96 M C K I N S EY Q UA RT E R LY Quantum’s Promise F OR YEARS, BUSINESS LE AD ers and corporate boards have viewed quantum com puting (QC) as a threat—and for good reason: It has the potential to break today’s strongest encryptions. That moment, commonly known as Q-Day, will occur when quantum computers succeed in factoring exceptionally large numbers, undermining the math that public-key cryptography depends on. - - - - - - - - - - - Though business leaders are keeping Q-Day top of mind, they are viewing QC through a new lens— less a threat and more an opportunity. Many are spurring their companies to experiment with QC now so that they will be ready to deploy it at scale once quantum computers become mainstream, which could happen within the next five years. The potential benefits for early adopters are considerable. McKinsey research suggests that QC could create multibillions of dollars in enterprise value in the coming decade—and that’s just for the industries we analyzed that are most likely to bene fit (Exhibit 1). Providers of quantum computing have accelerated their engineering road maps and made algorithmic breakthroughs that suggest that scal able applications could arrive in a matter of years. Unlike classical computers, which process infor mation in a linear way, quantum computers leverage the principles of quantum mechanics to explore many potential solutions in parallel. While quantum computers themselves are extremely complex, they differ from classical computers in one fundamental way. Classical com puters are built on units of information called bits, which can be represented by either a zero or a one. Quantum computers, on the other hand, are built on quantum bits, or qubits, which can represent any combination of zero, one, or both simultaneously. This form of nonlinear processing allows quantum computers to solve complex tasks far faster than even today’s most powerful supercomputers. QC’s greatest strength lies in its ability to solve problems that overwhelm classical computers, such as advanced simulation and probabilistic modeling. These capabilities make QC attractive for applications such as drug discovery, material simulation, supply chain optimization, and financial modeling—all areas where early QC applications are gaining traction. Already today, some orga nizations claim that QC outperforms classical computing by a wide margin (what’s known as “quantum supremacy”) and that the technology has matured to the point where companies are deriving incremental value from it. QC has yet to hit the mainstream, however, because of two key challenges: Qubits are fragile and prone to errors, and QC hardware is expensive to build and operate. These constraints mean that for most companies today, QC is best suited to a small number of high-value use cases, rather than as a replacement for classical computing. How ever, advances in software are quickly helping to address these limitations. Algorithms that mitigate and correct errors could soon enable even imper fect quantum computers to deliver high-impact results. This algorithmic leap means that raw quan tum hardware could become less important, making large-scale QC use happen sooner than hardware road maps alone suggest. QC’s greatest strength lies in its ability to solve problems that overwhelm traditional computers. P R E V I O U S S P R E A D : M A X G E R / G E T T Y I M A G E S CEOs don’t need to understand the intrica cies of quantum computing to derive value from it. But they do need to know enough about the technology to understand where QC is headed and how it could affect their P&L. They also need to develop a clear view of the use cases that are relevant for their companies and partner with