Elena & Fabrice's Web

__ Two-photon spectra of quantum emitters__. A. González-Tudela, F. P. Laussy, C. Tejedor, M. J Hartmann and E. del Valle in New J. Phys.

This paper introduces for the first time—and computes explicitely for various cases—the *two-photon correlation spectrum* (or "two-photon spectrum" as per the nomenclature of the paper), that is, the 2D landcape of photon correlations when retaining their frequency degree of freedom.

We made a "video abstract" to explain the main idea:

This is, for instance, the 2PS (two-photon spectrum) for the Mollow triplet:

We would understand the triplet of red antidiagonal lines right away (they are leapfrog processes) but it would take another decade for us to figure out the blue circles!

The two-photon spectrum has been measured experimentally for the first time by Peiris et al.,^{[1]} which is the most interesting case, and shortly after that by Silva *et al.*^{[2]} but for something with much less quantum structure.

Such 2D structures remain ignored by the bulk of quantum opticians, who fail to understand that to look at two-photon observables, one must look at two-photon spectra. In this way, peopled remained oblivious to the strongly-correlated emission away from the spectral peaks that, if you Purcell-enhance it, gives rise to a new regime of quantum emission.^{[3]}

- ↑
__Two-color photon correlations of the light scattered by a quantum dot__. M. Peiris, B. Petrak, K. Konthasinghe, Y. Yu, Z. C. Niu and A. Muller in Phys. Rev. B**91**:195125 (2015). - ↑
__The colored Hanbury Brown-Twiss effect__. B. Silva, C. Sánchez Muñoz, D. Ballarini, A. González-Tudela, M. de Giorgi, G. Gigli, K. West, L. Pfeiffer, E. del Valle, D. Sanvitto and F. P. Laussy in Sci. Rep.**6**:37980 (2016). - ↑
__Emitters of $N$-photon bundles__. C. Sánchez Muñoz, E. del Valle, A. González Tudela, K. Müller, S. Lichtmannecker, M. Kaniber, C. Tejedor, J.J. Finley and F.P. Laussy in Nature Photon.**8**:550 (2014).