Towards fault-tolerant quantum computing with trapped ions

By J. Benhelm, G. Kirchmair, C. F. Roos, Rainer Blatt. 2008

478 citations recorded by the source corpus.

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.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/9b264b0ca5b4526880a0f9a2aec695b53312c3c4

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Citations in the corpus

Programmable quantum simulations of spin systems with trapped ions (2019, background): “Alternatively, optically-defined spin levels can be coupled with a single laser beam (Benhelm et al., 2008), but this is more difficult technically, as the spins acquire an optical phase that requires extreme positional stability of the optical setup.”
State-independent experimental test of quantum contextuality (2009, methodology): “If instead a bichromatic light field near-resonant with the upper and lower sideband transitions of the axial centre-ofmass (COM) mode is used, a Mølmer-Sørensen gate[24] U(θ, φ) = exp(−i θ 2σ (1) φ ⊗σ (2) φ ) is implemented[23, 25].”
Engineered Open Systems and Quantum Simulations with Atoms and Ions (2012, background): “In particular, multi-ion entangling gates have been realized with fidelities higher than 99% for two ions (Benhelm et al., 2008; Roos, 2008), and for up to 14 qubits (Monz et al.”
Entangled states of trapped atomic ions (2008, unknown): “The best error probability achieved so far is approximately 10 −2 , which was inferred from the fidelity of Bell-state generatio”
Quantum Simulation of a Lattice Schwinger Model in a Chain of Trapped Ions (2013, background): “For optical qubits, highfidelity gates of xx type [3, 5] and zz type have been demonstrated [4].”
Macroscopic quantum states: Measures, fragility, and implementations (2017, background): “From high fidelity quantum gates (Benhelm et al., 2008), GHZ states (see Eq.”
Colloquium: Quantum networks with trapped ions (2010, methodology): “For the trapped ion system, given recent experimental advances ͑Benhelm et al., 2008; Blatt and Wineland, 2008͒, it appears possible to meet such thresholds using local Coulomb gates.”
Quantum computing with atomic qubits and Rydberg interactions: progress and challenges (2016, background): “1, there is a large gap between the fidelity results summarized in Table 1 and the very high entanglement fidelities that have been demonstrated with trapped ion[2, 3, 4] and superconducting[6, 5, 136] qubits.”
Quantum information with Rydberg atoms (2009, background): “In this way coherence times of many seconds have been observed with trapped ions in Paul traps(Benhelm et al., 2008a; Langer et al., 2005).”