The quantum cryptographic switch

TL;DR

This paper introduces a quantum cryptographic switch enabling a third party to control the amount of information a receiver can access after transmission, with analysis under noisy quantum channels and practical applications.

Contribution

It proposes a novel quantum cryptographic switch protocol using Bell states and dense coding, allowing controlled information access by a third party, with performance analysis under noise.

Findings

The protocol allows continuous control of information transfer by the third party.

Performance is analyzed under the squeezed generalized amplitude damping channel.

Practical scenarios for implementing the cryptographic switch are discussed.

Abstract

We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.