Department of Applied Physics

Quantum Nanomechanics

The Quantum Nanomechanics group focuses on the quantum-mechanical behavior of macroscopic moving objects, using micro- and nanomechanical resonators at the ground state of motion. We also use superconducting qubits with micro acoustics for quantum technology, and explore the coupling of spin waves to acoustics.
The group is part of the national Centre of Excellence – Quantum Technology Finland (QTF).
An illustration of the 15-micrometre-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Image: Aalto University / Petja Hyttinen & Olli Hanhirova, ARKH Architects.


Hands touching an art piece on the quantum exhibition.
Studies Published:

InstituteQ launches new doctoral school in quantum technology

The Doctoral School in Quantum Technology and the industrial doctorates are now in operation
The InstituteQ logo on black background
Cooperation, Press releases, Research & Art Published:

Finnish Quantum Agenda details road ahead and stresses need for national quantum strategy

What are Finland’s strengths in quantum technology? How can Finland ensure it stays on top of the groundbreaking changes quantum technology will cause in the coming years and decades? These are the questions the Finnish Quantum Agenda answers.
Vivian Phan leaning on a grey wall
Studies Published:

“Have the tenacity and believe in your progress" – Studying quantum, the field of the future, now

Vivian Phan is a recent BSc graduate of Aalto University’s Quantum Technology studies and currently working as part of the Micro and Quantum Systems research group. She shares what it’s like to build a career in a field that’s new and will most likely have its biggest impact years or decades from now.
The drumheads exhibit a collective quantum motion. Picture: Juha Juvonen.
Press releases Published:

Aalto researchers awarded Physics World Breakthrough of the Year for macroscopic quantum entanglement

Aalto University Professor Mika A. Sillanpää, his team and collaborators at the University of New South Wales in Canberra, Australia, have won the Physics World 2021 Breakthrough of the Year. The prize was awarded for establishing quantum entanglement between a pair of macroscopic drumheads – two mechanical resonators that were tiny but still much larger than the subatomic particles that are usually entangled. The award has previously been given for the first direct observation of a black hole and for the detection of gravitational waves, which also received a Nobel Prize.
Professor Mika Sillanpää

Group leader

Prof. Mika Sillanpää

Entangled mechanical oscillators

Entanglement is perhaps the most intriguing feature of quantum mechanics. It allows objects to affect each other across arbitrary distances without any direct interaction, defying both classical physics and our common-sense understanding of reality. Entanglement is now commonly observed in experiments with microscopic systems such as light or atoms, and is also the key resource for quantum technologies such as quantum computation, cryptography and measurement.

Quantum entanglement is, however, extremely fragile, and it will disappear if the entangled particles interact with their surroundings, through thermal disturbances, for example. For this reason, entanglement between the motion of macroscopic objects has long been an elusive goal.

In recent works we created and stabilised entanglement between the center-of-mass motion of two drumhead resonators. The drumheads, 15 micrometer in diameter, are capacitively coupled to a single microwave "cavity" formed by a superconducting circuit. By driving the system with suitable microwave fields, we cool the thermal disturbances and bring the drumheads to a steady state where they are entangled indefinitely. Our work qualitatively extends the range of entangled physical systems and has implications for quantum information processing, precision measurements and tests of the limits of quantum mechanics.

Quantum Backaction Evading Measurement of Collective Mechanical Modes

The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum backaction of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the backaction and be made with arbitrary precision. We have demonstrated quantum backaction evading measurements of a collective quadrature of two mechanical oscillators, both coupled to a common microwave cavity. The work allows for quantum state tomography of two mechanical oscillators, and provides a foundation for macroscopic mechanical entanglement and force sensing beyond conventional quantum limits.

Microwave optomechanics

Besides studying fundamental quantum concepts such as entanglement and backaction evasion, microwave optomechanics can be utilized for signal processing.

We have demonstrated that microwave optomechanical systems can be used as ultra-low-noise microwave amplifiers. In a phase-preserving mode the incoming microwave signal can be amplified while adding only half a quantum of noise, the minimum amount required by Heisenberg's uncertainty principle. When configured as a phase-senstive amplifier, the device amplifies a single quadrature of the incoming signal while adding almost no noise at all. The novel type of amplifiers may offer improved performance for information processing in certain applications.

Additionally, we have investigated nonreciprocal (i.e., directional) transport and amplification of electromagnetic or mechanical signals.

    Examle of a drumhead resonator

    Example of a drumhead resonator, imaged with a scanning electron microscope 

    Two microwave LC cavities coupled to a single mechanical drumhead resonator.

    Schematic of a sample with two microwave LC cavities coupled to a single mechanical drumhead resonator.

    Nanobeam mechanical resonator coupled to a superconducting microwave cavity.

    Nanobeam mechanical resonator coupled to a superconducting microwave cavity.

    Micro acoustics coupled to superconducting qubits

    Quantum systems with different types of degrees of freedom can intertwine, forming hybrid states with intriguing properties. We have explored setups for coupling transmon qubits to either low-frequency flexural resonators, or GHz-regime micro acoustic overtone (HBAR) resonances.

    In a HBAR system, the modes mostly reside in the substrate chip and hence feature diluted strain and low acoustic losses. The system exhibits a dense spectrum of acoustic modes that interact near resonance with the qubit, suggesting a possibility to manipulate the many-mode system through the qubit. We have shown a qubit-HBAR system by controlling the qubit with longitudinal fields, allowing individually access a large number of acoustic modes.

      HBAR qubit.

      Assembly of a high-overtone bulk acoustic wave resonator (blue) on top of the Xmon qubit. The acoustic medium is a sapphire crystal that is first covered by a thin layer of molybdenum (60 nm), on top of which there is an approximately 1-micron-thick layer of polycrystalline aluminum nitride. The piezoelectric AlN layer acts as a transducer between the electric field of the qubit and the acoustic modes.

      transmon qubit and bridge resonator.

      Right: Scanning electron micrograph showing the 5-micron-long and 4-micron-wide bridge-type mechanical resonator (dashed box).

      Magneto acoustics

      In a new research effort, we integrate magnetic materials with nano- and micromechanical devices to advance fundamental science and to obtain new functionalities that can lead to disruptive technologies. We study strain-mediated interactions between magnons and phonons in magnetic mechanical oscillators. The hybrid potential is provided by magnetostriction, which couples mechanical strain to magnetization. This activity can be regarded as a strong analog to cavity optomechanics, with magnons replacing the electromagnetic cavity.

      Optomechanics with macroscopic quartz resonators

      We observe optomechanical physics in a truly macroscopic oscillator close to the quantum ground state. As the mechanical system, we use a mm-sized piezoelectric quartz disk oscillator. Its motion is coupled to a charge qubit which translates the piezo-induced charge into an effective radiation–pressure interaction between the disk and a microwave cavity. The work opens up opportunities for macroscopic quantum experiments.

      Millimeter-scale piezoelectric quartz resonators
      Millimeter-scale piezoelectric quartz resonators.

      Latest publications

      Mechanical Resonators at Low Temperatures

      Eddy Collin, Mika A. Sillanpää 2023 Journal of Low Temperature Physics

      Special Issue on Mechanical Resonators at Low Temperatures

      Eddy Collin, Mika Sillanpää 2023 Journal of Low Temperature Physics

      Fast Feedback Control of Mechanical Motion Using Circuit Optomechanics

      Cheng Wang, Louise Banniard, Laure Mercier De Lépinay, Mika A. Sillanpää 2023 Physical Review Applied

      Quantum backaction evading measurements of a silicon nitride membrane resonator

      Yulong Liu, Jingwei Zhou, Laure Mercier De Lépinay, Mika A. Sillanpää 2022 New Journal of Physics

      Multiphonon Transitions in a Quantum Electromechanical System

      Alpo Välimaa, Wayne Crump, Mikael Kervinen, Mika A. Sillanpää 2022 Physical Review Applied

      A macroscopic object passively cooled into its quantum ground state of motion beyond single-mode cooling

      D. Cattiaux, I. Golokolenov, S. Kumar, M. Sillanpää, L. Mercier de Lépinay, R. R. Gazizulin, X. Zhou, A. D. Armour, O. Bourgeois, A. Fefferman, E. Collin 2021 Nature Communications

      Microwave single-Tone optomechanics in the classical regime

      Ilya Golokolenov, Dylan Cattiaux, Sumit Kumar, Mika Sillanpää, Laure Mercier De Lépinay, Andrew Fefferman, Eddy Collin 2021 New Journal of Physics

      Energy-level attraction and heating-resistant cooling of mechanical resonators with exceptional points

      Cheng Jiang, Yu Long Liu, Mika A. Sillanpää 2021 Physical Review A

      Magnomechanics in suspended magnetic beams

      Kalle S.U. Kansanen, Camillo Tassi, Harshad Mishra, Mika A. Sillanpää, Tero T. Heikkilä 2021 Physical Review B

      Gravitational Forces between Nonclassical Mechanical Oscillators

      Yulong Liu, Jay Mummery, Jingwei Zhou, Mika A. Sillanpaä¨ 2021 Physical Review Applied
      More information on our research in the Research database.
      Research database
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