Linear-optical fusion boosted by high-dimensional entanglement

TL;DR

This paper introduces a probabilistic linear-optical measurement for projecting qudit pairs onto Bell states, enabling higher-probability entanglement of high-dimensional states and improving quantum repeater protocols.

Contribution

It presents a novel measurement scheme that enhances entanglement fusion efficiency for high-dimensional qudits using linear optics without ancillas.

Findings

Success probability of $1-d^{-1}$ without ancillas.

Success probability of $1-d^{-(k+1)}$ with ancillas.

Application to a fast quantum repeater protocol.

Abstract

We propose a quantum measurement that probabilistically projects a pair of qudits of dimension $d$ onto a Bell state in a two-qubit subspace. It can be performed using linear-optical circuits with the success probabilities of $1-d^{-1}$ without ancilla photons and $1-d^{-(k+1)}$ with $2(2^{k}-1)$ ancilla photons. It allows us to entangle two independently-prepared high-dimensional entangled states two-dimensionally with higher probabilities than ones of linear-optical fusion gates on qubits. As an application, we propose a fast quantum repeater protocol with three-qudit GHZ states and quantum memories.