Fig. 1: Optically detected nuclear magnetic resonance (NMR) of a single quantum dot.
From: Storing quantum coherence in a quantum dot nuclear spin ensemble for over 100 milliseconds
a Right inset shows schematic diagram of Ga and As nuclear spins in a GaAs/AlGaAs quantum dot (QD). NMR spectrum of the spin-3/2 75As nuclei (black and blue solid lines, left scale) measured in an uncharged (0e) QD. The frequency offset is shown with respect to the Larmor frequency νL ≈ 37.981 MHz arising from the Zeeman splitting at external field of Bz ≈ 5.16 T (left inset). Out of the three magnetic dipole transitions, the two satellite transitions (STs) undergo a first-order quadrupolar shift \(\pm {\nu }_{Q}^{(1)}\) (where \({\nu }_{Q}^{(1)}\approx 255.1\) kHz), while the central transition (CT) is affected only by the second-order quadrupolar shift \({\nu }_{Q}^{(2)}\approx 3.3\) kHz. The CT linewidth (Δν−1/2↔+1/2 ≈ 0.8 kHz) is much narrower than the ST linewidths (Δν+1/2↔+3/2 ≈ Δν−3/2↔−1/2 ≈ 13.8 kHz). Dashed lines (right scale) show spectral profiles of the radio frequency (Rf) pulse bursts with duration TRf = 10 or 20 μs, tuned in resonance with the CT. b Schematic diagram of a CHASE-10 sequence cycle, letters and signs denote Rf pulse phases. The pulses are separated by the free-evolution intervals τ. The total nuclear evolution time is TEvolTot = 10TRf + 12τ, while TFreeEvol = 12τ is the pure free evolution time for one cycle. c The CHASE-40 supercycle constructed of four CHASE-10 steps, with pulse carrier phase incremented by π/2 in each step. d Timing of the ODNMR measurement cycle. Optical pumping creates longitudinal nuclear spin polarization. The initialization π/2 Rf pulse converts this into transverse (coherent) nuclear polarization in the xy plane. Dynamical decoupling is applied, followed by a finalization π/2 pulse to rotate the remaining transverse polarization back along the z-axis. Finally, the nuclear polarization is read out using photoluminescence (PL) spectroscopy under an optical probe pulse. The sample bias is pulsed to maximize optical nuclear spin pumping and PL intensity during optical probing.
