Tunable Noise Cross-Correlations in a Double Quantum Dot
C.M. Marcus

a) Electron micrograph of parallel double quantum dot. The dots are tuned into the Coulomb blockade regime with purely capacitive inter-dot coupling (the central point contact is pinched off, preventing inter-dot tunneling). The schematic shows the detection system measuring the auto- and cross-correlation of fluctuations, or noise, in currents It and Ib through top and bottom quantum dots. (b) Zero-bias differential conductances gt and gb as a function of plunger gate voltages Vbc and Vtc. Dark regions correspond to fixed electron number (M, N) in the double dot. The superimposed white lines indicate the honeycomb structure that results from inter-dot capacitive coupling.  (c) Measured noise cross-correlation at fixed bias VT=VB=-100 mV in the vicinity of the central honeycomb vertex in (b). The sign of the noise cross-correlation is tunable by gate voltage. (d) A master equation simulation of sequential tunneling with inter-dot capacitive coupling reproduces the characteristic quadrupole pattern of positive and negative cross-correlation that is observed experimentally. From “Tunable Noise Cross-Correlations in a Double Quantum Dot” by  D.T. McClure, L. DiCarlo, Y. Zhang, H.-A. Engel, C.M. Marcus, M.P. Hanson, and A.C. Gossard (submitted to Physical Review Letters, cond-mat/0607280).