Determining the output port from the distance

TL;DR

This paper explores how entangled quantum states and multi-input devices can be used to determine output ports in quantum systems, identifying the multi-input-port quantum sorter as the key device and analyzing multi-observer scenarios with GHZ and W states.

Contribution

It proves that the multi-input-port quantum sorter is the black-box enabling port determination and extends the analysis to multi-observer cases with GHZ and W states.

Findings

The black-box is the multi-input-port quantum sorter.

Port determination is possible with two observers using entangled states.

Analysis of three-observer scenarios with GHZ and W states.

Abstract

In this paper we discuss the following scenario. Suppose that two distant observers share an entangled state of two $D$-level systems. The two observers, Alice and Bob, have to send randomly their particles through a multi-input multi-output device. The task is to determine the nature of this device or black-box, such that Alice will be able to determine with certainty the output port of Bob's particle. We prove that this black-box is the multi-input-port quantum sorter. Further, we investigate if it is possible to determine the output port in the case when three observers are involved by analyzing the cases when the Greenberger-Horne-Zeilinger (GHZ) state and the W state are used.