Peter Maunz, University of Maryland and JQI, College Park, MD 20742,
USA
Ultrafast pulses for the entanglement of cold trapped atomic ions
Ultrafast laser pulses open up new possibilities for the quantum
manipulation of laser-cooled trapped ion systems. Appropriately
tailored pulses should allow the operation of fast multi-ion
entangling gates [1-3]. Ultrashort pulses can also be used to
efficiently excite an atom on a timescale much faster than the excited
state lifetime, and the resulting single emitted photon can be
entangled with the final quantum state of the atom for applications in
quantum networking [4].
In a recent experiment, we have exploited this atom-photon
entanglement in order to couple two single 171Yb atomic ions
separated by one meter. The ions are simultaneously excited with an
ultrafast pulse and the resulting two scattered photons are detected
in an antisymmetric Bell state [5,6]. This projects the quantum state
of the two ions in a likewise antisymmetric superposition state. We
demonstrate entanglement using a photonic frequency qubit [3] as well
as a polarization qubit [4] and fully characterize the produced
entangled state using quantum state tomography. Even though this
entanglement scheme is probabilistic, it allows for high fidelity
entanglement that can be used as a resource for entangling larger
numbers of qubits or for the propagation of quantum information over
very large distances. .
[1] J.J. Garcia-Ripoll, P. Zoller, and J. I. Cirac, Phys. Rev. Lett.
91, 157901 (2003)
[2] L.-M. Duan, Phys. Rev. Lett. 93, 100502 (2004).
[3] M. J. Madsen, et. al., Phys. Rev. Lett. 97, 040505 (2006).
[4] B. B. Blinov, et. al., Nature 428, 153 (2004).
[5] C. Simon and W.T.M. Irvine, Phys. Rev. Lett. 91, 110405 (2003)
[6] D.L. Moehring et al., Nature 449, 68 (2007)