Random Numbers Certified by Bell's Theorem

Randomness is a fundamental feature in nature and a valuable resource for applications ranging from cryptography and gambling to numerical simulation of physical and biological systems. Random numbers, however, are difficult to characterize mathematically, and their generation must rely on an unpredictable physical process. Inaccuracies in the theoretical modelling of such processes or failures of the devices, possibly due to adversarial attacks, limit the reliability of random number generators in ways that are difficult to control and detect. Here, inspired by earlier work on nonlocality based and device independent quantum information processing, we show that the nonlocal correlations of entangled quantum particles can be used to certify the presence of genuine randomness. It is thereby possible to design of a new type of cryptographically secure random number generator which does not require any assumption on the internal working of the devices. This strong form of randomness generation is impossible classically and possible in quantum systems only if certified by a Bell inequality violation. We carry out a proof-of-concept demonstration of this proposal in a system of two entangled atoms separated by approximately 1 meter. The observed Bell inequality violation, featuring near-perfect detection efficiency, guarantees that 42 new random numbers are generated with 99% confidence. Our results lay the groundwork for future device-independent quantum information experiments and for addressing fundamental issues raised by the intrinsic randomness of quantum theory.Comment: 10 pages, 3 figures, 16 page appendix. Version as close as possible to the published version following the terms of the journa

Trading isolation for certifiable randomness expansion

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (page 41).A source of random bits is an important resource in modern cryptography, algorithms and statistics. Can one ever be sure that a "random" source is truly random, or in the case of cryptography, secure against potential adversaries or eavesdroppers? Recently the study of non-local properties of entanglement has produced an interesting new perspective on this question, which we will refer to broadly as Certifiable Randomness Expansion (CRE). CRE refers generally to a process by which a source of information-theoretically certified randomness can be constructed based only on two simple assumptions: the prior existence of a short random seed and the ability to ensure that two or more black-box devices do not communicate (i.e. are non-signaling). In this work we make progress on a conjecture of [Col09] which proposes a method for indefinite certifiable randomness expansion using a growing number of devices (we actually prove a slight modification of the original conjecture in which we use the CHSH game as a subroutine rather than the GHZ game as originally proposed). The proof requires a technique not used before in the study of randomness expansion, and inspired by the tools developed in [RUV12]. The result also establishes the existence of a protocol for constant factor CRE using a finite number of devices (here the constant factor can be much greater than 1). While much better expansion rates (polynomial, and even exponential) have been achieved with only two devices, our analysis requires techniques not used before in the study of randomness expansion, and represents progress towards a protocol which is provably secure against a quantum eavesdropper who knows the input to the protocol.by Matthew Ryan Coudron.S.M

Quantum reality and squeezed states of light

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 67-71).by Ilya Lyubomirsky.M.S

Students’ view of Quantum Information Technologies

The article is a sort of advanced publication workshop prepared by a group of M.Sc. students in ICT participating in the course on QIT. The idea behind the publishing exercise is to try to link, if possible, individual own work just under realization for the thesis with new unique possibilities offered by the QIT. Each chapter is written by a single author defining concisely her/his research interest in the classical ICT field and trying to find possible correlations with respective abruptly developing branches of the QIT. The chapter texts are somehow moderated by the tutor but are exclusively authored by young researchers. The aim was to present their views on the possible development directions of particular subfields of QIT, if not fully mature, but still based on their own ideas, research and dreams