📣 همکاوی 1:
آقای دکتر امیر یوسفی (دانش‌آموخته دکترای دانشگاهEPFL سوئیس، برنده جایزه بهترین دانشنامه دکتری فناوری نانو در سوئیس، دارنده مدال طلای المپیاد‌ دانش‌آموزی و دانشجویی)

💭 موضوع:
Superconducting circuit optomechanics: from milli-second quantum decoherence to topological lattices
⏳ زمان:
یکشنبه 16 مهر ساعت 11:30 به وقت تهران - 8 اکتبر ساعت 10 به وقت اروپای مرکزی

🎞 ویدیو:
https://youtu.be/qdH49c8fFaM

📜 چکیده:
Quantum control and measurement of mechanical oscillators have been achieved by coupling mechanical oscillators to auxiliary degrees of freedom in the form of optical or microwave cavities, allowing numerous advances such as quantum state transfer or mechanical entanglement. An enduring challenge in constructing such hybrid systems is the dichotomy of engineered coupling to an auxiliary degree of freedom, while being mechanically well isolated from the environment, that is, low quantum decoherence – which consists of both thermal decoherence and dephasing. We overcome this challenge by introducing a superconducting circuit optomechanical platform with a directly measured thermal decoherence rate of 20.5 Hz (corresponding to 7.7 milli-second T1) as well as a pure dephasing rate of 0.09 Hz [1]. This enables us to reach to 0.07 quanta motional ground state occupation (93% fidelity) and realize mechanical squeezing of -2.7 dB below zero-point-fluctuation. To directly measure the quantum-state lifetime, we observe the free evolution of the phase-sensitive squeezed state for the first time, preserving its non-classical nature over milli-second timescales.
Furthermore, we show how to scale up optomechanical systems to arrays and lattices, realizing non-trivial topological modes in such multimode systems [2]. Using a novel technique to directly measure collective modeshapes, we explore the physics of edge states in optomechanical strained-graphene lattices.
Such ultra-low quantum decoherence and reproducible platform not only increases the fidelity of quantum control and measurement of macroscopic mechanical systems but may equally benefit interfacing with qubits, exploring emergent nonlinear dynamics in complex optomechanical systems, and places the system in a parameter regime suitable for tests of quantum gravity.

References
[1] A. Youssefi, S. Kono, M. Chegnizadeh, and T.J. Kippenberg. A squeezed mechanical oscillator with milli-second quantum decoherence. Nature Physics, 2023.
[2] A. Youssefi, S. Kono, A. Bancora, M. Chegnizadeh, J. Pan, T. Vovk, and T.J. Kippenberg, Topological lattices realized in superconducting circuit optomechanics. Nature, 2022.