Generating quantum states of sound inside a microscopic device

Towards quantum states of sound.


Scientists have made it possible to generate and control quantum states in different physical systems. This control allows scientists to develop powerful new quantum technologies. In addition, it offers a roadmap to test the foundations of quantum physics.

The main challenge is to create quantum states on a larger scale.

In collaboration with the University of Oxford, scientists at Imperial College London, the Niels Bohr Institute, the Max Planck Institute for the Science of Light, and the Australian National University have generated and observed non-Gaussian states high-frequency sound waves comprising more than a trillion atoms. Certainly, they transformed a randomly fluctuating sound field in thermal equilibrium to a pattern thrumming with a more specific magnitude.

The findings pave the way towards generating more macroscopic quantum states. Such quantum states could enable the development of future quantum internet components. Moreover, it allows testing of quantum mechanics limits.

Co-first author of the project, John Price from Imperial, said, “To perform this research, we confine laser light to circulate inside a micro-scale resonator. Impressively, the light can circulate up to a million times around the edge of this tiny structure in what’s called a whispering-gallery mod.”

Co-first author Andreas Svela from Imperial said, “As the light circulates, it interacts with high-frequency sound waves, and we can use the laser light to both generate and characterize interesting states of the acoustic field.”

Co-first author Lars Freisem from Imperial said, “Then when we observe a single photon that this light-sound interaction has created, the detection event gives us the signal that we’ve created our target state.”

Detection of single photon indicates that a single phonon- a quantum of sound energy is subtracted from the initial state of the acoustic field. Scientists observed the addition and subtraction of a single phonon to a counterintuitive doubling of the average number of sound quanta.

This study makes a significant advancement by precisely characterizing the fluctuations of the sound wave generated and observing the resulting non-Gaussian pattern.

Co-first author Georg Enzian, now pursuing research at the Niels Bohr Institute, Copenhagen, said, “Generating non-Gaussian quantum states is important for research in quantum information and the foundations of physics, and excitingly, this research brings us closer to generating such states at a macroscopic scale using sound fields.”

Imperial’s Quantum Measurement Lab principal investigator Michael Vanner said, “Future work using this approach offers a practical route to store and retrieve quantum information coherently. That is, make a quantum RAM for a quantum computer. Moreover, this type of research can shed much-needed light on the different mechanisms that cause fragile quantum phenomena to decay and become classical.”

Journal References:

  1. Enzian, L. Freisem, J. J. Price, A. Ø. Svela, J. Clarke, B. Shajilal, J. Janousek, B. C. Buchler, K. Lam & M. R. Vanner. Non-Gaussian Mechanical Motion via Single and Multiphonon Subtraction from a Thermal State. Doi: 10.1103/PhysRevLett.127.243601
  2. Enzian, J. J. Price, L. Freisem, J. Nunn, J. Janousek, B. C. Buchler, P. K. Lam, and M. R. Vanner. Single-phonon addition and subtraction to a mechanical thermal state. DOI: 10.1103/PhysRevLett.126.033601
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