Compact linear optical scheme for Bell state generation

TL;DR

This paper presents a compact linear optical scheme using fewer components to generate Bell states with higher success probability, leveraging four-photon interference for improved efficiency.

Contribution

It introduces the most compact five-mode interferometer scheme for Bell state generation, optimizing component use and increasing success probability compared to previous methods.

Findings

Uses five-mode interferometer and single detector, fewer than previous schemes.

Achieves success probability of 1/9, higher than 2/27 of prior schemes.

Employs four-photon interference, enhancing entanglement generation efficiency.

Abstract

The capability of linear optics to generate entangled states is exploited in photonic quantum information processing, however, it is challenging to obtain entangled logical qubit states. We report, to the best of our knowledge, the most compact scheme producing the dual-rail-encoded Bell states out of four single photons. Our scheme requires a five-mode interferometer and a single photon detector, while the previously known schemes use six-mode interferometers and two photon detectors. Using computer optimization, we have found a decomposition of the five-mode interferometer with a minimum number of beam-splitters and phase-shift elements. Besides compactness, our scheme also offers a success probability of $1/9$, which is higher than $2/27$ provided by the six-mode counterparts. The analysis suggests that the elevated success probability is connected to higher order of photon interference realized by our scheme, in particular, four-photon interference is implemented in our scheme, while three-photon interference was implemented in previous counterparts.