# Quantum Computers Explained: Qubits, Superposition and Where We Are in 2026 > A quantum computer uses qubits to solve some problems far faster than classical machines. Here is how it works and where the field stands in 2026. *2026-10-29T13:06:13Z* # Quantum Computers Explained: Qubits, Superposition and Where We Are in 2026 *Originally published in Arabic on parmgy.com on June 8, 2019. Updated October 2026.* A quantum computer uses qubits instead of ordinary bits, which lets it solve certain problems far faster than a classical computer. It is not a faster laptop, though. Today's quantum machines are still small, noisy and experimental. ## In the short video 1. **The hook:** Google framed its Willow chip as a random-circuit-sampling benchmark done in under five minutes that it estimated would take Frontier, one of the fastest supercomputers, about 10^25 years. It is a benchmark with no practical use, so read it as a milestone. 2. **The idea:** a quantum computer, such as IBM's Quantum System One. 3. **Bit vs qubit:** a bit is 0 or 1; a qubit can be in a combination of both (the Bloch sphere picture). 4. **Superposition and entanglement:** the combination state, and two qubits whose results stay correlated even when far apart (the Bell-test picture). 5. **Willow:** announced in December 2024: as the error-correcting grid grew, the logical error rate roughly halved at each step. 6. **The security angle:** estimates for breaking RSA-2048 fell from about 20 million qubits to far fewer, so the world is preparing post-quantum encryption. ## Bits vs qubits A classical computer stores information in **bits**, and each bit is either 0 or 1. Chips are made of silicon transistors. A quantum computer uses **qubits**. A qubit is a quantum system, such as a superconducting circuit or a trapped ion, that can be in a combination of 0 and 1 at once. This is called **superposition**. It is often described as "both 0 and 1", but more precisely a qubit has probability-like amplitudes for each outcome, and when you measure it you get either 0 or 1. Qubits also exploit two other effects: - **Entanglement:** qubits can be linked so their measured results are correlated, even if physically apart. - **Interference:** a quantum algorithm is arranged so that wrong answers cancel out and right answers are reinforced. The point is not that a quantum computer tries every answer at once and reads them all. The skill is in designing algorithms where interference makes the right answer likely when you measure. ## Classical vs quantum at a glance | | Classical computer | Quantum computer | |---|---|---| | Unit of information | Bit (0 or 1) | Qubit (superposition of 0 and 1) | | Hardware | Silicon chips | Superconducting circuits, trapped ions, photons and others, often at extremely low temperatures | | Strength | Almost everything we do daily | Specific problems such as simulating molecules or factoring numbers | | Errors | Very rare | Frequent, and the main engineering challenge | ## What they could be good for - **Chemistry and materials:** simulating molecules to design drugs, batteries and catalysts. - **Cryptography:** Shor's algorithm (1994) could factor large numbers and break today's RSA and elliptic-curve encryption on a large enough machine. - **Optimization and search:** Grover's algorithm (1996) gives a quadratic speedup for unstructured search, and research continues on optimization problems. They are not expected to speed up web browsing, games or everyday programs. Several claims you may have read, such as quantum computers replacing silicon or "solving everything", are hype. ## Where we are in 2026 - **1998:** the first quantum computers with 2 qubits showed the idea was feasible. - **2019:** Google claimed "quantum supremacy" with a 54-qubit processor. IBM disputed the claim, arguing a classical supercomputer could do the task in far less time. - **December 2024:** Google's 105-qubit **Willow** chip showed error correction working "below threshold": adding more qubits to a logical qubit reduced its errors, an important step for scaling. - **October 2025:** Google reported its "Quantum Echoes" algorithm on Willow, which it said ran about 13,000 times faster than the best classical method for that task. That figure is Google's own estimate. - **March 2026:** a Caltech and Oratomic preprint (arXiv 2603.28627, 31 March) estimated that Shor's algorithm could run at cryptographically relevant scale on as few as 10,000 reconfigurable neutral-atom qubits: elliptic-curve P-256 in a few days with about 26,000 qubits, and 2,048-bit RSA one to two orders of magnitude slower, versus the roughly 20 million qubits estimated in 2019. The paper had not been peer-reviewed at the time, and neutral-atom machines of that quality do not exist yet. - **Roadmaps:** IBM plans a large fault-tolerant system, Starling, by 2029, with 200 logical qubits running 100 million quantum operations. This is a company plan, not a delivered machine. The big remaining problem is noise. Qubits lose their state quickly (decoherence), so useful machines will need error correction that turns many physical qubits into a few reliable logical ones. Even with the lower 2026 estimates, breaking today's encryption still needs a machine far larger and more reliable than anything that exists. Fully fault-tolerant quantum computing is still out of reach as of 2026. ## What it means for security Governments and companies are not waiting. In August 2024 NIST published its first post-quantum encryption standards (FIPS 203, 204 and 205), and in March 2025 it chose HQC as another algorithm to standardize. Moving systems to these algorithms is called **post-quantum cryptography**. ## FAQ ### What is a quantum computer in simple words? A computer that uses qubits and the rules of quantum mechanics to solve certain problems much faster than ordinary computers. ### Is a qubit really 0 and 1 at the same time? It is in a superposition of the two. When measured, it gives 0 or 1 with certain probabilities. ### Can quantum computers break encryption today? No. A machine big enough to break RSA or elliptic-curve encryption doesn't exist yet. But organizations are already moving to post-quantum algorithms to be ready. ### Will quantum computers replace regular computers? No. They will work alongside classical computers for specific tasks. ## Sources - Google, «Meet Willow, our state-of-the-art quantum chip» (9 Dec 2024): https://blog.google/technology/research/google-willow-quantum-chip/ - Nature, «Quantum error correction below the surface code threshold»: https://www.nature.com/articles/s41586-024-08449-y - Gidney (2025), «How to factor 2048 bit RSA integers with less than a million noisy qubits»: https://arxiv.org/abs/2505.15917 - Caltech and Oratomic (2026), «Shor's algorithm is possible with as few as 10,000 reconfigurable atomic qubits» (preprint): https://arxiv.org/abs/2603.28627 - Image credits (video): Frontier supercomputer (Oak Ridge National Laboratory, CC BY 2.0), IBM Quantum System One (IBM Research, CC BY 2.0), Bloch sphere (Qupybara, CC0), Bell test (Manwesulimo2004, CC BY 3.0), Wikimedia Commons. --- Source: https://fadymondy.com/en/blog/quantum-computers-explained