A quantum microphone can record human speech better than an equivalent classical version, and it could also be adapted for high-resolution biological imaging.
Standard microphones detect the vibrations from sound and convert them into an equivalent electrical signal. Quantum versions should potentially be able to do the same thing, but create a clearer recording because of the phenomenon of entanglement, in which particles 鈥� such as photons of flight 鈥� have linked properties. This potential exists because pairs of entangled photons can measure more information than single classical photons can.
Extracting that information from entangled photons is difficult, however, because many photons have to be measured at once.
Advertisement
Now, at the University of Stuttgart in Germany and his colleagues have designed a quantum microphone that can measure enough photons per second to handle human speech. The microphone consists of a laser interferometer, which can detect small displacements of photons, attached to a mirrored membrane. When sound vibrates the membrane, entangled photons are displaced and the measurements of this are converted to an electrical signal corresponding to the sound.
鈥淲hen you use quantum light with entangled photons, you can measure these displacements a bit more precisely with a better signal-to-noise ratio,鈥� says Kaiser.
He and his team recorded spoken five-word sentences in German using both their microphone and a classical microphone that also uses a laser interferometer. When they played these samples to a group of 45 people at progressively lower volumes, 71 per cent of the volunteers could understand the quantum-recorded words for longer.
The use of quantum sensors has long held great promise, but demonstrating it in the real world is often difficult, says at the University of Glasgow, UK. 鈥淯sing this approach, the authors demonstrate a tangible quantum advantage in a real-world sensing scenario, namely speech recognition.鈥�
The higher cost of the quantum microphone means it is unlikely to be used in the real world any time soon, especially given how effective even cheap classical microphones are, but a similar technique could be used to create a quantum microscope for high-resolution biological imaging, says Kaiser.
PRX Quantum
Sign up to Lost in Space-Time, a free monthly newsletter on the weirdness of reality
