MajuLab Seminar by Carlos Antón Solanas – 25 June 2024

Carlos Antón Solanas finished his PhD in 2015 in the Universidad Autónoma de Madrid, on fundamental properties and applications of exciton-polaritons. He did a postdoc in the group of Pascale Senellart (Centre de Nanoscience et de Nanotechnologies, Saclay, France) between 2015 and 2019, working on quantum dots coupled to micropillar cavities. Then, he continued between 2019 and 2022 with a second postdoc in the group of Christian Schneider, collaborating to create the group of Quantum Materials in the University of Oldenburg (Germany), during this time he researched on 2D materials for polaritonics and quantum optics. In 2022, Carlos came back to Spain under the “Talentum” tenure track position creating his own group on Quantum Optics in the Solid-State.

Photon number encoding: superposition, entanglement and beyond

A two-level system, excited under a pulsed resonant drive of area ?, emits a photon-number superposition state composed by vacuum and a single photon in the form cos(?/2)|0⟩+sin(?/2)|1⟩. [1,2] It has been observed that such superposition states may affect the performance of heralded quantum gates, and they could be useful in photon-based quantum information protocols. [3] For example, these states have been recently used in a teleportation scheme. [4] In parallel, recent experiments with natural and artificial atoms, using a sequential two-pulse excitation, have demonstrated the generation of time-entangled states of the form (|0_?0_?⟩+|1_?1_?⟩)/√2 or (|1_?0_?⟩+|0_?1_?⟩)/√2, where the subindex e and l refer to early and late time-bins, respectively. [5,6] The generation of such entanglement is rooted to the atomic spontaneous emission mechanism, and it is easily scalable towards multi-partite entanglement simply by adding more consecutive laser pulses.

In this talk, I will discuss such superposition and entanglement generation schemes and show recent experimental results to generate high-dimensional entanglement (encoded in the photon number basis) from a three-level system (a biexciton-exciton cascade in a semiconductor quantum dot), using again a simple excitation scheme composed by two delayed resonant pulses. These complex states could offer some advantageous solutions in quantum communication protocols. [7] 

[1] J. C. Loredo et al., Generation of Non-Classical Light in a Photon-Number Superposition, Nat. Photonics 13, 803 (2019).

[2] Y. Karli et al., Controlling the Photon Number Coherence of Solid-State Quantum Light Sources for Quantum Cryptography, Npj Quantum Inf 10, 1 (2024).

[3] I. M. de B. Wenniger et al., Photonic Quantum Interference in the Presence of Coherence with Vacuum, arXiv:2401.01187.

[4] B. Polacchi, F. Hoch, G. Rodari, S. Savo, G. Carvacho, N. Spagnolo, T. Giordani, and F. Sciarrino, Quantum Teleportation of a Genuine Vacuum-One-Photon Qubit Generated via a Quantum Dot Source, arXiv:2310.20521.

[5] S. C. Wein et al., Photon-Number Entanglement Generated by Sequential Excitation of a Two-Level Atom, Nat. Photon. 16, 5 (2022).

[6] J.-R. Álvarez, M. IJspeert, O. Barter, B. Yuen, T. D. Barrett, D. Stuart, J. Dilley, A. Holleczek, and A. Kuhn, How to Administer an Antidote to Schrödinger’s Cat, J. Phys. B: At. Mol. Opt. Phys. 55, 054001 (2022).

[7] A. C. Santos, C. Schneider, R. Bachelard, A. Predojević, and C. Antón-Solanas, Multipartite Entanglement Encoded in the Photon-Number Basis by Sequential Excitation of a Three-Level System, Opt. Lett. 48, 6332 (2023).

MajuLab is an international joint research unit of the CNRS, UCA, SU, NUS and NTU in Singapore (IRL 3654), hosted by CQT and SPMS.