Multilayer ion trap with three-dimensional microwave circuitry for scalable quantum logic applications

Hahn, H.; Zarantonello, Giorgio; Bautista-Salvador, A.; Wahnschaffe, M.; Kohnen, M.; Schoebel, Joerg; Schmidt, Piet O.; Ospelkaus, C.

doi:10.1007/s00340-019-7265-1

Cited by 19 publications

(15 citation statements)

References 40 publications

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“…We therefore compare the gate fidelity to a square pulse gate with seven loops in phase space and τ = 1122 µs since the pulse energies are equal. From finite element simulations [39], the microwave conductor reflects 91.1 % of the amplitude; the energy dissipated per gate is about 1 mJ. To prove the resilience in a direct comparison, we amplitude modulate the RF trap drive with Gaussian noise [40], thereby introducing fluctuations of the radial mode frequency.…”

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Robust and Resource-Efficient Microwave Near-Field Entangling Be+9 Gate

et al. 2019

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Microwave trapped-ion quantum logic gates avoid spontaneous emission as a fundamental source of decoherence. However, microwave two-qubit gates are still slower than laser-induced gates and hence more sensitive to fluctuations and noise of the motional mode frequency. We propose and implement amplitude-shaped gate drives to obtain resilience to such frequency changes without increasing the pulse energy per gate operation. We demonstrate the resilience by noise injection during a two-qubit entangling gate with 9 Be + ion qubits. In absence of injected noise, amplitude modulation gives an operation infidelity in the 10 −3 range.Trapped ions are a leading platform for scalable quantum logic [1, 2] and quantum simulations [3]. Major challenges towards larger-scale devices include the integration of tasks and components that have been so far only demonstrated individually, as well as single and multiqubit gates with the highest possible fidelity to reduce the overhead in quantum error correction. Microwave control of trapped-ion qubits has the potential to address both challenges [4,5] as it allows the gate mechanism, potentially including control electronics, to be integrated into scalable trap arrays. Because spontaneous emission as a fundamental source of decoherence is absent and microwave fields are potentially easier to control than the laser beams that are usually employed, microwaves are a promising approach for high fidelity quantum operations. In fact, microwave two-qubit gate fidelities seem to improve more rapidly than laser-based gates. However, observed two-qubit gate speeds of laser-based gates [6,7] are still about an order of magnitude faster than for microwave gates [8][9][10]. This makes gates more susceptible to uncontrolled motional mode frequency changes, as transient entanglement with the motional degrees of freedom is the key ingredient in multi-qubit gates for trapped ions. As other error sources have been addressed recently, this is of growing importance. Merely increasing Rabi frequencies may not be the most resource-efficient approach, as it will increase energy dissipation in the device. A more efficient use of available resources could be obtained using pulse shaping or modulation techniques. In fact, a number of recent advances in achieving highfidelity operations or long qubit memory times have been proposed or obtained by tailored control fields. Examples include pulsed dynamic decoupling [11], Walsh modulation [12], additional dressing fields to increase coherence times [13], phase [14], amplitude [15][16][17][18][19][20] and fre-quency modulation [21] as well multi-tone fields [22][23][24]. In many cases, these techniques lead to significant advantages. For multi-qubit gates, one mechanism is to optimize the trajectory of the motional mode in phase space for minimal residual spin-motional entanglement in case of experimental imperfections. This effectively reduces the distance between the origin and the point in phase space at which the gate terminates in case of errors.Here we propo...

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Robust and Resource-Efficient Microwave Near-Field Entangling Be+9 Gate

et al. 2019

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“…27 on an AlN substrate (for the present trap, we chose the single-layer process in order to quickly test improvements that were made to the setup and trap orientation compared with ref. 28 ). Gold electrodes are about 10 μm thick and separated by 5 μm gaps.…”

Section: Resultsmentioning

confidence: 99%

Integrated 9Be+ multi-qubit gate device for the ion-trap quantum computer

et al. 2019

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We demonstrate the experimental realization of a two-qubit Mølmer-Sørensen gate on a magnetic field-insensitive hyperfine transition in 9 Be + ions using microwave near-fields emitted by a single microwave conductor embedded in a surface-electrode ion trap. The design of the conductor was optimized to produce a high oscillating magnetic field gradient at the ion position. The measured gate fidelity is determined to be 98.2 ± 1.2% and is limited by technical imperfections, as is confirmed by a comprehensive numerical error analysis. The conductor design can potentially simplify the implementation of multi-qubit gates and represents a self-contained, scalable module for entangling gates within the quantum CCD architecture for an ion-trap quantum computer.

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“…By overlapping two 1D gases comprising different spin states, a spin-specific potential could be used to control interactions and the resulting spin-charge separation [30]. The microwave ACZ traps could also be used to realize spin-based quantum gates, in which entanglement between internal atomic spin states can be mediated by the spin-specific ACZ potential, as is pursued in the ion quantum computing community [31][32][33][34].…”

Section: Discussionmentioning

confidence: 99%

Microwave Atom Chip Design

Miyahira

Rotunno

et al. 2021

Atoms

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We present a toolbox of microstrip building blocks for microwave atom chips geared towards trapped atom interferometry. Transverse trapping potentials based on the AC Zeeman (ACZ) effect can be formed from the combined microwave magnetic near fields of a pair or a triplet of parallel microstrip transmission lines. Axial confinement can be provided by a microwave lattice (standing wave) along the microstrip traces. Microwave fields provide additional parameters for dynamically adjusting ACZ potentials: detuning of the applied frequency to select atomic transitions and local polarization controlled by the relative phase in multiple microwave currents. Multiple ACZ traps and potentials, operating at different frequencies, can be targeted to different spin states simultaneously, thus enabling spin-specific manipulation of atoms and spin-dependent trapped atom interferometry.

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Multilayer ion trap with three-dimensional microwave circuitry for scalable quantum logic applications

Cited by 19 publications

References 40 publications

Robust and Resource-Efficient Microwave Near-Field Entangling Be+9 Gate

Robust and Resource-Efficient Microwave Near-Field Entangling Be+9 Gate

Integrated 9Be+ multi-qubit gate device for the ion-trap quantum computer

Microwave Atom Chip Design

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