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We propose an efficient quantum key distribution protocol based on the photon-pair generation from parametric down-conversion (PDC). It uses the same experimental setup as the conventional protocol, but a refined data analysis enables…

Quantum Physics · Physics 2009-11-13 Yoritoshi Adachi , Takashi Yamamoto , Masato Koashi , Nobuyuki Imoto

High-rate entanglement generation is essential for the realization of practical quantum repeaters. To this end, frequency multiplexing of the photons employed is an effective approach. In particular, schemes using cavity-enhanced…

Quantum Physics · Physics 2026-04-02 Ryoma Komatsudaira , Tomoyuki Horikiri

Device-independent quantum key distribution (DIQKD) guarantees unconditional security of secret key without making assumptions about the internal workings of the devices used. It does so using the loophole-free violation of a Bell's…

Quantum Physics · Physics 2016-05-04 Kaushik P. Seshadreesan , Masahiro Takeoka , Masahide Sasaki

We present time- and frequency-resolved simulations of quantum key distribution~(QKD) systems employing highly entangled biphoton quantum states. Our simulations are based on expansions of the covariance matrix and photon detection…

Quantum Physics · Physics 2024-12-03 Philipp Kleinpaß , Thomas Walther , Erik Fitzke

Unwanted multiphoton emission commonly reduces the degree of entanglement of photons generated by non-classical light sources and, in turn, hampers their exploitation in quantum information science and technology. Quantum emitters have the…

Fault tolerant on-chip photonic quantum computation is enormously helped by (a) deterministic generation of the needed thousands to millions of photon qubits from (b) quantum emitters in designed spatially ordered arrays to enable networks…

Quantum Physics · Physics 2024-11-12 Qi Huang , Swarnabha Chattaraj , Lucas Jordao , Jiefei Zhang , Siyuan Lu , Anupam Madhukar

The ability to engineer pairs of entangled photons is essential to quantum information science, and generating these states using spontaneous parametric down-conversion (SPDC) in nano- and micrometer-scale materials offers numerous…

Quantum Physics · Physics 2025-03-11 Nicholas J. Sorensen , Vitaliy Sultanov , Maria V. Chekhova

To generate entangled photon pairs via quantum dots (QDs), the exciton fine structure splitting (FSS) must be comparable to the exciton homogeneous line width. Yet in the (In,Ga)As/GaAs QD, the intrinsic FSS is about a few tens $\mu$eV. To…

Materials Science · Physics 2009-11-13 Lixin He , Ming Gong , Chuan-Feng Li , Guang-Can Guo , Alex Zunger

Entangled photon generation from semiconductor quantum dots via the biexciton-exciton cascade underlies various decoherence mechanisms related to the solid-state nature of the quantum emitters. So far, this has prevented the demonstration…

Entanglement generation between distant nodes is a fundamental process in distributed quantum information processing. Qudits, high-dimensional quantum states, are promising candidates for enhancing entanglement distribution capabilities.…

Quantum Physics · Physics 2026-03-26 Kazufumi Tanji , Hikaru Shimizu , Masahiro Takeoka

Various quantum key distribution (QKD) protocols require bright single-photon sources with a very low probability of multiphoton emission. In this work, we investigate single-photon generation from a negatively charged quantum dot embedded…

Quantum Physics · Physics 2026-03-31 Parvendra Kumar

We present the novel embodiment of a photonic qubit that makes use of one continuous spatial degree of freedom of a single photon and relies on the the parity of the photon's transverse spatial distribution. Using optical spontaneous…

Quantum Physics · Physics 2008-05-06 Timothy Yarnall , Ayman F. Abouraddy , Bahaa E. A. Saleh , Malvin C. Teich

As a waveguide circuit QED architecture, we investigate theoretically the single-photon pair emission of a Cooper pair splitter composed of two double quantum dots, each coupled to a microwave transmission line. We find that this system can…

Mesoscale and Nanoscale Physics · Physics 2025-05-30 Michele Governale , Christian Schönenberger , Pasquale Scarlino , Gianluca Rastelli

Satellite-assisted entanglement distribution is a promising approach for realizing long-range quantum networking. However, the limited coherence time of existing quantum memories makes it challenging to obtain multiple event-ready entangled…

Quantum Physics · Physics 2025-05-23 V. Domínguez Tubío , M. C. Dijksman , J. Borregaard

To fulfill the security requirements of quantum cryptography, photon number coherence (PNC) of single photon sources has recently become an important figure of merit. Quantum dots (QDs) embedded in photonic microcavities offer a mature…

Integrated entangled photon pair source is an essential resource for both fundamental investigations and practical applications of quantum information science. Currently there have been several types of entanglement, among which the…

Quantum Physics · Physics 2019-01-18 Lan-Tian Feng , Ming Zhang , Yang Chen , Guo-Ping Guo , Guang-Can Guo , Dao-Xin Dai , Xi-Feng Ren

Quantum optical microcombs in integrated ring resonators generate entangled photon pairs over many spectral modes, and allow the preparation of high dimensional qudit states. Ideally, those sources should be programmable and have a high…

Entanglement distribution is at the heart of most quantum communication protocols. Inevitable loss of photons along quantum channels is a major obstacle for distributing entangled photons over long distances, as the no-cloning theorem…

We investigate the evolution of quantum correlations over the lifetime of a multi-photon state. Measurements reveal time-dependent oscillations of the entanglement fidelity for photon pairs created by a single semiconductor quantum dot. The…

Entangled photon pairs are essential for many applications in quantum technologies. Recent theoretical studies demonstrated that different types of entangled Bell states can be created in a constantly driven four-level quantum…

Mesoscale and Nanoscale Physics · Physics 2023-02-21 Tim Seidelmann , Michael Cosacchi , Moritz Cygorek , Doris E. Reiter , Alexei Vagov , Vollrath Martin Axt