ITR: Improving the Security of Quantum Cryptography with Modified Coherent State

Indiana University, Bloomington IN

Investigators

Abstract

Intellectual Merit Progress has been made in producing single photon states. But so far those sources have small efficiency and are wavelength dependent and are limited for practical applications. Recently a new scheme was proposed and demonstrated for producing photon source with sub-Poissonian photon statistics. The scheme relies on a two-photon quantum interference phenomenon to reduce and eventually cancel the two-photon events from a coherent state. In this program, we propose to implement the scheme in an optical communication environment. More specifically, we will start with a fiber pulsed laser as the primary source and use a combination of wave guide nonlinear optical materials to produce a two-photon state for canceling the two-photon events in a coherent state. The technical challenge will primarily be the temporal mode match for a complete destructive two-photon interference. Such a source has the advantages of high secure data rate, well-defined direction and wavelength independence for practical application in quantum cryptography. This source can also be used to form a three-photon interferometer for nonlocality test of quantum mechanics. Broader Impacts Quantum cryptography, when implemented in the correct condition, will provide unbreakable codes for secure communication. The potential benefit of this technology is tremendous, given the current status of security issue in information technology. The proposed program will significantly improve the applicability of quantum cryptography. Participation of graduate students and undergraduate students in the research is an integral part of the proposed program, which will train and prepare next generation quantum physicists for the information age in the new century. Results of the research will be published in international journals to enhance scientific and technological understanding.