Gaussian private quantum channel with squeezed coherent states

TL;DR

This paper introduces an enhanced Gaussian private quantum channel using squeezed coherent states, demonstrating improved security bounds and advantages over traditional coherent states in continuous variable quantum communication.

Contribution

It proposes a new GPQC scheme with squeezed coherent states, showing it outperforms the coherent state version in accessible information and security against beam splitting attacks.

Findings

GPQCwSC surpasses GPQCo in accessible information bounds.

Squeezed states offer better security against beam splitting attacks.

Squeezing approximated by superposition of displacements in small regimes.

Abstract

While the objective of conventional quantum key distribution (QKD) is to secretly generate and share the classical bits concealed in the form of maximally mixed quantum states, that of private quantum channel (PQC) is to secretly transmit individual quantum states concealed in the form of maximally mixed states using shared one-time pad and it is called Gaussian private quantum channel (GPQC) when the scheme is in the regime of continuous variables. We propose a GPQC enhanced with squeezed coherent states (GPQCwSC), which is a generalization of GPQC with coherent states only (GPQCo) [Phys. Rev. A 72, 042313 (2005)]. We show that GPQCwSC beats the GPQCo for the upper bound on accessible information. As a subsidiary example, it is shown that the squeezed states take an advantage over the coherent states against a beam splitting attack in a continuous variable QKD. It is also shown that a squeezing operation can be approximated as a superposition of two different displacement operations in the small squeezing regime.