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.

News

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.
Researchers were able to time the extraction and splitting of entangled Cooper pairs from a superconductor. Picture: Aalto University.
Research & Art Published:

Novel quantum device design promises a regular flow of entangled electrons on demand

Quantum computer and many other quantum technologies rely on our ability to generate quantum entangled pairs of electrons. By dynamically controlling two quantum dots near a superconductor, researchers could time the extraction and splitting of entangled Cooper pairs from a superconductor.
The drumheads exhibit a collective quantum motion. Picture: Juha Juvonen.
Press releases Published:

Evading the uncertainty principle in quantum physics

New technique gets around 100-year-old rule of quantum physics for the first time
The highly competed ERC Advanced Grant, awarded to leading top researchers, is the third ERC grant won by Professor Mika A. Sillanpää. In 2009, he received the ERC Starting Grant targeted at talented young researchers and, in 2013, he was awarded the ERC Consolidator Grant intended for top researchers establishing their careers. Picture: Aalto University.
Press releases Published:

Physicist Mika A. Sillanpää wins a multi-million euro research grant to support work reconciling quantum mechanics and general relativity

The team is trying to solve a hundred-year-old mystery of physics with the help of small gold spheres and extremely low temperatures. The observation of tiny gravitational forces between vibrating spheres may solve the mystery.
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.

Research group members

Latest publications

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

Gravitational Forces between Nonclassical Mechanical Oscillators

Yulong Liu, Jay Mummery, Jingwei Zhou, Mika A. Sillanpaä¨ 2021 Physical Review Applied

Quantum mechanics-free subsystem with mechanical oscillators

Laure Mercier de Lépinay, Caspar F. Ockeloen-Korppi, Matthew J. Woolley, Mika A. Sillanpää 2021 Science (New York, N.Y.)

Optomechanical Anti-Lasing with Infinite Group Delay at a Phase Singularity

Yulong Liu, Qichun Liu, Shuaipeng Wang, Zhen Chen, Mika A. Sillanpää, Tiefu Li 2021 Physical Review Letters

Multiphonon transitions in a quantum electromechanical system

Wayne Crump, Alpo Välimaa, Mika Sillanpää, Mikael Kervinen 2021 arXiv

Magnomechanics in suspended magnetic beams

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

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

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

Beyond linear coupling in microwave optomechanics

D. Cattiaux, X. Zhou, Sumit Kumar, I. Golokolenov, R. R. Gazizulin, A. Luck, Laure Mercier de Lepinay, Mika Sillanpää, A. D. Armour, A. Fefferman, E. Collin 2020 PHYSICAL REVIEW RESEARCH

Sideband Control of a Multimode Quantum Bulk Acoustic System

Mikael Kervinen, Alpo Välimaa, Jhon E. Ramírez-Muñoz, Mika Sillanpää 2020 Physical Review Applied
More information on our research in the Research database.
Research database
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