Electron spin can be detected as a magnetic field having one of two orientations, known as down and up. This provides an additional two binary states to the conventional low and high logic values, which are represented by simple currents. With the addition of the spin state to the mix, a bit can have four possible states, which might be called down-low, down-high, up-low, and up-high. These four states represent quantum bits (qubits).
Spintronic technology has been tested in mass-storage components such as hard drives. The technology also holds promise for digital electronics in general. The existence of four, rather than two, defined states for a logic bit translates into higher data transfer speed, greater processing power, increased memory density, and increased storage capacity, provided the properties of electron spin can be sufficiently controlled for practical applications.
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Lisa Zyga explains how a newly discovered spintronics effect could lead to magnetic batteries.