Why the advantages and disadvantages of quantum computing matter now
Quantum computing has moved from physics textbooks to boardroom agendas. The United States federal government enacted the National Quantum Initiative Act of 2018 and followed it with funding through the CHIPS and Science Act. On the other hand, the European Union is positioning quantum technologies as a priority with initiatives such as the Quantum Flagship program. These and other facts serve as signal that this technology is no longer a distant curiosity. Organizations across government and the private sector are investing in quantum capabilities, and cybersecurity leaders are paying close attention.
Understanding the advantages and disadvantages of quantum computing is essential, not just for those responsible for protecting data and managing IT infrastructure, but also for those looking for technology adoption opportunities and are planning long-term technology strategy. The benefits are real and potentially transformative. The risks, particularly to much of modern public-key cryptography, are equally significant.
If you need a refresher on the underlying technology, learn the fundamentals of quantum computing before diving into the trade-offs below.
The advantages of quantum computing
Solving problems classical computers cannot handle
The most fundamental advantage of quantum computing is its ability to tackle problems that classical computers simply cannot solve in a practical timeframe. In simple terms, quantum computers can solve some problems that traditional computers cannot handle.
The difference is qualitative, not just quantitative. Classical computers process information sequentially, even when running in parallel. Some problems, however, cannot be broken into smaller pieces. For several problems, some calculations must be performed all at once, and classical computers (even supercomputers) are not built for it, but quantum technology is.
This capability stems from superposition, a quantum property that allows qubits to exist in a combination of states rather than being locked into a single zero or one. One easy way to think of it is like solving a maze. A classical computer tests each path one after another. A quantum computer, through carefully designed algorithms, arranges for wrong answers to cancel each other out so that the correct path is what remains when the computation finishes. Quantum computers do not simply try every answer at once through brute-force parallelism. Instead, they rely on interference patterns that suppress incorrect results and amplify the right one.
This opens up entirely new categories of computation: simulating quantum systems (the use case physicist Richard Feynman originally proposed in 1981), modeling complex molecular interactions, and solving optimization problems that grow exponentially beyond classical reach. To understand how superposition enables quantum computing, the evergreen guide walks through the mechanics in detail.
Speed and quantum economic advantage
Beyond solving the previously unsolvable, quantum computing also offers the potential to solve certain problems faster at comparable cost. This is usually described as “quantum economic advantage,” where quantum systems complete tasks that classical computers can handle, but do so with far fewer computational steps.
Consider supply chain optimization. Classical computers already manage routing and logistics for global supply chains, but they require enormous processing power to evaluate every variable. Quantum computers could apply the same fundamental approach used to navigate a maze and optimize those routes far more efficiently.
It is important to note that quantum computers are not universally faster. Classical computers generally operate faster than quantum computers, however, for many problems they require more steps than their quantum counterparts. The advantage emerges in specific categories of problems involving large combinatorial search spaces, where reducing the number of steps from computationally impractical to feasible represents a breakthrough.
Accelerating AI, drug discovery, and scientific research
Quantum computing’s ability to process complex calculations has promising applications across several research-intensive fields.
Artificial intelligence and machine learning.
With its capacity to tackle computations that strain classical hardware, quantum computing could accelerate AI’s ability to learn, adapt, and evolve. Training complex models requires evaluating enormous datasets and adjusting millions of parameters, a process that quantum speedups could compress significantly. This promising application, however, must wait for quantum computers to improve their ability to handle large amounts of data.
Drug discovery and molecular modeling.
Understanding complex gene interactions requires mathematics that classical computers struggle with. Sterling Thomas first explored quantum computing to accelerate computations related to genetic mutations, and companies like D-Wave Systems are already promoting advances in materials science and drug discovery as prime applications for their quantum technology.
Building stronger cybersecurity foundations
While quantum computing’s threat to much of currently deployed cryptography gets most of the attention, the technology also offers a significant upside for cybersecurity. Quantum information protocols such as Quantum Key Distribution (QKD) could provide the basis for much stronger security guarantees that can potentially enhance the systems used to detect and respond to cyber threats. This is the other side of the encryption coin. The same computational power that can break current cryptographic methods can also be harnessed to create more resilient ones.
To protect data from quantum attacks, NIST has already released post-quantum cryptographic (PQC) standards that establish new algorithms designed to be run on classical computers and resist both classical and quantum attacks. As quantum technology matures, it may enable entirely new approaches to threat detection, anomaly identification, and secure communications that go beyond what classical systems can achieve.
For a deeper look at the quantum threat to cryptography and how the same technology creates opportunities for defense, the evergreen guide covers both sides.
The disadvantages of quantum computing
Hardware fragility and environmental sensitivity
Qubits are extraordinarily sensitive. Vibrations, temperature fluctuations, and electromagnetic interference can knock a qubit out of its quantum state through a process called decoherence. Even the smallest environmental disturbance introduces errors that compromise calculations.
This fragility has practical implications. Several of the leading quantum computing approaches require operating environments near absolute zero (approximately minus 273.15 degrees Celsius), demanding supercooled refrigerators, insulation, and vacuum chambers. This is the case for superconductors used in quantum computing, which rely on extremely cold temperatures and even fractions of a degree above absolute zero introduces errors. Alternative approaches like ion capture require less extreme cooling, but use magnets to move atoms around, “which causes interference between qubits.”
Experts have recognized that quantum systems are much more fragile than classical computers, which don’t make mistakes very often because the technology is highly robust.
Error correction overhead
Errors in quantum computing do not stay contained. Because qubits are entangled, an error in one qubit can propagate rapidly across others, rapidly deteriorating the state of the system.
Quantum error correction addresses this by distributing information across multiple qubits and taking measurements to detect mistakes without disturbing the underlying computation. The goal is to create “logical qubits” that are theoretically protected from errors. But this approach requires many physical qubits for each logical qubit, meaning the systems needed for meaningful computation are far larger than what current hardware delivers.
Classical computers also rely on error correction, however, it goes unnoticed because traditional systems have become great at adjusting for mistakes. Quantum computing is still going through that maturation process, and the overhead consumed by error correction directly reduces the processing power available for actual computation.
Extreme cost and energy requirements
The infrastructure demands of quantum computing translate into significant financial and energy costs. The near-absolute-zero cooling systems required by several quantum computers architectures are large, complex, and expensive. Other approaches demand large vacuum chambers. These requirements make on-premise deployment of quantum computers impractical for most organizations.
Energy consumption is an emerging concern that challenges earlier optimism about quantum efficiency. Early in the development of quantum computingm the hope was it would not need large data centers to do the computations, since a single qubit can “pack” much more information. However, if powering smaller quantum computers requires more energy than the classical alternatives, that benefit does not exist.
As generative AI and other technologies already consume tremendous electricity, adding quantum computing energy demands creates additional pressure on infrastructure and sustainability goals.
Limited real-world applicability today
Quantum computing, for all its promise, remains a work in progress. Current systems cannot yet run the algorithms needed for production-scale problems at meaningful input sizes. Small quantum computers exist and produce interesting results, but the theory aspect is far more advanced than what is actually possible to achieve in a lab, and there is a disconnect that needs to be closed.
Some experts consider the state of modern quantum technology as only “somewhat helpful,lacking the performance where the advantages obtained from it represent an improvement on what we already have.
Industry timelines reflect this reality. According to a McKinsey survey, 72% of experts predict a fully fault-tolerant quantum computer will be available by 2035, but the remaining 28% say that will not happen until 2040 or later. Jim McGregor, a principal analyst at TIRIAS Research, compared quantum’s trajectory to AI’s: “You might say that quantum computing is where AI was in 2015, fascinating but not widely utilized.”
When quantum computing does become commercially viable, most organizations will likely access it through cloud services rather than operating their own hardware, given the extreme infrastructure requirements.
Quantum advantage vs commercial advantage
It is important to distinguish between a term that is known quantum advantage (or quantum supremacy) and the commercial advantages that we’re referring to in this article. Quantum advantage is the common term that refers to any instance of a problem that can be demonstrably solved with an existing quantum computer, while remaining impractical for any classical computer. The existing examples, however, consist of problems that are merely theoretical and have no commercial application. For quantum computers to demonstrate an advantage in real terms, it is not sufficient for them to solve some problem; they need to solve problems with real impact.
The encryption threat is a double-edged sword
Quantum computing’s potential to break current encryption standards represents one of its most discussed disadvantages. Using Shor’s algorithm, a sufficiently powerful quantum computer could break RSA, Diffie-Hellman and elliptic curve cryptography, undermining the mathematical foundations that protect digital certificates, TLS connections, and encrypted communications.
The most immediate concern is not a future quantum computer breaking your encryption in real time. It is what is happening right now. It is widely acknowledged that data is being stolen now for decryption later, following what is known the “harvest now, decrypt later” strategy. This means that data with long-term sensitivity is already at risk, regardless of when quantum computers reach full cryptographic capability. For the complete breakdown of how quantum threatens encryption and what your organization can do, see harvest now, decrypt later attacks in the evergreen guide.
Advantages vs. disadvantages at a glance
The following table outlines the advantages and disadvantages that future quantum computers will have, as well as the limitations that they currently suffer.
| Future Advantages | Disadvantages and Current Limitations |
|---|---|
| Solves problems classical computers cannot handle | Hardware is extremely fragile and sensitive to environmental disturbance |
| Offers quantum economic advantage for specific problem categories | Error correction requires many physical qubits per logical qubit, limiting scale |
| Accelerates AI, drug discovery, molecular modeling, and scientific research | Near-absolute-zero cooling demands extreme cost and energy |
| Enables stronger cryptographic techniques and enhanced threat detection | Current systems cannot yet run production-scale algorithms |
| Opens new mathematical and computational possibilities | Threatens existing public key cryptographic standards through Shor’s algorithm |
What the advantages and disadvantages mean for your organization
The advantages of quantum computing tell you that this technology is coming. Industries from pharmaceuticals to finance to national security are investing in quantum capabilities, and the pace of progress is accelerating. The limitations tell you that quantum computers are hard to build and are not yet cryptographically capable, which buys time. Nonetheless, a disadvantage of a large-scale quantum computer becoming real will be severe, and necessary precautions must be taken starting now.
But that window is narrowing. Some experts believe that within five to eight years, quantum will become available in a more reliable way, with systems that have larger and larger qubits. And the harvest-now-decrypt-later threat means that waiting to update your cryptography is itself a risk.
The takeaway for security and IT leaders is straightforward: start preparing now.
That preparation starts with understanding your current cryptographic posture, identifying what needs to be protected, and building the agility to transition to quantum-resistant algorithms when the time comes. For a detailed walkthrough of organizational readiness, see steps to prepare for the quantum era in the evergreen guide.
How Keyfactor can help
Preparing for quantum computing does not require waiting for the technology to mature. The steps that make your organization quantum-ready are the same steps that strengthen your cryptographic posture today.
Cryptographic discovery and inventory.
The first step is knowing what you have. Keyfactor’s platform connects to appliances and applications across your infrastructure to discover certificates and keys that might otherwise go untracked, including those embedded in IoT devices and open-source code.
Certificate lifecycle management.
Discovery is not a one-time exercise. Keyfactor’s platform includes a certificate lifecycle manager that detects them, finds them, brings them all in, and is able to manage them on an ongoing basis. This continuous visibility is essential for maintaining cryptographic hygiene and ensuring you can act quickly when migration becomes necessary.
Hands-on PQC experimentation.
Keyfactor’s PQC Lab provides a sandbox environment where your team can explore post-quantum cryptographic algorithms, test compatibility, and build confidence before production migration. The company also offers an open-source cryptography stack that allows organizations to implement post-quantum standards in their own custom software development.
Building crypto-agility now means you will be able to swap algorithms efficiently when quantum computing reaches the threshold that demands action. For the detailed product breakdown, see how Keyfactor supports quantum-safe readiness in the evergreen guide.
Got quantum computing questions? We’ve got answers.
What are the main advantages of quantum computing over classical computing?
Quantum computers can solve certain categories of problems that classical computers cannot handle efficiently, including molecular simulation, complex optimization, and cryptographic factoring. They achieve this through superposition, which allows qubits to represent multiple states simultaneously, and through algorithms that use interference to amplify correct answers and suppress incorrect ones. For problems in these categories, quantum computing offers exponential speedups over classical approaches.
What are the biggest limitations of quantum computing right now?
The most significant limitation are hardware fragility (qubits lose their quantum state through decoherence), the overhead of error correction (requiring many physical qubits per logical qubit), extreme infrastructure costs (near-absolute-zero cooling for superconducting architectures), and limited current applicability (today’s systems cannot yet run production-scale algorithms). These challenges are actively being addressed, but they constrain what quantum computers can accomplish today.
Is quantum computing faster than classical computing?
Not always. Classical computers generally operate faster than quantum computers for routine tasks. Quantum’s advantage applies to specific categories of problems involving large combinatorial search spaces, optimization, and certain mathematical operations. For these problems, quantum computers can reduce the number of steps required from computationally impractical to feasible, which is what researchers call “quantum economic advantage.”
What is the advantage of superposition in quantum computing?
Superposition allows a qubit to exist in a combination of zero and one simultaneously, rather than being locked into a single state. This enables quantum algorithms to evaluate many possible inputs within a single computational operation. Combined with interference, superposition allows quantum computers to amplify the probability of correct answers while canceling out wrong ones. This is fundamentally different from classical parallel processing.
How does quantum computing threaten cybersecurity?
Quantum computers running Shor’s algorithm could break the mathematical problems underlying RSA and elliptic curve cryptography, making digital certificates, TLS connections, and encrypted communications vulnerable. The threat is compounded by “harvest now, decrypt later” attacks, where adversaries capture encrypted data today for future decryption once quantum computers are capable. Learn more about the quantum threat to cryptography.
Can quantum computing also improve cybersecurity?
Yes. While quantum computing threatens current cryptography, it can also enable stronger cryptographic techniques and enhance threat detection systems. NIST has published post-quantum cryptography (PQC) standards that establish new algorithms designed to work on classical computers and resist both classical and quantum attacks. As the technology matures, quantum capabilities may enable entirely new approaches to secure communications and anomaly detection.
When will quantum computers become powerful enough to break encryption?
Expert estimates vary. A McKinsey survey found that 72% of experts predict a fully fault-tolerant quantum computer by 2035, while the remaining 28% expect that milestone by 2040 or later. However, the more pressing consideration is that data with long-term sensitivity is already at risk from harvest-now-decrypt-later attacks, regardless of when full cryptographic capability arrives.
What should organizations do to prepare for quantum computing?
Start with a comprehensive cryptographic asset inventory to understand what certificates, keys, and algorithms are deployed across your infrastructure. Build continuous visibility through certificate lifecycle management. Develop a prioritized post-quantum cryptography migration roadmap. And build cryptographic agility into your architecture so you can swap algorithms efficiently when the time comes. The best time to start is now.
