Joint Seminar on Quantum Information and Technologies

When two indistinguishable photons impinge on a beam splitter, the particles leave the device together in the same output due to the underlying two-photon interference [1]. This well-known Hong-Ou-Mandel effect is at the basis of photonic quantum information processing and various other applications. For more than two particles, the dynamics gets increasingly complex and a rich variety of interference phenomena can arise. In this talk, I will present our latest experimental results on four-photon interference obtained from spontaneous parametric down-conversion (SPDC). In particular, I will demonstrate how symmetries can affect the ability of interference [2] and how entanglement can lead to a collective four-particle interference, which is completely invisible when smaller subsets of particles are detected [3]. I will also highlight how semiconductor quantum dots can be used as a multi-photon source via active temporal-to-spatial mode demultiplexing [4]. Finally, I will introduce our new project on establishing an interface between SPDC and quantum-dot emitted photons enabled by active spectral-temporal shaping of the photon wavepackets.

[1] Hong, Ou, Mandel, Phys. Rev. Lett. 59, 2044 (1987),
[2] Münzberg et al., PRX Quantum 2, 020326 (2021),
[3] Faleo et al., Sci. Adv. 10, eadp9030 (2024),
[4] Münzberg et al., APL Photonics 7, 070802 (2022)