A single nanoscale hybrid system for studying the vacuum fluctuation field

When you think of empty space, you almost certainly imagine a void where nothing interesting happens. However, if we zoom out to small length scales where quantum effects start to matter, what you thought was empty is filled with mass of electromagnetic activity all the time as virtual photons flash in and out. .

This unexpected phenomenon is called vacuum fluctuation field. But because these fluctuations in light energy are so small and so rapid in time, it’s difficult to find ways to interact with matter, especially in an integrated device.

In a study titled „Electrical detection of ultrastrong coherent interactions between terahertz fields and electrons using quantum point interactions,” Published This month Nano letters, researchers at the Institute of Industrial Science at the University of Tokyo succeeded in creating a nanoscale hybrid system to do this. In their design, a quantum point contact connects a single on-chip split-ring resonator to a two-dimensional electron system.

A split-ring resonator, a nanosized square metal ring with a small gap, responds very strongly when excited with specific resonant frequencies of terahertz electromagnetic radiation. Conventional optical measurements previously required arrays with multiple resonators, but the team is now able to detect ultrastrong coupling using a single terahertz split-ring resonator coupled to 2D electrons.

A simple, single resonator structure can be used to determine the quantum state, making quantum information processing even more feasible in the future. This goal can be achieved using electrical, rather than optical, sensing performed using quantum dot contacts.

„Matter that can interact with vacuum fluctuations of the electromagnetic field is said to exist in the ultrastrong coupling regime,” says Kazuyuki Kuroyama, first author of the study. The experiment shows that the current signal in quantum dot contact can be used to detect ultrastrong coupling of a single slit-ring resonator to a 2D electron gas.

Additionally, the current can be measured in the quantum dot contact even without the application of external radiation. Current modulations allowed the researchers to conclude that interactions between the 2D electron gas and vacuum field fluctuations of the resonator still take place in the absence of terahertz radiation.

„Our findings may allow for highly sensitive quantum sensors based on the coupling between vacuum fluctuations and an integrated hybrid quantum device,” says senior author Kazuhiko Hirakawa.

In addition to learning more about the fundamental laws of nature at very small scales, the findings of this study could help build future quantum computers that can use regular phenomena to process or transmit data.