In a thin sandwich of gallium arsenide, electrons don't behave like individual balls but like a single quantum liquid. If the layer is made just 70 nanometers thick, this liquid separates into two nearly independent flows, like oil on water. Under these conditions, a strong magnetic field gives rise to a state with the fractional quantum Hall effect at filling factor 1/2.
Quantum point contact, a narrow constriction etched into the semiconductor, acts as a turnstile, letting quasiparticles through one at a time. By measuring shot noise (random current fluctuations, like the crackle of popcorn in a microwave), scientists determined the charge of the carriers. It turned out to be e/4—a quarter of the electron's charge. It's like cutting a coin into four pieces and finding that each piece still rings like a whole one.
The result matters beyond itself. Quasiparticles with charge e/4 may obey unusual statistics: when exchanged, their wave function changes differently than for ordinary particles. If confirmed, such systems could be used to shield quantum information from disturbances, like a safe that knows when someone tried to open it.
Charge e/4 is like cutting a banknote into quarters, and each quarter still works as full currency.