What is quantum computing?

Quantum computing is an emerging approach designed for problems conventional systems can’t easily solve. It can represent and process information in fundamentally different ways and offers unprecedented power for specialized use cases. For example, 300 interacting quantum bits (qubits) can represent more possible states than there are atoms in the visible universe.¹

Most organizations won’t access quantum hardware directly; they’ll use third-party resources, introducing data-security exposure.

• Quantum computing doesn’t just make today’s computers faster. Quantum computers are designed for specialized problems that conventional systems struggle to solve efficiently.
• Its biggest near-term business impact may be security. Future quantum systems could threaten widely used encryption, making post-quantum planning important now.
• Its value depends on the problem. The strongest candidates include optimization, chemistry, materials science, and certain cryptographic workloads.
• Its power comes with fragility. Noise, scale, and error correction remain major barriers to broad commercial use.
• Its future will be hybrid. Quantum computers are expected to work alongside classical systems, not replace them.

The technology’s still early, but its implications for cybersecurity, operations, and research already matter to business leaders. For business leaders, quantum computing is less an immediate platform shift than a planning issue tied to encryption, research, optimization, and long-term technology strategy.

Before your organization can assess those risks and opportunities, you need a clear understanding of what quantum computing is, how it differs from classical computing, and why those differences matter for practical business decisions today.

Quantum computing uses quantum systems to store and process information. Conventional computers use bits, which represent either 0 or 1. Quantum computers use quantum bits (qubits), which can hold a combination of 0 and 1 before measurement.

It’s not a universal replacement for today’s computers. It’s a different model of computation that uses quantum effects, including superposition, entanglement, and interference, to approach certain complex problems in new ways.

A few terms are central:

• Quantum: The smallest discrete unit of a physical property, such as energy.
• Qubit: The basic unit of quantum information.
• Quantum state: The mathematical description of a qubit or group of qubits.
• Superposition: The ability of a qubit to hold a combination of states before measurement.
• Entanglement: A link between qubits so that measuring one will instantly tell you something about the other’s state.  
• Interference: The way quantum probability waves strengthen some outcomes and weaken others.

Quantum algorithms steer probability toward useful results rather than testing every possible answer one by one. That’s what superposition, entanglement, and interference make possible.

Several quantum concepts explain why these systems behave differently from classical computers. The most important are superposition, entanglement, and interference, which together allow quantum algorithms to shape probabilities. These ideas can sound abstract, but they’re central to how quantum computing creates potential value. Three principles drive quantum computing:

• Superposition means a qubit can be both 0 and 1 at the same time, like a spinning coin that is heads and tails until it lands on one.
• Entanglement connects two qubits so that measuring one instantly tells you something about the other.
• Interference helps quantum computers find the right answer by amplifying good outcomes and canceling bad ones.

Classical computers follow fixed rules, moving bits through circuits step by step. Quantum computers work differently, using gates that adjust probabilities until a final measurement picks an answer.

Quantum computers are best suited for specific problems like simulating molecules, tackling certain optimization challenges, and working with encryption.

Classical and quantum computing aren’t rivals. Classical systems will continue to handle most everyday workloads, and quantum systems will take on specialized tasks where they have an edge. Knowing the differences helps set realistic expectations for both.

Here is how they compare:

• Information unit: Classical computers use bits. Quantum computers use qubits.
• State: A bit is 0 or 1. A qubit can hold a mix of both until it’s measured.
• Logic: Classical systems use predictable logic gates. Quantum systems use gates that work with probabilities.
• Output: Classical programs give you a fixed answer. Quantum programs give you a distribution of possible answers.
• Error correction: Classical error correction is mature and reliable. Quantum error correction is still developing and requires many physical qubits to protect one working qubit.
• Best-fit workloads: Classical systems are built for broad business use. Quantum systems are best for specific problems in simulation, optimization, and cryptography.

The two models are meant to work together. Quantum computers will lean on classical systems for data preparation, control, and analysis. Classical systems will keep handling the work they already do well.

Quantum computers work differently from classical ones. Rather than running bits through fixed logic, they prepare qubits, adjust quantum states, and read the results.

Every quantum computation follows four basic steps:

• Preparation: Qubits are set to a starting state.
• Gates: Quantum operations adjust one or more qubits.
• Circuit: Those gates are arranged into an algorithm.
• Measurement: The final state is converted into a usable output.

This sequence usually runs many times. One run produces one result, but running it repeatedly reveals the pattern that holds the useful answer.

Qubits can be built in several ways, including superconducting circuits, trapped ions, neutral atoms, photons, and semiconductor systems. Each approach involves trade-offs in speed, stability, connectivity, and scale.

The hardest engineering problem is keeping qubits stable. They need to hold their state long enough to complete useful work, but heat, vibration, stray signals, and control errors can all cause problems.

Quantum error correction helps by distributing one logical qubit across many physical qubits. It requires a lot of overhead but is still the most promising path to fault-tolerant quantum computing.

Quantum computing isn't a fit for every business problem. It's best suited for problems with complex constraints, large search spaces, or physics-based modeling needs. That's why most business applications tend to fall into a few categories: security, optimization, chemistry, materials science, and research.

The main business use-case categories include:

• Cybersecurity: Large fault-tolerant quantum computers could break widely used public-key systems like Rivest-Shamir-Adleman (RSA) encryption and elliptic-curve cryptography (ECC).
• Quantum-safe security planning: Organizations can audit their cryptography and start preparing for post-quantum cryptography before fault-tolerant systems become a reality.
• Optimization: Quantum and quantum-inspired methods may help with routing, scheduling, network optimization design, supply chain planning, and other complex decisions.
• Chemistry and materials science: Quantum systems could help researchers model molecules, catalysts, batteries, carbon capture materials, and pharmaceuticals.
• Machine learning research: Researchers are testing quantum methods for classification, sampling, optimization, and feature mapping.
• Hybrid workflows: Future systems may use a quantum processor for a narrow step while conventional software manages data, control logic, and evaluation.

Security's the most pressing business concern right now. In 2024, NIST finalized the first three federal post-quantum cryptography standards, calling them a major step toward protecting encrypted data from future quantum attacks.²

But the risk isn't just about the future. Attackers can capture encrypted data today and hold it until they've got the tools to crack it. This is known as “harvest now, decrypt later,” and it's already pushing organizations to act before large fault-tolerant quantum computers exist.

The highest-risk data is anything with a long shelf life, particularly intellectual property and regulated records that could still be valuable years from now.

Quantum computing is promising, but today's systems are still limited. Most are better suited for learning, experimentation, and research than broad production workloads. Real business impact depends on progress in hardware quality, error correction, and practical benchmarking.

Current systems are often described as part of the noisy intermediate-scale quantum (NISQ) era. These machines have enough qubits for meaningful experiments, but noise still limits their ability to run deep, reliable circuits for commercial use.

The main limitations are:

• Noise: Quantum states are fragile, and small disturbances can produce wrong results.
• Scale: Many valuable applications may require large numbers of high-quality physical qubits.
• Error correction: Fault-tolerant systems need protected logical qubits, which require many physical qubits.
• Circuit depth: Current machines struggle to run long, complex calculations reliably.
• Benchmarking: Quantum methods must prove value against strong conventional systems.

These limits explain why commercial adoption is still gradual. Today's systems can support learning, research, and experimentation, but broad production advantage isn't here yet.

Federal agencies continue to treat quantum information science as a strategic priority. The National Quantum Initiative's budget materials point to sustained U.S. focus on research, standards, infrastructure, and workforce development.³

For businesses, adoption will likely unfold in stages: education, cybersecurity planning, focused experimentation, post-quantum cryptography migration, and eventual use of fault-tolerant systems for deeper simulation and cryptographic workloads.

For business and IT leaders, quantum computing isn't just a future opportunity; it's a current planning issue. The most pressing concern isn't whether to buy a quantum computer, but how to prepare systems, data, and teams for the risks and possibilities ahead. That means balancing security readiness with focused experimentation.

Boards, security leaders, and technology chiefs should focus on several practical actions:

• Inventory cryptography: Identify where public-key cryptography lives across applications, devices, cloud services, certificates, virtual private networks (VPNs), software-defined wide area network (SD-WAN) environments, and embedded systems.
• Plan for post-quantum migration: Use finalized National Institute of Standards and Technology (NIST) standards, including Federal Information Processing Standards (FIPS) 203, 204, and 205, as a foundation for transition planning.⁴
• Build crypto-agility: Design systems so algorithms can change without major redesign.
• Select focused pilots: Choose optimization or simulation workloads with clear baselines, trusted data, and measurable business outcomes.
• Set governance early: Decide how data moves, how you review vendors, how security controls apply, and how legal requirements shape experimentation.

Enterprise networks are a natural place to start. SD-WAN environments, VPNs, and certificate-based systems often depend on cryptography that may need to evolve as post-quantum standards mature.⁵ Reviewing these environments now helps IT teams understand where encryption, vendor dependencies, routing policies, and operational processes may need to change.

These questions tackle the most common points of confusion about quantum computing for business and technology leaders. They summarize the core concepts, likely applications, and current limitations.

What is quantum computing in simple terms?

Quantum computing is a way to use quantum physics to process information. It uses qubits instead of ordinary bits. By controlling qubits through circuits, a quantum computer can shape probabilities and sample results in ways that may help solve certain hard problems that are too complex for classical systems.

What is a quantum bit?

A quantum bit, or qubit, is the basic unit of information in a quantum computer. A regular computer bit is always either a 0 or a 1. A qubit can exist as a combination of both states until it's measured, which is what gives quantum computers their unique processing potential.

What is quantum computing used for?

Quantum computing is being tested for cybersecurity, optimization, chemistry, materials science, and machine learning research. Today's systems are best suited for experiments, benchmarking, and hybrid workflows that combine quantum and classical computing.

Will quantum computers replace classical computers?

No. Quantum computers are specialized systems built for certain hard problems, not general-purpose replacements for classical computers. Classical computers will continue to run most business applications for the foreseeable future.

What is Q-Day, and why should boards care?

Q-Day refers to the point when a fault-tolerant quantum computer can break widely used public-key cryptography in practice. Boards should care because attackers can collect encrypted data now and hold it until they have the tools to decrypt it. Starting post-quantum cryptography planning today reduces that long-term risk.

Quantum computing is a specialized technology, not a replacement for classical systems. Its most immediate relevance is in security planning, research, and selective experimentation. Broader business value will depend on continued progress in hardware, error correction, and practical use cases.

For most organizations, readiness is the right starting point. Leaders should understand where quantum computing could create risk, especially for encryption, and where focused pilots might create future value. A practical roadmap starts with cryptographic inventory, post-quantum cryptography planning, targeted experimentation, and governance to track progress as the technology matures.

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¹ “Quantum Computing Explained,” National Institute of Standards and Technology, updated May 28, 2026, https://www.nist.gov/quantum-information-science/quantum-computing-explained.

²“NIST Releases First 3 Finalized Post-Quantum Encryption Standards,” National Institute of Standards and Technology, August 13, 2024, https://www.nist.gov/news-events/news/2024/08/nist-releases-first-3-finalized-post-quantum-encryption-standards.

³National Science and Technology Council, National Quantum Initiative Supplement to the President’s FY 2025 Budget (Washington, DC: Office of Science and Technology Policy, 2024), https://www.quantum.gov/wp-content/uploads/2024/12/NQI-Annual-Report-FY2025.pdf.

⁴National Institute of Standards and Technology, FIPS 203: Module-Lattice-Based Key-Encapsulation Mechanism Standard (Gaithersburg, MD: National Institute of Standards and Technology, 2024), https://doi.org/10.6028/NIST.FIPS.203; National Institute of Standards and Technology, FIPS 204: Module-Lattice-Based Digital Signature Standard (Gaithersburg, MD: National Institute of Standards and Technology, 2024), https://doi.org/10.6028/NIST.FIPS.204; National Institute of Standards and Technology, FIPS 205: Stateless Hash-Based Digital Signature Standard (Gaithersburg, MD: National Institute of Standards and Technology, 2024), https://doi.org/10.6028/NIST.FIPS.205.

⁵“Preparing for The Quantum Era: AT&T Business Debuts Post-Quantum Cryptography Secure SD-WAN, Powered by Cisco,” AT&T, May 11, 2026, https://about.att.com/story/2026/cisco-post-quantum-cryptography.html.