What Is Quantum Computing?

Quantum computing is an advanced form of computational power that uses quantum bits, or qubits, to perform tasks that conventional computers can’t. Qubits can be in more than one state at the same time, unlike classical bits, which can only be 0 or 1. This difference gives quantum computers an amazing ability to process information, with profound effects on the cryptographic systems that protect business data today.

The best way to learn the mechanisms behind quantum computing is to examine how it differs from other types of computing.

Bits are tiny switches that can be on (1) or off (0), and traditional computers use them for all forms of processing. Every calculation, every encrypted file, and every packet sent over the network is turned into those two numbers. That model has worked well for decades, but it has limitations that quantum computing surpasses.

Instead of bits, quantum computers use qubits, which function by a completely different set of rules.

Classical Bits vs. Qubits

A classical bit is like a coin on a table: it can only be heads or tails, not both. A qubit is not the same. Before it is measured, it holds both possibilities at once.

Superposition

This dual state property is called superposition. A qubit in superposition shows both 0 and 1 at the same time until it is measured or observed.

A quantum computer can hold about a million possible states at once with only 20 qubits working in superposition. A classical computer would have to go through each of those states one by one.

Entanglement

The second principle that differentiates quantum computing from everything else is entanglement. When two qubits are entangled, any change to one will instantly affect the other, no matter how far apart they are. If you add more entangled qubits, the system doesn’t get more powerful in a linear fashion; it becomes more powerful exponentially.

Parallel Processing Potential

Combining superposition and entanglement gives you a computer that can evaluate a wide range of possible solutions at once. Classic computing works on a problem one step at a time. A quantum computer can look at the whole solution space at once and use quantum “interference” to find the answer that is most likely to be correct.

That’s the part of quantum computing that matters most for CISOs and security architects. RSA encryption (Rivest-Shamir-Adleman) and elliptic-curve cryptography are secure today because brute-forcing their underlying math would take a classical computer an impractical amount of time. In a few hours, a robust quantum computer could close that gap.

The reality is that threats don’t wait for quantum computers to fully arrive. Today, enemies are already collecting encrypted data to decrypt it when quantum technology becomes more advanced. The security community even has a catchphrase for it: “harvest now, decrypt later.” In direct response, NIST has already finished its first post-quantum cryptographic standards.

Most modern encryption is based on the practical fact that some math problems are so difficult for classical computers to solve that they become the basis for security itself. We’ll try to keep it simple. For instance, RSA encryption is based on the fact that it’s nearly impossible to quickly compute enormous prime numbers. Elliptic-curve cryptography (ECC) depends on a similar hard math principle called the “discrete logarithm problem.”

Along comes Shor’s algorithm, a quantum algorithm, which can solve the math problems that RSA and ECC are based on much faster than any classical method. Chuck Brooks, Global Thought Leader in Cybersecurity and Emerging Tech, puts this in perspective: “The RSA-2048 encryption standard would require a billion years for a conventional computer to break, but a quantum computer could theoretically do so in less than two minutes.”

However, AES (Advanced Encryption Standard) and other asymmetric encryption types (public and private keys are not interchangeable) are in a different place. Shor’s algorithm can’t break it, but Grover’s algorithm cuts the strength of an asymmetric key in half. AES-128 doesn’t work well with this model. AES-256, on the other hand, still offers about 128 bits of effective protection and is thought to be quantum-resistant for the time being.

This is a sign to security architects that it’s time to make an encryption inventory. What’s critical isn’t just the type of encryption you’re using, but how long it can protect data. Most companies have already encrypted sensitive data with keys that quantum computing could eventually break. That’s a challenge for compliance leaders tasked with protecting data for years or decades.

The main idea behind what the security community calls “harvest now, decrypt later” is that quantum computing doesn’t have to be ready today to pose a current threat.

What makes this possible is simple. Adversaries now gather encrypted data, keep it, and wait. When quantum technology becomes powerful enough to break current cryptographic protections, attackers will be able to read the stored data.

This changes the timeline for any group that has sensitive long-term data. Today, encrypted intellectual property, M&A communications, employee records, and regulated customer data could be breached and made public. What matters is how strong your encryption was when you collected the data, not how strong it is now.

This scenario is not in the distant future. Nation-state actors have both the motive and the tools to carry out long-term plans. CISOs and compliance leaders should consider this an urgent data classification and retention issue that needs to be solved now, not in the future.

Post-quantum cryptography (PQC) is an entirely new generation of cryptographic algorithms intended to protect data against the capabilities of quantum computers. PQC solutions don’t rely on the same types of mathematical problem-solving as the RSA and ECC algorithms. Instead, they use mathematical problems that aren’t considered efficiently solvable by a quantum machine.

The NIST’s three latest post-quantum encryption standards marked the transition of PQC from research to implementation. This was a landmark moment. While it provided CISOs with a definitive foundation to assist in roadmap planning, instead of an ever-changing target, it also represented a daunting task.

The process of migrating to PQC is very complex. Many enterprise environments rely heavily upon legacy cryptographic infrastructure. Replacing this infrastructure requires time, money, and interdepartmental collaboration. The longer CISOs delay transitioning to PQC, the fewer options they’ll have when they finally decide to transition.

Quantum computing and AI are both making progress, but they’re doing so in different ways. But paths are merging, and security leaders should keep a close eye on what happens when they do.

Brooks puts it plainly: “The era of quantum computing is approaching faster than anticipated, with artificial intelligence likely to be integrated with quantum technology. The convergence of these technologies will have significant implications.”

The combination makes the risk on the offensive side even worse. AI already lets enemies automate attacks, make convincing phishing emails on a large scale, and take advantage of weaknesses at machine speed. Add quantum computing to that, and the adversarial toolkit gets a huge boost in reach and power.

The defensive stance is equally as powerful. Quantum-enhanced AI could make it easier to find unusual patterns, speed up threat modeling, and help create the next generation of cryptographic protections. Companies that start teaching their employees about both technologies now will be better positioned to use them as tools for resilience, rather than reacting after the fact.

Quantum readiness isn’t a one-and-done. Security teams and executives need to start building this strategic posture now, before quantum computing becomes a real threat. Preparation requires a logical order that starts with visibility.

1. Cryptographic Inventory

You can’t protect something if you don’t know where it is. A cryptographic inventory shows security teams exactly where weak encryption is in the environment, such as which systems use RSA or ECC, which protocols rely on asymmetric key exchange, and where certificates will need to be replaced in the future.

This step alone can be lengthy for companies with complicated infrastructure. But it’s the base for everything that follows.

2. Risk Prioritization

Not all data has the same level of quantum risk. The focus should be on information that will last a long time, like intellectual property, financial records, healthcare data, and strategic communications. If that data is encrypted today and needs to stay secret for ten years or more, it’s in the “harvest now, decrypt later” zone.

Risk prioritization helps executives make better decisions about resource use—it’s better to protect the most sensitive long-lived data first than to try to move everything at once.

3. Migration Planning

NIST’s final post-quantum standards give security teams a solid base to work from. It won’t happen overnight, and planning needs to take into account old systems, dependencies on third parties, and implementation timelines that can last for years.

Any new infrastructure built today should be “crypto-agile,” the ability to swap cryptographic algorithms without requiring a complete system overhaul. Teams that make things more flexible now will have a much easier time in the future.

4. Vendor Assessment

Quantum readiness goes beyond just your own systems. You need to check that every technology provider in your stack, from cloud platforms to security tools, is ready for the post-quantum world.

Directly ask vendors about their plans for cryptography and whether their products are being updated to meet NIST standards. Purchasing and contract renewal decisions should align with those standards.

Waiting to deal with vendor risk until your own migration is already in progress makes things more expensive and complicated, which can be avoided with early due diligence.

Quantum computing gets a lot of coverage, and not all of it is accurate. A few misconceptions have taken hold that are worth addressing directly.

• “Quantum computers are already widespread.” They’re not. There are working quantum computers in research labs and tech companies today, but they’re still very experimental and only work in very controlled environments. No enemy is currently using a quantum machine that’s strong enough to break modern encryption. The threat is real and worth getting ready for, but it hasn’t happened yet.
• “Encryption will collapse overnight.” A gradual change is more likely. To break important cryptographic keys will require quantum computers that can handle errors and have much more stable qubits. The change will probably happen over several years, which is why it’s important to get ready now. Companies that think of this as a problem to solve in the future will likely fall behind.
• “Quantum computing will replace classical computing entirely.” Quantum computers are very good at solving certain types of problems, especially those that involve complicated math and big optimization. For most everyday computing tasks, classical computers will still be the best choice. It’s better to think of the two architectures as working together, not against each other.