Authentication of continuous-variable quantum messages

We introduce the first quantum authentication scheme for continuous-variable (CV) states. Our scheme is based on trap states, and is an adaptation of a discrete-variable scheme by Broadbent et al. [15], but with more freedom in choosing the number of traps.The CV traps are squeezed states.As the CV variant of quantum one-time pad (QOTP) encryption we introduce gaussian-distributed displacements.We provide a security proof, mostly following the approach of Broadbent and Wainewright [13]. We take into account the inevitable imperfections due to the finite squeezing and the finite width of the gaussian QOTP distribution.As a necessary ingredient for the proof we derive the CV analogue of the Pauli Twirl. Since CV quantum systems fit well with existing optical communication infrastructure, they provide a promising platform for implementing quantum-cryptographic schemes and distributed quantum-computational tasks. This work expands the toolbox for securing CV quantum communication.