Theoretical physicists working at Harvard and the Joint Quantum Institute in the US have joined forces with their Danish colleagues at the Niels Bohr Institute, to design a nanoscale loud speaker that could help make MRI scanners smaller, and might one day find a use in a future quantum computer.
The 'speaker' they have conceived still needs to be tested experimentally. But the theory goes something like this: a nanomembrane is rigged up to a circuit (rigged is a technical term) so that any electrical signal – even very faint – will cause it to vibrate. That vibration will be related to the strength of the signal, so if the vibration can be measured very precisely, the signal can be amplified.
Fortunately, the technology needed to measure tiny vibrations of the sort the physicists are considering, is already up to the task. JQI physicist Jake Taylor is quoted in the NIST press announcement here: "We can bounce photons from a laser off that membrane and read the signal by measuring the modulation of the reflected light as it is shifted by the motion of the membrane. This leads to a change in the wavelength of the light."
As well as allowing engineers to reduce the size of the superconducting magnets in an MRI scanner – potentially to the point where no one would need to go through the tube – the ideas sketched out by the research team might have applications in quantum computing.
From the announcement: One popular quantum information system design uses light to transfer information among qubits, entangled particles that will exploit the inherent weirdness of quantum phenomena to perform certain calculations impossible for current computers. The 'nanospeaker' could be used to translate low-energy signals from a quantum processor to optical photons, where they can be detected and transmitted from one qubit to another.
And finally, the system is self cooling. The researchers have calculated that the energy required to translate the mechanical energy of the membrane into photons will cool the system from room temperature to roughly 3 degrees Kelvin, or -270 degrees C.
The work was published here in Physics Review Letters on December 27th.