|Nov 05, 2019|
Ultrafast quantum motion in a nanoscale trap detected(Nanowerk News) When an electron is captured in a nanoscale trap in solids, its quantum mechanical wave function can exhibit spatial oscillation at sub-terahertz frequencies. Time-resolved detection of such picosecond dynamics of quantum waves is important, as the detection provides a way of understanding the quantum behavior of electrons in nano-electronics.
|It also applies to quantum information technologies such as the ultrafast quantum-bit operation of quantum computing and high-sensitivity electromagnetic-field sensing.|
|However, detecting picosecond dynamics has been a challenge since the sub-terahertz scale is far beyond the latest bandwidth measurement tools.|
|A KAIST team led by Professor Heung-Sun Sim developed a theory of ultrafast electron dynamics in a nanoscale trap, and proposed a scheme for detecting the dynamics, which utilizes a quantum-mechanical resonant state formed beside the trap (Nature Nanotechnology, "Picosecond coherent electron motion in a silicon single-electron source"). The coupling between the electron dynamics and the resonant state is switched on and off at a picosecond so that information on the dynamics is read out on the electric current being generated when the coupling is switched on.|
|Left: Measurement scheme. Right: Electron trap in a silicon transistor. (Image: KAIST) (click on image to enlarge)|
|Nippon Telegraph and Telephone Corp. (NTT) in Japan realized, together with National Physical Laboratory (NPL) in the UK, the detection scheme and applied it to electron motions in a nanoscale trap formed in a silicon transistor.|
|A single electron was captured in the trap by controlling electrostatic gates, and a resonant state was formed in the potential barrier of the trap.|
|The switching on and off of the coupling between the electron and the resonant state was achieved by aligning the resonance energy with the energy of the electron within a picosecond. An electric current from the trap through the resonant state to an electrode was measured at only a few Kelvin degrees, unveiling the spatial quantum-coherent oscillation of the electron with 250 GHz frequency inside the trap.|
|Professor Sim said, “This work suggests a scheme of detecting picosecond electron motions in submicron scales by utilizing quantum resonance. It will be useful in dynamical control of quantum mechanical electron waves for various purposes in nano-electronics, quantum sensing, and quantum information”.|
|Source: KAIST (Korea Advanced Institute of Science and Technology)|
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