Trapped-ion probing of light-induced charging effects on dielectrics

Harlander, Maximilian; Brownnutt, Michael; Hänsel, Wolfgang; Blatt, R.

doi:10.1088/1367-2630/12/9/093035

Cited by 135 publications

(146 citation statements)

References 31 publications

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“…For the stretch mode, the sources of frequency fluctuations (which are slow compared to the gate durations shown in Fig. 6) are (i) fluctuations in the DC potentials applied to electrodes for trapping, (ii) fluctuating electric-field gradients from uncontrolled charging of electrode surfaces [42], and (iii) non-linear coupling to transverse "rocking" modes [43,44]. By measuring the lineshape for exciting the motional state of a single ion with injected RF "tickle" potentials on the trap electrodes at frequencies near the mode frequencies, we estimate the first two sources contribute fluctuations of approximately 50 Hz.…”

Section: Error Sourcesmentioning

confidence: 99%

High-Fidelity Universal Gate Set forBe9+Ion Qubits

et al. 2016

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We report high-fidelity laser-beam-induced quantum logic gates on magnetic-field-insensitive qubits comprised of hyperfine states in 9 Be + ions with a memory coherence time of more than 1 s. We demonstrate single-qubit gates with error per gate of 3.8(1) × 10 −5 . By creating a Bell state with a deterministic two-qubit gate, we deduce a gate error of 8(4) × 10 −4 . We characterize the errors in our implementation and discuss methods to further reduce imperfections towards values that are compatible with fault-tolerant processing at realistic overhead.Quantum computers can solve certain problems that are thought to be intractable on conventional computers. An important general goal is to realize universal quantum information processing (QIP), which could be used for algorithms having a quantum advantage over processing with conventional bits as well as to simulate other quantum systems of interest [1][2][3]. For large problems, it is generally agreed that individual logic gate errors must be reduced below a certain threshold, often taken to be around 10 −4 [4][5][6], to achieve fault tolerance without excessive overhead in the number of physical qubits required to implement a logical qubit. This level has been achieved in some experiments for all elementary operations including state preparation and readout, with the exception of two-qubit gates, emphasizing the importance of improving multi-qubit gate fidelities. [7,8]. As various ions differ in mass, electronic, and hyperfine structure, they each have technical advantages and disadvantages. For example, 9 Be + is the lightest ion currently considered for QIP, and as such, has several potential advantages. The relatively light mass yields deeper traps and higher motional frequencies for given applied potentials, and facilitates fast ion transport [9,10]. Light mass also yields stronger laser-induced effective spin-spin coupling (inversely proportional to the mass), which can yield less spontaneous emission error for a given laser intensity [11]. However, a disadvantage of 9 Be + ion qubits compared to some heavier ions such as 40 Ca + and 43 Ca + [12, 13] has been the difficulty of producing and controlling the ultraviolet (313 nm) light required to drive 9 Be + stimulated-Raman transitions. In the work reported here, we use an ion trap array designed for scalable QIP [14] and take advantage of recent technological developments with lasers and optical fibers that improve beam quality and pointing stability. We also implement active control of laser pulse intensities to re- duce errors. We demonstrate laser-induced single-qubit computational gate errors of 3.8(1) × 10 −5 and realize a deterministic two-qubit gate to ideally produce the Bell state |Φ + = 1 √ 2 (|↑↑ + |↓↓ ). By characterizing the effects of known error sources with numerical simulations and calibration measurements, we deduce an entangling gate infidelity or error of = 8(4) × 10 −4 , where = 1 -F, and F is the fidelity. Along with Ref.[13]; these appear to be the highest two-qubit gate fidelitie...

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Section: Error Sourcesmentioning

confidence: 99%

High-Fidelity Universal Gate Set forBe9+Ion Qubits

et al. 2016

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“…Integrated optics are not easily made reconfigurable, so their alignment to the ions must be partially built into the trapping architecture. The second problem is that dielectric surfaces are susceptible to light-induced charging, which results in strong and difficult-to-control forces on the ions, inducing micromotion, large displacements, or even making the ions untrappable [79][80][81]. Nonetheless, these challenges have started to be addressed in the last several years by a number of groups integrating various optical elements with ion traps, including microfabricated phase Fresnel lenses [82,83], embedded micromirrors [84,85] and fibers [45,86], transparent trap electrodes [44], nanophotonic dielectric waveguides [87], macroscopic optical cavities [46,[88][89][90][91], and microscopic, fiber-based cavities [92].…”

Section: Incorporating Optical Componentsmentioning

confidence: 99%

Technologies for trapped-ion quantum information systems

Eltony

Gangloff

Shi

et al. 2016

Quantum Inf Process

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Scaling up from prototype systems to dense arrays of ions on chip, or vast networks of ions connected by photonic channels, will require developing entirely new technologies that combine miniaturized ion trapping systems with devices to capture, transmit, and detect light, while refining how ions are confined and controlled. Building a cohesive ion system from such diverse parts involves many challenges, including navigating materials incompatibilities and undesired coupling between elements. Here, we review our recent efforts to create scalable ion systems incorporating unconventional materials such as graphene and indium tin oxide, integrating devices like optical fibers and mirrors, and exploring alternative ion loading and trapping techniques.

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“…While strong coupling can be achieved by reducing the cavity's mode volume, shrinking the physical volume of the cavity around trapped ions is technically challenging. This is because the dielectric surfaces of the cavity mirrors can adversely affect the trapping potential [13]. For this reason, strong coupling remains elusive for a single ion despite many proposed designs and implementations [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Novel Ion Trap Design for Strong Ion-Cavity Coupling

Seco

Takahashi

Keller

2016

Atoms

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Abstract:We present a novel ion trap design which facilitates the integration of an optical fiber cavity into the trap structure. The optical fibers are confined inside hollow electrodes in such a way that tight shielding and free movement of the fibers are simultaneously achievable. The latter enables in situ optimization of the overlap between the trapped ions and the cavity field. Through numerical simulations, we systematically analyze the effects of the electrode geometry on the trapping characteristics such as trap depths, secular frequencies and the optical access angle. Additionally, we simulate the effects of the presence of the fibers and confirm the robustness of the trapping potential. Based on these simulations and other technical considerations, we devise a practical trap configuration that isviable to achieve strong coupling of a single ion.

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Trapped-ion probing of light-induced charging effects on dielectrics

Cited by 135 publications

References 31 publications

High-Fidelity Universal Gate Set forBe9+Ion Qubits

High-Fidelity Universal Gate Set forBe9+Ion Qubits

Technologies for trapped-ion quantum information systems

Novel Ion Trap Design for Strong Ion-Cavity Coupling

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