Single-Shot Measurement of One and Two-Electron Spin States in Si/SiGe Gated Quantum Dots

In this talk we discuss recent experiments involving single-shot measurements of electron spins in both a single-spin basis and a two-electron spin basis. In both cases, to measure the spin state we use a spin-to-charge conversion technique based on the energy difference between the two spin states. For single spins, this approach involves applying a magnetic field large enough that the Zeeman splitting between up and down spins Ez = gμ_BB is larger than the electron temperature T. Here g ≅ 2 is the g-factor, μ_B is the Bohr magneton, B is the magnetic field, and T ≅ 140 mK for the single-spin experiments. For measurements of two-electron spin states, we make use of the energy difference between singlet and triplet states with two electrons in a single dot; in this case, we require the singlet-triplet splitting to be larger than the temperature T, which was less than 50 mK for the two-electron measurements.