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Photonic Crystals for Integrated Communication Systems
Published in Filippo Capolino, Applications of Metamaterials, 2017
Henri Benisty, Jean-Michel Lourtioz
Clearly, the above results represent meaningful steps toward ultimate photon sources. The use of a single QD emitter instead of QWs in PhC microcavities offers additional opportunities, especially toward on-demand single-photon sources for quantum cryptography applications. Another challenge would be to funnel most of the emitted photons into a neighboring low-loss PhC waveguide instead of extracting them vertically. Although extensive simulation might be necessary to optimize the overall design, cavity-waveguide coupling efficiencies as high as 90% have already been demonstrated for a system composed of a L3 microcavity and a W1 waveguide [60]. Finally, the optimization of PhC microcavities in the substrate approach also merits to be considered for operating microlasers at higher power with better heat sinking, be it at the cost of an increase of the effective volume of the cavity mode and of a lower Q factor. Having in mind the impressive progress of PhC cavities and lasers over the last 10 years, major developments can reasonably be expected in the midterm for PhC microcavity lasers.
Quantum Cryptography and Teleportation
Published in F.J. Duarte, Quantum Optics for Engineers, 2017
A schematic of an experimental apparatus based on the description of Bennett et al. (1992a) is given in Figure 19.5. In essence what we have here is a single-photon source followed by a polarizer that polarizes the light horizontally (↔). Next, the polarized photon goes through two electro-optics phase shifters (Pockels cells, see Chapter 15), which enable the generation of light polarized in the ↔, ↕, L, and R states. These are the emitter’s, or sender’s, Pockels cells (EPC). Next the polarized photon propagates in free space and is received at the receiver’s Pockels cell (RPC). The arriving photon then goes through a calcite Wollaston prism (WP) that provides two different paths for the ↔ and ↕ polarized photons onto their respective photomultiplier tubes.
The Second Quantum Revolution
Published in Jonathan P. Dowling, Schrödinger’s Web, 2020
The ideal BB84 protocol should be carried out with single photons. However, the single-photon source technology is still slow, expensive, and cumbersome. Many deterministic single-photon guns require the source to be refrigerated to near absolute zero. Instead, the community has turned to using faint laser pulses.39 Laser technology is well advanced, and it is relatively easy and cheap to make attenuated laser pulses with very rapid repetition rates for high-speed quantum cryptography. The pulses are time-binned so that in each picosecond time slot, there is at most one pulse. The problem with faint laser pulses is that they do not contain exactly one photon – they sometimes contain two or more – and they often contain zero. (See Figure 4.5.) Let us suppose we have time-binned the laser pulses – we get one pulse per picosecond. That corresponds to a gigahertz transmission rate. If the pulses contain more than one photon, then Eve can put a non-50–50 beam splitter in the laser path and occasionally split off that extra photon, which gives her some information about the private key. To mitigate this beam splitter attack, Alice chooses laser pulses that are so weak that, most of the time, the pulse contains zero photons. Sometimes it includes one, and with a minuscule probability it includes two or more. Decreasing the odds of two or more increases the odds that the pulse contains zero photons, which reduces the key transmission rate. Even then, Eve still can be sifting off the very few extra photons in the pulses that contain two or more. It is impossible for Alice and Bob to detect Eve because photons are lost all the time in any communication system. Eve is hiding in the background photon loss.
Photon blockade through microcavity-engineered plasmonic resonances
Published in Journal of Modern Optics, 2019
Yue Yu, Hong-Yu Liu, Rong-Can Yang
The single-photon source plays an important role in quantum information technologies, and the most significant aspect of a single-photon source is to realize photon blockade (PB). It is well known that PB comes from the strong photon–photon interaction. This is called the PB effect which is the excitation of a first photon that blocks the transport of a next photon for the coupling in the system. Imamolu (1) first proposed the concept on condition that strong kerr nonlinearity, they find that photon antibunching is accounted for PB. Up to now, a great number of schemes with PB have been proposed, for instance, four-level quantum emitter coupled to a photonic-crystal nanocavity, dot-cavity system, weakly nonlinear photonic molecules (2,3,4) such as circuit cavity quantum electrodynamics systems (5,6,7,8). Among the applications, PB can also be achieved in optomechanical systems (9,10), and photonic-crystal cavities, quantum-reservoir engineering (11), semiconductor microcavities with nonlinearities (12,13,14) and optical nanocavities (15,16,17). Recently, a scheme has been proposed that utilized localized-surface plasmon resonance (LSPR) (18) to achieve microcavity-engineered plasmonic resonances by Pai Peng. They have found that it can enhance coherent light-matter interactions. So in this article, we find that it can achieve PB by LSPR; furthermore, this scheme is not only more feasible in experiments but also has more obvious photon antibunching. The observation of CPB is based on large nonlinearities to change the energy-level structure of the system except for the difference that the principle of UPB can be understood as the destructive quantum interference between distinct driven-dissipative pathways.
Engineering the spectral and temporal properties of a GHz-bandwidth heralded single-photon source interfaced with an on-demand, broadband quantum memory
Published in Journal of Modern Optics, 2018
P. S. Michelberger, M. Karpiński, I. A. Walmsley, J. Nunn
Parametric single-photon sources, based on downconversion in a non-linear medium, rely on heralding the presence of a signal photon by detection of a correlated idler photon. A strong pump pulse drives a multi-mode pairwise squeezing interaction that generates signal and idler photons in pairs. It produces the bi-photon state
Photon statistics of twisted heralded single photons
Published in Journal of Modern Optics, 2020
Nijil Lal, Anindya Banerji, Ayan Biswas, Ali Anwar, R. P. Singh
Single photon sources are one of the most important quantum sources of light finding applications in quantum key distribution, random number generation, quantum computing with photons and quantum metrology (1–4). One of the most popular technique to produce a single photon source is to use the spontaneous parametric down conversion (SPDC) process in a nonlinear crystal (5, 6). In this process, one photon of the pump is converted to two photons of lower energies, which propagate in a certain direction following the conservation laws of energy and momentum. Since the two down converted photons are generated at the same time, detection of one photon heralds the presence of the other (7, 8). Therefore, single photon sources obtained by using this technique are generally called as heralded single photon sources. Optical vortices or Laguerre Gaussian (LG) beams with zero radial index are gaining popularity in implementing various quantum information protocols (9, 10) as they provide an extra degree of freedom in the form of orbital angular momentum (OAM) (11, 12) that can be measured using standard experimental techniques (13–15). Optical vortices of different orders or azimuthal indices form different spatial modes of light with their characteristic properties (16–20). Intensity correlations of classical optical vortices are found to have dependence on the order of the vortex while scattered from a rotating ground-glass plate (16). Such studies evoke interest in the correlation properties of single photons carrying OAM generated in spontaneous processes such as parametric down conversion. In the present work, starting with the Gaussian mode, we take different orders of vortices as a pump to the nonlinear crystal and study the intensity correlations of down converted photons to characterize them for single photon sources of light including twisted single photons.