En un estudio reciente, los investigadores lograron una interferencia cuántica de alta visibilidad entre dos puntos cuánticos de semiconductores independientes, un avance crucial hacia las redes cuánticas escalables.
Los investigadores demostraron la interferencia cuántica de alta visibilidad entre dos puntos cuánticos de semiconductores independientes, un paso importante hacia las redes cuánticas escalables.
El Premio Nobel de Física del año pasado celebró el interés fundamental del entrelazamiento cuántico y también consideró aplicaciones potenciales en “la segunda revolución cuántica”, una nueva era en la que podemos manipular la extrañeza de la mecánica cuántica, incluida la superposición cuántica y el entrelazamiento. Una red cuántica completamente funcional a gran escala es el santo grial de la ciencia de la información cuántica. Abrirá una nueva frontera de la física, con nuevas posibilidades para la computación cuántica, la comunicación y la metrología.
Uno de los mayores desafíos es extender la distancia de comunicación cuántica a una escala útil en la práctica. A diferencia de las señales clásicas que pueden amplificarse sin ruido, los estados cuánticos superpuestos no pueden amplificarse porque no pueden clonarse perfectamente. Por lo tanto, una red cuántica de alto rendimiento requiere no solo canales cuánticos de pérdida ultrabaja y memoria cuántica, sino también fuentes de luz cuántica de alto rendimiento. Recientemente ha habido avances emocionantes en las comunicaciones cuánticas por satélite y los repetidores cuánticos, pero la falta de[{” attribute=””>photon sources has hampered further advances.
Experimental configuration of quantum interference between two independent solid-state QD single-photon sources separated by 302 km fiber. DM: dichromatic mirror, LP: long pass, BP: band pass, BS: beam splitter, SNSPD: superconducting nanowire single-photon detector, HWP: half-wave plate, QWP: quarter-wave plate, PBS: polarization beam splitter. Credit: You et al., doi 10.1117/1.AP.4.6.066003
What is required of a single-photon source for quantum network applications? First, it should emit one (only one) photon at a time. Second, to attain brightness, the single-photon sources should have high system efficiency and a high repetition rate. Third, for applications such as in quantum teleportation that require interfering with independent photons, the single photons should be indistinguishable. Additional requirements include a scalable platform, tunable and narrowband linewidth (favorable for temporal synchronization), and interconnectivity with matter qubits.
A promising source is quantum dots (QDs), semiconductor particles of just a few nanometers. However, in the past two decades, the visibility of quantum interference between independent QDs has rarely exceeded the classical limit of 50% and distances have been limited to around a few meters or kilometers.
As reported in Advanced Photonics, an international team of researchers has achieved high-visibility quantum interference between two independent QDs linked with ~300 km optical fibers. They report efficient and indistinguishable single-photon sources with ultra-low-noise, tunable single-photon frequency conversion, and low-dispersion long fiber transmission. The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunications band. The observed interference visibility is up to 93%. According to senior author Chao-Yang Lu, professor at the University of Science and Technology of China (USTC), “Feasible improvements can further extend the distance to ~600 km.”
Lu remarks, “Our work jumped from the previous QD-based quantum experiments at a scale from ~1 km to 300 km, two orders of magnitude larger, and thus opens an exciting prospect of solid-state quantum networks.” With this reported jump, the dawn of solid-state quantum networks may soon begin breaking toward day.
Reference: “Quantum interference with independent single-photon sources over 300 km fiber” by Xiang You, Mingyang Zheng, Si Chen, Run-Ze Liu, Jian Qin, Mo-Chi Xu, Zheng-Xuan Ge, Tung-Hsun Chung, Yu-Kun Qiao, Yang-Fan Jiang, Han-Sen Zhong, Ming-Cheng Chen, Hui Wang, Yu-Ming He, Xiu-Ping Xie, Hao Li, Li-Xing You III, Christian Schneider, Juan Yin, Teng-Yun Chen, Mohamed Benyoucef, Yong-Heng Huo, Sven Höfling, Qiang Zhang, Chao-Yang Lu and Jian-Wei Pan, 27 December 2022, Advanced Photonics.
DOI: 10.1117/1.AP.4.6.066003
