest evaporation of such a vast personal fortune in all human history. Notably, SBF had promised to give virtually all of it away to various worthy causes, including mitigating existential risk and helping Democrats win elections, and the worldwide Effective Altruist community had largely reoriented itself around that pledge. That’s all now up in smoke.

I’ve never met SBF, although he was a physics undergraduate at MIT while I taught CS there. What little I knew of SBF before this week, came mostly from reading Gideon Lewis-Kraus’s excellent New Yorker article about Effective Altruism this summer. The details of what happened at FTX are at once hopelessly complicated and—it would appear—damningly simple, involving the misuse of billions of dollars’ worth of customer deposits to place risky bets that failed. SBF has, in any case, tweeted that he “fucked up and should have done better.”

You’d think none of this would directly impact me, since SBF and I inhabit such different worlds. He ran a crypto empire from the Bahamas, sharing a group house with other twentysomething executives who often dated each other. I teach at a large state university and try to raise two kids. He made his first fortune by arbitraging bitcoin between Asia and the West. I own, I think, a couple bitcoins that someone gave me in 2016, but have no idea how to access them anymore. His hair is large and curly; mine is neither.

Even so, I’ve found myself obsessively following this story because I know that, in a broader sense, I will be called to account for it. SBF and I both grew up as nerdy kids in middle-class Jewish American families, and both had transformative experiences as teenagers at Canada/USA Mathcamp. He and I know many of the same people. We’ve both been attracted to the idea of small groups of idealistic STEM nerds using their skills to help save the world from climate change, pandemics, and fascism.

Aha, the sneerers will sneer! Hasn’t the entire concept of “STEM nerds saving the world” now been utterly discredited, revealed to be just a front for cynical grifters and Ponzi schemers? So if I’m also a STEM nerd who’s also dreamed of helping to save the world, then don’t I stand condemned too?

I’m writing this post because, if the Greek tragedy of SBF is going to be invoked as a cautionary tale in nerd circles forevermore—which it will be—then I think it’s crucial that we tell the right cautionary tale.

It’s like, imagine the Apollo 11 moon mission had almost succeeded, but because of a tiny crack in an oxygen tank, it instead exploded in lunar orbit, killing all three of the astronauts. Imagine that the crack formed partly because, in order to hide a budget overrun, Wernher von Braun had secretly substituted a cheaper material, while telling almost none of his underlings.

There are many excellent lessons that one could draw from such a tragedy, having to do with, for example, the construction of oxygen tanks, the procedures for inspecting them, Wernher von Braun as an individual, or NASA safety culture.

But there would also be bad lessons to not draw. These include: “The entire enterprise of sending humans to the moon was obviously doomed from the start.” “Fate will always punish human hubris.” “All the engineers’ supposed quantitative expertise proved to be worthless.”

From everything I’ve read, SBF’s mission to earn billions, then spend it saving the world, seems something like this imagined Apollo mission. Yes, the failure was total and catastrophic, and claimed innocent victims. Yes, while bad luck played a role, so did, shall we say, fateful decisions with a moral dimension. If it’s true that, as alleged, FTX raided its customers’ deposits to prop up the risky bets of its sister organization Alameda Research, multiple countries’ legal systems will surely be sorting out the consequences for years.

To my mind, though, it’s important not to minimize the gravity of the fateful decision by conflating it with everything that preceded it. I confess to taking this sort of conflation extremely personally. For eight years now, the rap against me, advanced by thousands (!) on social media, has been: sure, while by all accounts Aaronson is kind and respectful to women, he seems like exactly the sort of nerdy guy who, still bitter and frustrated over high school, could’ve chosen instead to sexually harass women and hinder their scientific careers. In other words, I stand condemned by part of the world, not for the choices I made, but for choices I didn’t make that are considered “too close to me” in the geometry of conscience.

And I don’t consent to that. I don’t wish to be held accountable for the misdeeds of my doppelgängers in parallel universes. Therefore, I resolve not to judge anyone else by their parallel-universe doppelgängers either. If SBF indeed gambled away his customers’ deposits and lied about it, then I condemn him for it utterly, but I refuse to condemn his hypothetical doppelgänger who didn’t do those things.

Granted, there are those who think all cryptocurrency is a Ponzi scheme and a scam, and that for that reason alone, it should’ve been obvious from the start that crypto-related plans could only end in catastrophe. The “Ponzi scheme” theory of cryptocurrency has, we ought to concede, a substantial case in its favor—though I’d rather opine about the matter in (say) 2030 than now. Like many technologies that spend years as quasi-scams until they aren’t, maybe blockchains will find some compelling everyday use-cases, besides the well-known ones like drug-dealing, ransomware, and financing rogue states.

Even if cryptocurrency remains just a modern-day tulip bulb or Beanie Baby, though, it seems morally hard to distinguish a cryptocurrency trader from the millions who deal in options, bonds, and all manner of other speculative assets. And a traditional investor who made billions on successful gambles, or arbitrage, or creating liquidity, then gave virtually all of it away to effective charities, would seem, on net, way ahead of most of us morally.

To be sure, I never pursued the “Earning to Give” path myself, though certainly the concept occurred to me as a teenager, before it had a name. Partly I decided against it because I seem to lack a certain brazenness, or maybe just willingness to follow up on tedious details, needed to win in business. Partly, though, I decided against trying to get rich because I’m selfish (!). I prioritized doing fascinating quantum computing research, starting a family, teaching, blogging, and other stuff I liked over devoting every waking hour to possibly earning a fortune only to give it all to charity, and more likely being a failure even at that. All told, I don’t regret my scholarly path—especially not now!—but I’m also not going to encase it in some halo of obvious moral superiority.

If I could go back in time and give SBF advice—or if, let’s say, he’d come to me at MIT for advice back in 2013—what could I have told him? I surely wouldn’t talk about cryptocurrency, about which I knew and know little. I might try to carve out some space for deontological ethics against pure utilitarianism, but I might also consider that a lost cause with this particular undergrad.

On reflection, maybe I’d just try to convince SBF to weight money logarithmically when calculating expected utility (as in the Kelly criterion), to forsake the linear weighting that SBF explicitly advocated and that he seems to have put into practice in his crypto ventures. Or if not logarithmic weighing, I’d try to sell him on some concave utility function—something that makes, let’s say, a mere $1 billion in hand seem better than $15 billion that has a 50% probability of vanishing and leaving you, your customers, your employees, and the entire Effective Altruism community with less than nothing.

At any rate, I’d try to impress on him, as I do on anyone reading now, that the choice between linear and concave utilities, between risk-neutrality and risk-aversion, is not bloodless or technical—that it’s essential to make a choice that’s not only in reflective equilibrium with your highest values, but that you’ll still consider to be such regardless of which possible universe you end up in.

Magnetism or no magnetism? The influence of substrates on electronic interactions

Wed, 09 Nov 2022 17:43:07 +0000

A new study illustrates how substrates affect electronic interactions in 2D metal-organic frameworks. With electronic properties tuneable by electrical charge, mechanical strain, and hybridization, such structures can be 'switched' off and on, allowing potential applications in future energy-efficient electronics.

The Caesar problem remains open

Scott — Tue, 08 Nov 2022 17:59:42 +0000

If I haven’t blogged until now about the midterm election, it’s because I find the state of the world too depressing. Go vote, obviously, if you’re eligible and haven’t yet. How many more chances will you have?

While I’m (to put it mildly) neither especially courageous nor useful as an infantryman, I would’ve been honored to give up my life for the Israel of Herzl and Ben-Gurion, or for the America of Franklin and Lincoln. Alas, the Israel of Herzl and Ben-Gurion officially ceased to exist last week, with the election of a coalition some of whose members officially endorse discrimination against Israeli Arab citizens, effectively nullifying Ben-Gurion’s founding declaration that the new state would ensure “complete equality of social and political rights to all its inhabitants irrespective of religion, race, or sex.” The America of Franklin and Lincoln might follow it into oblivion starting tonight, with the election of hundreds of candidates who acknowledge the legimitacy of elections only when their party wins.

The Roman Republic lasted until Caesar. Weimar Germany lasted until Hitler (no, the destroyer of democracy isn’t always literally Hitler, but in that instance it was). Hungary lasted until Orbán. America lasted until Trump. Israel lasted until Netanyahu. After two millennia, democracy still hasn’t solved this problem, and it’s always basically the same problem: one individual, one populist authoritarian, who uses the machinery of democracy to end democracy. How would one design a democracy to prevent this the next time around?

New blue quantum dot technology could lead to more energy-efficient displays

Tue, 08 Nov 2022 13:26:12 +0000

Quantum dots are nanoscale crystals capable of emitting light of different colors. Display devices based on quantum dots promise greater power efficiency, brightness and color purity than previous generations of displays. Of the three colors typically required to display full color images -- red, green and blue -- the last has proved difficult to produce. A new method based on self-organizing chemical structures offers a solution, and a cutting-edge imaging technique to visualize these novel blue quantum dots proved essential to their creation and analysis.

Seeing clearly into a new realm -- researchers prototype a new generation of quantum microscopy

Mon, 07 Nov 2022 16:44:43 +0000

With the advance of quantum technologies, new microscopy modalities are becoming possible -- ones that can see electric currents, detect fluctuating magnetic fields, and even see single molecules on a surface. A prototype of such a microscope, demonstrating high resolution sensitivity, has been developed by an Australian research team.

New Physics specialization prepares MSc students for quantum technology future

Amisha Kaur — Wed, 02 Nov 2022 00:00:00 +0000

Wednesday, November 2, 2022

The new Physics course-based MSc with a specialization in Quantum Technology enables students to study quantum concepts in theory, and practice them in a hands-on, collaborative environment.

Quantum dots form ordered material

Tue, 01 Nov 2022 14:07:23 +0000

Quantum dots are clusters of some 1,000 atoms which act as one large 'super-atom'. It is possible to accurately design the electronic properties of these dots just by changing their size. A team has succeeded in making a highly conductive optoelectronic metamaterial through self-organization.

2022 recipient of Laflamme and Gregson Award for Women in Quantum Information Science announced

Amisha Kaur — Tue, 01 Nov 2022 00:00:00 +0000

Tuesday, November 1, 2022

En français

Congratulations to Megan Byres who has been chosen as the recipient of the 2022 Raymond Laflamme and Janice Gregson Graduate Scholarship for Women in Quantum Information Science.

Liang Fu and Patrick Lee receive Larkin Awards in Theoretical Physics

Sandi Miller | Department of Physics — Mon, 31 Oct 2022 20:45:00 +0000

MIT condensed matter theory professors of physics Liang Fu and Patrick A. Lee received the inaugural Larkin Awards in Theoretical Physics, awarded by the William I. Fine Theoretical Physics Institute at the University of Minnesota.

Fu received the 2022 Anatoly Larkin Award for a junior researcher for his work on 3D topological insulators and odd-parity topological superconductors, crystalline topological insulators, and Majorana zero modes, “and for being an intellectual leader of his generation.”

Fu is interested in novel topological phases of matter in solid state physics to predict new phases of matter and topological materials. He works on the theory of topological insulators and topological superconductors, and the potential applications of topological materials, ranging from tunable electronics and spintronics to quantum computation.

He received his BS in physics from the University of Science and Technology of China in 2004 and his PhD in physics from the University of Pennsylvania in 2009. He was a junior fellow at Harvard University before joining the MIT Department of Physics as an assistant professor in 2012.

His previous awards include the 2018 Simons Investigator Award, the 2016 New Horizons in Physics Prize, the 2014 Raymond and Beverly Sackler International Prize in Physics, the 2014 Packard Fellowship for Science and Engineering, and the 2013 Department of Energy Early Career Award.

“I am truly honored and grateful to receive the Larkin junior award,” says Fu. “I also thank my mentors, collaborators, and students for their contribution and support over the years.”

Lee, the William & Emma Rogers Professor of Physics, received the 2022 Anatoly Larkin Senior Researcher Award in Theoretical Physics for his influential research in strongly correlated electronic systems, which are materials where the interactions between electrons play a crucial role and lead to novel phenomena not explainable by single electron band structure effects.

The award mentioned his theories of the quantum transport phenomena in mesoscopic and superconducting systems, “and for his standing in the community.”

As a senior researcher in the Condensed Matter Theory Group, Lee’s interests are focused on high-temperature superconductors as well as “mesoscopic physics,” the study of small devices at low temperatures. He has also made important contributions to the theory of disordered electronic systems, including introducing the concept of universal conductance fluctuations to describe such small devices.

A native of Hong Kong, Lee studied physics at MIT, receiving his BS in 1966 and his PhD in 1970. He was a physics instructor at Yale University until 1972, and an assistant professor of physics at the University of Washington until 1974. He was at the Theoretical Physics Department at Bell Laboratories for 10 years until joining the MIT Department of Physics in 1982. Lee was awarded the 2005 Dirac Medal of the International Centre for Theoretical Physics and the 1991 Oliver Buckley Prize of the American Physical Society.

The award is named after the late Russian-American theoretical physicist Anatoly Larkin. Lee says that he has been a long-time admirer of Larkin, with whom he collaborated on several publications.

The awardees are invited to deliver a colloquium for the School of Physics and Astronomy at the University of Minnesota in March 2023.

Breakthrough in optical information transmission

Mon, 31 Oct 2022 17:40:13 +0000

Scientists have managed for the first time to create a unidirectional device that significantly increases the quality of a special class of transmitted signals in optical communications: optical vortices. By transmitting selective optical vortex modes exclusively unidirectionally, the developed device largely reduces detrimental backscattering to a minimum. The scientists emphasize the great practical utility of their discovery in many optical systems, with applications ranging from mode division multiplexed communications, optical tweezers, vortex lasers to quantum manipulation systems.

Oh right, quantum computing

Scott — Mon, 31 Oct 2022 05:26:35 +0000

These days, I often need to remind myself that, as an undergrad, grad student, postdoc, or professor, I’ve now been doing quantum computing research for a quarter-century—i.e., well over half of the subject’s existence. As a direct result, when I feel completely jaded about a new development in QC, it might actually be exciting. When I feel moderately excited, it might actually be the most exciting thing for years.

With that in mind:

(1) Last week National Public Radio’s Marketplace interviewed me, John Martinis, and others about the current state of quantum computing. While the piece wasn’t entirely hype-free, I’m pleased to report that my own views were represented accurately! To wit:

“There is a tsunami of hype about what quantum computers are going to revolutionize,” said Scott Aaronson, a professor of computer science at the University of Texas at Austin. “Quantum computing has turned into a word that venture capitalists or people seeking government funding will sprinkle on anything because it sounds good.”
Aaronson warned we can’t be certain that these computers will in fact revolutionize machine learning and finance and optimization problems. “We can’t prove that there’s not a quantum algorithm that solves all these problems super fast, but we can’t even prove there’s not an algorithm for a conventional computer that does it,” he said. [In the recorded version, they replaced this by a simpler but also accurate thought: namely, that we can’t prove one way or the other whether there’s a useful quantum advantage for these tasks.]

(2) I don’t like to use this blog to toot my own research horn, but on Thursday my postdoc Jason Pollack and I released a paper, entitled Discrete Bulk Reconstruction. And to be honest, I’m pretty damned excited about it. It represents about 8 months of Jason—a cosmologist and string theorist who studied under Sean Carroll—helping me understand AdS/CFT in the language of the undergraduate CS curriculum, like min-cuts on undirected graphs, so that we could then look for polynomial-time algorithms to implement the holographic mapping from boundary quantum states to the spatial geometry in the bulk. We drew heavily on previous work in the same direction, especially the already-seminal 2015 holographic entropy cone paper by Ning Bao et al. But I’d like to think that, among other things, our work represents a new frontier in just how accessible AdS/CFT itself can be made to CS and discrete math types. Anyway, here’s the abstract if you’re interested:

According to the AdS/CFT correspondence, the geometries of certain spacetimes are fully determined by quantum states that live on their boundaries — indeed, by the von Neumann entropies of portions of those boundary states. This work investigates to what extent the geometries can be reconstructed from the entropies in polynomial time. Bouland, Fefferman, and Vazirani (2019) argued that the AdS/CFT map can be exponentially complex if one wants to reconstruct regions such as the interiors of black holes. Our main result provides a sort of converse: we show that, in the special case of a single 1D boundary, if the input data consists of a list of entropies of contiguous boundary regions, and if the entropies satisfy a single inequality called Strong Subadditivity, then we can construct a graph model for the bulk in linear time. Moreover, the bulk graph is planar, it has O(N²) vertices (the information-theoretic minimum), and it’s “universal,” with only the edge weights depending on the specific entropies in question. From a combinatorial perspective, our problem boils down to an “inverse” of the famous min-cut problem: rather than being given a graph and asked to find a min-cut, here we’re given the values of min-cuts separating various sets of vertices, and need to find a weighted undirected graph consistent with those values. Our solution to this problem relies on the notion of a “bulkless” graph, which might be of independent interest for AdS/CFT. We also make initial progress on the case of multiple 1D boundaries — where the boundaries could be connected via wormholes — including an upper bound of O(N⁴) vertices whenever a planar bulk graph exists (thus putting the problem into the complexity class NP).

(3) Anand Natarajan and Chinmay Nirkhe posted a preprint entitled A classical oracle separation between QMA and QCMA, which makes progress on a problem that’s been raised on this blog all the way back to its inception. A bit of context: QMA, Quantum Merlin-Arthur, captures what can be proven using a quantum state with poly(n) qubits as the proof, and a polynomial-time quantum algorithm as the verifier. QCMA, or Quantum Classical Merlin-Arthur, is the same as QMA except that now the proof has to be classical. A fundamental problem of quantum complexity theory, first raised by Aharonov and Naveh in 2002, is whether QMA=QCMA. In 2007, Greg Kuperberg and I introduced the concept of quantum oracle separation—that is, a unitary that can be applied in a black-box manner—in order to show that there’s a quantum oracle relative to which QCMA≠QMA. In 2015, Fefferman and Kimmel improved this, to show that there’s a “randomized in-place” oracle relative to which QCMA≠QMA. Natarajan and Nirkhe now remove the “in-place” part, meaning the only thing still “wrong” with their oracle is that it’s randomized. Derandomizing their construction would finally settle this 20-year-old open problem (except, of course, for the minor detail of whether QMA=QCMA in the “real,” unrelativized world!).

(4) Oh right, the Google group reports the use of their superconducting processor to simulate non-abelian anyons. Cool.

On Bryan Caplan and his new book

Scott — Fri, 28 Oct 2022 16:54:52 +0000

Yesterday I attended a lecture by George Mason University economist Bryan Caplan, who’s currently visiting UT Austin, about his new book entitled Don’t Be a Feminist. (See also here for previous back-and-forth between me and Bryan about his book.) A few remarks:

(1) Maybe surprisingly, there were no protesters storming the lectern, no security detail, not even a single rotten vegetable thrown. About 30 people showed up, majority men but women too. They listened politely and asked polite questions afterward. One feminist civilly challenged Bryan during the Q&A about his gender pay gap statistics.

(2) How is it that I got denounced by half the planet for saying once, in a blog comment, that I agreed with 97% of feminism but had concerns with one particular way it was operationalized, whereas Bryan seems to be … not denounced in the slightest for publishing a book and going on a lecture tour about how he rejects feminism in its entirety as angry and self-pitying in addition to factually false? Who can explain this to me?

(3) For purposes of his argument, Bryan defines feminism as “the view that women are generally treated less fairly than men,” rather than (say) “the view that men and women ought to be treated equally,” or “the radical belief that women are people,” or other formulations that Bryan considers too obvious to debate. He then rebuts feminism as he’s defined it, by taking the audience on a horror tour of all the ways society treats men less fairly than women (expectations of doing dirty and dangerous work, divorce law, military drafts as in Ukraine right now, …), as well as potentially benign explanations for apparent unfairness toward women, to argue that it’s at least debatable which sex gets the rawer deal on average.

During the Q&A, I raised what I thought was the central objection to Bryan’s relatively narrow definition of feminism. Namely that, by the standards of 150 years ago, Bryan is obviously a feminist, and so am I, and so is everyone in the room. (Whereupon a right-wing business school professor interjected: “please don’t make assumptions about me!”)

I explained that this is why I call myself a feminist, despite agreeing with many of Bryan’s substantive points: because I want no one to imagine for a nanosecond that, if I had the power, I’d take gender relations back to how they were generations ago.

Bryan replied that >60% of Americans call themselves non-feminists in surveys. So, he asked me rhetorically, do all those Americans secretly yearn to take us back to the 19th century? Such a position, he said, seemed so absurdly uncharitable as not to be worth responding to.

Reflecting about it on my walk home, I realized: actually, give or take the exact percentages, this is precisely the progressive thesis. I.e., that just like at least a solid minority of Germans turned out to be totally fine with Nazism, however much they might’ve denied it beforehand, so too at least a solid minority of Americans would be fine with—if not ecstatic about—The Handmaid’s Tale made real. Indeed, they’d add, it’s only vociferous progressive activism that stands between us and that dystopia.

And if anyone were tempted to doubt this, progressives might point to the election of Donald Trump, the failed insurrection to maintain his power, and the repeal of Roe as proof enough to last for a quadrillion years.

Bryan would probably reply: why even waste time engaging with such a hysterical position? To me, though, the hysterical position sadly has more than a grain of truth to it. I wish we lived in a world where there was no point in calling oneself a pro-democracy anti-racist feminist and a hundred other banal and obvious things. I just don’t think that we do.

New form of universal quantum computers

Fri, 28 Oct 2022 15:15:40 +0000

Computing power of quantum machines is currently still very low. Increasing it is still proving to be a major challenge. Physicists now present a new architecture for a universal quantum computer that overcomes such limitations and could be the basis of the next generation of quantum computers soon.

New hybrid structures could pave the way to more stable quantum computers

Thu, 27 Oct 2022 16:39:29 +0000

A new way to combine two materials with special electrical properties -- a monolayer superconductor and a topological insulator -- provides the best platform to date to explore an unusual form of superconductivity called topological superconductivity. The combination could provide the basis for topological quantum computers that are more stable than their traditional counterparts.

Subatomic MRI could lead to new drug therapies

Elizabeth Kleisath — Thu, 27 Oct 2022 00:00:00 +0000

Thursday, October 27, 2022

A new imaging technique using quantum science may lead to novel drug therapies and treatment options, a recent study has found.

A faster experiment to find and study topological materials

David L. Chandler | MIT News Office — Wed, 26 Oct 2022 13:00:00 +0000

Topological materials, an exotic class of materials whose surfaces exhibit different electrical or functional properties than their interiors, have been a hot area of research since their experimental realization in 2007 — a finding that sparked further research and precipitated a Nobel Prize in Physics in 2016. These materials are thought to have great potential in a variety of fields, and might someday be used in ultraefficient electronic or optical devices, or key components of quantum computers.

But there are many thousands of compounds that may theoretically have topological characteristics, and synthesizing and testing even one such material to determine its topological properties can take months of experiments and analysis. Now a team of researchers at MIT and elsewhere have come up with a new approach that can rapidly screen candidate materials and determine with more than 90 percent accuracy whether they are topological.

Using this new method, the researchers have produced a list candidate materials. A few of these were already known to have topological properties, but the rest are newly predicted by this approach.

The findings are reported in the journal Advanced Materials in a paper by Mingda Li, the Class ’47 Career Development Professor at MIT, graduate students (and twin sisters) Nina Andrejevic at MIT and Jovana Andrejevic at Harvard University, and seven others at MIT, Harvard, Princeton University, and Argonne National Laboratory.

Topological materials are named after a branch of mathematics that describes shapes based on their invariant characteristics, which persist no matter how much an object is continuously stretched or squeezed out of its original shape. Topological materials, similarly, have properties that remain constant despite changes in their conditions, such as external perturbations or impurities.

There are several varieties of topological materials, including semiconductors, conductors, and semimetals, among others. Initially, it was thought that there were only a handful of such materials, but recent theory and calculations have predicted that in fact thousands of different compounds may have at least some topological characteristics. The hard part is figuring out experimentally which compounds may be topological.

Applications for such materials span a wide range, including devices that could perform computational and data storage functions similarly to silicon-based devices but with far less energy loss, or devices to harvest electricity efficiently from waste heat, for example in thermal power plants or in electronic devices. Topological materials can also have superconducting properties, which could potentially be used to build the quantum bits for topological quantum computers.

But all of this relies on developing or discovering the right materials. “To study a topological material, you first have to confirm whether the material is topological or not,” Li says, “and that part is a hard problem to solve in the traditional way.” A method called density functional theory is used to perform initial calculations, which then need to be followed with complex experiments that require cleaving a piece of the material to atomic-level flatness and probing it with instruments under high-vacuum conditions. “Most materials cannot even be measured due to various technical difficulties,” Nina Andrejevic says. But for those that can, the process can take a long time. “It’s a really painstaking procedure,” she says.

Whereas the traditional approach relies on measuring the material’s photoemissions or tunneling electrons, Li explains, the new technique he and his team developed relies on absorption, specifically, the way the material absorbs X-rays. Unlike the expensive apparatus needed for the conventional tests, X-ray absorption spectrometers are readily available and can operate at room temperature and atmospheric pressure, with no vacuum needed. Such measurements are widely conducted in biology, chemistry, battery research, and many other applications, but they had not previously been applied to identifying topological quantum materials.

X-ray absorption spectroscopy provides characteristic spectral data from a given sample of material. The next challenge is to interpret that data and how it relates to the topological properties. For that, the team turned to a machine-learning model, feeding in a collection of data on the X-ray absorption spectra of known topological and nontopological materials, and training the model to find the patterns that relate the two. And it did indeed find such correlations.

“Surprisingly, this approach was over 90 percent accurate when tested on more than 1500 known materials,” Nina Andrejevic says, adding that the predictions take only seconds. “This is an exciting result given the complexity of the conventional process.”

Though the model works, as with many results from machine learning, researchers don’t yet know exactly why it works or what the underlying mechanism is that links the X-ray absorption to the topological properties. “While the learned function relating X-ray spectra to topology is complex, the result may suggest that certain attributes the measurement is sensitive to, such as local atomic structures, are key topological indicators,” Jovana Andrejevic says.

The team has used the model to construct a periodic table that displays the model’s overall accuracy on compounds made from each of the elements. It serves as a tool to help researchers home in on families of compounds that may offer the right characteristics for a given application. The researchers have also produced a preliminary study of compounds that they have used this X-ray method on, without advance knowledge of their topological status, and compiled a list of 100 promising candidate materials — a few of which were already known to be topological.

“This work represents one of the first uses of machine learning to understand what experiments are trying to tell us about complex materials,” says Joel Moore, the Chern-Simons Professor of Physics at the University of California at Berkeley, who was not associated with this research. “Many kinds of topological materials are well-understood theoretically in principle, but finding material candidates and verifying that they have the right topology of their bands can be a challenge. Machine learning seems to offer a new way to address this challenge: Even experimental data whose meaning is not immediately obvious to a human can be analyzed by the algorithm, and I am excited to see what new materials will result from this way of looking.”

Anatoly Frenkel, a professor in the Department of Materials Science and Chemical Engineering at Stony Brook University and a senior chemist at Brookhaven National Laboratory, further commented that “It was a really nice idea to consider that the X-ray absorption spectrum may hold a key to the topological character in the measured sample.”

The research team included Andrei Bernevig and Nicolas Regnault at Princeton University, Fei Han and Thanh Nguyen and Nathan Drucker at MIT, Chris Rycroft at Harvard University, and Gilberto Fabbris at Argonne National Laboratory. The work was supported by the U.S. Department of Energy and National Science Foundation.

Miniaturized infrared detectors

Tue, 25 Oct 2022 15:25:49 +0000

Extreme miniaturization of infrared (IR) detectors is critical for their integration into next-generation consumer electronics, wearables and ultra-small satellites. Thus far, however, IR detectors have relied on bulky (and expensive) materials and technologies. A team of scientists has now succeeded in developing a cost-effective miniaturization process for IR spectrometers based on a quantum dot photodetector, which can be integrated on a single chip.

Advance brings quantum computing one step closer to implementation

Fri, 21 Oct 2022 17:27:31 +0000

Researchers identified possible solutions to some of the limitations of qubits for quantum computing. They looked at two different hybrid quantum systems: an electron-superconducting circuit and an electron-ion coupled system. Both systems were able to control the temperature and the movement of the electron.

New measurements quantifying qudits provide glimpse of quantum future

Thu, 13 Oct 2022 18:56:36 +0000

Using existing experimental and computational resources, a multi-institutional team has developed an effective method for measuring high-dimensional qudits encoded in quantum frequency combs, which are a type of photon source, on a single optical chip.

Making quantum computers more accurate

Rachel Yang | MIT News correspondent — Thu, 13 Oct 2022 04:00:00 +0000

In Building 13 on MIT’s campus, there sits a half-a-million-dollar piece of equipment that looks like a long stretched-out chandelier, with a series of gold discs connected by thin silver pipes. The equipment, known as a dilution refrigerator, is a key player in PhD student Alex Greene’s research, as it houses all their experiments. “My life gets shaped around its rhythms,” they say.

The first time Greene helped put new samples in the fridge, they were working with a postdoc at midnight on a Friday, blasting Danish screamo music. Ever since, the fridge has led them on both exciting and frustrating adventures throughout their PhD research on reducing errors in quantum computing systems.

Greene grew up in northern New Jersey with their identical twin, Jamie. The two were extremely competitive as children, and outside of school, they stayed busy through running, pole vaulting, and rock climbing. Their dad is a neurologist and their mom is a former electrical engineer who worked at Bell Labs, a research lab known for pioneering key technology for computers and phones.

In 2010, Alex and Jamie both came to MIT as undergraduates. Alex had been interested in biomedical engineering during high school, “But then I discovered that I hate working in ‘wet’ labs,” where scientists handle chemicals and biological materials, they say. Another influence was Carl Sagan’s “Contact,” a science fiction book about an astronomer searching for extraterrestrial intelligence. “It got me hooked on physics,” Greene says.

As an MIT undergraduate, Greene double-majored in physics and in electrical engineering and computer science. They found a home in the field of quantum computing, where researchers are working to build extremely powerful computers by leveraging physics concepts in quantum mechanics.

Greene stayed at MIT to pursue an MEng in quantum computing, working at the Lincoln Laboratory. There, they researched ways to improve a technology called trapped ion quantum computing, which uses atoms suspended in the air and controlled by lasers.

After completing their master’s, they pivoted to a different technology called superconducting quantum computing. Instead of suspended atoms, this technology uses tiny electric circuits that are exceptional at carrying electric current. To control these circuits, researchers only need to send electric signals.

For this project, Greene wanted to work with MIT Professor William Oliver, who directs the Center for Quantum Engineering in the Research Laboratory of Electronics. Once again, Greene chose to stay at the Institute — this time to pursue their PhD.

Adding randomness to quantum computers

Someday, quantum computers might solve problems beyond the reach of normal classical computers, enabling immense progress in many applications. However, manipulating hardware so it exhibits quantum behavior is challenging from a technological perspective. Currently, quantum computers, including superconducting ones, struggle with high error rates that limit the length and complexity of the “programs” they can run. Most experimental research in quantum computing is focused on addressing those errors.

Greene is working to make superconducting quantum computers more accurate by reducing the impact of these errors. To test their ideas, they need to run experiments on superconducting circuits. But for these circuits to work, they need to be cooled down to extremely low temperatures, around -273.13 degrees Celsius — within 0.02 degrees away from the coldest possible temperature in the universe.

This is where the chandelier-like dilution fridge comes into play. The fridge can easily reach the required cold temperatures. But sometimes it misbehaves, sending Greene on side quests to fix its problems.

Greene’s most arduous side quest involved chasing down a leak in one of the fridge’s pipes. The pipes carry an expensive and rare gas mixture used to cool the fridge, which Greene couldn’t afford to lose. Fortunately, even with the leak, the fridge was designed to remain functional without losing any mixture for around two weeks at a time. But, to keep the fridge in service, Greene had to constantly restart and clean it over a five-day process. After roughly seven stressful months, Greene and their lab mate finally located and fixed the leak, allowing Greene to resume their research at full speed.

To strategize how to effectively improve the accuracy of superconducting quantum computers, Greene needed to first take stock of the different types of errors in these systems. In quantum computing, there are two categories of errors: incoherent and coherent errors. Incoherent errors are random errors that occur even when the quantum computer is idling, while coherent errors are caused by imperfect control of the system. In quantum computers, coherent errors are often the worst culprits in system inaccuracies; researchers have mathematically shown that coherent errors compound much faster than incoherent errors.

To avoid the nasty compounding inaccuracies of coherent errors, Greene employed a clever tactic: disguising these errors to look like incoherent errors. “If you [strategically] introduce a little bit of randomness into superconducting circuits,” you can get coherent errors to compound as slowly as incoherent errors, they say. Other researchers in the field are also employing randomness tactics in different ways, Greene notes. Nevertheless, through their research, Greene is helping to pave the way for more accurate superconducting quantum computers.

Improving water sanitation in Pakistan

Outside of research, Greene is constantly engaged in a whirlwind of activities, adding new hobbies while painstakingly removing old ones to make room in their busy schedule. Over the years, their hobbies have included glassblowing, singing in a local queer choir, and competitive rock climbing. Currently, they spend their weekends working on home improvement projects with their partner at their rainbow-colored co-op.

For the past year and a half, Greene has also been involved with water sanitation projects through classes with MIT D-Lab, a project-based program aimed at helping poor communities around the world. Taking classes in D-Lab was “something that I always wanted to do from undergrad but I never had time for it,” they say. They were finally able to fit D-Lab into their schedule by using the classes to help fulfill their PhD requirements.

For one project, they’re developing a system to effectively and cheaply filter out harmful excess fluoride from water supplies in Pakistan. “It’s unintuitive that fluoride is bad because we have fluoride in our toothpaste,” they say. “But actually, too much fluoride changes the hardness of your teeth and bones.” One idea that they and their collaborators are exploring is to build a water filtration system using clay, an established yet cheap fluoride removal method.

A visiting assistant professor from Pakistan, who was participating in the D-Lab class, had originally pitched the fluoride filtration project. When the class ended, the professor returned to Pakistan but still kept the project going. Greene is now working virtually with the professor to help figure out the best type of clay for filtering out fluoride. Through their experiences with D-Lab, Greene sees themselves continuing to volunteer on water sanitation projects in the long term.

Greene plans to finish their PhD this December. After 12 years at MIT, Greene aims to leave the Institute to work at a quantum computing company. “It’s a really great time to be in the field” in industry, they say. “Companies are starting to scale up [quantum computing] technology.”

Explanation-Gödel and Plausibility-Gödel

Scott — Wed, 12 Oct 2022 21:52:31 +0000

Here’s an observation that’s mathematically trivial but might not be widely appreciated. In kindergarten, we all learned Gödel’s First Incompleteness Theorem, which given a formal system F, constructs an arithmetical encoding of

G(F) = “This sentence is not provable in F.”

If G(F) is true, then it’s an example of a true arithmetical sentence that’s unprovable in F. If, on the other hand, G(F) is false, then it’s provable, which means that F isn’t arithmetically sound. Therefore F is either incomplete or unsound.

Many have objected: “but despite Gödel’s Theorem, it’s still easy to explain why G(F) is true. In fact, the argument above basically already did it!” You might make a more general point: there are many, many mathematical statements for which we currently lack a proof, but we do seem to have a fully convincing heuristic explanation: one that “proves the statement to physics standards of rigor.” For example:

The Twin Primes Conjecture (there are infinitely many primes p for which p+2 is also prime).
The Collatz Conjecture (the iterative process that maps each positive integer n to n/2 if n is even, or to 3n+1 if n is odd, eventually reaches 1 regardless of which n you start at).
π is a normal number (or even just: the digits 0-9 all occur with equal limiting frequencies in the decimal expansion of π).
π+e is irrational.

And so on. No one has any idea how to prove any of the above statements—and yet, just on statistical grounds, it seems clear that it would require a ludicrous conspiracy to make any of them false.

Conversely, one could argue that there are statements for which we do have a proof, even though we lack a “convincing explanation” for the statements’ truth. Maybe the Four-Color Theorem or Hales’s Theorem, for which every known proof requires a massive computer enumeration of cases, belong to this class. Other people might argue that, given a proof, an explanation could always be extracted with enough time and effort, though resolving this dispute won’t matter for what follows.

You might hope that, even if some true mathematical statements can’t be proved, every true statement might nevertheless have a convincing heuristic explanation. Alas, a trivial adaptation of Gödel’s Theorem shows that, if (1) heuristic explanations are to be checkable by computer, and (2) only true statements are to have convincing heuristic explanations, then this isn’t possible either. I mean, let E be a program that accepts or rejects proposed heuristic explanations, for statements like the Twin Prime Conjecture or the Collatz Conjecture. Then construct the sentence

S(E) = “This sentence has no convincing heuristic explanation accepted by E.”

If S(E) is true, then it’s an example of a true arithmetical statement without even a convincing heuristic explanation for its truth (!). If, on the other hand, S(E) is false, then there’s a convincing heuristic explanation of its truth, which means that something has gone wrong.

What’s happening, of course, is that given the two conditions we imposed, our “heuristic explanation system” was a proof system, even though we didn’t call it one. This is my point, though: when we use the word “proof,” it normally invokes a specific image, of a sequence of statements that marches from axioms to a theorem, with each statement following from the preceding ones by rigid inference rules like those of first-order logic. None of that, however, plays any direct role in the proof of the Incompleteness Theorem, which cares only about soundness (inability to prove falsehoods) and checkability by a computer (what, with hindsight, Gödel’s “arithmetization of syntax” was all about). The logic works for “heuristic explanations” too.

Now we come to something that I picked up from my former student (and now AI alignment leader) Paul Christiano, on a recent trip to the Bay Area, and which I share with Paul’s kind permission. Having learned that there’s no way to mechanize even heuristic explanations for all the true statements of arithmetic, we could set our sights lower still, and ask about mere plausibility arguments—arguments that might be overturned on further reflection. Is there some sense in which every true mathematical statement at least has a good plausibility argument?

Maybe you see where this is going. Letting P be a program that accepts or rejects proposed plausibility arguments, we can construct

S(P) = “This sentence has no argument for its plausibility accepted by P.”

If S(P) is true, then it’s an example of a true arithmetical statement without even a plausibility argument for its truth (!). If, on the other hand, S(P) is false, then there is a plausibility argument for it. By itself, this is not at all a fatal problem: all sorts of false statements (IP≠PSPACE, switching doors doesn’t matter in Monty Hall, Trump couldn’t possibly become president…) have had decent plausibility arguments. Having said that, it’s pretty strange that you can have a plausibility argument that’s immediately contradicted by its own existence! This rules out some properties that you might want your “plausibility system” to have, although maybe a plausibility system exists that’s still nontrivial and that has weaker properties.

Anyway, I don’t know where I’m going with this, or even why I posted it, but I hope you enjoyed it! And maybe there’s something to be discovered in this direction.

Seeing electron movement at fastest speed ever could help unlock next-level quantum computing

Wed, 12 Oct 2022 17:25:02 +0000

The key to maximizing traditional or quantum computing speeds lies in our ability to understand how electrons behave in solids, and researchers have now captured electron movement in attoseconds--the fastest speed yet.

Professor Danna Freedman receives 2022 MacArthur Fellowship

Anne Trafton | MIT News Office — Wed, 12 Oct 2022 16:00:00 +0000

Danna Freedman, the F.G. Keyes Professor of Chemistry at MIT, and Moriba Jah, a Martin Luther King Jr. Visiting Scholar, have been named recipients of a 2022 MacArthur Fellowship.

Often referred to as “genius grants,” the fellowships come with a five-year, $800,000 prize, which recipients are free to use as they see fit. Freedman, who found out about the award in early September, before it was publicly announced, said she was “completely in shock” after hearing that she had been chosen for the fellowship.

“There are so many parts of being an academic that involve explicitly asking for letters of recommendation, when you know you’re going through a process like tenure, or evaluation for a fellowship. But with this, someone took it upon themselves to recommend me, and other people who I will never know wrote letters for me. It’s so unbelievably kind,” she says.

Freedman, whose research focuses on using inorganic chemistry to create new molecules for quantum information science, joined the MIT faculty in 2021. Before coming to MIT, she was a professor of chemistry at Northwestern University.

“When I was looking at new opportunities at the post-tenure, mid-career stage, I wanted to expand beyond the research that could be done just in my lab, to larger teams. And everyone I talked to at MIT just expanded every idea until it was so full of possibility,” she says. “It’s such an inspirational place.”

At MIT, Freedman designs molecules that can function as quantum units, or qubits. Applications for these kinds of molecules include quantum sensing and communication. Quantum sensors consist of systems in which some particles are in such a delicately balanced state that they are affected by miniscule variations in their environments. This allows them to detect tiny changes in electric and magnetic fields, as well physical properties of nanometer-scale systems.

Quantum sensors can be used to investigate exotic states of matter, or to characterize quantum computers or quantum memory devices.

“Molecules are uniquely suited for a lot of quantum sensing applications and for quantum communication applications,” Freedman says. “You can use a molecule to put atoms exactly where you want them to be and then tune them so you can get a whole array of properties, and that combination is incredibly powerful for applications where specificity is important.”

Freedman uses molecular chemistry to create qubits from the electron spin of paramagnetic coordination complexes — molecules with a metallic central atom surrounded by bonded molecules or ions, known as ligands. She has shown that the quantum properties of such complexes can be controlled using specific ligands and by adjusting the strength of the bonds connecting the ligands to the central metal atom.

In one recent paper, she and others reported that qubits containing a central chromium atom surrounded by four hydrocarbon molecules could be customized to interact with specific targets for quantum sensing and communication.

One direction she hopes to pursue with help from the MacArthur funding is working with scientists from other fields to develop sensors that would be useful in those fields, such as neurobiology or Earth sciences.

“What I’m passionate about moving forward is, if we’re going to push the community on sensing, we need to have a larger buy-in from the end-users of these applications. We need to bring in anyone who could benefit from the quantum advantage of measurement and see what features are essential and what features you can compromise on,” she says.

Freedman has garnered many other honors, including Presidential Early Career Awards for Scientists and Engineers through the U.S. Department of Defense and the National Science Foundation. She also received the American Chemical Society Award in Pure Chemistry in 2019 and the Camille-Dreyfus Teacher-Scholar Award in 2018.

She received her PhD from the University of California at Berkeley in 2009 and did postdoctoral research at MIT with former professor Daniel Nocera before joining the faculty at Northwestern in 2012.

Moriba Jah is an associate professor in the Aerospace Engineering and Engineering Mechanics Department at the University of Texas at Austin whose research interests include space sustainability and space traffic management.

As an MLK Visiting Scholar, he is hosted by Assistant Professor Danielle Wood in Media Arts and Sciences and the Department of Aeronautics and Astronautics, and Richard Linares in the Department of Aeronautics and Astronautics.

At MIT, he is developing and strengthening a joint MIT/UT-Austin research program to increase resources and visibility of space sustainability. Jah is also helping to host the AeroAstro Rising Stars symposium, which highlights graduate students, postdocs, and early-career faculty from backgrounds underrepresented in aerospace engineering.

Other MIT faculty members who have won MacArthur Fellowships in recent years include geologist Taylor Perron (2021); brain and cognitive scientist Joshua Tenenbaum (2019); health care economist Amy Finkelstein and media studies scholar Lisa Parks (2018); computer scientist Regina Barzilay (2017); and economist Heidi Williams (2015).

Researchers find simple method for creating 3-dimensional bridge structures on microchips

Elizabeth Kleisath — Wed, 12 Oct 2022 00:00:00 +0000

Wednesday, October 12, 2022

Researchers Noah Janzen and Adrian Lupascu from the Institute for Quantum Computing (IQC) have found a new one-step process to construct tiny bridge structures on microchips with superconducting circuits.

Physicists use 'electron correlations' to control topological materials

Tue, 11 Oct 2022 20:12:29 +0000

Topological states have stable, immutable features of great interest for quantum computing and communications, and physicists from the United States and Europe have now discovered how to switch a topological state on and off. The control is made possible by strong electron correlations, which create extreme responsiveness.