Artificial Intelligence (A Special Report) --- How Quantum Computing Works: And how it could supercharge -- and disrupt -- billion-dollar industries

 

“Microsoft, International Business Machines, Alphabet's Google and a host of other tech companies are in a race to disrupt the nature of computing.

 

Collectively in the U.S., these companies have spent hundreds of millions in the past few years to develop a new type of computer --known as a quantum computer --that leverages the principles of quantum physics to solve problems far beyond the capabilities of today's best supercomputers.

 

And the companies say they could do it in the next two to five years.

 

When this point is reached, some problems that would take a traditional computer more than trillions of years to solve could take a quantum computer mere minutes, changing business as usual for industries involved with financial trading, shipping logistics, pharmaceuticals, scientific discovery, data encryption, insurance, internet delivery and more.

 

But building a quantum computer large enough to perform meaningful calculations is more complicated than just throwing a ton of qubits on a chip.

 

Qubits can be extremely sensitive to changes in their external environment that disturb their superpositioned state [1] and introduce errors into a calculation. So companies need to not only scale up the number of qubits they have, but also make sure they're doing it in a way where those qubits still behave.

 

The real scale of problems for quantum computers would involve hundreds of thousands of variables, not tens.

 

Quantum computers would have the capacity to be faster than traditional computers at optimization problems like analyzing supply chains, simulation problems like discovering new chemical combinations for drugs, machine learning and factorization.

 

Those last two categories could supercharge artificial intelligence, and could decode current encryption technology, requiring banks and other institutions to develop new methods of encryption.

 

How quantum bits differ from traditional bits

 

Traditional computers use electronic circuits to store information in bits. Bits are digital 1s and 0s, physically measured by the presence and absence of electricity flowing through the circuits. They're like switches, and everything a traditional computer does uses them.

 

Quantum computers, instead, use quantum bits, or 'qubits.' Most qubits are subatomic particles, like electrons, that are put in 'superposition' with lasers or microwave beams. In superposition, qubits exist in many states at once: a 1, a 0, and all values between the two. When the qubit is measured, it is taken out of superposition, and its value between 1 and 0 -- representing a probability -- is captured.

 

Qubits are the base component of a quantum computer. A quantum computer's chip might have dozens or hundreds of qubits on it. With each qubit added to a chip, the chip becomes exponentially more powerful, as qubits can talk to each other, informing each other of their state. In this process, called 'entanglement,' qubits share the burden of calculating probabilities -- leading to faster, non-linear computing.

 

Why it works faster than traditional computers

 

Quantum computers will be much quicker and more powerful across many types of computing tasks. One of those is optimization problems. Imagine a shipping logistics company needs to find the most efficient route, given three origins and three destinations. Traditional computers solve these types of problems by trying each combination sequentially, until they find the best one.

 

A quantum computer however -- because of entangled qubits' ability to calculate many probabilities at once -- can evaluate all options at once. Now imagine it scaled up. If there were 10 origins and 10 destinations, there would be 100 unique options. A traditional computer still needs to try each combination sequentially, while a powerful-enough quantum computer can evaluate all options at once.

 

How the computers are used

 

These computers are already in use on a small scale, by financial institutions and other companies preparing for how they will one day use the more powerful versions.

 

And because of the fragile nature of qubits, they need a lot of hardware to keep them functioning.

 

For decades, big tech players and startups have been racing to build meaningful large-scale quantum computers that they say could change the world, often called "full-scale, error-corrected, fault-tolerant" machines.

 

In recent years, they've performed demonstrations, released smaller-scale machines for customers to experiment on, and made promises about future timelines.

 

Google's demonstration of advances in error correction on its 105-qubit Willow chip, Microsoft's announcement that it literally invented a new state of matter for its qubits, and International Business Machines' promise to deliver its full-scale computer by 2029 all stand out.

 

Several pure-play quantum companies, including PsiQuantum, Quantinuum, and IonQ, say they'll be able to deliver these full-scale computers anywhere from one to four years from now.

 

While the announcements have generated buzz, they have also spurred skepticism. To be sure, apples-to-apples comparisons between companies are difficult, in part because many are targeting different types, or modalities, of quantum computers. This means they're using different types of materials (from electrical circuits to atoms to ions to even photons) to be their qubits, making it virtually impossible to make a judgment call on who's winning the quantum race.

 

Among all the different modalities, "There's an entire zoo of benchmarks" for judging whose computer is best, said Jerry Chow, IBM's chief technology officer of Quantum-Centric Supercomputing.

 

What the companies can agree on is that progress is being made, and quantum might be closer than many realize.

 

"In the last few years, a number of really key milestones have been hit that skeptics said I wouldn't see in my lifetime," said Pete Shadbolt, co-founder and chief scientific officer of PsiQuantum. "There's still a lot of work to do to turn it into a commercial technology, but we're getting closer and this stuff actually works the way it's supposed to work."

 

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Peter Champelli and Isabelle Bousquette are Wall Street Journal reporters in New York. Email them at peter.champelli@wsj.com and isabelle.bousquette@wsj.com.” [2]

 

1. “A qubit in a superposition state exists as a probabilistic combination of both basis states:

 

 |ψ⟩ = α|0⟩ + β|1⟩.  [3]

 

In this equation, α (alpha) and β (beta) are complex numbers called probability amplitudes. Rather than being in two places at once, the qubit occupies a single point in a complex mathematical space.

 

The "multiplicity" only appears when we measure the qubit: the act of observation causes the state to collapse, yielding a 0 with probability |α|2 or a 1 with probability |β|2.

 

This allows quantum algorithms to perform calculations using these amplitudes, creating a form of interference—much like overlapping waves—to amplify correct answers and cancel out wrong ones.

 

This provides a path to exponential speedups for specific problems, such as factoring large integers (Shor’s algorithm). However, this state is extremely fragile. Decoherence, caused by interaction with the external environment, forces the qubit to "choose" a classical state prematurely. Protecting this delicate balance through error correction remains the primary challenge in building a functional quantum computer.

 

A common misconception is that both states exist simultaneously in a physical sense, as if the qubit were cloned or split into two versions of itself. In reality, the qubit is always in a single, definite quantum state. Superposition simply means that this state does not align with our classical "either/or" categories until an interaction with the environment (measurement) forces it to choose a side.”

 

2. Artificial Intelligence (A Special Report) --- How Quantum Computing Works: And how it could supercharge -- and disrupt -- billion-dollar industries. Champelli, Peter; Bousquette, Isabelle.  Wall Street Journal, Eastern edition; New York, N.Y.. 23 Mar 2026: R6.

 

 

3. In quantum mechanics, α|0⟩ represents a quantum state where a qubit is in the base state |0⟩ (often representing "ground state" or binary 0), multiplied by a complex number coefficient α. It defines the amplitude of the state |0⟩, which relates to the probability of measuring the qubit as 0. While α|0⟩ represents part of a state, a full, normalized qubit state usually includes another component: |ψ⟩ = α|0⟩ + β|1⟩.

 

In quantum computing, β|1⟩ represents the second part of a qubit's quantum state superposition, specifically the "1" state component. Β (beta) is the complex probability amplitude (weight) associated with the basis state |1⟩, where the probability of measuring the qubit as "1" is |β| squared.