Implementation of a symmetric surface-electrode ion trap with field compensation using a modulated Raman effect
TL;DR: In this paper, a two-photon process is used to compensate for micromotion compensation in all directions using a two photon process, which avoids the need for an ultraviolet laser directed to the trap plane.
Abstract: We describe a new electrode design for a surface-electrode Paul trap, which allows rotation of the normal modes out of the trap plane, and a technique for micromotion compensation in all directions using a two-photon process, which avoids the need for an ultraviolet laser directed to the trap plane. The fabrication and characterization of the trap are described, as well as its implementation for the trapping and cooling of single Ca+ ions. We also propose a repumping scheme that increases ion fluorescence and simplifies heating rate measurements obtained by time-resolved ion fluorescence during Doppler cooling.
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TL;DR: In this paper, the authors present various models for the origin of the electric noise, provide a critical review of the experimental findings, and summarizes the important questions that are still open in this active research area.
Abstract: How can the electric noise in the vicinity of a metallic body be measured and understood? Trapped ions, known as unique tools for metrology and quantum information processing, also constitute very sensitive probes of this electric noise for distances from micrometers to millimeters. This paper presents various models for the origin of the electric noise, provides a critical review of the experimental findings, and summarizes the important questions that are still open in this active research area.
349 citations
Cites methods from "Implementation of a symmetric surfa..."
...3 were measured in a single trap at Oxford University.3 The Doppler recooling method used for the heating-rate measurement (Allcock et al., 2010) cannot distinguish between signals arising from heating of different modes....
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Journal Article•
TL;DR: Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.
Abstract: Individual laser-cooled 24Mg+ ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 microm above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.
342 citations
TL;DR: An overview of different trapping techniques of ions as well as implementations for coherent manipulation of their quantum states and current approaches for scaling up to more ions and more-dimensional systems are given.
Abstract: Direct experimental access to some of the most intriguing quantum phenomena is not granted due to the lack of precise control of the relevant parameters in their naturally intricate environment. Their simulation on conventional computers is impossible, since quantum behaviour arising with superposition states or entanglement is not efficiently translatable into the classical language. However, one could gain deeper insight into complex quantum dynamics by experimentally simulating the quantum behaviour of interest in another quantum system, where the relevant parameters and interactions can be controlled and robust effects detected sufficiently well. Systems of trapped ions provide unique control of both the internal (electronic) and external (motional) degrees of freedom. The mutual Coulomb interaction between the ions allows for large interaction strengths at comparatively large mutual ion distances enabling individual control and readout. Systems of trapped ions therefore exhibit a prominent system in several physical disciplines, for example, quantum information processing or metrology. Here, we will give an overview of different trapping techniques of ions as well as implementations for coherent manipulation of their quantum states and discuss the related theoretical basics. We then report on the experimental and theoretical progress in simulating quantum many-body physics with trapped ions and present current approaches for scaling up to more ions and more-dimensional systems.
328 citations
Cites background from "Implementation of a symmetric surfa..."
...1 and see [176, 177] for schemes of micromotion compensation)....
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...The mesh shields the ions from charges on the camera viewport and provides a wavelength-independent alternative to a conductive coating (see, for example [176])....
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TL;DR: This study investigates the role of adsorbates on the electrodes by identifying contaminant overlayers, implementing an in situ argon-ion-beam cleaning treatment, and measuring ion heating rates before and after treating the trap electrodes' surfaces, finding a 100-fold reduction in heating rate after treatment.
Abstract: Motional heating of trapped atomic ions is a major obstacle to their use as quantum bits in a scalable quantum computer. The detailed physical origin of this heating is not well understood, but experimental evidence suggests that it is caused by electric-field noise emanating from the surface of the trap electrodes. In this study, we have investigated the role of adsorbates on the electrodes by identifying contaminant overlayers, implementing an in situ argon-ion-beam cleaning treatment, and measuring ion heating rates before and after treating the trap electrodes' surfaces. We find a 100-fold reduction in heating rate after treatment. The experiments described here are sensitive to low levels of electric-field noise in the MHz frequency range. Therefore, this approach could become a useful tool in surface science that complements established techniques.
180 citations
TL;DR: Hardware is demonstrated that reduces noise and drifts in sensitive quantum logic, and simultaneously offers a route to practical parallelization for high-fidelity quantum processors.
Abstract: Practical and useful quantum information processing requires substantial improvements with respect to current systems, both in the error rates of basic operations and in scale. The fundamental qualities of individual trapped-ion1 qubits are promising for long-term systems2, but the optics involved in their precise control are a barrier to scaling3. Planar-fabricated optics integrated within ion-trap devices can make such systems simultaneously more robust and parallelizable, as suggested by previous work with single ions4. Here we use scalable optics co-fabricated with a surface-electrode ion trap to achieve high-fidelity multi-ion quantum logic gates, which are often the limiting elements in building up the precise, large-scale entanglement that is essential to quantum computation. Light is efficiently delivered to a trap chip in a cryogenic environment via direct fibre coupling on multiple channels, eliminating the need for beam alignment into vacuum systems and cryostats and lending robustness to vibrations and beam-pointing drifts. This allows us to perform ground-state laser cooling of ion motion and to implement gates generating two-ion entangled states with fidelities greater than 99.3(2) per cent. This work demonstrates hardware that reduces noise and drifts in sensitive quantum logic, and simultaneously offers a route to practical parallelization for high-fidelity quantum processors5. Similar devices may also find applications in atom- and ion-based quantum sensing and timekeeping6. Scalable optics co-fabricated with a cryogenic surface-electrode ion trap are used to drive high-fidelity multi-ion quantum logic gates, demonstrating a route to simultaneously scale and reduce errors in quantum processors.
121 citations
References
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TL;DR: This work shows how to achieve massively parallel gate operation in a large-scale quantum computer, based on techniques already demonstrated for manipulating small quantum registers, and uses the use of decoherence-free subspaces to do so.
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.
1,469 citations
TL;DR: In this paper, three methods of detecting micromotion of ions in Paul traps have been described, including the change of the average ion position as the trap potentials are changed, and the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the ion's ion motion.
Abstract: Micromotion of ions in Paul traps has several adverse effects, including alterations of atomic transition line shapes, significant second-order Doppler shifts in high-accuracy studies, and limited confinement time in the absence of cooling. The ac electric field that causes the micromotion may also induce significant Stark shifts in atomic transitions. We describe three methods of detecting micromotion. The first relies on the change of the average ion position as the trap potentials are changed. The second monitors the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the micromotion. The last technique detects the Doppler shift induced modulation of the fluorescence rate of a broad atomic transition. We discuss the detection sensitivity of each method to Doppler and Stark shifts, and show experimental results using the last technique.
672 citations
TL;DR: In this article, a gate operation for entangling qubits has been implemented with a fidelity exceeding 99.3% on a pair of qubits encoded in two trapped calcium ions using an amplitude-modulated laser beam interacting with both ions at the same time.
Abstract: Like their classical counterparts, quantum computers can, in theory, cope with imperfections—provided that these are small enough. The regime of fault-tolerant quantum computing has now been reached for a system based on trapped ions, in which a gate operation for entangling qubits has been implemented with a fidelity exceeding 99%. Today, ion traps are among the most promising physical systems for constructing a quantum device harnessing the computing power inherent in the laws of quantum physics1,2. For the implementation of arbitrary operations, a quantum computer requires a universal set of quantum logic gates. As in classical models of computation, quantum error correction techniques3,4 enable rectification of small imperfections in gate operations, thus enabling perfect computation in the presence of noise. For fault-tolerant computation5, it is believed that error thresholds ranging between 10−4 and 10−2 will be required—depending on the noise model and the computational overhead for realizing the quantum gates6,7,8—but so far all experimental implementations have fallen short of these requirements. Here, we report on a Molmer–Sorensen-type gate operation9,10 entangling ions with a fidelity of 99.3(1)%. The gate is carried out on a pair of qubits encoded in two trapped calcium ions using an amplitude-modulated laser beam interacting with both ions at the same time. A robust gate operation, mapping separable states onto maximally entangled states is achieved by adiabatically switching the laser–ion coupling on and off. We analyse the performance of a single gate and concatenations of up to 21 gate operations.
511 citations
01 Jan 2002
TL;DR: In this paper, three methods of detecting micromotion of ions in Paul traps have been described, including the change of the average ion position as the trap potentials are changed, and the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the ion's ion motion.
Abstract: Micromotion of ions in Paul traps has several adverse effects, including alterations of atomic transition line shapes, significant second-order Doppler shifts in high-accuracy studies, and limited confinement time in the absence of cooling. The ac electric field that causes the micromotion may also induce significant Stark shifts in atomic transitions. We describe three methods of detecting micromotion. The first relies on the change of the average ion position as the trap potentials are changed. The second monitors the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the micromotion. The last technique detects the Doppler shift induced modulation of the fluorescence rate of a broad atomic transition. We discuss the detection sensitivity of each method to Doppler and Stark shifts, and show experimental results using the last technique.
469 citations
TL;DR: In this article, individual laser-cooled {sup 24}Mg{sup +} ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 m above this plane.
Abstract: Individual laser-cooled {sup 24}Mg{sup +} ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 {mu}m above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.
397 citations