# Photonic Qubit and Nuclear Qubit for Quantum Information Systems

Yoshihisa Yamamoto (Stanford Univ.)

## Abstract

Novel nonclassical light, indistinguishable single photons and
entangled photons are generated on demand
with a single quantum dot microvacity device [1] [2] and successfully applied
to quantum key distribution systems
[3][4] and fundamental test of quantum mechanics. The system replacing a
quantum dot with an ensemble of
impurities is expected to realize efficient quantum memory and quantum
repeater systems. Optical pumping and
optical detection of nuclear spins in solids are studied toward realization of
a large-scale solid state NMR quantum
computer. [5][6] Preliminary results are encouraging in terms of high nuclear
polarization and long decoherence time.

## References

[1] C. Santori, M. Pelton, G. S. Solomon, Y. Dale, and Y. Yamamoto. Triggered Single Photons from a Quantum Dot. *Phys. Rev. Lett.*, 86: 1502-1505, 2001.

[2] C. Santori, D. Fattal, J. Vuckovic, G. S. Solomon, and Y. Yamamoto. Indistinguishable photons from a singlephoton device. *Nature*, 419: 594-597, 2002.

[3] K. Inoue, E. Waks, and Y. Yamamoto. Differential Phase Shift Quantum Key Distribution. *Phys. Rev. Lett.* , 89: 037902-1 - 037902-3, 2002.

[4] E. Waks, K. Inoue, C. Santori, D. Fattal, J. Vuckovic, G. S. Solomon, and Y. Yamamoto. Quantum cryptography with a photon turnstile. *Nature*, 420: 762, 2002.

[5] T. D. Ladd, J. R. Goldman, F. Yamaguchi, Y. Yamamoto, E. Abe, and K. M.
Itoh. All-Silicon Quantum Computer. *Phys. Rev. Lett.*, 89: 017901-1 - 017901-4, 2002.

[6] C. P. Master, F. Yamaguchi, and Y. Yamamoto. Efficiency of Free Energy
Calculations of Spin Lattices by
Spectral Quantum Algorithms. *Phys. Rev.A*, 67: 032311-1 - 032311-9, 2003.

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