Figure 1

(a) and (b) Four-level representation. (a) Two-beam setup. (b) Three-beam setup. $|0⟩$ and $|1⟩$ are the crystal ground state and the qubit exciton, respectively, while $|R⟩$ is the readout exciton. The arrows in (a) and (b) denote the laser pulses, where the dashed lines are the probes, the normal solid lines are the pumps and the thick solid line is the prepump. (c) DT signal obtained by using the two-beam (blue, open circle) and three-beam (red, solid circle) setups. The state where the prepump is fixed is highlighted in green (gray). We indicate that a $\pi$ pulse inverts 88% of the population to state $|1⟩$, leaving 12% in state $|0⟩$.Reuse & Permissions

Figure 2

Phase dependent rotations of a qubit in the exciton system. The red (blue) plot corresponds to a relative phase of $\varphi =\pi (2\pi )$ between the two pump pulses, as indicated by the red (blue) arrow in the inset. The open circle plot is a single $\pi /2$ decay, which serves as a comparison. The inset is an interferogram. Here $\tau =10\mathrm{ps}$ and $\omega$ is the laser frequency.Reuse & Permissions

Figure 3

Decay plots of single $\pi /2$ pulse and interferogram taken at 10 ps delay from the creation pulse. The horizontal dashed lines mark the values of each population readout. $\mathbf{X}$ gives ${\rho }_{11}^{\mathrm{rot}}=0.73$, $\mathbf{Y}$ gives ${\rho }_{11}^{\mathrm{rot}}=0.42$, and $\mathbf{Z}$ gives ${\rho }_{11}=0.36$.Reuse & Permissions

Figure 4

Density matrices of a single qubit created by a $\pi /2$ pulse. (a) Ideal matrix. (b)[(c)] Calculated density matrices with decays excluding (including) rotation and probe pulses. (d) Measured density matrix from experiment.Reuse & Permissions