(Microsoft Word - Magnetometer\311)

We report transport measurements as a function of bias in open semiconductor quantum dots. These measurements are well described by an effective electron temperature derived from Joule heating at the point contacts and cooling by Wiedemann-Franz out-diffusion of thermal electrons. Using this model, we propose and analyze a quantum dot based sensor which measures absolute magnetic field at micron scales with a noise floor of ~ 50 Hz 0 µϕ at 300 mK. Quantum dots have been studied extensively as controllable systems in which quantum phenomena can be probed with transport measurements 1. Most experiments are performed at low bias, typically less than 20 µV for dots with total conductance g e h ≥ 2 (" open " dots), however many proposed applications will require higher bias to produce easily measurable signals. Experiments in quantum dots in the tunneling regime (g e h << 2) have exploited the nonlinear conduction of quantum dots at high bias for energy level spectroscopy 2. In open dots, conduction remains essentially linear, and the primary effect of the increased bias is to heat the electrons in the dot. In a quantum dot sensor , the optimum bias balances the increased signal from high bias with the loss of quantum interference and increased noise from the elevated electron temperature. In this Letter, we present measurements of high bias transport in open quantum dots in thermal equilibrium , and show that the data are well described by an effective electron temperature. We then apply this effective temperature model to a quantum dot magnetometer, optimize its design parameters, and compare it to alternative technologies for micron scale magnetome-try. The measurements were made in a 3 He cryostat over a temperature range 340 mK – 1.5 K with a quantum dot of area A = 4 0. m 2 µ (Fig. 1 inset) defined by electron beam lithography on a GaAs/AlGaAs heterostructure using Cr/Au gates 160 nm above the two