Assuring quantum randomness from simple optical measurements

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics


Random numbers are a fundamental part of science and technology, being especially relevant for
cryptography, gaming, simulations or statistics. Quantum random number generators (QRNG) rely on
the intrinsic randomness of quantum mechanics to generate true and unpredictable random numbers,
unachievable from the classical physics perspective. Methods and protocols to certify and quantify
the randomness in the output of a quantum system are a current subject of intensive research. In
this thesis, we focus on the emergent field of quantum random number generation proposing two semidevice-
independent schemes to harvest quantum entropy while discussing in detail their strengths and
weaknesses. With the purpose of developing a certification protocol for these approaches, we thoroughly
study the implementation of the photodetector and the possible vulnerabilities it might introduce in
our approaches. Finally, we perform a proof-of-concept experiment to demonstrate the feasibility of
the suggested schemes and experimentally investigate the correctness of the derived theoretical models.
The results for these experiments revealed a satisfactory agreement with the theory and enabled us to
extract 1.58 bits of quantum randomness per sample with an 8-bit digitisation out of our QRNG.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510257/1 01/04/2016 30/09/2021
2012610 Studentship EP/P510257/1 01/10/2017 30/01/2022 Santiago SEMPERE LLAGOSTERA
Description School Challenge Exhibitor 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact We exhibited our QRNG demo in an event that included more than 100 students from different local schools. These students were participating in an interschool challenge. The students approached our stand and learnt about quantum in general and about why QRNG are and will be important in the near future. This activity raised awareness about the capabilities and the importance of the so-called emerging quantum technologies.
Year(s) Of Engagement Activity 2019