Entanglement of two individual neutral atoms using Rydberg blockade.

We report the generation of entanglement between two individual 87Rb atoms in hyperfine ground states |F=1,M=1> and |F=2,M=2> which are held in two optical tweezers separated by 4 microm. Our scheme relies on the Rydberg blockade effect which prevents the simultaneous excitation of the two atoms to a Rydberg state. The entangled state is generated in about 200 ns using pulsed two-photon excitation. We quantify the entanglement by applying global Raman rotations on both atoms. We measure that 61% of the initial pairs of atoms are still present at the end of the entangling sequence. These pairs are in the target entangled state with a fidelity of 0.75.

[1]  C. Monroe,et al.  Experimental entanglement of four particles , 2000, Nature.

[2]  C. S. Wood,et al.  Deterministic Entanglement of Two Trapped Ions , 1998 .

[3]  P. Grangier,et al.  Experimental Tests of Realistic Local Theories via Bell's Theorem , 1981 .

[4]  William D. Phillips,et al.  Controlled exchange interaction between pairs of neutral atoms in an optical lattice , 2007, Nature.

[5]  A. Lance,et al.  Energy distribution and cooling of a single atom in an optical tweezer , 2008, 0805.3510.

[6]  V. Vedral,et al.  Entanglement in many-body systems , 2007, quant-ph/0703044.

[7]  P. Zoller,et al.  Mesoscopic Rydberg gate based on electromagnetically induced transparency. , 2008, Physical review letters.

[8]  M. Saffman,et al.  Consequences of Zeeman Degeneracy for van der Waals Blockade between Rydberg Atoms , 2007, 0712.3438.

[9]  R. Blatt,et al.  Entangled states of trapped atomic ions , 2008, Nature.

[10]  J. Raimond,et al.  Generation of Einstein-Podolsky-Rosen Pairs of Atoms , 1997 .

[11]  B. Julsgaard,et al.  Experimental long-lived entanglement of two macroscopic objects , 2001, Nature.

[12]  Matison,et al.  Experimental Test of Local Hidden-Variable Theories , 1972 .

[13]  D. Comparat,et al.  Observation of collective excitation of two individual atoms in the Rydberg blockade regime , 2008, 0810.2960.

[14]  A. Aspect.  Bell's inequality test: more ideal than ever , 1999, Nature.

[15]  M. Steffen,et al.  Measurement of the Entanglement of Two Superconducting Qubits via State Tomography , 2006, Science.

[16]  M. Saffman,et al.  Analysis of a quantum logic device based on dipole-dipole interactions of optically trapped Rydberg atoms , 2005 .

[17]  Igor Protsenko,et al.  Sub-poissonian loading of single atoms in a microscopic dipole trap , 2001, Nature.

[18]  M. Saffman,et al.  Observation of Rydberg blockade between two atoms , 2008, 0805.0758.

[19]  J. Cirac,et al.  Dipole blockade and quantum information processing in mesoscopic atomic ensembles. , 2000, Physical review letters.

[20]  Klaus Mølmer,et al.  Quantum gates and multiparticle entanglement by Rydberg excitation blockade and adiabatic passage. , 2008, Physical review letters.

[21]  Thomas G. Walker,et al.  Demonstration of a neutral atom controlled-NOT quantum gate. , 2009, Physical review letters.

[22]  P. Grangier,et al.  Fast Quantum State Control of a Single Trapped Neutral Atom , 2006, quant-ph/0609134.

[23]  H. J. Kimble,et al.  Measurement-induced entanglement for excitation stored in remote atomic ensembles , 2005, Nature.

[24]  R. Rosenfeld.  Nature , 2009, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.

[25]  C. F. Roos,et al.  ‘Designer atoms’ for quantum metrology , 2006, Nature.

[26]  Lukin,et al.  Fast quantum gates for neutral atoms , 2000, Physical review letters.

[27]  C. Monroe,et al.  Observation of entanglement between a single trapped atom and a single photon , 2004, Nature.

[28]  T. Hänsch,et al.  Controlled collisions for multi-particle entanglement of optically trapped atoms , 2003, Nature.