| Multi pulse operation and optical detection of nuclear spin coherence in a GaAs/AlGaAs quantum well |
We demonstrate manipulation of nuclear spin coherence in a GaAs/AlGaAs quantum well by optically-detected nuclear magnetic resonance (NMR). Phase shift of the Larmor precession of photoexcited electron spins is detected to read out the hyperfine-coupled nuclear spin polarization. Multi pulse NMR sequences are generated to control the population and examine the phase coherence in quadrupolar-split spin-3/2 75As nuclei. The phase coherence among the multi-level nuclear spin states is addressed by application of pulse sequences that are used in quantum gate operations.
| Figure 1 | (a) Energy level diagram of quadrupolar-split I =3/2 nuclear spin states |m>. (b) The experimental setup of the TRFR experiments. The (110) GaAs/AlGaAs QW was set so that the [001] crystalline axis in the QW plane was tilted about 2 degree from B0//z. |
| Figure 2 | Rabi oscillations for I (upper) and II (lower) transitions are shown. The gray lines are the fitting curves. The decoherence time T2Rabi for transitions II is 2.1 ms, and that for I is 0.9 ms, respectively. The inset is a cw-NMR spectrum of 75As taken by measuring Faraday rotation at fixed B0 = 0.727 T and time delay of 672 ps. |
| Figure 3 | Experimental results of the phase control at transitions I, II, and III. Faraday rotation is shown as a function of φ after application of X(π/2)II-φ(π/2)II (squares) and X(π)II-φ(π)II (circles). For each transition, the width of π/2 pulse ~ 70 ms was determined from their Rabi oscillations. |
| Figure 4 | The schematic diagram of the multi pulse sequence of generation of a pseudo-pure state |00>pps, a superposition of two states (|00>+|01>), the Bell state (|00>+|11>), and the QST are shown. (b) The experimental NMR spectra for |00>pps, |00>+|01>, |00>+|11>, and the QST are shown. (c) The simulation results of the NMR spectra for |00>pps, |00>+|01>, |00>+|11>, and QSTs with the off-diagonal element a = -1 (thin solid line), -0.5 (thick solid line), and 0 (thin dotted line), respectively. |
Related publications:
1. Y. Kondo, M. Ono, S. Matsuzaka, K. Morita, H. Sanada, Y. Ohno, and H. Ohno, Physical Review Letters, Vol. 101, pp. 207601, (2008).