• Open Access

Fast Multiqubit Gates by Adiabatic Evolution in Interacting Excited-State Manifolds of Rydberg Atoms and Superconducting Circuits

Mohammadsadegh Khazali and Klaus Mølmer
Phys. Rev. X 10, 021054 – Published 11 June 2020

Abstract

Quantum computing and quantum simulation can be implemented by concatenation of one- and two-qubit gates and interactions. For most physical implementations, however, it may be advantageous to explore state components and interactions that depart from this universal paradigm and offer faster or more robust access to more advanced operations on the system. In this article, we show that adiabatic passage along the dark eigenstate of excitation exchange interactions can be used to implement fast multiqubit Toffoli (Ck-NOT) and fan-out (C-NOTk) gates. This mechanism can be realized by simultaneous excitation of atoms to Rydberg levels, featuring resonant exchange interaction. Our theoretical estimates and numerical simulations show that these multiqubit Rydberg gates are possible with errors below 1% for up to 20 qubits. The excitation exchange mechanism is ubiquitous across experimental platforms, and we show that similar multiqubit gates can be implemented in superconducting circuits.

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  • Received 30 September 2019
  • Revised 13 February 2020
  • Accepted 28 April 2020

DOI:https://doi.org/10.1103/PhysRevX.10.021054

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalQuantum Information, Science & Technology

Authors & Affiliations

Mohammadsadegh Khazali1,2 and Klaus Mølmer3

  • 1Department of Physics, Sharif University of Technology, Tehran 14588, Iran
  • 2School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran
  • 3Department of Physics and Astronomy, Aarhus University, DK 8000 Aarhus C, Denmark

Popular Summary

Several candidate systems for quantum computing permit direct and efficient implementation of multiqubit gates and hence reduce the number of operations and errors incurred during the execution of a given algorithm. One candidate system relies on Rydberg states, in which a laser excites electrons in neutral atoms to very high energy levels. Here, we show that by collectively following a state with constant energy during the application of a smooth laser pulse, the atoms can implement multiqubit gates with prominent applications in quantum computing and quantum error correction algorithms.

Our simple estimates and numerical simulations of the errors show acceptable fidelities for gates composed of up to 20 qubits. We show that the central idea of the proposal may also be implemented in other systems, such as superconducting qubits, where we predict similar performances. Our proposal goes beyond the traditional circuit model paradigm of quantum computing, where algorithms are implemented as sequences of one- and two-qubit gates.

Our work suggests that now may be a good time to supplement the circuit model paradigm with physically motivated shortcuts to multiqubit gates, for which entire families are already explored within current implementations of quantum computing.

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Vol. 10, Iss. 2 — April - June 2020

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