| 研究実績の概要 |
(i) Coaxing vibrations in the regimes of both large mass and high temperature into their motional quantum ground states is extremely challenging, because it requires an ultra-high optical power, which introduces extraneous excessive heating and intricate instabilities. In our project, we propose how to overcome these obstacles and cool vibrational networks by simply harnessing the power of an exceptional point (EP) induced in parity-time symmetric structures; and we reveal its exceptional cooling properties otherwise unachievable in conventional devices. This work was published on Optica 11 (4), 485-491.
(ii) Imposing topological operations encircling an exceptional point (EP) engenders unconventional oneway topological phonon transfer (TPT), strictly depending on the direction of EP-inclusive control loops and inherently limited to the small-mass regime of practical resonators. In our project, we show how to beat these limitations and predict a mass-free unidirectional TPT by combining topological operations with the Fizeau light-dragging effect, which splits countercirculating optical modes. This work was submitted to Physical Review Letters (2024).
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
(i) In the first project, we proposed a simple EP-cooling mechanism to amplify the net cooling rate of the vibration, and to effectively cool the motional degree of freedom down to the quantum ground state. We showed that the final mean thermal occupation numbers in the EP-cooling case are three orders of magnitude smaller than those for the standard cooling. In particular, we revealed that in the standard-cooling case, optomechanical cooling becomes much worse with increasing either environmental temperature or resonator mass, while in the EP-cooling case, it is almost independent of these parameters. This study enables the exploration of quantum physics in large mass and high-temperature quantum mechanical systems, and paves a way towards realizing pure quantum cavity optomechanics, with immunity against both resonator mass and environmental noise.
(ii) In the second project, we showed a both mass-insensitive and EP-encircling-direction-independent nonreciprocal TPT arising from the Fizeau light-dragging effect, without which it vanishes. Our study describes a general mechanism, and maps a new way of manipulating one-way TPT, independent of the encircling direction of the EP. In a broader view, it enables constructing novel topological chiral phononics with both device-mass tolerance and TPT-velocity tunablility.
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