51
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McKeever J, Buck JR, Boozer AD, Kuzmich A, Nägerl HC, Stamper-Kurn DM, Kimble HJ. State-insensitive cooling and trapping of single atoms in an optical cavity. PHYSICAL REVIEW LETTERS 2003; 90:133602. [PMID: 12689287 DOI: 10.1103/physrevlett.90.133602] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2002] [Indexed: 05/24/2023]
Abstract
Single cesium atoms are cooled and trapped inside a small optical cavity by way of a novel far-off-resonance dipole-force trap, with observed lifetimes of 2-3 s. Trapped atoms are observed continuously via transmission of a strongly coupled probe beam, with individual events lasting approximately 1 s. The loss of successive atoms from the trap N>/=3-->2-->1-->0 is thereby monitored in real time. Trapping, cooling, and interactions with strong coupling are enabled by the trap potential, for which the center-of-mass motion is only weakly dependent on the atom's internal state.
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Affiliation(s)
- J McKeever
- Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125, USA
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52
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Yi XX, Su XH, You L. Conditional quantum phase gate between two 3-state atoms. PHYSICAL REVIEW LETTERS 2003; 90:097902. [PMID: 12689256 DOI: 10.1103/physrevlett.90.097902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2002] [Indexed: 05/24/2023]
Abstract
We propose a scheme for conditional quantum logic between two 3-state atoms that share a quantum data bus such as a single mode optical field in cavity QED systems, or a collective vibrational state of trapped ions. Making use of quantum interference, our scheme achieves successful conditional phase evolution without any real transitions of atomic internal states or populating the quantum data bus. In addition, it requires only common addressing of the two atoms by external laser fields.
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Affiliation(s)
- X X Yi
- School of Physics, Georgia Institute of Technology, Atlanta Georgia 30332, USA
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53
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Solano E, Agarwal GS, Walther H. Strong-driving-assisted multipartite entanglement in cavity QED. PHYSICAL REVIEW LETTERS 2003; 90:027903. [PMID: 12570582 DOI: 10.1103/physrevlett.90.027903] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2002] [Indexed: 05/24/2023]
Abstract
We propose a method of generating multipartite entanglement by considering the interaction of a system of N two-level atoms in a cavity of high quality factor with a strong classical driving field. It is shown that, with a judicious choice of the cavity detuning and the applied coherent field detuning, vacuum Rabi coupling produces a large number of important multipartite entangled states. It is even possible to produce entangled states involving different cavity modes. Tuning of parameters also permits us to switch from Jaynes-Cummings to anti-Jaynes-Cummings-like interaction.
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Affiliation(s)
- E Solano
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany.
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54
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Bouhelier A, Beversluis M, Hartschuh A, Novotny L. Near-field second-harmonic generation induced by local field enhancement. PHYSICAL REVIEW LETTERS 2003; 90:013903. [PMID: 12570612 DOI: 10.1103/physrevlett.90.013903] [Citation(s) in RCA: 204] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2002] [Indexed: 05/19/2023]
Abstract
The field near a sharp metal tip can be strongly enhanced if irradiated with an optical field polarized along the tip axis. We demonstrate that the enhanced field gives rise to local second-harmonic (SH) generation at the tip surface thereby creating a highly confined photon source. A theoretical model for the excitation and emission of SH radiation at the tip is developed and it is found that this source can be represented by a single on-axis oscillating dipole. The model is experimentally verified by imaging the spatial field distribution of strongly focused laser modes.
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Affiliation(s)
- A Bouhelier
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
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55
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Gulde S, Riebe M, Lancaster GPT, Becher C, Eschner J, Häffner H, Schmidt-Kaler F, Chuang IL, Blatt R. Implementation of the Deutsch-Jozsa algorithm on an ion-trap quantum computer. Nature 2003; 421:48-50. [PMID: 12511949 DOI: 10.1038/nature01336] [Citation(s) in RCA: 354] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 11/27/2002] [Indexed: 11/09/2022]
Abstract
Determining classically whether a coin is fair (head on one side, tail on the other) or fake (heads or tails on both sides) requires an examination of each side. However, the analogous quantum procedure (the Deutsch-Jozsa algorithm) requires just one examination step. The Deutsch-Jozsa algorithm has been realized experimentally using bulk nuclear magnetic resonance techniques, employing nuclear spins as quantum bits (qubits). In contrast, the ion trap processor utilises motional and electronic quantum states of individual atoms as qubits, and in principle is easier to scale to many qubits. Experimental advances in the latter area include the realization of a two-qubit quantum gate, the entanglement of four ions, quantum state engineering and entanglement-enhanced phase estimation. Here we exploit techniques developed for nuclear magnetic resonance to implement the Deutsch-Jozsa algorithm on an ion-trap quantum processor, using as qubits the electronic and motional states of a single calcium ion. Our ion-based implementation of a full quantum algorithm serves to demonstrate experimental procedures with the quality and precision required for complex computations, confirming the potential of trapped ions for quantum computation.
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Affiliation(s)
- Stephan Gulde
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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56
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Abstract
Modern cavity quantum electrodynamics (cavity QED) illuminates the most fundamental aspects of coherence and decoherence in quantum mechanics. Experiments on atoms in cavities can be described by elementary models but reveal intriguing subtleties of the interplay of coherent dynamics with external couplings. Recent activity in this area has pioneered powerful new approaches to the study of quantum coherence and has fueled the growth of quantum information science. In years to come, the purview of cavity QED will continue to grow as researchers build on a rich infrastructure to attack some of the most pressing open questions in micro- and mesoscopic physics.
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Affiliation(s)
- H Mabuchi
- Department of Physics, Mail Code 12-33, California Institute of Technology, Pasadena, CA 91125, USA.
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57
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Pachos J, Walther H. Quantum computation with trapped ions in an optical cavity. PHYSICAL REVIEW LETTERS 2002; 89:187903. [PMID: 12398638 DOI: 10.1103/physrevlett.89.187903] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2002] [Indexed: 05/24/2023]
Abstract
Two-qubit logical gates are proposed on the basis of two atoms trapped in a cavity setup and commonly addressed by laser fields. Losses in the interaction by spontaneous transitions are efficiently suppressed by employing adiabatic transitions and the quantum Zeno effect. Dynamical and geometrical conditional phase gates are suggested. This method provides fidelity and a success rate of its gates very close to unity. Hence, it is suitable for performing quantum computation.
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Affiliation(s)
- Jiannis Pachos
- Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
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58
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Mundt AB, Kreuter A, Becher C, Leibfried D, Eschner J, Schmidt-Kaler F, Blatt R. Coupling a single atomic quantum bit to a high finesse optical cavity. PHYSICAL REVIEW LETTERS 2002; 89:103001. [PMID: 12225188 DOI: 10.1103/physrevlett.89.103001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2002] [Indexed: 05/23/2023]
Abstract
The quadrupole S(1/2)-D(5/2) optical transition of a single trapped Ca+ ion, well suited for encoding a quantum bit of information, is coherently coupled to the standing wave field of a high finesse cavity. The coupling is verified by observing the ion's response to both spatial and temporal variations of the intracavity field. We also achieve deterministic coupling of the cavity mode to the ion's vibrational state by selectively exciting vibrational state-changing transitions and by controlling the position of the ion in the standing wave field with nanometer precision.
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Affiliation(s)
- A B Mundt
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, Austria
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59
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Kuhn A, Hennrich M, Rempe G. Deterministic single-photon source for distributed quantum networking. PHYSICAL REVIEW LETTERS 2002; 89:067901. [PMID: 12190611 DOI: 10.1103/physrevlett.89.067901] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2002] [Indexed: 05/23/2023]
Abstract
A sequence of single photons is emitted on demand from a single three-level atom strongly coupled to a high-finesse optical cavity. The photons are generated by an adiabatically driven stimulated Raman transition between two atomic ground states, with the vacuum field of the cavity stimulating one branch of the transition, and laser pulses deterministically driving the other branch. This process is unitary and therefore intrinsically reversible, which is essential for quantum communication and networking, and the photons should be appropriate for all-optical quantum information processing.
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Affiliation(s)
- Axel Kuhn
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
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60
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Kielpinski D, Monroe C, Wineland DJ. Architecture for a large-scale ion-trap quantum computer. Nature 2002; 417:709-11. [PMID: 12066177 DOI: 10.1038/nature00784] [Citation(s) in RCA: 243] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Among the numerous types of architecture being explored for quantum computers are systems utilizing ion traps, in which quantum bits (qubits) are formed from the electronic states of trapped ions and coupled through the Coulomb interaction. Although the elementary requirements for quantum computation have been demonstrated in this system, there exist theoretical and technical obstacles to scaling up the approach to large numbers of qubits. Therefore, recent efforts have been concentrated on using quantum communication to link a number of small ion-trap quantum systems. Developing the array-based approach, we show how to achieve massively parallel gate operation in a large-scale quantum computer, based on techniques already demonstrated for manipulating small quantum registers. The use of decoherence-free subspaces significantly reduces decoherence during ion transport, and removes the requirement of clock synchronization between the interaction regions.
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Affiliation(s)
- D Kielpinski
- Research Laboratory of Electronics and Center for Ultracold Atoms, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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61
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Fischer T, Maunz P, Pinkse PWH, Puppe T, Rempe G. Feedback on the motion of a single atom in an optical cavity. PHYSICAL REVIEW LETTERS 2002; 88:163002. [PMID: 11955231 DOI: 10.1103/physrevlett.88.163002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Indexed: 05/23/2023]
Abstract
We demonstrate feedback on the motion of a single neutral atom trapped in the light field of a high-finesse cavity. Information on the atomic motion is obtained from the transmittance of the cavity. This is used to implement a feedback loop in analog electronics that influences the atom's motion by controlling the optical dipole force exerted by the same light that is used to observe the atom. In spite of intrinsic limitations, the time the atom stays within the cavity could be extended by almost 30% beyond that of a comparable constant-intensity dipole trap.
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Affiliation(s)
- T Fischer
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany
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62
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Abstract
Quantum information processors exploit the quantum features of superposition and entanglement for applications not possible in classical devices, offering the potential for significant improvements in the communication and processing of information. Experimental realization of large-scale quantum information processors remains a long-term vision, as the required nearly pure quantum behaviour is observed only in exotic hardware such as individual laser-cooled atoms and isolated photons. But recent theoretical and experimental advances suggest that cold atoms and individual photons may lead the way towards bigger and better quantum information processors, effectively building mesoscopic versions of 'Schrödinger's cat' from the bottom up.
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Affiliation(s)
- C Monroe
- FOCUS Center and Department of Physics, University of Michigan, Ann Arbor 48109-1120, USA.
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63
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