High-Fidelity Preparation, Gates, Memory, and Readout of a Trapped-Ion Quantum Bit

Harty, T. P.; Allcock, D. T. C.; Ballance, C. J.; Guidoni, Luca; Janacek, H. A.; Linke, Norbert; Stacey, D. N.; Lucas, David M.

doi:10.1103/physrevlett.113.220501

Cited by 570 publications

(595 citation statements)

References 34 publications

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“…8,110 These small error-correcting procedures only require 17-25 total ions per logical qubit to generate fault-tolerant circuits that can have error thresholds near 10 − 3 . This error rate is compatible with the best current ion trap gates and measurements 20,25,26,[64][65][66] , and the whole procedure can easily fit within a single ELU. These small codes are only guaranteed to correct single errors, so the total number of reliable, but non-universal, operations on many logical qubits will scale as the error threshold divided by the square of the physical error per operation.…”

Section: Topology Of Interactionsmentioning

confidence: 56%

“…61 The design and fabrication of complex surface traps using silicon microfabrication processes has now matured, with examples of the Sandia high-optical access (HOA) trap 62 and the GTRI/Honeywell ball-grid array (BGA) trap 63 shown in Figure 3. Recent experiments have demonstrated high-performance qubit measurement 20 and single-qubit quantum gates [64][65][66] in such microfabricated surface traps that outperform conventional manually assembled macroscopic traps. The ability to design and simulate the electromagnetic trapping parameters prior to fabrication provides an attractive path to developing complex trap structures that are both repeatable and produced with high yield.…”

Section: Integration Technologies For Trapped Ion Quantum Computersmentioning

confidence: 99%

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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: Topology Of Interactionsmentioning

confidence: 56%

Section: Integration Technologies For Trapped Ion Quantum Computersmentioning

confidence: 99%

Co-designing a scalable quantum computer with trapped atomic ions

2016

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“…We hope our work helps accelerate research into the many outstanding challenges that remain, such as development of twodimensional qubit arrays, improving gate and measurement fidelities 26 , and investigating the many-cycle behavior of error correction schemes.…”

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confidence: 99%

State preservation by repetitive error detection in a superconducting quantum circuit

Kelly

Barends

Fowler

et al. 2015

Nature

886

1,004

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Quantum computing becomes viable when a quantum state can be preserved from environmentally-induced error. If quantum bits (qubits) are sufficiently reliable, errors are sparse and quantum error correction (QEC) 1-6 is capable of identifying and correcting them. Adding more qubits improves the preservation by guaranteeing increasingly larger clusters of errors will not cause logical failure -a key requirement for large-scale systems. Using QEC to extend the qubit lifetime remains one of the outstanding experimental challenges in quantum computing. Here, we report the protection of classical states from environmental bit-flip errors and demonstrate the suppression of these errors with increasing system size. We use a linear array of nine qubits, which is a natural precursor of the twodimensional surface code QEC scheme 7 , and track errors as they occur by repeatedly performing projective quantum non-demolition (QND) parity measurements. Relative to a single physical qubit, we reduce the failure rate in retrieving an input state by a factor of 2.7 for five qubits and a factor of 8.5 for nine qubits after eight cycles. Additionally, we tomographically verify preservation of the non-classical Greenberger-Horne-Zeilinger (GHZ) state. The successful suppression of environmentally-induced errors strongly motivates further research into the many exciting challenges associated with building a large-scale superconducting quantum computer.The ability to withstand multiple errors during computation is a critical aspect of error correction. We define n-th order fault-tolerance to mean that any combination of n errors is tolerable. Previous experiments based on nuclear magnetic resonance 8,9 , ion traps 10 , and superconducting circuits [11][12][13] have demonstrated multi-qubit states that are first-order tolerant to one type of error. Recently, experiments with ion traps and superconducting circuits have shown the simultaneous detection of multiple types of errors 14,15 . The above hallmark experiments demonstrate error correction in a single round; however, quantum information must be preserved throughout computation using multiple error correction cycles. The basics of repeating cycles have been shown in ion traps 16 and superconducting circuits 17 . Until now, it has been an open challenge to combine these elements to make the information stored in a quantum system robust against errors which intrinsically arise from the environment.The key to detecting errors in quantum information is to perform QND parity measurements. In the surface code, this is done by arranging qubits in a chequerboard pattern -with data qubits corresponding to the white, and measure qubits to the black squares (see Fig. 1) -and using these ancilla measure qubits to repetitively perform parity measurements to detect bit-flip (X) and phase-flip (Ẑ) errors 7 . A square chequerboard with (4n + 1) 2 qubits is n-th order fault tolerant, meaning at least n+1 errors must occur to cause failure in preserving a state if fidelities are above a threshold. W...

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“…Numerous advances have been achieved in this system, including realization of faithful quantum gates [1][2][3][4][5][6][7], preparation of many-body quantum states [8][9][10][11][12][13][14][15], and quantum teleportation [16,17]. There are also developments to scale up this system, based on either ion shuttling [18][19][20] or quantum networks [21][22][23][24][25][26]).…”

Section: Introductionmentioning

confidence: 99%

Sympathetic cooling in a large ion crystal

Lin

Duan

2015

Quantum Inf Process

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We analyze the dynamics and steady state of a linear ion array when some of the ions are continuously laser cooled. We calculate the ions' local temperature measured by its position fluctuation under various trapping and cooling configurations, taking into account background heating due to the noisy environment. For a large system, we demonstrate that by arranging the cooling ions evenly in the array, one can suppress the overall heating considerably. We also investigate the effect of different cooling rates and find that the optimal cooling efficiency is achieved by an intermediate cooling rate. We discuss the relaxation time for the ions to approach the steady state, and show that with periodic arrangement of the cooling ions, the cooling efficiency does not scale down with the system size.

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High-Fidelity Preparation, Gates, Memory, and Readout of a Trapped-Ion Quantum Bit

Cited by 570 publications

References 34 publications

Co-designing a scalable quantum computer with trapped atomic ions

Co-designing a scalable quantum computer with trapped atomic ions

State preservation by repetitive error detection in a superconducting quantum circuit

Sympathetic cooling in a large ion crystal

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