Measurement-device-independent randomness source based on mode-competition in a gain-switched VCSEL

Measurement-device-independent randomness source based on mode-competition in a gain-switched VCSEL

Seminar author:Tomás Fernández Martos

Event date and time:02/20/2025 02:30:pm

Event location:Seminar Room, GIQ

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In this work, we prove the security of a randomness generation protocol based on operating a vertical-cavity surface-emitting laser in a gain-switching manner. The source of entropy is the random alternation between orthogonal polarization modes induced by spontaneous emission inside the laser cavity. Our prepare-and-measure protocol features two trusted preparations and a single uncharacterized and untrusted measurement. First, using semidefinite programming techniques, we upper bound the maximum probability for an attacker to guess the outcome for a single use of the device. Then, combined with the entropy accumulation theorem and with a study of finite-size effects, we use this result to lower bound the minimum amount of secure smooth min-entropy that can be generated without making assumptions of an i.i.d. regime. We are able to certify positive entropy rates in the finite-size regime for as low as 7E4 rounds.