Novel single photon sources for new generation of quantum communications

P. M. Intallura

Anjali Jatwani, Amit Verma

A single-photon source is a key advancement for quantum computing, quantum sensing, metrology, and quantum communication. These applications use single photons and have demanding standards for the effectiveness of single-photon generation. All available single photon source (SPS) is probabilistic and the search for deterministic SPS is challenging and relatively new. In this work, we explore a quantitative approach that can be applied to various sources with well-defined mathematical distribution functions in photon emission. If we have a photon number distribution, then we can easily compute the possibility of emission of a single photon from the source. Here, we observe the single photon possibility in a quantum state named as New Generalised Binomial State. Furthermore, this criterion has been applied to a single photon added New Generalised Binomial state and a single photon subtracted New Generalised Binomial State too. This technique helps us to characterize the quality of a single photon source. We explore the variation of SPS probability with different parameters and it is found that probability varies with the total number of photons in a system, the q parameter should be negative and the addition of a Photon is more suitable than subtraction for single photon source criterion.

S. V. Sorokin, N. A. Maleev, M. M. Kulagina +13 more

Maria Tengner

For any communication, the conveyed information must be carried by some physical system. If this system is a quantum system rather than a classical one, its behavior will be governed by the laws of quantum mechanics. Hence, the properties of quantum mechanics, such as superpositions and entanglement, are accessible, opening up new possibilities for transferring information. The exploration of these possibilities constitutes the field of quantum communication. The key ingredient in quantum communication is the qubit, a bit that can be in any superposition of 0 and 1, and that is carried by a quantum state. One possible physical realization of these quantum states is to use single photons. Hence, to explore the possibilities of optical quantum communication, photonic quantum states must be generated, transmitted, characterized, and detected with high precision. This thesis begins with the first of these steps: the implementation of single-photon sources generating photonic qubits. The sources are based on photon-pair generation in nonlinear crystals, and designed to be compatible with fiber optical communication systems. To ensure such a compatibility and to create a high-quality source, a theoretical analysis is made, optimizing the coupling of the photons into optical fibers. Based on the theoretical analysis, a heralded single-photon source and a two-crystal source of entangled photons-pairs are experimentally implemented. The source of entangled photons is further developed into a compact source with a narrow bandwidth compatible with standard telecommunication wavelength-division multiplexers, and even further developed to a more stable one-crystal source. The sources are to be used for quantum communication in general and quantum cryptography in particular. Specifically, a heralded single-photon source is implemented and then used for a full test of a decoy-state quantum cryptography protocol.

Shengzhi Wang, Minjie Wang

High-quality single-photon sources are crucial for the development of simple quantum devices. Quantum communication stands at the forefront of cutting-edge technologies, promising unprecedented levels of security and efficiency. A cornerstone of this revolutionary field is the development of high-speed single-photon sources, which play a pivotal role in quantum key distribution and other quantum communication protocols. In this context, the concept of space multimode emerges as a promising avenue to propel the capabilities of single-photon sources to new heights. We have spatial multiplexing technology to develop single-photon sources that deliver high-speed heralded single photons in the Duan-Lukin-Cirac-Zoller (DLCZ) scheme. We propose a spatial multiplexing single-photon source scheme based on the DLCZ. Compared to a single spatial mode, by adding six spatial modes through spatial multiplexing, the single-photon generation rate increases 4.3 times. And the second-order correlation function of single photons is less than 0.5. We show that expanding the spatial degrees of freedom of the quantum storage scheme based on DLCZ does not affect the single-photon properties. The generation rate of the single photon can be significantly increased through spatial multiplexing with a feedback circuit. Our approach offers a promising path to creating a high-speed photon source based on a spatial multimode scheme.

Timm Gao, Martin von Helversen, C. Antón +2 more