Quantum reservoir for microwaves

May 15, 2017
Photograph of the chip used in the experiment to couple a microwave cavity to a micrometer-size drum (the sharp purple pencil tip is placed as a scale). Inset shows a scanning electron micrograph of the drum. The top membrane of the drum is suspended only 50nm (1/2000th of the diameter of hair) above a metal plate. This is then used to manipulate and amplify microwaves in the quantum regime. Credit: N. R. Bernier and L. D. Tóth (EPFL).

In a recent experiment at EPFL, a microwave resonator, a circuit that supports electric signals oscillating at a resonance frequency, is coupled to the vibrations of a metallic micro-drum. By actively cooling the mechanical motion close to the lowest energy allowed by quantum mechanics, the micro-drum can be turned into a quantum reservoir - an environment that can shape the states of the microwaves. The findings are published as an advanced publication in Nature Physics.

László Dániel Tóth, Nathan Bernier, and Dr Alexey Feofanov led the research effort in Tobias Kippenberg's Laboratory of Photonics and Quantum Measurements at EPFL, with support from Dr Andreas Nunnenkamp, a theorist at the University of Cambridge, UK.

Microwaves are electromagnetic waves, just like visible light, but with a frequency that is four orders of magnitude smaller. Microwaves form the backbone of several everyday technologies, from ovens and cellular phones to satellite communication, and have recently gained further importance in manipulating quantum information in superconducting circuits—one of the most promising candidates to realize future quantum computers.

The micro-drum, only 30 microns in diameter, 100 nanometers thick and fabricated in the Center of MicroNanotechnology (CMi) at EPFL, constitutes the top plate of a capacitor in a superconducting microwave resonator. The drum's position modulates the resonator's and, conversely, a voltage across the capacitor exerts a force on the micro-drum. Through this bidirectional interaction, energy can be exchanged between mechanical vibrations and the microwave oscillations in the superconducting circuit.

In the experiment, the micro-drum is first cooled close to its lowest energy quantum level by a suitably tuned microwave tone. Every microwave photon (a quantum of light) carries away the energy of a phonon (a quantum of mechanical motion) such that the mechanical energy is reduced. This cooling process increases the dissipation and turns the micro-drum into a dissipative reservoir for the microwave resonator.

By tuning the interactions between the cavity and the cooled micro-drum, which is now an environment for the microwaves, the cavity can be turned into a . The most interesting aspect of this amplification process is the added noise, that is, how much random, unwanted fluctuations are added to the amplified signal.

Albeit counter-intuitive, dictates that this added noise cannot be suppressed completely, even in principle. The amplifier realized in the EPFL experiment operates very close to this limit, therefore it is as "quiet" as it can be. Interestingly, in a different regime, the micro-drum turns the microwave resonator into a maser (or microwave laser).

"There has been a lot of research focus on bringing mechanical oscillators into the quantum regime in the past few years." says Dr. Alexey Feofanov, postdoctoral researcher on the project. "However, our experiment is one of the first which actually shows and harnesses their capabilities for future quantum technologies."

Looking ahead, this experiment enables novel phenomena in cavity optomechanical systems like noiseless microwave routing or microwave entanglement. Generally, it proves that mechanical oscillators can be a useful resource in the rapidly growing field of science and engineering.

Future activities on the emerging research possibilities created by this work will be supported by two recently started EC Horizon 2020 projects: Hybrid Optomechanical Technologies (HOT) and Optomechanical Technologies (OMT), both coordinated at EPFL.

Explore further: Physicists 'squeeze' light to cool microscopic drum below quantum limit

More information: A dissipative quantum reservoir for microwave light using a mechanical oscillator, Nature Physics (2017). DOI: 10.1038/nphys4121

Related Stories

Physicists use mechanical micro-drum used as quantum memory

March 13, 2013

JILA researchers demonstrated thatinformation encoded as a specific point in atraveling microwave signal—the vertical and horizontal positions of a wave pattern at a certain ime—can be transferred to the mechanical beat ...

Tiny graphene drum could form future quantum memory

August 28, 2014

Scientists from TU Delft's Kavli Institute of Nanoscience have demonstrated that they can detect extremely small changes in position and forces on very small drums of graphene. Graphene drums have great potential to be used ...

Recommended for you

New scaling law predicts how wheels drive over sand

May 30, 2017

When engineers design a new aircraft, they carry out much of the initial testing not on full-sized jets but on model planes that have been scaled down to fit inside a wind tunnel. In this more manageable setting, they can ...

Toward mass-producible quantum computers

May 26, 2017

Quantum computers are experimental devices that offer large speedups on some computational problems. One promising approach to building them involves harnessing nanometer-scale atomic defects in diamond materials.

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

gculpex
not rated yet May 15, 2017
Microwaves are electromagnetic waves, just like visible light, but with a frequency that is four orders of magnitude smaller.

smaller?
antialias_physorg
not rated yet May 15, 2017
Frequency is smaller (wavelength is longer)
Sonhouse
5 / 5 (1) May 15, 2017
Poor writing. Should have said 4 orders of magnitude lower frequency. Or just said 1 to 100 Ghz or some such.
EmceeSquared
not rated yet May 17, 2017
Does this device convert heat phonons into microwave lasers (primed with a microwave it amplifies)? Could a fabric of these devices convert heat to microwave lasers while delivering industrial useful cooling?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.