Experimental entanglement distillation using Schmidt projection on multiple qubits

TL;DR

This paper demonstrates an experimental implementation of Schmidt projection for entanglement distillation on multiple qubits, confirming its efficiency and potential applicability to various quantum systems.

Contribution

It presents the first experimental realization of Schmidt projection on four-qubit states using single-photon quantum logic, showing consistent maximally entangled outputs.

Findings

Output is always maximally entangled regardless of input quality

Measured efficiency matches theoretical predictions

Implementation strategy is adaptable to other quantum systems

Abstract

Entanglement distillation is a procedure for extracting from one or more pairs of entangled qubits a smaller number of pairs with a higher degree of entanglement that is essential for many applications in quantum information science. Schmidt projection is a unique distillation method that can be applied to more than two pairs of entangled qubits at the same time with high efficiency. We implement the Schmidt projection protocol by applying single-photon two-qubit quantum logic to a partially hyperentangled four-qubit input state. The basic elements of the procedure are characterized and we confirm that the output of Schmidt projection is always maximally entangled independent of the input entanglement quality and that the measured distillation efficiency agrees with theoretical predictions. We show that our implementation strategy can be applied to other quantum systems such as trapped atoms and trapped ions.