title: Quantum key distribution with higher-order alphabets using spatially encoded qudits.
abstract: We present a proof of principle demonstration of a quantum key distribution scheme in higher-order -dimensional alphabets using spatial degrees of freedom of photons. Our implementation allows for the transmission of 4.56 bits per sifted photon, while providing improved security: an intercept-resend attack on all photons would induce an average error rate of 0.47. Using our system, it should be possible to send more than a byte of information per sifted photon.
authors.affiliation: Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972, Brazil. swalborn@if.ufrj.br
authors.forename: S P
authors.initials: SP
authors.lastname: Walborn
authors.forename: D S
authors.initials: DS
authors.lastname: Lemelle
authors.forename: M P
authors.initials: MP
authors.lastname: Almeida
authors.forename: P H Souto
authors.initials: PH
authors.lastname: Ribeiro