A persistent myth has formed around quantum computing about a "super-powerful processor" that is about to replace familiar PCs. This is a deep misconception. A quantum computer is not an accelerator of all conceivable operations, but a highly specialized tool, effective only for a strictly defined class of problems. Its architecture and operating principles are fundamentally different, and this is precisely where both its power and its limitations lie.
The Essence of the Phenomenon: Superposition and Entanglement
At the core of quantum computing lies not a "parallel enumeration" of options, as is often simplistically written. The key idea is the use of qubits, which, unlike classical bits (0 or 1), can exist in a state of superposition. Formally, this is described as a combination of states |0⟩ and |1⟩ with certain probability amplitudes. However, until the moment of measurement, a qubit has no specific value—it exists in an indeterminate state, described by a single wave function for the entire system of N qubits (2ⁿ amplitudes).
The second fundamental phenomenon is quantum entanglement. This is not merely correlation, as in the example of gloves in boxes. Entangled qubits form a single quantum system, and their state cannot be described independently, even if they are separated by vast distances. Measuring one instantly affects the state of the other, but before that, they have no "hidden" pre-defined properties.
Interference: The Main Secret of Computation
The third, most underestimated element is the interference of probability amplitudes. A quantum algorithm is not a "checking of all options in one clock cycle," but a skillful manipulation of these amplitudes. The correct sequence of quantum operations is arranged so that incorrect answers cancel each other out (destructive interference), while the correct one is amplified. This is precisely why the speedup is not universal. Shor's algorithm provides an exponential advantage in factorization and discrete logarithms, Grover's algorithm offers only a quadratic improvement in unstructured search, and for most other problems, efficient quantum solutions simply do not yet exist.
What This Means for the Market and Industry
The term "quantum supremacy" today is more of a marketing label than an engineering achievement. Demonstrations on synthetic problems (e.g., random circuit sampling) have no practical value, and classical algorithms often catch up to quantum ones in such benchmarks. To assess the maturity of the technology, what matters more is not the number of physical qubits, but the accuracy of operations, error rates, and coherence time.
For the crypto industry, the specific threat is Shor's algorithm applied to ECDSA. According to my estimates, breaking a 256-bit elliptic curve requires on the order of 1,200 logical qubits. At the same time, the resource requirements for breaking RSA-2048 have decreased in recent years from 20 million to less than 1 million physical qubits. It is precisely this dynamic and the share of bitcoins on addresses with exposed public keys that should be monitored, not the loud headlines.
Q-Check: Key Takeaways
Will a quantum computer replace PCs?
No, it is a highly specialized device, not a replacement for classical systems.
What is its advantage?
In its ability to solve specific problems (quantum chemistry, optimization, cryptanalysis) in time that is unattainable for classical algorithms.
Where should real impact be expected?
In materials science, pharmacology, catalyst development, and hybrid computing with classical supercomputers.
Is the speedup universal?
No. Only Shor's algorithm provides an exponential advantage, and Grover's provides a quadratic one. For other problems, efficient solutions do not yet exist.
Does supremacy equal usefulness?
Not yet. It is merely a demonstration of physical capabilities on artificial tests, far from commercial application.
My comment: It is important for investors and analysts to understand: quantum computers are neither "bitcoin killers" nor "magic accelerators." They are tools for solving specific problems. Their real impact on cryptography will be determined not by records on paper, but by engineers' ability to cope with decoherence and create a reliable error correction system. It is these metrics that should be monitored, not the PR.