Quantum Entanglement of research in quantum advanced to establish how to leverage entanglement to enhance the effectiveness, security, and scalability of quantum communication networks. Quantum entanglement underpins the development of secure quantum communication systems, a key step in surpassing classical security limitations. Quantum key distribution (QKD) is an example of an entanglement-based protocol, a technology named after Ekert. QKD relies on quantum correlations between entangled particles to detect eavesdropping (Pirandola et al., 2020). When two parties share photon pairs in an entangled state, measuring one of the pair automatically reveals the state of the other party.

Interception of the photons compromises the correlations. Scientists have proven entanglement-based QKD can be conducted over substantial distances, with a satellite link of over 1,200 kilometers recorded (Liao et al., 2017. Some of the barriers to implementing long-range communication have already been addressed, with quantum repeaters and high-quality entangled photon devices promising to upscale the entanglement range. Quantum repeaters can leverage entanglement swapping and purification to extend the entanglement range beyond the maximum direct transmission of photons. These technologies have proved critical in surmounting attenuation and noise challenges in the channel (Sangouard et al., 2011). In addition, new coding and multiplexing technology has improved fault tolerance and transmission rates in quantum repeaters, thus revolutionizing long-haul optical networks (Muralidharan et al., 2016). The entanglement and the violation of Bell inequalities have created device-independent QKD, removing the vulnerability to side-channel interception and sabotage (Acín et al., 2007). This enhancement offers practical advantages for real-world applications.

Quantum networks require multiple entangled nodes to enable quantum teleportation and distributed quantum computing. This has greatly expanded the application of secure quantum communication in a wide range of complex tasks. The integration of classical infrastructure, along with photonic integrated circuit advancements, has resulted in the quantum computation becoming scalable and increasingly feasible. Considering the above, it can be concluded the future is promising in terms of developing robust and global quantum communication networks, using quantum entanglement to exploit non-classical correlations in a fundamentally secure communication model.

References:

Acín, A., Gisin, N., Masanes, L., Pironio, S., Scarani, V., & Winter, A. (2007). Device-independent security of quantum cryptography against collective attacks. Physical Review Letters, 98(23), 230501.

Ekert, A. K. (1991). Quantum cryptography based on Bell’s theorem. Physical Review Letters, 67(6), 661–663. https://journals.aps.org/prl/cited-by/62279/22

Liao, S.-K., Cai, W.-Q., Liu, W.-Y., Zhang, L., Li, Y., Ren, J.-G., Yin, J., Shen, Q., Cao, Y., Li, Z.-P., Jia, J.-J., & Pan, J.-W. (2017). Satellite-relayed intercontinental quantum network. Physical Review Letters, 120(3), 030501.

Muralidharan, S., Kim, J., Lütkenhaus, N., Lukin, M. D., & Jiang, L. (2016). Ultrafast and fault-tolerant quantum communication across long distances. Physical Review Letters, 112(25), 250501.

Pirandola, S., Andersen, U. L., Banchi, L., Berta, M., Bunandar, D., Colbeck, R., Englund, D., Gehring, T., Lupo, C., Ottaviani, C., Pereira, J., Razavi, M., Shaari, J. S., Tomamichel, M., & Wallden, P. (2020). Advances in quantum cryptography. Advances in Optics and Photonics, 12(4), 1012–1236.

Sangouard, N., Simon, C., de Riedmatten, H., & Gisin, N. (2011). Quantum repeaters based on atomic ensembles and linear optics. Reviews of Modern Physics, 83(1), 33–80.