  We propose a spintronic magnetic field sensor, fashioned out of quantum
wires, which may be capable of detecting very weak magnetic fields with a
sensitivity of ~ 1 femto-Tesla per root Hertz at a temperature of 4.2 K and ~
80 femto-Tesla per root Hertz at room temperature. Such sensors have
applications in magnetometry, quantum computing, solid state nuclear magnetic
resonance, magneto-encephalography, mine detection, ground incursion detection
and anti-submarine warfare.
