Quantum Infeasability

bc1984adam

Oct 21, 2025 • 4 min read

[NOTE: Written with GPT-5]

Satoshi's coins won't be stolen within your lifetime, most likely.

The concept of quantum computing has captured scientific and public attention for decades. It promises a new form of computation based on the principles of quantum mechanics, where information is encoded in quantum bits known as qubits. These qubits can exist in superposition and can become entangled, allowing quantum computers to perform certain tasks faster than classical computers. However, the practical development of large scale quantum computers that could break modern encryption remains far from reality.

Many experts and organizations have invested heavily in quantum research. Companies like Google, IBM, Microsoft, and Amazon have all announced progress in creating small prototypes. Some predict useful quantum machines will appear within a few years, showing advantages in chemistry, materials science, or optimization. Yet, most of these claims refer to near term or hybrid systems and not to the large fault tolerant quantum computers necessary for breaking strong encryption like RSA 2048.

The major technical challenge lies in maintaining quantum coherence. Quantum states are fragile and lose coherence due to interaction with their environment. Maintaining coherence while operating on thousands or millions of qubits requires conditions of extreme precision and isolation. No experiment so far has achieved the stability needed to run deep quantum algorithms over long durations.

Another obstacle is error correction. Quantum error correction methods require many additional physical qubits to form a single logical qubit that can resist noise. Estimates suggest that millions of physical qubits would be needed to factor large integers such as those used in cryptographic keys. Currently, the largest systems contain only a few thousand noisy qubits, none of which form a fully error corrected logical unit.

Gate fidelity is also a limiting factor. A quantum computer performs operations called gates that manipulate qubits. These gates must act with extremely high accuracy because small errors accumulate through a computation. Present devices achieve single gate fidelities near 99.9 percent for specific conditions, but complex circuits require far greater stability. Any error above a small threshold renders long algorithms unreliable.

The hardware itself remains a major barrier. Quantum processors rely on superconducting circuits, trapped ions, photons, or topological effects. Each platform faces unique engineering problems. Scaling any of these approaches to millions of qubits would demand unprecedented advances in materials, manufacturing, and control electronics. Maintaining such systems at cryogenic temperatures and ensuring signal integrity across large networks is far beyond today’s capability.

Recent public demonstrations, such as Google's quantum supremacy experiment, show quantum devices performing specific sampling tasks faster than supercomputers. However, these tasks were not useful computations. They demonstrated hardware behavior rather than real algorithmic advantage. Such benchmarks do not imply progress toward useful quantum factoring or cryptographic attacks.

Skeptics argue that the field overstates its achievements. They point to the lack of progress in factoring even small numbers with general purpose quantum algorithms like Shor’s. Since the first demonstration of factoring the number 15 in the early 2000s, no larger or fully functional implementations have appeared. Critics claim that many demonstrations involve partial compilation or prior knowledge of the solution, which invalidates them as true computations.

Theoretical estimates suggest that breaking 2048-bit RSA encryption would require on the order of tens of millions of logical qubits and trillions of error free gate operations. To reach that level within fifty years (by 2075) would mean several orders of magnitude of improvement in coherence, error correction, and manufacturing. Even optimistic projections from major research groups do not foresee such capability within that time frame.

Some futurists anticipate breakthroughs in topological qubits or other exotic materials that could simplify error correction. These ideas remain speculative. No experiment has yet proven a stable topological qubit capable of scalable computation. If such a discovery occurred soon, new progress could follow, but nothing indicates it will arrive quickly.

A small number of scholars and engineers have questioned whether large scale quantum computation is possible in principle. They argue that real matter may not support the continuous precision required to manipulate quantum amplitudes accurately across huge state spaces. According to this view, control errors, correlated noise, and physical imperfections could make full scale quantum computing unachievable even in theory.

Most scientists remain cautiously optimistic but acknowledge that the timeline is uncertain. It is possible that small quantum devices will continue to serve in specific research fields such as quantum chemistry, materials modeling, or limited optimization tasks. These systems may offer valuable insights into physics itself but will not threaten public key cryptography.

If progress continues at the present pace, useful commercial quantum computers may appear in limited roles within two or three decades. Cryptographically relevant quantum computers, capable of undermining secure communications, are likely much farther in the future, if they ever arrive. The resources required to construct such machines are beyond foreseeable technology.

In summary, the expectations placed on quantum computing are far greater than what current science supports. Despite major investments and periodic announcements of progress, every significant barrier remains unresolved. Unless new physical phenomena or manufacturing methods are discovered, the dream of a machine that can break RSA 2048 encryption appears infeasible within our lifetime.

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