Tunable Noise Cross-Correlations
in a Double Quantum Dot
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