TEP Seminar - Carlos Antón-Solanas

A two-level system (such as a charged semiconductor quantum dot), excited under a pulsed resonant drive of area θ, emits photon-number superposition states composed by vacuum and a single-photon in the form cos(θ/2)|0⟩ + sin(θ/2)|1⟩.^1,2 Additionally, a sequential two-pulse excitation can generate photon-number encoded time-entangled states of the form 1/√2(|0_e0_l⟩ + |1_e1_l⟩) or 1/√2(|1_e0_l⟩ + |0_e1_l⟩), where the subindex e and l refer to early and late time-bins, respectively.^3,4 The expansion of this sequential excitation to a three-level system (such as one polarisation cascade of the biexciton-exciton decay) generates entanglement in time and energy,⁵ with prospects to allow secure quantum communication protocols.⁶

In this seminar, I will revisit these works and will discuss ongoing experiments on (1) the photon-number emission from the Ramsey sequence and its connection to quantum energetics, and (2) the constrained metrology performance of photon-number encoded Fibonacci states and alternatives to reach Heisenberg scaling in metrology protocols.⁷

References

1. Loredo, J. C. et al. Generation of non-classical light in a photon-number superposition. Nat. Photonics 13, 803–808 (2019).
2. Karli, Y. et al. Controlling the photon number coherence of solid-state quantum light sources for quantum cryptography. npj Quantum Inf 10, 1–9 (2024).
3. Wein, S. C. et al. Photon-number entanglement generated by sequential excitation of a two-level atom. Nat. Photon. 16, 374–379 (2022).
4. Álvarez, J.-R. et al. How to administer an antidote to Schrödinger’s cat. J. Phys. B: At. Mol. Opt. Phys. 55, 054001 (2022).
5. Heindel, T. et al. Exploring Photon-Number-Encoded High-dimensional Entanglement from a Sequentially Excited Quantum Three-Level System. Optica Quantum (2024) doi:10.1364/OPTICAQ.538134.
6. Santos, A. C., Schneider, C., Bachelard, R., Predojević, A. & Antón-Solanas, C. Multipartite entanglement encoded in the photon-number basis by sequential excitation of a three-level system. Opt. Lett. 48, 6332 (2023).
7. Paulisch, V., Perarnau-Llobet, M., González-Tudela, A. & Cirac, J. I. Quantum metrology with one-dimensional superradiant photonic states. Phys. Rev. A 99, 043807 (2019).