Inside How IBM engineers design quantum computers

A few weeks ago, I woke up unusually early in the morning in Brooklyn, got in my car, and drove up the Hudson River to the small Westchester County community of Yorktown Heights. There, amid rolling hills and old farmhouses, sits the Thomas J. Watson Research Center Designed by Eero SaarinenHeadquarters for IBM Research in the Jet Age in the 1960s.

Inside that building, through endless corridors and security gates manned by iris scanners, company scientists are working hard to develop what IBM Research Director Dario Gill told me, the “next branch of computing”: quantum computers.

I was at the Watson Center for an IBM preview Updated technical roadmap To achieve large-scale and practical quantum computing. This included quite a bit of talk about ‘qubits’, ‘quantum coherence’, ‘error mitigation’, ‘software coordination’ and other topics you would need to be an electrical engineer with a background in computer science and knowledge of quantum mechanics to fully follow.

I’m neither of those things, but I have I watched the quantum computing space long enough To find out that the work that IBM researchers are doing here — along with their competitors at companies like Google and Microsoft, along with countless startups around the world — would drive the next big leap in computing. Since computing is a “horizontal technology that touches everything,” Gilles tells me, it will have major implications for advances in everything from cyber security to Artificial intelligence to Better battery design.

Provided, of course, that they can actually make these things work.

Entering the quantum world

The best way to understand a quantum computer — apart from dedicating several years to graduate school at MIT or Caltech — is to compare it to the kind of machine I’m writing this piece on. on: classic computer.

My MacBook Air runs on the M1 chip that is packed with 16 billion transistors. Each of these transistors can represent either a “1” or a “0” of binary information simultaneously – a bit. The sheer number of transistors is what gives the machine its computing power.

Sixteen billion transistors packed into a 120.5 mm square chip is plenty – TRADIC, the first transistor computer, less than 800. The semiconductor industry’s ability to engineer more transistors on a chip, a trend predicted by Intel co-founder Gordon Moore in The law that bears his nameis what made the exponential growth of computing power possible, which in turn made pretty much everything else possible.

The exterior of an IBM System One quantum computer, as seen in the Thomas J. Watson Research Center.
Brian Walsh/Fox

But there are things that classic computers cannot and will never be able to do, no matter how many transistors are stuffed into a silicon box at a Taiwanese semiconductor manufacturing plant (or “Fab” in industry parlance). This is where the unique and strange properties of quantum computers come in.

Instead of qubits, quantum computers process information using qubits, which can represent “0” and “1” simultaneously. How do they do it? You’re straining my level of expertise here, but essentially qubits benefit from a quantum mechanics phenomenon known as “superposition,” in which the properties of some subatomic particles are not determined until they are measured. Think of Schrödinger’s cat, Alive and dead at the same time Until she opens her box.

Single qubits are nice, but things get really interesting as you start adding more. Classical computing power increases linearly with each transistor added, but the power of a quantum computer increases exponentially With the addition of each new reliable qubit. This is due to another quantum mechanical property called “entanglement,” in which the individual possibilities of each qubit can be influenced by other qubits in the system.

All of this means that the upper limit of a practical quantum computer’s power far exceeds what would be possible in classical computing.

So quantum computers can theoretically solve problems that a classical computer, no matter how powerful, cannot. What kind of problem? What about the fundamental nature of physical reality, which, after all, ultimately operates on quantum mechanics, not classical mechanics? (Sorry Newton.) “Quantum computers simulate problems we find in nature and in chemistry,” said Jay Gambetta, IBM’s vice president for quantum computing.

Quantum computers can simulate the properties of a theoretical battery to help design a battery that is far more efficient and powerful than today’s versions. They can solve complex logistical problems, discover optimal delivery methods, or improve forecasts for climate science.

On the security side, quantum computers can crack encryption methods, potentially making everything from emails to financial data to national secrets insecure — which is why the race for quantum supremacy is also an international, competition The Chinese government is pumping billions into. Those concerns helped push the White House earlier this month to… Issuing a new note To build national leadership in quantum computing and prepare the country for quantum-assisted cybersecurity threats.

Beyond security issues, the potential financial gain can be significant. Companies are already providing early quantum computing services via the cloud for Clients like ExxonMobil and the Spanish Bank BBVA. While the global quantum computing market was worth less than $500 million in 2020, International Data Corporation projects It will reach $8.6 billion in revenue by 2027, with more than $16 billion in investments.

But none of that will be possible unless researchers can do the hard engineering work of turning the quantum computer from what remains largely a science experiment into a credible industry.

cold room

Inside the Watson Building, Jerry Chow—who runs IBM’s Experimental Quantum Computer Center—opens a 9-foot glass cube to show me something that looks like a gold chandelier: IBM’s Quantum System One. Much of the Chandelier is a high-tech refrigerator, with super-fluid-carrying coils capable of cooling appliances to 100 degrees Celsius above absolute zero—cooler than outer space, Zhao told me.

Cooling is key to making IBM’s quantum computers work, and it also shows why doing so is an engineering challenge. While quantum computers are likely to be much more powerful than their classical counterparts, they are also much more difficult.

Remember what I said about the quantum properties of superposition and entanglement? While qubits can do things you can’t even dream of, the slightest difference in temperature, noise, or radiation can cause them to lose those properties through something called decoherence.

This massive cooling is designed to keep the system’s qubits from being decoded before the computer has completed its calculations. Older superconducting qubits lost coherence in less than a nanosecond, while today’s most advanced quantum computers from IBM can maintain coherence for up to 400 microseconds. (Every second contains one million microseconds.)

The challenge for IBM and other companies, Zhao said, is to engineer quantum computers that are less error-prone while “scaling systems beyond thousands or even tens of thousands of qubits to millions of them.”

It could be years. Last year, IBM introduced the Eagle processor, a 127-kilobit processor, and in its new technology roadmap, it aims to unveil a 433-kilobit processor called the Osprey later this year, and a more than 4,000-kilobit computer by 2025. By then Time, quantum computing can go beyond the experimental stage, IBM CEO, Arvind Krishna reporters At a news event earlier this month.

Many experts doubt that IBM or any of its competitors will ever get there, raising the possibility that the engineering problems presented by quantum computers are simply very Difficult In order for the systems to be really reliable at all. “What has happened over the past decade is that there have been a huge number of claims about the more pressing things you can do with a quantum computer, like solving all these machine learning problems,” said Scott Aaronson, a quantum computing expert at the University of Texas, He told me last year. “But these allegations are nearly 90 percent nonsense.” To fulfill that promise, “you’ll need some revolutionary development.”

In an increasingly digital world, further progress will depend on our ability to make more use of the computers we make. It will draw on the work of researchers like Zhao and his colleagues, toiling in windowless labs to make a revolutionary new twist around some of the toughest problems in computer engineering — and along the way, trying to build the future.

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