Throughout this century, there have been great efforts for developing new technologies based on the specific design and control of individual quantum systems, giving way for the second quantum revolution. The aim is to exploit quantum features -entanglement, collapse and superposition- as a resource: this resulted in disrupting applications in computation, cryptography, communications and metrology.
Photons are one of the most promising physical implementations involved in this revolution, as recently stated by the 2022 physics nobel prize. They can be easily manipulated and represent the only realistic option for long-distance communications and cryptography [1]. Also, schemes for efficient quantum computation with linear optics have been proposed [2] and recently absolute quantum computational advantage has been obtained in a boson-sampling experiment using photons [3]. Quantum metrology is not left behind, with great success in surpassing classical precision limits both in resolution and sensitivity[4].
Non-classical light sources, such as single-photons and twin-beams, are the key elements of this physical implementation. In this talk, I will explain the state-of-the-art in the race of obtaining a near-ideal single-photon source, with both single-emitters [5] and non-linear optics based strategies [6], giving detail about the experimental implementations. Also I will describe the latest developments of twin-beam sources based on spontaneous parametric down-conversion (SPDC), and talk about their great impact in quantum metrology.
[1] Pirandola, S., Andersen, U. L., Banchi, L., Berta, M., Bunandar, D., Colbeck, R., ... & Wallden, P. (2020). Advances in quantum cryptography. Advances in optics and photonics, 12(4), 1012-1236.
[2] Knill, E., Laflamme, R., & Milburn, G. J. (2001). A scheme for efficient quantum computation with linear optics. nature, 409(6816), 46-52.
[3] Zhong, H. S., Wang, H., Deng, Y. H., Chen, M. C., Peng, L. C., Luo, Y. H., ... & Pan, J. W. (2020). Quantum computational advantage using photons. Science, 370(6523), 1460-1463.
[4] Moreau, P. A., Toninelli, E., Gregory, T., & Padgett, M. J. (2019). Imaging with quantum states of light. Nature Reviews Physics, 1(6), 367-380.
[5] Aharonovich, I., Englund, D., & Toth, M. (2016). Solid-state single-photon emitters. Nature Photonics, 10(10), 631-641.
[6] Meyer-Scott, E., Silberhorn, C., & Migdall, A. (2020). Single-photon sources: Approaching the ideal through multiplexing. Review of Scientific Instruments, 91(4), 041101.