Anonymous transmission in a noisy quantum network using the W state

The protocol allows a sender $S$ to transmit an arbitrary quantum state $|\psi \rangle$ to a receiver $R$ in an anonymous way and uses the $N$-partite $W$ state as a quantum resource.

Assumptions

The protocol relies on a set of classical subroutines (collision detection, receiver notification, veto and logical OR). Their proposed implementation [1] has been shown to be information-theoretically secure in the classical regime, even with an arbitrary number of corrupted participants, assuming the parties share pairwise authenticated private channels and a broadcast channel.

The protocol assumes that the implementations listed above remain secure even in the presence of a quantum adversary.

Outline

The $N$ nodes first ensure that a single one is willing to send information. They go on with notifying the receiver of its role. They use a trusted source of $W$ states to share entanglement between the $N$ nodes. This is done via a measurement performed by all nodes except the sender and receiver. Entanglement is only established probabilistically, but when it is successful, it can be used to teleport an arbitrary quantum state chosen by $S$. The classical communication for teleporting the state is performed anonymously.

References

1. A. Broadbent and A. Tapp, inAdvances in Cryptology– ASIACRYPT 2007, edited by K. Kurosawa (Springer Berlin Heidelberg, Berlin, Heidelberg, 2007) pp. 410–426.