Quantum information processing with space-division multiplexing optical fibres

Abstract

The optical fibre is an essential tool for our communication infrastructure since it is the main transmission channel for optical communications. The latest major advance in optical fibre technology is spatial division multiplexing (SDM), where new fibre designs and components establish multiple co-existing data channels based on light propagation over distinct transverse optical modes. Simultaneously, there have been many recent developments in the field of quantum information processing (QIP), with novel protocols and devices in areas such as computing, communication and metrology. Here, we review recent works implementing QIP protocols with SDM optical fibres, and discuss new possibilities for manipulating quantum systems based on this technology.Quantum information processing (QIP) is a field that has seen tremendous growth over the many years since Richard Feynman's seminal talk on the use of quantum computers to simulate physical systems [1]. When information bits are encoded on individual or entangled quantum states, a gain over traditional systems can be seen for some information processing tasks. A famous example is the well-known Shor's algorithm for prime number factorisation running on a quantum computer, where an impressive reduction in resources is obtained when compared to classical algorithms [2]. Another major application of QIP is in communication security, where the fact that unknown quantum states cannot be faithfully cloned [3] is exploited to detect the presence of an eavesdropper. This concept was used as the core foundation behind quantum key distribution (QKD), a communication protocol designed to distribute random private keys among remote parties [4,5]. As the first application to showcase in practice the benefits of QIP, QKD has experienced huge development ever since [6][7][8]. QKD is part of a more general family of protocols called quantum communications (QC), which includes other schemes such as quantum teleportation and entanglement swapping [9], aiming to be the communication backbone supporting future networks of quantum computers [10].During the last decades a number of technological features were developed by the telecommunication community in order to support the continuous increase in demand for more transmission bandwidth over a communication channel. These developments have been motivated by several applications that have cropped up along the years, from the internet to social networking and high-quality on-demand video streaming. Arguably the optical fibre has played a major role in the success of the telecommunication infrastructure, mainly due to its high transparency and highbandwidth support [11]. Technologies such as wavelength division multiplexing (WDM) [12], and the erbium doped fibre amplifier (EDFA) [13,14] have been major catalysts to the extremely high capacities and ultra-long transmission distances available today. The latest technological drive towards maintaining the bandwidth growth is called spatial division multiplexing (SDM), and it consists of employi...

High-fidelity spatial mode transmission through a 1-km-long multimode fiber via vectorial time reversal

“…Numerous methods have been proposed to increase the secure key rate in QKD, such as the development of new protocols 3 , use of high-performance detectors 4 , and wavelength-division multiplexing 5 . The spatial degree of freedom in a multimode fiber (MMF) has long been recognized as an additional resource to further increase the communication rate by either mode-division multiplexing 6 – 13 or high-dimensional encoding 14 – 18 . It is compatible with other multiplexing methods such as wavelength-division multiplexing and can be also used to enhance quantum teleportation 19 and entanglement distribution 20 , 21 .…”

Multi-core fiber integrated multi-port beam splitters for quantum information processing

“…Arguably, the development of a major part of experimental quantum information (QI) relies on the fact that it is based heavily on the same hardware employed by classical optical communication [9][10][11][12][13]. Therefore, it is natural to expect that future development will take place using SDM hardware [14]. Indeed, in the past couple of years, the first quantum communication experiments based on MCFs have appeared.…”

Stable Transmission of High-Dimensional Quantum States Over a 2-km Multicore Fiber

“…One of the main challenges of this approach is the reliable transmission of such states: a possibility is to couple each path to different fibers, but superposition states would be impaired by the different phase drifts. Instead, using different cores of a multicore fiber improve the quality of the transmission, as the relative phase drifts of each core are strongly suppressed since they are placed within the same cladding [18], [19]. Multicore fibers propagation losses are similar to those of standard single mode fibers, and their inter-core cross-talk is low enough to ensure the reliable transmission of quantum states [20]- [22].…”