Device-independent randomness amplification with a single device

• We propose a protocol for device independent randomness amplification.
• Our protocol repeatedly re-uses a single device decomposable into three parts.
• Weak random sources with min-entropy rate greater than 14log2⁡(10) can be amplified.
• Security against all-quantum adversaries is achieved.

Expansion and amplification of weak randomness with untrusted quantum devices has recently become a very fruitful topic of research. Here we contribute with a procedure for amplifying a single weak random source using tri-partite GHZ-type entangled states. If the quality of the source reaches a fixed threshold R=log2⁡(10)R=log2⁡(10), perfect random bits can be produced. This technique can be used to extract randomness from sources that can't be extracted neither classically, nor by existing procedures developed for Santha–Vazirani sources. Our protocol works with a single fault-free device decomposable into three non-communicating parts, that is repeatedly reused throughout the amplification process.