Quantum randomness from multi-pixel optical detection

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


Random numbers have many uses in science, statistics, cryptography, gaming, and other
fields. Quantum random number generators are developed with certified randomness.
Randomness in this thesis is characterized by the unpredictability of outcomes. Bell
inequality violation, min-entropy bound, and entropy estimation are the three methods for
randomness certification. Different methods of implementing quantum random number
generators are introduced and compared with their scheme and challenges.
Two-mode certification is discussed with separable two-mode input and two detectors
at the output of a beam splitter, where Fock state input achieves the maximum optimal
guessing probability. The binomial distribution model is employed to describe the twomode
outcomes and a guessing probability confidence interval is obtained.
Multi-pixel certification is introduced with spatial transformation. The guessing probability
for joint pixel detection number is calculated. The optimum beam radius for a
Gaussian illumination is 0:56 times of the detector size. Multiple trials with the same
total photon number are discussed with both Gaussian illumination and uniform illumination.
A Gaussian illumination is more convenient and economic for building the
A CMOS detector from a Samsung Galaxy S7 phone is used in the experiment to
verify both two-mode certification and multi-pixel certification. The optimal guessing
probability and min-entropy are calculated with two-mode certification and 81200-pixel
certification. The min-entropy is estimated with experimental measurements. A minentropy
of around 300 000 bits can be reached with 81200 pixels and it will be larger
with 12 million pixels on CMOS.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510257/1 31/03/2016 29/09/2022
1992201 Studentship EP/P510257/1 30/09/2017 30/03/2022 Mengbo Long
Description The random numbers generated from multipixel detection is proved to be unpredictable both theoretically and experimentally. The unpredictability is verified to be intrinsic randomness. And the random level is scaled with the pixel number given that the detectors are not saturated. It demonstrates an approach that does not need assumptions about the light source, which can cut down the cost of random number generators.
Apart from the above topic, we also developed the theory for cavity-enhanced squeezed state generation. In this project, we focus on generating squeezed states with high squeezing parameter as well as high purity.
Exploitation Route The random number generation can be used in quantum communication, cryptography, and scientific simulations. The cavity-enhanced squeezed state generation can be applied as the key component of quantum information and quantum communication.
Sectors Digital/Communication/Information Technologies (including Software),Security and Diplomacy

Description National Quantum Showcase 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Our QRNG demo has received great popularity at the National Quantum Showcase for two consecutive years. There are policymakers and industry who show enthusiasm to our QRNG demo. Some ask about the industrialisation of the QRNG.
Year(s) Of Engagement Activity 2018,2019
URL https://nqit.ox.ac.uk/event/national-quantum-technologies-showcase-2019
Description Quantum in the City: the shape of things to come 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact The public showed a lot of interest in our QRNG demo and our research about quantum information. There are a lot of families attending the event. The questions and discussions during the event helped to connect our research to the general public.
Year(s) Of Engagement Activity 2019
URL https://www.rigb.org/whats-on/events-2019/november/public-quantum-in-the-city
Description Schools challenge STEM Market 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact This event is the culmination of The Schools Challenge 2018, which is run as a collaboration between Imperial College London and J.P. Morgan. Since October, year 9 students (13-14 years old) have been challenged to come up with solutions to some of London's most pressing environmental issues: air pollution, making London more sustainable or improving London's biodiversity - a challenge set by the Mayor of London's Office. Working in teams of eight, the teams have been asked to design a product that can solve one of these issues, conduct market research, create a prototype to demonstrate their ideas, develop a brand and ideas on how to market the product, devise a basic business plan and present their ideas using a posterboard and a seven minute spoken presentation. The students explored our STEM market place, where we exhibited our demo. The STEM market place becomes a great opportunity to inspire students to continue to pursue their interests in Science, Technology, Engineering and Maths, through interactive exhibits and the opportunity to interact with STEM specialists.
Year(s) Of Engagement Activity 2019
URL https://www.imperial.ac.uk/news/190274/london-school-students-science-solve-city/