Near-Maximal Two-Photon Entanglement for Optical Quantum Communication at 2.1μm

Abstract

Owing to a reduced solar background and low propagation losses in the atmosphere, the 2-to 2.5-µm waveband is a promising candidate for daylight quantum communication. This spectral region also offers low losses and low dispersion in hollow-core fibers and in silicon waveguides. We demonstrate near-maximally entangled photon pairs at 2.1 µm that could support device independent quantum key distribution (DIQKD) assuming sufficiently high channel efficiencies. The state corresponds to a positive secure-key rate (0.254 bits/pair, with a quantum bit error rate of 3.8%) based on measurements in a laboratory setting with minimal channel loss and transmission distance. This is promising for the future implementation of DIQKD at 2.1 µm.

Advances in Mid-Infrared Single-Photon Detection

“…To date, SNSPDs seem to be the best choice for detecting single photons in the midinfrared region, in terms of detection efficiency and timing performance. The first application study of QKD in the mid-infrared region was carried out precisely with these devices [20,22]. SPADs and PV detectors, on the other hand, show important progress and can, in the near future, pave the way for the use of out-of-lab quantum technologies at large wavelengths, due to their easy portability, lower energy consumption, and lower costs, although their high dark count rates still remain an unsolved problem.…”

“…First of all, it overcomes the capacity crunch [21] shown by guided wave optics at 1.5 µm. Moreover, the 2-2.5 µm band allows the reduction in intrinsic losses mainly due to Rayleigh scattering, showing minimal losses in the hollow-core photonic band gap fiber [22,23].…”

“…The single-photon detection in MIR with SNSPD has reached almost the same level obtained in NIR in an enormously short period of time. Achievements in saturated quantum efficiency and the progress made in radiation sensor coupling represent the firs great result, which has already led researchers to search for technological applications For example, Prabhakar et al [20] and Dada et al [22] demonstrated the possibility o implementing device-independent quantum key distribution (DI-QKD) with SNSPD a 2.1 µm with a secure key rate of 0.254 bits/pair, by using a NbTiN SNSPDs with detection efficiency rates of roughly one order of magnitude lower than that developed by Chang et al A lidar system with MIR SNSPDs operating at 2.3 µm has been developed [55] demonstrating the viability of these detectors for future free-space photon counting applications. Further improvements for lidar experiments can be achieved by developing lidar systems exploiting an array of detectors with an appropriate read-out circuit [56].…”

Polarization Purity and Dispersion Characteristics of Nested Antiresonant Nodeless Hollow-Core Optical Fiber at Near- and Mid-IR Wavelengths for Quantum Communications

“…The exploration of the 2 𝜇m spectral window indeed goes beyond conventional applications in communication. Notably, both squeezed light and entangled photons have been demonstrated at ∼ 2 𝜇m [17][18][19], marking a significant leap in the realm of high-sensitivity metrology. These advancements are particularly crucial for applications requiring high-sensitivity detection.…”

Quantum entanglement generation on magnons assisted with microwave cavities coupled to a superconducting qubit

“…The quantum entangled states [1][2][3][4] are significant ingredients in quantum information processing. Over past decades, various theoretical and experimental proposals have been presented for processing quantum information by using various systems such as atoms [5][6][7][8][9][10][11][12][13][14], spins [15][16][17][18][19][20][21], ions [22][23][24][25][26][27][28][29], photons [5,[30][31][32][33][34][35][36][37][38][39], phonons [40][41][42], and so on. With the development of technologies, the quantum entanglement has been established not only in microscopic systems, but also in the macroscopic systems such as superconducting circuits [43][44][45][46]…”