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  • 1.
    Higgins, Gerard
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Universität Innsbruck, Austria.
    Li, Weibin
    Pokorny, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Chi
    Stockholm University, Faculty of Science, Department of Physics.
    Kress, Florian
    Maier, Christine
    Haag, Johannes
    Bodart, Quentin
    Stockholm University, Faculty of Science, Department of Physics.
    Lesanovsky, Igor
    Hennrich, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Single Strontium Rydberg Ion Confined in a Paul Trap2017In: Physical Review X, ISSN 2160-3308, E-ISSN 2160-3308, Vol. 7, no 2, article id 021038Article in journal (Refereed)
    Abstract [en]

    Trapped Rydberg ions are a promising new system for quantum information processing. They have the potential to join the precise quantum operations of trapped ions and the strong, long-range interactions between Rydberg atoms. Combining the two systems is not at all straightforward. Rydberg atoms are severely affected by electric fields which may cause Stark shifts and field ionization, while electric fields are used to trap ions. Thus, a thorough understanding of the physical properties of Rydberg ions due to the trapping electric fields is essential for future applications. Here, we report the observation of two fundamental trap effects. First, we investigate the interaction of the Rydberg electron with the trapping electric quadrupole fields which leads to Floquet sidebands in the excitation spectra. Second, we report on the modified trapping potential in the Rydberg state compared to the ground state that results from the strong polarizability of the Rydberg ion. By controlling both effects we observe resonance lines close to their natural linewidth demonstrating an unprecedented level of control of this novel quantum platform.

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  • 2.
    Higgins, Gerard
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Universität Innsbruck, Austria.
    Pokorny, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Chi
    Stockholm University, Faculty of Science, Department of Physics.
    Bodart, Quentin
    Stockholm University, Faculty of Science, Department of Physics.
    Hennrich, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Coherent Control of a Single Trapped Rydberg Ion2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 22, article id 220501Article in journal (Refereed)
    Abstract [en]

    Trapped Rydberg ions are a promising novel approach to quantum computing and simulations. They are envisaged to combine the exquisite control of trapped ion qubits with the fast two-qubit Rydberg gates already demonstrated in neutral atom experiments. Coherent Rydberg excitation is a key requirement for these gates. Here, we carry out the first coherent Rydberg excitation of an ion and perform a single-qubit Rydberg gate, thus demonstrating basic elements of a trapped Rydberg ion quantum computer.

  • 3.
    Higgins, Gerard
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Universität Innsbruck, Austria.
    Pokorny, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Chi
    Stockholm University, Faculty of Science, Department of Physics.
    Hennrich, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Highly Polarizable Rydberg Ion in a Paul Trap2019In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 123, no 15, article id 153602Article in journal (Refereed)
    Abstract [en]

    Usually the influence of the quadratic Stark effect on an ion's trapping potential is minuscule and only needs to be considered in atomic clock experiments. In this work we excite a trapped ion to a Rydberg state with polarizability similar to 8 orders of magnitude higher than a low-lying electronic state; we find that the highly polarizable ion experiences a vastly different trapping potential owing to the Stark effect. We observe changes in trap stiffness, equilibrium position, and minimum potential, which can be tuned using the trapping electric fields. These effects lie at the heart of several proposed studies, including a high-fidelity submicrosecond entangling operation; in addition we demonstrate these effects may be used to minimize ion micromotion. Mitigation of Stark effects is important for coherent control of Rydberg ions; we illustrate this by carrying out the first Rabi oscillations between a low-lying electronic state and a Rydberg state of an ion.

  • 4.
    Pokorny, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Microwave dressing of a trapped strontium Rydberg ion2019Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Trapped Rydberg ions are a novel platform for quantum technologies, envisaged to combine the excellent control of trapped ions with the strong interactions found in neutral Rydberg atom systems. While in recent years trapped ions have been coherently excited to Rydberg states and were shown to be stable in the trapping field, strongly interacting trapped Rydberg ions have yet to be realized.

    Strong interactions between Rydberg ions are facilitated by microwave dressing.

    In this work the microwave dressing of a single trapped Rydberg ions is studied.

    The ion is used as a microwave field probe and the polarizability of Rydberg S- and P superposition states is investigated.

    This work presents an important stepping stone on the way to the goal of trapped Rydberg ion quantum gates.

  • 5.
    Pokorny, Fabian
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Chi
    Stockholm University, Faculty of Science, Department of Physics.
    Higgins, Gerard
    Stockholm University, Faculty of Science, Department of Physics.
    Cabello, Adan
    Kleinmann, Matthias
    Hennrich, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Tracking the Dynamics of an Ideal Quantum Measurement2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 8, article id 080401Article in journal (Refereed)
    Abstract [en]

    The existence of ideal quantum measurements is one of the fundamental predictions of quantum mechanics. In theory, an ideal measurement projects a quantum state onto the eigenbasis of the measurement observable, while preserving coherences between eigenstates that have the same eigenvalue. The question arises whether there are processes in nature that correspond to such ideal quantum measurements and how such processes are dynamically implemented in nature. Here we address this question and present experimental results monitoring the dynamics of a naturally occurring measurement process: the coupling of a trapped ion qutrit to the photon environment. By taking tomographic snapshots during the detection process, we show that the process develops in agreement with the model of an ideal quantum measurement with an average fidelity of 94%.

  • 6.
    Zhang, Chi
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Pokorny, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Li, Weibin
    Higgins, Gerard
    Stockholm University, Faculty of Science, Department of Physics.
    Pöschl, Andreas
    Stockholm University, Faculty of Science, Department of Physics.
    Lesanovsky, Igor
    Hennrich, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Submicrosecond entangling gate between trapped ions via Rydberg interaction2020In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 580, no 7803, p. 345-349Article in journal (Refereed)
    Abstract [en]

    Generating quantum entanglement in large systems on timescales much shorter than the coherence time is key to powerful quantum simulation and computation. Trapped ions are among the most accurately controlled and best isolated quantum systems(1) with low-error entanglement gates operated within tens of microseconds using the vibrational motion of few-ion crystals(2,3). To exceed the level of complexity tractable by classical computers the main challenge is to realize fast entanglement operations in crystals made up of many ions (large ion crystals)(4). The strong dipole-dipole interactions in polar molecule(5) and Rydberg atom(6,7) systems allow much faster entangling gates, yet stable state-independent confinement comparable with trapped ions needs to be demonstrated in these systems(8). Here we combine the benefits of these approaches: we report a two-ion entangling gate with 700-nanosecond gate time that uses the strong dipolar interaction between trapped Rydberg ions, which we use to produce a Bell state with 78 per cent fidelity. The sources of gate error are identified and a total error of less than 0.2 per cent is predicted for experimentally achievable parameters. Furthermore, we predict that residual coupling to motional modes contributes an approximate gate error of 10(-4) in a large ion crystal of 100 ions. This provides a way to speed up and scale up trapped-ion quantum computers and simulators substantially.

1 - 6 of 6
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