Quantum Random Number Generator

A device that produces true randomness from quantum measurements, not pseudo-randomness from algorithms.

A Quantum Random Number Generator (QRNG) exploits the fundamental randomness of quantum mechanics to generate provably random numbers. Unlike classical pseudo-random number generators (PRNGs), QRNGs produce true randomness.

Why Quantum?

Classical “Random” Numbers

• PRNGs are deterministic algorithms
• Given the seed, output is predictable
• Technically pseudo-random, not truly random

Quantum Randomness

• Measurement outcomes are fundamentally unpredictable
• Not due to ignorance: nature itself is random
• No hidden variables determine outcomes (Bell’s theorem)

Basic Principle

Simplest QRNG:

1. Prepare qubit in $|+⟩=\frac{1}{\sqrt{2}}(|0⟩+|1⟩)$
2. Measure in computational basis
3. Result (0 or 1) is truly random with 50/50 probability

Implementation Methods

Photon-Based

Other Platforms

• Superconducting qubits
• Atomic systems
• Quantum dots

Rates and Devices

Commercial QRNGs are available from companies like ID Quantique, Quantis, and others.

Applications

Cryptography

• Key generation for encryption
• Nonces and initialization vectors
• QKD bit choices

Scientific

• Monte Carlo simulations
• Statistical sampling
• Randomized algorithms

Gaming and Lotteries

• Provably fair random selection
• Online gambling
• Government lotteries

Certifying Randomness

How do you know the QRNG is working properly?

Device-Dependent

Trust that the device implements quantum measurement correctly.

Device-Independent

Use Bell inequality violations to certify randomness without trusting devices:

• CHSH violation proves quantum process
• Randomness certified by physics, not device specifications

Self-Testing

Intermediate approaches that verify some properties.

Challenges

Solutions

• Randomness extraction (post-processing to remove bias)
• Statistical testing (NIST tests, Diehard tests)
• Device certification

See also: Quantum Key Distribution, Measurement, Bell Inequality