Demonstration of Entanglement Purification and Swapping Protocol to Design Quantum Repeater in IBM Quantum Computer

TL;DR

This paper demonstrates a quantum repeater protocol on IBM's quantum computer, utilizing entanglement swapping and a novel purification method to improve entanglement fidelity over noisy channels.

Contribution

It presents the first implementation of a quantum repeater with entanglement purification on a real quantum processor, combining swapping and purification techniques.

Findings

Successful entanglement swapping verified by quantum state tomography

Purification protocol enhances entanglement fidelity in noisy channels

Implementation on IBM's quantum processor validates practical quantum repeater design

Abstract

Quantum communication is a secure way to transfer quantum information and to communicate with legitimate parties over distant places in a network. Although communication over a long distance has already been attained, technical problem arises due to unavoidable loss of information through the transmission channel. Quantum repeaters can extend the distance scale using entanglement swapping and purification scheme. Here we demonstrate the working of a quantum repeater by the above two processes. We use IBM's real quantum processor `ibmqx4' to create two pair of entangled qubits and design an equivalent quantum circuit which consequently swaps the entanglement between the two pairs. We then develop a novel purification protocol which enhances the degree of entanglement in a noisy channel that includes combined errors of bit-flip, phase-flip and phase-change error. We perform quantum state tomography to verify the entanglement swapping between the two pairs of qubits and working of the purification protocol.