A basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit1,2,3,4,5,6. For qubits based on electron spin, a universal single-qubit gate is realized by a rotation of the spin by any angle about an arbitrary axis. Driven, coherent Rabi oscillations between two spin states can be used to demonstrate control of the rotation angle. Ramsey interference, produced by two coherent spin rotations separated by a variable time delay, demonstrates control over the axis of rotation. Full quantum control of an electron spin in a quantum dot has previously been demonstrated using resonant radio-frequency pulses that require many spin precession periods7,8,9,10. However, optical manipulation of the spin allows quantum control on a picosecond or femtosecond timescale11,12,13,14,15,16,17,18, permitting an arbitrary rotation to be completed within one spin precession period6. Recent work in optical single-spin control has demonstrated the initialization of a spin state in a quantum dot19,20,21,22, as well as the ultrafast manipulation of coherence in a largely unpolarized single-spin state17. Here we demonstrate complete coherent control over an initialized electron spin state in a quantum dot using picosecond optical pulses. First we vary the intensity of a single optical pulse to observe over six Rabi oscillations between the two spin states; then we apply two sequential pulses to observe high-contrast Ramsey interference. Such a two-pulse sequence realizes an arbitrary single-qubit gate completed on a picosecond timescale. Along with the spin initialization and final projective measurement of the spin state, these results demonstrate a complete set of all-optical single-qubit operations.
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Imamoglu, A. et al. Quantum information processing using quantum dot spins and cavity QED. Phys. Rev. Lett. 83, 4204–4207 (1999)
Combescot, M. & Betbeder-Matibet, O. Theory of spin precession monitored by laser pulse. Solid State Commun. 132, 129–134 (2004)
Chen, P., Piermarocchi, C., Sham, L. J., Gammon, D. & Steel, D. G. Theory of quantum optical control of a single spin in a quantum dot. Phys. Rev. B 69, 075320 (2004)
Pryor, C. E. & Flatté, M. E. Predicted ultrafast single-qubit operations in semiconductor quantum dots. Appl. Phys. Lett. 88, 233108 (2006)
Economou, S. E., Sham, L. J., Wu, Y. & Steel, D. G. Proposal for optical U(1) rotations of electron spin trapped in a quantum dot. Phys. Rev. B 74, 205415 (2006)
Clark, S. M., Fu, K.-M. C., Ladd, T. D. & Yamamoto, Y. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses. Phys. Rev. Lett. 99, 040501 (2007)
Koppens, F. H. L. et al. Driven coherent oscillations of a single electron spin in a quantum dot. Nature 442, 766–771 (2006)
Tokura, Y., van der Wiel, W., Obata, T. & Tarucha, S. Coherent single electron spin control in a slanting Zeeman field. Phys. Rev. Lett. 96, 047202 (2006)
Nowack, K. C., Koppens, F. H. L., Nazarov, Y. V. & Vandersypen, L. M. K. Coherent control of a single electron spin with electric fields. Science 318, 1430–1433 (2007)
Koppens, F. H. L., Nowack, K. C. & Vandersypen, L. M. K. Spin echo of a single electron spin in a quantum dot. Phys. Rev. Lett. 100, 236802 (2008)
Gupta, J. A., Knobel, R., Samarth, N. & Awschalom, D. D. Ultrafast manipulation of electron spin coherence. Science 292, 2458–2461 (2001)
Dutt, M. V. G. et al. Ultrafast optical control of electron spin coherence in charged GaAs quantum dots. Phys. Rev. B 74, 125306 (2006)
Greilich, A. et al. Mode locking of electron spin coherences in singly charged quantum dots. Science 313, 341–345 (2006)
Wu, Y. et al. Selective optical control of electron spin coherence in singly charged GaAs-Al0.3Ga0.7As quantum dots. Phys. Rev. Lett. 99, 097402 (2007)
Greilich, A. et al. Robust manipulation of electron spin coherence in an ensemble of singly charged quantum dots. Phys. Rev. B 75, 233301 (2007)
Carter, S. G., Chen, Z. & Cundiff, S. T. Ultrafast below-resonance Raman rotation of electron spins in GaAs quantum wells. Phys. Rev. B 76, 201308(R) (2007)
Berezovsky, J., Mikkelson, M. H., Stoltz, N. G., Coldren, L. A. & Awschalom, D. D. Picosecond coherent optical manipulation of a single electron spin in a quantum dot. Science 320, 349–352 (2008)
Fu, K.-M. C. et al. Ultrafast control of donor-bound electron spins with single detuned optical pulses. Nature Phys. 4, 780–784 (2008)
Atatüre, M. et al. Quantum-dot spin-state preparation with near-unity fidelity. Science 312, 551–553 (2006)
Gerardot, B. D. et al. Optical pumping of a single hole spin in a quantum dot. Nature 451, 441–443 (2008)
Xu, X. et al. Fast spin state initialization in a singly charged InAs-GaAs quantum dot by optical cooling. Phys. Rev. Lett. 99, 097401 (2007)
Ramsay, A. J. et al. Fast optical preparation, control, and readout of a single quantum dot spin. Phys. Rev. Lett. 100, 197401 (2008)
Petta, J. R. et al. Coherent manipulation of coupled electron spins in semiconductor quantum dots. Science 309, 2180–2184 (2005)
Bayer, M. et al. Fine structure of neutral and charged excitons in self-assembled In(Ga)As/(Al)GaAs quantum dots. Phys. Rev. B 65, 195315 (2002)
Krizhanovskii, D. N. et al. Individual neutral and charged In x Ga1-x As-GaAs quantum dots with strong in-plane optical anisotropy. Phys. Rev. B 72, 161312(R) (2005)
Cirac, J. I., Zoller, P., Kimble, H. J. & Mabuchi, H. Quantum state transfer and entanglement distribution among distant nodes in a quantum network. Phys. Rev. Lett. 78, 3221–3224 (1997)
Berezovsky, J. et al. Nondestructive optical measurements of a single electron spin in a quantum dot. Science 314, 1916–1920 (2006)
Atatüre, M., Dreiser, J., Badolato, A. & Imamoglu, A. Observation of Faraday rotation from a single confined spin. Nature Phys. 3, 101–105 (2007)
Shabaev, A., Efros, A. L., Gammon, D. & Merkulov, I. A. Optical readout and initialization of an electron spin in a single quantum dot. Phys. Rev. B 68, 201305(R) (2003)
This work was supported by JST/SORST, NICT, MEXT, MURI (ARMY, DAAD 19-03-1-0199) and Special Coordination Funds for Promoting Science and Technology. We thank S. Koseki, S. Götzinger, C. Santori and Q. Zhang for their assistance.
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Press, D., Ladd, T., Zhang, B. et al. Complete quantum control of a single quantum dot spin using ultrafast optical pulses. Nature 456, 218–221 (2008) doi:10.1038/nature07530
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