Seminar @Institute of Physics in Zagreb - Dr. Nenad Kralj: Room-temperature quantum optomechanics

Room-temperature quantum optomechanics and the development of a mechanical quantum memory for single photons

Optomechanics [1] is a relatively new branch of physics, which studies the interaction of light and mechanical objects. Its beginnings are related to studying the limits of stability of interferometric gravitational wave detectors. Owing to the ever better understanding of optomechanical principles and the advancements in fabricating high-quality nanomechanical oscillators, optomechanical systems are nowadays among the best sensors of small displacements and forces, while also setting a benchmark for fundamental tests of quantum mechanics, as well as showing great potential for a variety of quantum applications. To begin today's lecture, I will give a brief overview of the aforementioned basic optomechanical principles and phenomena, such as the so-called optical sideband cooling and optomechanically induced transparency (OMIT). This introduction will also serve to explain the figures of merit and main challenges in improving the performance of optomechanical systems, as required for the transition from cryogenic operation to working at room temperature. The latter is of particular interest in the community as doing away with the necessity for cryogenic cooling should further facilitate the spread of optomechanical quantum technologies. In the following, I will show the results of sideband cooling a novel mechanical oscillator (the so-called soft-clamped membrane), with a record-low phonon occupancy in a single vibrational mode at room temperature (30 phonons) [2]. I will also explain how OMIT can be used to store individual photons, i.e. to develop a mechanical quantum memory for said photons. Our results with short optical pulses suggest that OMIT-based quantum memories employing a soft-clamped membrane would exhibit record coherence time and storage efficiency among optomechanical systems [3]. I will dedicate the very end of the lecture to something slightly different, namely trefoil knots and non-commutativity of braids in the spectra of non-Hermitian operators, which we have experimentally demonstrated for the first time, using a standard optomechanical system [4].



References

[1] M. Aspelmeyer, T. J. Kippenberg and F. Marquardt. “Cavity optomechanics”. Rev. Mod. Phys. 86 (December 4, 2014), p. 1391–1452. DOI: 10.1103/RevModPhys.86.1391. URL: https://link.aps.org/doi/10.1103/RevM....

[2] S. A. Saarinen, N. Kralj, E. C. Langman, Y. Tsaturyan and A. Schliesser. “Laser cooling a membrane-in-the-middle system close to the quantum ground state from room temperature”. Optica 10.3 (March 2023), p. 364–372. DOI: 10.1364/OPTICA.468590. URL: https://opg.optica.org/optica/abstrac....

[3] M. Bjerregaard Kristensen, N. Kralj, E. Langman and A. Schliesser. “A Long-lived and Efficient Optomechanical Memory for Light”. 2023. arXiv: 2308.05206 [quant-ph].

[4] Y. S. S. Patil, J. Höller, P. A. Henry, C. Guria, Y. Zhang, L. Jiang, N. Kralj, N. Read, and J. G. E. Harris. “Measuring the knot of non-Hermitian degeneracies and non-commuting braids”. Nature 607.7918 (July 2022), p. 271–275. ISSN: 1476-4687. DOI: 10.1038/s41586-022-04796-w. URL: https://doi.org/10.1038/s41586-022-04...