Fibre based hyperentanglement generation for dense wavelength division multiplexing

Abstract

Entanglement is a key resource in quantum information science and associated emerging technologies. Photonic systems offer a large range of exploitable entanglement degrees of freedom (DOF) such as frequency, time, polarization, and spatial modes. Hyperentangled photons exploit multiple DOF simultaneously to enhance the performance of quantum information protocols. Here, we report a fully guided-wave approach for generating polarization and energy-time hyperentangled photons at telecom wavelengths. Moreover, by demultiplexing the broadband emission spectrum of the source into five standard telecom channel pairs, we demonstrate compliance with fibre network standards and improve the effective bit rate capacity of the quantum channel up to one order of magnitude. In all channel pairs, we observe a violation of a generalised Bell inequality by more than 27 standard deviations, underlining the relevance of our approach.

Simultaneous transmission of hyper-entanglement in 3 degrees of freedom through a multicore fiber

“…Since our entanglement source naturally produces wavelength-correlated photon pairs, the presented approach offers high scalability by additionally integrating dense wavelength-division multiplexing, as is done for example in Ref. [14]. The used wavelength of 1560 nm makes our approach readily integrable into current telecommunication infrastructure, thus paving the way for highly efficient quantum information protocols over deployed fiber networks.…”

“…In recent years, the interest in multiplexing of entangled photons in different DOFs has grown [13][14][15][16][17]. Achieving coherence and entanglement in the multiplexed DOFs offers another exciting avenue for high-rate quantum communication: directly encoding in energy-time or spatial DOFs also allows for high-dimensional protocols, which offer increased capacity in high-dimensional QKD protocols [18][19][20] as well as improved noise resilience [21][22][23], essentially only limited by the spatial or temporal resolution of the detection scheme.…”

On-chip generation of hybrid polarization-frequency entangled biphoton states

“…This would lead to an hyper-entangled polarization-frequency state, in the tensor product form (|H s |V i + |V s |H i ) / √ 2 ⊗ dωdω φ(ω, ω ) |ω s |ω i . This situation opens stimulating perspectives for the implementation of quantum information tasks [53][54][55], in particular in the field of quantum communication to improve bit rates and resilience to noise [56][57][58][59].…”

Broadband polarization-entangled source for C+L-band flex-grid quantum networks

“…The polarization DoF is a staple of quantum optics due to the ease of manipulation and measurement, while the frequency DoF can facilitate deterministic splitting of the photon pairs and various bandwidth allocation and distribution schemes. Such sources have been explored in various material platforms including periodically poled lithium niobate (PPLN) waveguides [6][7][8][9][10][11][12][13][14][15], periodically poled silica fibers [16,17], and semiconductor chips [18,19]. In order to characterize the quality of the entanglement, a common technique is to utilize tunable filters to select a few channel pairs across the spectrum and perform quantum state tomography (QST) [6,15,16].…”

“…In order to characterize the quality of the entanglement, a common technique is to utilize tunable filters to select a few channel pairs across the spectrum and perform quantum state tomography (QST) [6,15,16]. For quantum network deployment, passive optical add/drop multiplexers can slice the spectrum into multiple channels either with a single, multichannel DWDM [7,10,18] or a cascade of DWDM filters [9,11]. In addition, advanced flexgrid bandwidth allocation for broadband bandwidth have been explored based on WSSs [12-14, 17, 19].…”