# Quantum control attack on quantum key distribution systems

## TL;DR

This paper introduces a quantum control attack on quantum key distribution systems, where an eavesdropper uses advanced quantum measurement and control techniques to intercept and alter quantum states without detection.

## Contribution

It presents a novel quantum control attack method utilizing unitary decomposition for eavesdropping on QKD, expanding understanding of potential vulnerabilities.

## Key findings

- The attack can successfully intercept quantum keys under certain conditions.
- Different discrimination strategies affect the attack's effectiveness.
- Example with two non-orthogonal states illustrates the attack's application.

## Abstract

In this paper we present the quantum control attack on quantum key distribution systems. The cornerstone of the attack is that Eve can use unitary (polar) decomposition of her positive-operator valued measure elements, which allows her to realize the feed-forward operation (quantum control), change the states in the channel after her measurement and impose them to Bob. Below we consider the general eavesdropping strategy and the conditions those should be satisfied to provide the attack successfully. Moreover we consider several types of the attack, each of them is based on a different type of discrimination. We also provide the example on two non-orthogonal states and discuss different strategies in this case.