Multi-element logic gates for trapped-ion qubits

Tan, Ting Rei; Gaebler, John; Lin, Yiheng; Wan, Yong; Bowler, Ryan; Leibfried, D.; Wineland, David J.

doi:10.1038/nature16186

Cited by 160 publications

(160 citation statements)

References 35 publications

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“…It may be necessary to physically separate (shuttle) the communication qubit away from the others, invoking techniques from the QCCD approach, but ultimately using two different atomic species can eliminate this crosstalk, [53][54][55] such as 171 Yb + for memory qubits and 138 Ba + for communication qubits. Here the communication qubits are connected through the photonic channel, and then mapped to neighbouring memory qubits through Coulomb gates as described above.…”

Section: Ion Trap Qubits and Wiresmentioning

confidence: 99%

Co-designing a scalable quantum computer with trapped atomic ions

2016

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The first generation of quantum computers are on the horizon, fabricated from quantum hardware platforms that may soon be able to tackle certain tasks that cannot be performed or modelled with conventional computers. These quantum devices will not likely be universal or fully programmable, but special-purpose processors whose hardware will be tightly co-designed with particular target applications. Trapped atomic ions are a leading platform for first-generation quantum computers, but they are also fundamentally scalable to more powerful general purpose devices in future generations. This is because trapped ion qubits are atomic clock standards that can be made identical to a part in 10 15 , and their quantum circuit connectivity can be reconfigured through the use of external fields, without modifying the arrangement or architecture of the qubits themselves. In this forwardlooking overview, we show how a modular quantum computer with thousands or more qubits can be engineered from ion crystals, and how the linkage between ion trap qubits might be tailored to a variety of applications and quantum-computing protocols. Quantum information processors have the potential to perform computational tasks that are difficult or impossible using conventional modes of computing. 1-3 In a radical departure from classical information, the qubits of a quantum computer can simultaneously store bit values 0 and 1, and when measured they probabilistically assume definite states. Many interacting qubits, isolated from their environment, can represent huge amounts of information: there are exponentially many binary numbers that can co-exist, with entangled qubit correlations that can behave as invisible wires between the qubits. Even in the face of Moore's Law, or the doubling in conventional computer power every year or two, the complexity of massively entangled quantum states of just a few hundred qubits can easily eclipse the capacity of classical information processing. 4 There are but a few known applications that exploit this quantum advantage, such as Shor's factoring algorithm, 5 and future quantum information processors will likely be applied to special-purpose applications. On the other hand, a quantum computer has not yet been built; therefore, new quantum applications and algorithms will likely follow from the evolution and capability of quantum hardware.In the 20 years since the advent of Shor's algorithm 5 and the discovery of quantum error correction, 6-8 there has been remarkable progress in demonstrations of entangling quantum gates on o10 qubits in certain physical systems. Current efforts aim to scale to hundreds, thousands or even millions of interacting qubits. Unlike the classical scaling of bits and logic gates, however, large quantum systems are not comparable to the behaviour of just a few qubits. Just because 2 or 4 qubits can be completely controlled with negligible errors does not mean that this system can readily scale to 4100 qubits.In the last few years, two particular quantum hardware platforms have e...

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Section: Ion Trap Qubits and Wiresmentioning

confidence: 99%

Co-designing a scalable quantum computer with trapped atomic ions

2016

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“…Atoms and ions have longer coherence times but correspondingly longer quantum gate times [12][13][14]. Superconducting qubits are promising both for large-scale quantum computations [15,16], and for hybrid systems with other more stable qubits [11].…”

Section: Introductionmentioning

confidence: 99%

Annulled van der Waals interaction and fast Rydberg quantum gates

Shi¹,

Kennedy²

2017

Phys. Rev. A

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A pair of neutral atoms separated by several microns and prepared in identical s-states of large principal quantum number experience a van der Waals interaction. If microwave fields are used to generate a superposition of s-states with different principal quantum numbers, a null point may be found at which a specific superposition state experiences no van der Waals interaction. An application of this novel Rydberg state in a quantum controlled-Z gate is proposed, which takes advantage of GHz rate transitions to nearby Rydberg states. A gate operation time in the tens of nanoseconds is predicted.

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“…For universal quantum computation, two-qubit gates need to be performed between arbitrary pairs of ions, such that reordering ion strings becomes a necessary. Furthermore, if multiple ion species [16] are employed for sympathetic cooling [17] or ancilla-based syndrome readout via inter-species entangling gates [18,19], deterministic ion reconfiguration is ultimately required.To that end, segmented ion traps bearing junctions with T[20], X [21,22] or Y[23] geometry have been developed and tested. Junctions increase the design complexity of the traps and allow only for sequential ion transport.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Fast ion swapping for quantum-information processing

Kaufmann¹,

Ruster²,

Schmiegelow³

et al. 2017

Phys. Rev. A

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We demonstrate a SWAP gate between laser-cooled ions in a segmented microtrap via fast physical swapping of the ion positions. This operation is used in conjunction with qubit initialization, manipulation and readout, and with other types of shuttling operations such as linear transport and crystal separation and merging. Combining these operations, we perform quantum process tomography of the SWAP gate, obtaining a mean process fidelity of 99.5(5)%. The swap operation is demonstrated with motional excitations below 0.05(1) quanta for all six collective modes of a two-ion crystal, for a process duration of 42 µs. Extending these techniques to three ions, we reverse the order of a three-ion crystal and reconstruct the truth table for this operation, resulting in a mean process fidelity of 99.96(13)% in the logical basis.The last decade has seen substantial progress towards scalable quantum computing with trapped ions. Gate fidelities reach fault-tolerance thresholds [1], and first steps towards realizing decoherence-free qubits have been demonstrated [2]. Moreover, microfabricated, segmented ion traps continue to mature as an experimental low-noise environment [3,4] hosting multi-qubit systems [5,6]. In the seminal proposal from Kielpinsky, Monroe and Wineland [7] for such quantum CCD chip, scalability is reached through ion shuttling operations, where trapped-ion qubits are moved between different trap sites through application of suitable voltage waveforms to the trap electrodes. Since the first demonstration of ion shuttling in segmented traps [8], the development of trap control hardware has progressed [9,10]. This has recently led to demonstrations of fast ion shuttling at low final motional excitation [11,12]. It is currently an open question if a trapped-ion quantum computer should be based on large processing units hosting thousands of qubits [13,14] or on a modular architecture of medium-sized nodes with photonic interconnectivity [15]. With current technology, the possibilities for high-fidelity coherent control and readout of ion strings consisting of more than a few ions are limited, such that ion shuttling is required in either case. For universal quantum computation, two-qubit gates need to be performed between arbitrary pairs of ions, such that reordering ion strings becomes a necessary. Furthermore, if multiple ion species [16] are employed for sympathetic cooling [17] or ancilla-based syndrome readout via inter-species entangling gates [18,19], deterministic ion reconfiguration is ultimately required.To that end, segmented ion traps bearing junctions with T[20], X [21,22] or Y[23] geometry have been developed and tested. Junctions increase the design complexity of the traps and allow only for sequential ion transport. Shuttling through junctions may yield large motional excitations, which precludes the execution of two-qubit gates. In this work, we perform ion reorder- ing via on-site swapping of ions through application of suitable electric potentials. , where an external magnetic field lifts t...

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Multi-element logic gates for trapped-ion qubits

Cited by 160 publications

References 35 publications

Co-designing a scalable quantum computer with trapped atomic ions

Co-designing a scalable quantum computer with trapped atomic ions

Annulled van der Waals interaction and fast Rydberg quantum gates

Fast ion swapping for quantum-information processing

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