Quantum Computing

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更新時間 Sep 22, 2026

What Is Quantum Computing?

Quantum computing is a form of computing that uses quantum bits, or qubits, which can represent 0, 1, or both values at the same time through superposition.

How Does Quantum Computing Work?

Classical computers store information in bits that are always either 0 or 1. Quantum computers use qubits built from particles that follow the rules of quantum mechanics.

Two properties are key to how quantum computers work:

Superposition: the condition in which a quantum system can exist in multiple states or configurations simultaneously. This allows a qubit to hold a mix of both states.
Entanglement: where two qubits are so deeply linked that their physical states depend on one another, regardless of distance. Entangled qubits work together as a single system, which is what gives quantum computers their power advantage over classical machines.

These properties let quantum computers explore many possible outcomes in parallel, which can make them much faster than classical machines when solving certain specialized problems.

A quantum computer runs an algorithm by placing qubits into carefully controlled quantum states, letting them interact, and then measuring the result. When a qubit is measured, its superposition collapses to a single value of 0 or 1. The skill in quantum algorithm design is arranging the calculation so that, when measured, the correct answer is far more likely to appear than the wrong ones.

Building stable qubits is extremely difficult. They are highly sensitive to noise and heat, so many systems operate at temperatures close to absolute zero and still suffer from frequent errors. As of 2026, quantum computers remain experimental, and large, error-corrected machines capable of breaking modern encryption are widely regarded as years away.

Quantum Computing and Crypto

Quantum computing matters to crypto because a sufficiently powerful quantum computer could, in theory, threaten the cryptography that secures blockchains and wallets. Some examples are:

Shor’s algorithm: solves integer factorization and discrete logarithm problems in polynomial time. This allows it to potentially break elliptic-curve signatures and reveal private keys through reverse-engineering of public keys.
Grover’s algorithm: provides a quadratic speedup for unstructured search problems. This weakens the security provided by symmetric key cryptography and hash functions by halving their effective key length. However, it is less effective in breaking public key cryptography compared to Shor’s algorithm.

Because private keys could one day be at risk, some experts warn about "harvest now, decrypt later" scenarios, where data is collected today in the hope of decrypting it in the future. This has pushed the industry to research quantum-resistant designs well before any practical quantum attack is possible.

Post-Quantum Cryptography

Post-quantum cryptography refers to encryption methods designed to resist attacks from both classical and quantum computers. In August 2024, the US National Institute of Standards and Technology (NIST) finalized its first three post-quantum standards: FIPS 203 (ML-KEM) for key exchange, FIPS 204 (ML-DSA) for digital signatures, and FIPS 205 (SLH-DSA) as a hash-based signature backup.