Observation of collective excitation of two individual atoms in the Rydberg blockade regime

The dipole blockade between Rydberg atoms has been proposed as a basic tool in quantum information processing with neutral atoms. Here we demonstrate experimentally the Rydberg blockade of two individual atoms separated by 4 $\mu$m. Moreover, we show that, in this regime, the single atom excitation is enhanced by a collective two-atom behavior associated with the excitation of an entangled state. This observation is a crucial step towards the deterministic manipulation of entanglement of two or more atoms using the Rydberg dipole interaction.Comment: 5 pages, 4 figure

Observation of Rydberg blockade between two atoms

We demonstrate experimentally that a single Rb atom excited to the $79d_{5/2}$ level blocks the subsequent excitation of a second atom located more than $10 \mu\rm m$ away. The observed probability of double excitation of $\sim 30$ is consistent with a theoretical model based on calculations of the long range dipole-dipole interaction between atoms.Comment: 4 figure

Two-dimensional transport and transfer of a single atomic qubit in optical tweezers

Quantum computers have the capability of out-performing their classical counterparts for certain computational problems1. Several scalable quantum-computing architectures have been proposed. An attractive architecture is a large set of physically independent qubits arranged in three spatial regions where (1) the initialized qubits are stored in a register, (2) two qubits are brought together to realize a gate and (3) the readout of the qubits is carried out2, 3. For a neutral-atom-based architecture, a natural way to connect these regions is to use optical tweezers to move qubits within the system. In this letter we demonstrate the coherent transport of a qubit, encoded on an atom trapped in a submicrometre tweezer, over a distance typical of the separation between atoms in an array of optical traps4, 5, 6. Furthermore, we transfer a qubit between two tweezers, and show that this manipulation also preserves the coherence of the qubit

Intrication de deux atomes en utilisant le blocage de Rydberg

Considérons un système quantique constitué de deux sous-systèmes: on dit qu'il est dans un état intriqué s'il existe des corrélations quantiques entre les états de ces derniers. La compréhension et la mise en œuvre d'états intriqués ont de nombreuses applications (métrologie quantique, étude des systèmes fortement corrélés, traitement quantique de l information, etc.) et constituent le contexte général de ce travail de thèse. Plus en détail, nous démontrons la réalisation d'un état intriqué de deux atomes neutres piégés indépendamment. Pour cela, nous exploitons le phénomène de blocage de Rydberg : lorsqu on essaie d exciter simultanément deux atomes séparés de quelques micromètres vers un état de Rydberg donné, la forte interaction entre atomes de Rydberg peut empêcher cette excitation simultanée. Dans ce cas, seul un des deux atomes est excité et l'on génère ainsi des corrélations quantiques entre les états des deux atomes, c'est-à-dire de l'intrication. Dans notre expérience deux atomes de rubidium 87 dans l'état fondamental 5S1/2 sont piégés chacun dans une pince optique microscopique, à une distance relative de 4 micromètres. En réalisant des transitions entre l état 5S1/2 et l'état de Rydberg 58D3/2 par des transitions à deux photons, nous obtenons un état intriqué des deux atomes dans les sous-niveaux 5S1/2 , F=1,mF=1 et 5S1/2 , F=2,mF=2. Afin de quantifier l intrication, nous mesurons la fidélité par rapport à l'état-cible en réalisant des transitions Raman entre ces deux sous-niveaux. La fidélité des paires d'atomes présentes à la fin de l'expérience est supérieure à la valeur seuil de 0,5, ce qui prouve la création d'un état intriqué.Consider a quantum system composed of two sub-systems: this system is said to be entangled if there are quantum correlations between the states of the latters. The understaning and the engineering of entanglement have implications in quantum metrology, quantum information processing and in the study of strongly correlated systems, and constitute the general context of our work. In this thesis, we demonstrate the realisation of an entangled state of two independently trapped atoms. We generate etanglement using Rydberg blockade. This phenomenon occurs when two atoms are close enough so that the interaction between two Rydberg atoms is strong: in this case the simultaneous excitation of the two atoms by the same driving pulse may be prevented. Thus, only one atom is excited and this creates quantum correlations between their states, namely entanglement. In our experiment, two ground state (5S1/2) rubidium 87 atoms are independently trapped in optical tweezers, with a relative separation of 4 micrometers. By driving two-photon transitions between the 5S1/2 state and the 58D3/2 Rydberg state, we entangle the two atoms in the 5S1/2 , F=1,mF=1 and 5S1/2 , F=2,mF=2 sublevels. To quantify the amount of entanglement, we measure the fidelity with respect to the target state by driving Raman transitions between those two sublevels. The fidelity of the pairs of atoms present at the end of the experiment is higher than the threshold value of 0.5, proving the creation of an entangled state of the two atoms.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Analysis of the entanglement between two individual atoms using global Raman rotations

International audienceMaking use of the Rydberg blockade, we generate entanglement between two atoms individually trapped in two optical tweezers. In this paper we detail the analysis of the data and show that we can determine the amount of entanglement between the atoms in the presence of atom losses during the entangling sequence. Our model takes into account states outside the qubit basis and allows us to perform a partial reconstruction of the density matrix describing the two atom state. With this method we extract the amount of entanglement between pairs of atoms still trapped after the entangling sequence and measure the fidelity with respect to the expected Bell state. We find a fidelity $F_{\rm pairs} =0.74(7)$ for the 62% of atom pairs remaining in the traps at the end of the entangling sequence

Entanglement of two atoms using the rydberg blockade

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Studying the Rydberg blockade with individually trapped single atoms in optical tweezers

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Observation of the coupling between two single Rydberg atoms

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Observation of the coupling between two single Rydberg atoms

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Vers l'observation du blocage de Rydberg avec deux atomes

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