Observation of Entangled States of a Fully Controlled 20-Qubit System

Friis, Nicolai; Marty, Oliver; Maier, C.; Hempel, Cornelius; Holzäpfel, Milan; Jurcevic, Petar; Plenio, Martin B.; Huber, Marcus; Roos, C. F.; Blatt, R.; Lanyon, B. P.

doi:10.1103/physrevx.8.021012

Cited by 332 publications

(296 citation statements)

References 35 publications

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“…Trapped ions exhibit remarkably useful properties for the purposes of quantum information applications, including stability on the order of minutes [47], single-photon-matter quantum interfaces [48][49][50][51][52], high-fidelity universal gates [53,54], and entanglement in quantum registers, involving as many as 20 trapped ions [55,56]. Critically, the required integration of these techniques is already underway [57].…”

Section: Experimental Realizationsmentioning

confidence: 99%

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Generation of arbitrary all-photonic graph states from quantum emitters

2019

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We present protocols to generate arbitrary photonic graph states from quantum emitters that are in principle deterministic. We focus primarily on two-dimensional cluster states of arbitrary size due to their importance for measurement-based quantum computing. Our protocols for these and many other types of two-dimensional graph states require a linear array of emitters in which each emitter can be controllably pumped, rotated about certain axes, and entangled with its nearest neighbors. We show that an error on one emitter produces a localized region of errors in the resulting graph state, where the size of the region is determined by the coordination number of the graph. We describe how these protocols can be implemented for different types of emitters, including trapped ions, quantum dots, and nitrogen-vacancy centers in diamond. is a 2×m cluster state, where m is the number of cycles. Schemes to create ladder-type cluster states using trapped ions have also been proposed [29]. However, for universal quantum computation, a larger twodimensional grid (n by m, with n, m?2) is needed; moreover, fault-tolerant universal computation requires a three-dimensional grid [30]. One interesting proposal to create a larger two-dimensional grid using feedback and atom-photon interactions in a cavity has been put forward [31]. However, this approach requires coupling the emitter to a chiral waveguide, which has yet to be demonstrated experimentally with high efficiency.In this paper, we propose an in-principle deterministic method to produce an arbitrary graph state that does not require photon-photon interactions. Instead, the entanglement is created between emitters and then transferred onto photons through optical pumping. This is similar to the idea presented in [28], although here, in addition to being able to create states corresponding to arbitrary graphs of any size, our scheme also allows for the entangling operations between emitters to occur after the photon pumping. Combined with heralding of the emission process, this allows one to perform the typically costly entangling operation only if there is a successful photon emission. Moreover, we show that, in a precise sense, our approach allows for the maximum possible delay in transferring the entanglement from the emitters onto the photons. Our protocol allows for arbitrary sized n by m clusters, given a linear array of n emitters, where each emitter can be entangled with its nearest neighbors. The operations required of the linear array are only a single two-emitter entangling gate and a photon pumping operation. For three-dimensional clusters, which permit fault-tolerant universal computation, our protocol requires a two-dimensional grid of nearest-neighbor connected emitters.This paper is organized as follows. First, a brief overview of the graph state formalism is provided. Second, our new framework to produce arbitrary graph states using emitters, assuming entangling gates are available between emitters, is presented. Then, we discuss concrete realizations ...

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Section: Experimental Realizationsmentioning

confidence: 99%

“…Fast ( m10 s), high-fidelity (99%) two-qubit gates have already been realized in cavities [54], suggesting that the g gates required for our protocol could be implemented with high precision. In fact, well-controlled entangling operations driven by laser fields have very recently been demonstrated with up to 20 ions [56].…”

Section: Experimental Realizationsmentioning

confidence: 99%

Generation of arbitrary all-photonic graph states from quantum emitters

2019

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“…Pros and cons characterize each specific choice, and a dedicated experimental apparatus must necessarily be developed for one qubit type or the other. Among the different possibilities, particularly advanced appear the technologies based on 40 Ca + as optical qubits, and 43 Ca + or 171 Yb + as hyperfine qubits, respectively, although several other atomic species with a single outer electron can be successfully trapped . In fact, irrespective of the specific qubit realization, initialization and readout of their quantum state is performed through coherent manipulation, for example, by using external lasers of suitable frequency to optically pump the ion state into the desired one (preparation), or by detecting resonantly scattered radiation from an optical transition (readout).…”

Section: Experimental Achievements and Prospective Technologiesmentioning

confidence: 99%

“…Without restricting to the main object of the present Review, it is worth mentioning recent results obtained on trapped ion quantum technology. First, a 20‐qubit register has been shown to reliably allow for the creation of multi‐qubit entangled states, thus opening the door to quantum simulations of larger spin systems. The same quantum hardware has been used to show a hybrid quantum‐classical approach to the simulation of the Schwinger model .…”

Section: Experimental Achievements and Prospective Technologiesmentioning

confidence: 99%

Quantum Computers as Universal Quantum Simulators: State‐of‐the‐Art and Perspectives

et al. 2019

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The past few years have witnessed the concrete and fast spreading of quantum technologies for practical computation and simulation. In particular, quantum computing platforms based on either trapped ions or superconducting qubits have become available for simulations and benchmarking, with up to few tens of qubits that can be reliably initialized, controlled, and measured. The present Review aims at giving a comprehensive outlook on the state‐of‐the‐art capabilities offered from these near‐term noisy devices as universal quantum simulators, that is, programmable quantum computers potentially able to calculate the time evolution of many physical models. First, a pedagogic overview on the basic theoretical background pertaining digital quantum simulations is given, with a focus on hardware‐dependent mapping of spin‐type Hamiltonians into the corresponding quantum circuit as a key initial step toward simulating more complex models. Then, the main experimental achievements obtained in the last decade are reviewed, focusing on the digital quantum simulation of such spin models by employing two leading quantum architectures. Their performances are compared, and future challenges are outlined, also in view of prospective hybrid technologies, towards the ultimate goal of reaching the long‐sought quantum advantage for the simulation of complex many‐body models in the physical sciences.

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“…Qubitzustände sind über unterschiedliche Energiezustände der Ionen realisierbar, die Kontrolle geschieht durch Laserpulse. Bis zu 20 Ionen konnten bereits in einen gemeinsamen verschränkten Zustand gebracht werden [9].…”

Section: Ionenunclassified

Schreiben und Rechnen mit Atomen

Bernien

Omran

2018

Physik in unserer Zeit

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Schreiben und Rechnen mit AtomenHannes Bernien | aHmed Omran Wir befinden uns derzeit auf dem spannenden Weg vom einzelnen Quantensystem zu gut kontrollierten, großen Quanten-Vielteilchensystemen. Die Suche nach Systemen und Methoden, die eine solche Skalierung ermöglichen, ist eine enorme Herausforderung. Ein vielversprechender Weg sind mit optischen Pinzetten manipulierbare Atomketten. Diese dienen als Quantensimulator und erlauben es, grundlegende Effekte wie Quantenphasenübergänge zu untersuchen. Ein Ziel ist es, Quantentechnologien weiter zu entwickeln und Quantencomputer zu realisieren. Blick in die Glaszelle der Vakuumkammer.

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Observation of Entangled States of a Fully Controlled 20-Qubit System

Cited by 332 publications

References 35 publications

Generation of arbitrary all-photonic graph states from quantum emitters

Generation of arbitrary all-photonic graph states from quantum emitters

Quantum Computers as Universal Quantum Simulators: State‐of‐the‐Art and Perspectives

Schreiben und Rechnen mit Atomen

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