Periodic Reporting for period 4 - MODULAR (Modular mechanical-atomic quantum systems)
Reporting period: 2020-07-01 to 2022-06-30
Mechanical oscillators are widely used as force or acceleration sensors and signal transducers, with applications ranging from atomic force microscopy and gravitational wave detection to consumer electronics. In today’s devices, the vibrations of these oscillators are governed by classical physics and the readout sensitivity is limited by thermal noise. To reach the quantum limits of operation in such devices will likely have a strong impact on technology, enabling sensors with improved precision as well as conceptually new quantum technology.
In this project, we explored the new possibilities offered by hybrid systems in which the vibrations of a mechanical oscillator are coupled to an ensemble of ultracold atoms. The coupling is realized in a modular way by connecting the two systems with laser light. The coupled mechanical-atomic systems were used for a range of experiments on quantum control of mechanical vibrations by means of their coupling to the atoms and by means of optical coherent feedback. Besides the interesting perspective of observing quantum phenomena in engineered mechanical devices that are visible to the bare eye, the project opened up new avenues for quantum control of mechanical vibrations with potential impact on the development of mechanical quantum sensors and transducers for accelerations, forces and fields.
In this project, we explored the new possibilities offered by hybrid systems in which the vibrations of a mechanical oscillator are coupled to an ensemble of ultracold atoms. The coupling is realized in a modular way by connecting the two systems with laser light. The coupled mechanical-atomic systems were used for a range of experiments on quantum control of mechanical vibrations by means of their coupling to the atoms and by means of optical coherent feedback. Besides the interesting perspective of observing quantum phenomena in engineered mechanical devices that are visible to the bare eye, the project opened up new avenues for quantum control of mechanical vibrations with potential impact on the development of mechanical quantum sensors and transducers for accelerations, forces and fields.
To explore the intriguing new possibilities offered by hybrid mechanical-atomic systems, we built a membrane optomechanics setup in a cryostat and an ultracold atom setup. Our setup allows to engineer light-mediated interactions in a very flexible way, coupling the mechanical oscillator either to the motion of the atoms or to their collective spin, realizing unidirectional or bidirectional interactions, and in particular also interactions where the two systems are connected in a loop geometry. In parallel, we developed a rigorous theoretical framework for describing the light-mediated Hamiltonian interactions that can be generated between the two systems over long distances [1].
With our experimental setup, and guided by our theoretical work, we obtained a number of exciting new results. Initial experiments focused on coupling of the mechanical oscillator to the atomic motion, demonstrating cooling of the mechanical vibrations and a range of further interesting phenomena [2,3]. A breakthrough was the observation of light-mediated strong coupling between the mechanical oscillator and the atomic spins across a distance of 1 meter [4]. This first demonstration of strong Hamiltonian coupling at a distance represents a major breakthrough of the project. The power and flexibility of the approach were demonstrated by realizing different dynamical regimes, observing normal mode splitting and coherent state swaps between the atoms and the membrane, two-mode squeezing dynamics, as well as dissipative interactions and exceptional points [4]. In a next step, we explored the light-mediated strong coupling for a demonstration of feedback cooling of the mechanical oscillator using the atomic spins as a coherent controller [5].
In the final stage of the project, we switched our attention to a new and unexpected possibility that emerged from our theoretical analysis of light-mediated interactions in loop geometries. In our optomechanics setup we realized an optical coherent feedback loop that allows us to control the vibrations of the nanomechanical membrane. By adjusting the phase and time delay of the feedback, we were able to demonstrate coherent feedback cooling of the membrane, which we demonstrated to overcome the fundamental limits of standard cavity optomechanical cooling and control techniques in the unresolved sideband regime [6].
The results of the project were published in leading peer-review journals and presented at numerous conferences in the field.
[1] T. M. Karg, B. Gouraud, P. Treutlein, and K. Hammerer, Remote Hamiltonian interactions mediated by light, Phys. Rev. A 99, 063829 (2019).
[2] A. Jöckel, A. Faber, T. Kampschulte, M. Korppi, M. T. Rakher, and P. Treutlein, Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system, Nature Nanotechnology 10, 55-59 (2015).
[3] A. Vochezer, T. Kampschulte, K. Hammerer, and P. Treutlein, Light-Mediated Collective Atomic Motion in an Optical Lattice Coupled to a Membrane, Phys. Rev. Lett. 120, 073602 (2018).
[4] T. M. Karg, B. Gouraud, C. T. Ngai, G.-L. Schmid, K. Hammerer, and P. Treutlein, Light-mediated strong coupling between a mechanical oscillator and atomic spins one meter apart, Science 369, 174 (2020).
[5] G.-L. Schmid, C. T. Ngai, M. Ernzer, M. Bosch Aguilera, T. M. Karg, and P. Treutlein, Coherent feedback cooling of a nanomechanical membrane with atomic spins, Phys. Rev. X 12, 011020 (2022).
[6] M. Ernzer, M. Bosch Aguilera, M. Brunelli, G.-L. Schmid, C. Bruder, P. P. Potts, and P. Treutlein, Optical coherent feedback control of a mechanical oscillator, preprint arXiv:2210.07674
With our experimental setup, and guided by our theoretical work, we obtained a number of exciting new results. Initial experiments focused on coupling of the mechanical oscillator to the atomic motion, demonstrating cooling of the mechanical vibrations and a range of further interesting phenomena [2,3]. A breakthrough was the observation of light-mediated strong coupling between the mechanical oscillator and the atomic spins across a distance of 1 meter [4]. This first demonstration of strong Hamiltonian coupling at a distance represents a major breakthrough of the project. The power and flexibility of the approach were demonstrated by realizing different dynamical regimes, observing normal mode splitting and coherent state swaps between the atoms and the membrane, two-mode squeezing dynamics, as well as dissipative interactions and exceptional points [4]. In a next step, we explored the light-mediated strong coupling for a demonstration of feedback cooling of the mechanical oscillator using the atomic spins as a coherent controller [5].
In the final stage of the project, we switched our attention to a new and unexpected possibility that emerged from our theoretical analysis of light-mediated interactions in loop geometries. In our optomechanics setup we realized an optical coherent feedback loop that allows us to control the vibrations of the nanomechanical membrane. By adjusting the phase and time delay of the feedback, we were able to demonstrate coherent feedback cooling of the membrane, which we demonstrated to overcome the fundamental limits of standard cavity optomechanical cooling and control techniques in the unresolved sideband regime [6].
The results of the project were published in leading peer-review journals and presented at numerous conferences in the field.
[1] T. M. Karg, B. Gouraud, P. Treutlein, and K. Hammerer, Remote Hamiltonian interactions mediated by light, Phys. Rev. A 99, 063829 (2019).
[2] A. Jöckel, A. Faber, T. Kampschulte, M. Korppi, M. T. Rakher, and P. Treutlein, Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system, Nature Nanotechnology 10, 55-59 (2015).
[3] A. Vochezer, T. Kampschulte, K. Hammerer, and P. Treutlein, Light-Mediated Collective Atomic Motion in an Optical Lattice Coupled to a Membrane, Phys. Rev. Lett. 120, 073602 (2018).
[4] T. M. Karg, B. Gouraud, C. T. Ngai, G.-L. Schmid, K. Hammerer, and P. Treutlein, Light-mediated strong coupling between a mechanical oscillator and atomic spins one meter apart, Science 369, 174 (2020).
[5] G.-L. Schmid, C. T. Ngai, M. Ernzer, M. Bosch Aguilera, T. M. Karg, and P. Treutlein, Coherent feedback cooling of a nanomechanical membrane with atomic spins, Phys. Rev. X 12, 011020 (2022).
[6] M. Ernzer, M. Bosch Aguilera, M. Brunelli, G.-L. Schmid, C. Bruder, P. P. Potts, and P. Treutlein, Optical coherent feedback control of a mechanical oscillator, preprint arXiv:2210.07674
Overall, the project has achieved its objectives, by theoretically developing and experimentally demonstrating a new toolbox for light-mediated coupling and control of quantum systems. The observation of light-mediated strong coupling between the mechanical oscillator and the atomic spins across a distance and the different dynamical regimes and control techniques for mechanical vibrations realized with it go far beyond the state of the art. The project has also led to unexpected results, in particular on optical coherent feedback control of mechanical oscillators and collective atomic motion in optical lattices. Our toolbox of light-mediated interactions is far from being fully explored and exhausted, and we expect many more exciting results in the near future. In the longer term, these techniques open up new avenues for enhancing the capabilities of mechanical quantum sensors and transducers for accelerations, forces and fields.