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...

We report on the first detailed study of motional heating in a cryogenic Penning trap using a single antiproton. Employing the continuous Stern-Gerlach effect we observe cyclotron quantum transition rates of 6(1) quanta/h and an electric field noise spectral density below 7.5(3.4)×10 −20 V 2 m −2 Hz −1 , which corresponds to a scaled noise spectral density below 8.8(4.0) × 10 −12 V 2 m −2 , results which are more than two orders of magnitude smaller than those reported by other ion trap experiments.Quantum control techniques applied to trapped charged particles, well-isolated from environmental influences, have very versatile applications in metrology and quantum information processing. For example, elegant experiments on co-trapped laser cooled ions in Paul traps have provided highly precise state-of-the-art quantum logic clocks [1], enabled the development of exquisite atomic precision sensors [2] and the implementation of quantum information algorithms applied with highly entangled ion-crystals [3]. Decoherence effects from noise driven quantum transitions, commonly referred to as anomalous heating [4,5], affect the scalability of multiion systems, which would enable even more powerful algorithms. Trapped particles are also highly sensitive probes to test fundamental symmetries, and to search for physics beyond the standard model [6,7]. The most precise values of the mass of the electron [8] and the most stringent tests of bound-state quantum electrodynamics [9] are based on precise frequency measurements on highly-charged ions in Penning traps. Measurements of the properties of trapped electrons [10] and positrons [11] provide the most sensitive tests of quantum electrodynamics and of the fundamental charge-parity-time (CPT) invariance in the lepton sector [12,13]. Our experiments [14] make high-precision comparisons of the fundamental properties of protons and antiprotons, and provide stringent tests of CPT invariance in the baryon sector. We recently reported on an improved determination of the proton magnetic moment with a fractional precision of 300 parts in a trillion [16] and the * matthias.joachim.borchert@cern.ch first high-precision determination of the antiproton magnetic moment with a fractional precision of 1.5 parts in a billion [15]. This measurement, based on a newly invented multi-trap method, improves the fractional precision achieved in previous studies [17,18] by more than a factor of 3000. These multi-trap based high-precision magnetic moment measurements on protons and antiprotons require low-noise conditions much more demanding than in any other ion trap experiment. Compared to experiments on electrons and positrons [10,11], the 660fold smaller proton/antiproton magnetic moment makes it much more challenging to apply high-fidelity single particle spin-quantum spectroscopy techniques [19]. Our experiments become possible only in cryogenic ultra-lownoise Penning-trap instruments, which provide energy stabilities of the particle motion on the peV/s range, effectively corresponding to a para...

We present a novel ion trap fabrication method enabling the realization of multilayer ion traps scalable to an in principle arbitrary number of metal-dielectric levels. We benchmark our method by fabricating a multilayer ion trap with integrated three-dimensional microwave circuitry. We demonstrate ion trapping and microwave control of the hyperfine states of a laser cooled 9 Be + ion held at a distance of 35 m m above the trap surface. This method can be used to implement large-scale ion trap arrays for scalable quantum information processing and quantum simulation.