Neutrons are subatomic particles that lack electric charge, making them immune to the electromagnetic force and held together in an atom’s nucleus by the strong force. Researchers at MIT have discovered that neutrons can be made to cling to quantum dots, which consist of tens of thousands of atomic nuclei, solely through the strong force. This finding could lead to new tools for studying materials at the quantum level and exploring quantum information processing devices. The research, published in ACS Nano, was conducted by MIT graduate students Hao Tang and Guoqing Wang, along with professors Ju Li and Paola Cappellaro.
Neutrons are commonly used in neutron scattering to probe material properties by directing a neutron beam at a sample and detecting the reflected neutrons to reveal the material’s internal structure and dynamics. The discovery that neutrons can bind to the materials they are probing was unexpected and has not been previously described, as neutrons do not interact with electromagnetic forces. The high energy of the strong force that holds atomic nuclei together allows neutrons to form stable bound states within quantum dots, similar to Thomson’s plum pudding model of an atom but with diffuse wavefunctions at a larger scale.
The newly discovered neutronic molecules are made up of quantum dots, nano-sized crystalline particles where the properties are defined more by their size and shape than by their composition. Neutronic quantum dots can trap neutrons, displaying quantized energies that could be utilized for storing quantum information. The development of these molecules was based on theoretical calculations and computational simulations that verified the potential of binding neutrons to quantum dots. Creating neutronic molecules in the lab poses challenges due to the specialized equipment needed to maintain extremely low temperatures.
These artificial molecules offer a model system to study quantum mechanical problems and potentially mimic the electron shell structure of atoms. By controlling the neutron state within the quantum dot, researchers could manipulate neutron beams for specific applications. Neutrons could serve as mediators between nuclear spins of separate nuclei, facilitating the development of new quantum information systems. The system offers a different approach from electromagnetics-based quantum information processing, opening up possibilities for novel applications in fields such as nuclear imaging and materials analysis.
The research was supported by the U.S. Office of Naval Research and builds on previous work in quantum dots and nanocrystals. The potential applications of neutronic molecules include precise control over individual neutrons, affecting nuclear spins, and advancing quantum information processing beyond the electromagnetics-based paradigm. Neutron imaging, with its strong interactions with light elements, could provide valuable information about elemental composition and isotopes. The discovery of neutronic molecules opens up new avenues for exploring quantum phenomena at the nanoscale and developing cutting-edge technologies in quantum information processing.
