Design and characterization of a fully integrated InP continuous variable quantum key distribution transmitter with radiofrequency antenna

Abstract

Current advances in quantum computers and quantum decryption algorithms make possible something unimaginable: the decryption and subsequent obtaining of the encryption key in a reasonable amount of time from previously encrypted messages. For a conventional computer it becomes a brute force attack taking hundreds of years, however for a quantum computer is an inmmediate task. For this reason the useful life of the encryption keys is drastically reduced and their renewal and transmission in a safe and reliable way is necessary. The main movation of the present Ph.D. Thesis was the emerging interest by the quantum key distribution in cryptography. To this aim, the design and manufacturing of a CV-QKD transmitter was carried out in InP technology. For the development of the work, the in-house implemented measurement setup has been critical for the experimental characterization of the transmitter functional modules. This Thesis provides a viable and low-cost quantum key transmission solution through a continuous variable quantum transmitter. The choice of the technology used makes it possible to facilitate a high integration of all the devices within the same chip and increase its modulation rate through the use of current injection modulators, so that it is not required to use external lasers or other elements of large dimensions. In turn, by using continuous variable, the use of costly cryogenic and adaptation systems is not necessary to guarantee the correct operation of single-photon optical sources. Being a quantum states key encoded transmitter, a secure transmission of the key along the channel is guaranteed, allowing detection if there is an interception of the key during its transmission along the channel. Among other milestones, having provided the transmitter with independent optical and radiofrequency outputs has expanded the possibilities of using the device. The design of on-chip and off-chip antennas carried out for different frequency bands has completed the achievements of this Thesis.