When a ballerina pirouettes, twirling a full revolution, she looks just as she did when she started. But for electrons and other subatomic particles, which follow the rules of quantum theory, that’s not necessarily so. When an electron moves around a closed path, ending up where it began, its physical state may or may not be the same as when it left.
Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices.
To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene—an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit.
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