Cryptography & Communication
Quantum Random Number Generator
A device that produces random numbers from quantum processes, whose outcomes are fundamentally unpredictable.
Definition
A quantum random number generator uses a quantum event, such as which way a single photon goes at a beam splitter, as the source of randomness. According to quantum mechanics, that outcome is not just hard to predict but genuinely undetermined in advance, so the numbers are random in a deeper sense than the pseudo-random numbers computers usually make with formulas. Such devices already appear in commercial hardware, including phones, and the strongest versions can even prove their randomness.
In depth
Randomness is essential for cryptography: keys, nonces, and protocol challenges must be unpredictable. Most systems use pseudo-random generators seeded from physical noise in hardware, which is fine when the entropy source is good, and a disaster when it is not. Quantum sources offer a clear physical basis for entropy. A simple design sends photons to a half-silvered mirror and records which of two detectors fires, and compact versions based on image sensors, which detect shot noise, are small enough for phones.
Commercial products are widespread. ID Quantique's Quantis chips went into a Samsung phone developed with SK Telecom in 2020, and quantum entropy sources are sold as PCIe cards and chips. Standards bodies assess them: the NIST SP 800-90B framework evaluates entropy sources, and certification bodies test devices against it.
The strongest form is certified randomness. A device-independent generator uses a Bell test to prove that its outputs cannot have been predetermined, even if the manufacturer is untrusted. In 2025 NIST and the University of Colorado launched a public randomness beacon whose bits are certified by a Bell test, and JPMorgan Chase with Quantinuum and U.S. national laboratories published in Nature a protocol that uses a 56-qubit quantum computer to generate randomness that can be verified with classical supercomputers.
Technical Definition
Quantum random number generators measure quantum processes with intrinsic randomness: photon path or arrival time, vacuum fluctuations, or the phase noise of a laser. Raw output is processed by randomness extractors to remove bias and classical noise. Device-independent generators certify randomness by observing a violation of a Bell inequality, without trusting the internals of the device.
Visual Explanation: An Analogy
A coin toss seems random but follows physics, so a perfect camera could in principle predict it. A quantum random generator is like a coin that, by the laws of nature, has no hidden mechanism to predict, even in principle.
Key facts
| Item | Detail |
|---|---|
| Sources | Photon path, arrival time, vacuum noise, laser phase noise |
| Commercial examples | ID Quantique Quantis, and the Samsung and SK Telecom quantum phone (2020) |
| Standards | NIST SP 800-90B for entropy sources |
| Certified randomness | Bell-test beacons (NIST and CU Boulder, 2025) and the JPMorgan, Quantinuum protocol (Nature, 2025) |
| Output rates | Megabits to gigabits per second for photonic generators |
Where the idea comes from
Early quantum random number generators were demonstrated in the 1990s, commercial devices appeared around 2001, and compact chip-scale versions emerged in the 2010s. Certified randomness moved from theory to experiment in the 2010s and 2020s.
Real-World Use Cases
- Generating cryptographic keys with strong entropy sources.
- Seeding simulations, lotteries, and gaming systems.
- Providing public randomness beacons for audits and fair selection.
- Testing quantum devices through certified randomness protocols.
How it differs from related ideas
- Pseudo-random generators are deterministic algorithms seeded with entropy, and quantum generators draw on intrinsic randomness.
- Classical physical generators use thermal noise, which is random in practice but not fundamentally unpredictable.
- Certified generators prove their randomness from the observed statistics, and simple quantum generators rely on trust in the device.
Common Misconceptions
- Quantum random numbers are not automatically better for every purpose. Good classical generators are adequate for most uses.
- Raw quantum output still needs processing to remove bias and technical noise.
- A quantum generator that is not certified can still be flawed by engineering defects.
Frequently asked questions
What is a quantum random number generator?
A device that gets random bits from quantum processes, such as which detector a photon hits.
Why use quantum randomness?
Its unpredictability is guaranteed by physics, which gives a firm basis for cryptographic keys, and some designs can prove it.
Are QRNGs in consumer devices?
Yes. A Samsung phone in 2020 included an ID Quantique chip, and similar chips are sold for embedded use.
Related Terms
Keep exploring
- Algorithm: Random Circuit Sampling (Quantum Supremacy Experiments)
- Algorithm: E91 Quantum Key Distribution
- Hardware: Quantinuum H2
- Industry: Quantum Computing for Finance
- Industry: Quantum Computing for Cybersecurity