What is quantum computing? | McKinsey

Qubit bloch sphere

Flip a coin. Heads or tails, right? Sure, once we see how the coin lands. But while the coin is still spinning in the air, its neither heads nor tails. Its some probability of both.

This grey area is the simplified foundation of quantum computing.

Digital computers have been making it easier for us to process information for decades. But quantum computers are poised to take computing to a whole new level. Quantum computersrepresent a completely new approach to computing. And while they wont replace todays computers, by using the principles of quantum physics, they will be able to solvevery complex statistical problems that todays computers cant. Quantum computing has so much potential and momentum that McKinsey has identified it as one of the next big trends in tech. Quantum computing alonejust one of three main areas of emerging quantum technologycould account for nearly $1.3 trillion in valueby 2035.

Heres how it works: classical computing, the technology that powers your laptop and smartphone, is built on bits. A bit is a unit of information that can store either a zero or a one. By contrast, quantum computing is built on quantum bits, or qubits, which can store zeros and ones. Qubits can represent any combination of both zero and one simultaneouslythis is called a superposition.

When classical computers solve a problem with multiple variables, they must conduct a new calculation every time a variable changes. Each calculation is a single path to a single result. Quantum computers, however, have a larger working space, which means they can explore a massive number of paths simultaneously. This possibility means that quantum computers can be much, much fasterthan classical computers.

But the first real proof that quantum computers could handle problems too complicated for classical computers didnt arrive until 2019, when Google announced that its quantum computer had made a major breakthrough: it solved a problem in 200 seconds that would have taken a classical computer 10,000 years.

Although this was an important milestone in computing, it was more of a theoretical leap forward rather than a practical one, since the problem the quantum computer solved had no real-world use at all. But were rapidly approaching a time when quantum computers will have a real impact on our lives. Read on to find out how.

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Todays classical computers are relatively straightforward. They work with a limited set of inputs and use an algorithm and spit out an answerand the bits that encode the inputs do not share information about one another. Quantum computers are different. For one thing, when data are input into the qubits, the qubits interact with other qubits, allowing for many different calculations to be done simultaneously. This is why quantum computers are able to work so much faster than classical computers. But thats not the end of the story: quantum computers dont deliver one clear answer like classical computers do; rather, they deliver a range of possible answers.

For calculations that are limited in scope, classical computers are still the preferred tools. But for very complex problems, quantum computers can save time by narrowing down the range of possible answers.

Quantum computers arent like your average desktop computer. Its unlikely that you will be able to wander down to a store and pick one up. The kind of quantum computers that are capable of solving major problems will be expensive, complicated machines operated by just a few key players.

Over the next few years, the major players in quantum computing, as well as a small cohort of start-ups, will steadily increase the number of qubits that their computers can handle. Progress is expected to be slow: McKinsey estimates that by 2030, only about 5,000 quantum computerswill be operational. The hardware and software required to handle the most complex problems may not exist until 2035 or later.

But some businesses will begin to derive value from quantum well before then. At first, businesses will receive quantum services via the cloud, from the same providers they use now. Several major computing companies have already announced their quantum cloud offerings.

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One major obstacle to the advancement of quantum computing is that qubits are volatile. Whereas a bit in todays computers can be in a state of either one or zero, a qubit can be any possible combination of the two. When a qubit changes its status, inputs can be lost or altered, throwing off the accuracy of the results. Another obstacle to development is that a quantum computer operating at the scale needed to deliver significant breakthroughs will require potentially millions of qubits to be connected. The few quantum computers that exist today are nowhere near that number.

Slowly, at first. For the time being, quantum computing will be used alongsideclassical computing to solve multivariable problems. One example? Quantum computers can narrow the range of possible solutions to a finance or logistics problem, helping a company reach the best solution a little bit faster. This kind of slower progress will be the norm until quantum computing advances enough to deliver massive breakthroughs.

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Quantum computers can narrow the range of possible solutions to a finance or logistics problem, helping a company reach the best solution a little bit faster.

Quantum computers have four fundamental capabilitiesthat differentiate them from todays classical computers:

As these capabilities develop at pace with quantum computing power, use cases will proliferate.

Experts believe that quantum computers are powerful enough to eventually be able to model even the most complex molecules in the human body.

Research suggests that four industries stand to reap the greatest short-term benefits from quantum computing based on the use cases discussed in the previous section. Collectivelyand conservativelythe value at stake for these industries could be as much as $1.3 trillion.

These four industries likely stand to gain the most from quantum computing. But leaders in every sector canand shouldprepare for the inevitable quantum advancements of the next few years.

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According to McKinseys analysis, quantum computing is still years away from widespread commercial application. Other quantum technologies such as quantum communication (QComms) and quantum sensing (QS) could become available much earlier. Quantum communication will enable strong encryption protocols that could greatly increase the security of sensitive information. QComms enables the following functions:

Quantum sensing allows for more accurate measurements than ever before, including of physical properties like temperature, magnetic fields, and rotation. Plus, once optimized and decreased in size, quantum sensors will be able to measure data that cant be captured by current sensors.

The markets for QComms and QS are currently smaller than those for quantum computing, which has so far attracted most of the headlines and funding. But McKinsey expects both Qcomms and QS to attract serious interest and funding in the future. The risks are significant, but the potential payoff is high: by 2030, QS and QComms could generate $13 billion in revenues.

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A wide talent gap exists between the business need for quantum computing and the number of quantum professionals available to meet that need. This skill gap could jeopardize potential value creation, which McKinsey estimates to be as much as $1.3 trillion.

McKinsey research has found that there is only one qualified quantum candidatefor every three quantum job openings. By 2025, McKinsey predicts that less than 50 percent of quantum jobs will be filled, unless there are significant changes to the talent pool or predicted rate of quantum-job creation.

Here are five lessons derived from the AI talent journey that can help organizations build the quantum talent they need to capture value:

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What is quantum computing? | McKinsey