Sound at the quantum level using Surface Acoustic Waves (SAW)


On the right, an artificial atom generates sound waves consisting of ripples on the surface of a solid. The sound, known as a surface acoustic wave (SAW) is picked up on the left by a "microphone" composed of interlaced metal fingers. According to theory, the sound consists of a stream of quantum particles, the weakest whisper physically possible. The illustration is not to scale. Credit: Philip Krantz, Krantz NanoArt.
 
 
This project focuses on using a special form of sound called Surface Acoustic Waves (SAWs) at the quantum level. SAWs are ripples on the surface of a piezoelectric substrate that can be electrically generated and received. Artificial atoms (also known as superconducting transmon qubits) and single electron transistors (SETs) can thus directly interact with the SAWs. The main goal of this project is to speak and listen to a single quantum particle of sound known as a phonon, the most quiet whisper imaginable!
 
Sound has many features that make it unique compared to light interacting with an atom. Primary among these is that sound propagates five orders of magnitude slower than light. This could allow real time manipulation of carriers of quantum information, coupling to sound at certain frequencies or even the size of the atom to be small compared to the wavelength (i.e. a "giant atom", much larger than the radiation it is interacting with).
 
Future work in this project will focus on both emitting and detecting single quanta of sound. In addition, we will explore differences arising from using giant atoms, time domain manipulation of sound quanta and the coupling of atoms to sound
 
 


 

 

Microscope image: The artificial atom, in grey-blue to the upper right, can emit and absorb sound that moves across the surface of a microchip. The grey-blue structure to the lower left is the combined loudspeaker/microphone used to communicate acoustically with the atom.
Credit: Martin Gustafsson and Maria Ekström

 

 

 

 


Microscope image: Zoom-in of the artificial atom, with its integrated Superconducting Quantum Interference Device (SQUID) in violet. The SQUID gives the atom its quantum properties, and the fingers sticking up to the left provide the coupling to sound waves.
Credit: Martin Gustafsson and Maria Ekström
Project leader
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​Swedish Research Council

The Knut and Alice Wallenberg Foundation

The European Research Council

 
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Published: Mon 13 Nov 2017.