Antoine Browaeys
Entanglement of two atoms using the Rydberg Blockade
A. Browaeys, A. GaÎtan, C. Evellin, T. Wilk, Y. Miroshnychenko, P. Grangier
Laboratoire Charles Fabry, Institut d'Optique, CNRS, Univ Paris-Sud,
Campus Polytechnique, RD 128, 91127 Palaiseau cedex, France.
A. Chotia, M. Viteau, D. Comparat, and P. Pillet
Laboratoire AimÈ Cotton, CNRS, Univ Paris-Sud, B‚timent 505,
Campus d'Orsay, 91405 Orsay cedex, France.
When two quantum systems interact strongly, their simultaneous excitation by the same driving pulse may be forbidden: this is called blockade of excitation. Recently, extensive studies have been devoted to the so-called Rydberg blockade between neutral atoms, which appears due to the interaction induced by their large dipole moments when they are in Rydberg states. In particular, this blockade has been proposed as a basic tool in quantum information processing with neutral atoms [1,2] and can be used to deterministically generate entanglement of several atoms.
This talk will describe our demonstration [3] of the Rydberg blockade between two atoms individually trapped in optical tweezers at a distance of 4 micrometers. The rubidium 87 atoms are prepared in the state |1> = |F =2, M=2>, and subsequently excited to the Rydberg state 58d3/2, |r>, by a two-photon transition. In the blockade regime, two atoms can not be excited at the same time.
A consequence of this blockade mechanism is that the atoms are excited in an entangled state of the form (|r,1> + eiφ |1,r>) / √2,where φ is a phase depending on the position of the atoms. The signature of the production of this state is the enhanced Rabi frequency of the oscillation of the probability to excite only one of the two atoms, with respect to the Rabi frequency of the excitation of one atom when it is alone. The talk will detail this experimental demonstration.
The entangled state produced in this way has a short lifetime, due to the fact that the atoms are not trapped while in the Rydberg state. We are working towards entangling the atoms in the two hyperfine ground states |0> = |F =1, M=1> and |1> = |F =2, M=2>. The talk will report on the status of the experiment.
[1] D. Jaksch, et al., ´Fast quantum gates for neutral atoms, Phys. Rev. Lett. 85, 2208 (2000).
[2] M. D. Lukin, et al., ´Dipole blockade and quantum information processing in mesoscopic atomic ensembles, Phys. Rev. Lett. 87, 037901 (2001).
[3] A. GaÎtan, et al., ´Observation of collective excitation of two individual atoms
in the Rydberg blockade regime, Nature Physics 5, 115 (2009).
