Nanomechanically Amplified Weak Electric Signals to Create Better MRI Scanners

A team of international physicists has developed a hypothesis on how to both detect weak electrical signals and cool electrical circuits using light and something very similar to a nanosized loudspeaker. If validated through research, the project could have an impact on detection of low-power radio signals, magnetic resonance imaging (MRI), and the developing field of quantum data science.

JQI is pursuing that goal through the work of leading quantum scientists from the department of physics of the University of Maryland (UMD; College Park, USA), the US National Institute of Standards and Technology (NIST; Gaithersburg, MD, USA) and the Laboratory for Physical Sciences (LPS) at UMD. Each institution brings to JQI major experimental and theoretic research programs that are focused the goals of controlling and exploiting quantum systems.


The team was composed of investigators from the Joint Quantum Institute (JQI; Copenhagen, Denmark), Neils Bohr Institute (Copenhagen, Denmark), and Harvard University (Cambridge, MA, USA). JQI researchers believe they have discovered a way to amplify faint electrical signals using the motion of a nanomechanical membrane, or loudspeaker. If shown in experiments, the scheme could prove a boon to magnetic resonance imaging and quantum information science.

“We envision coupling a nanomechanical membrane to an electrical circuit so that an electrical signal, even if exceedingly faint, will cause the membrane to quiver slightly as a function of the strength of that signal,” said JQI physicist Dr. Jake Taylor. “We can then 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.”

Current technology for measuring the wavelength of light is very sensitive, which makes it suitable for detecting the nanoscopic motions of the loudspeaker caused by extremely faint electrical signals. Moreover, the ability to detect extremely faint electrical signals may make MRI medical procedures much easier in the future. “MRI machines are so big because they are stuffed with really powerful superconducting magnets, but if we can reduce the strength of the signals we need for a reading, we can reduce the strength, and the size, of the magnets,” Prof. Taylor stated. “This may mean that one could get an MRI while sitting quietly in a room and forgo the tube.”

The same arrangement could be used to generate data-carrying photons from one qubit to another, according to Prof. Taylor. One prevalent quantum information-system design utilizes light to transfer data among qubits, entangled particles that will exploit the inherent strangness of quantum phenomena to perform specific 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.

According to their calculations, converting the mechanical motion of the little loudspeaker into photons will siphon a considerable amount of heat out of the system (from room temperature to 3 K), which in turn will reduce noise in the system and provide for better signal detection.

The researchers published their findings in the journal December 27, 2011, in the journal Physical Review Letters.

Related Links:
Joint Quantum Institute
Neils Bohr Institute
US National Institute of Standards and Technology