Abstract
Trapped-ion quantum computers have demonstrated high-performance gate operations in registers of about ten qubits. However, scaling up and parallelizing quantum computations with long one-dimensional (1D) ion strings is an outstanding challenge due to the global nature of the motional modes of the ions which mediate qubit-qubit couplings. Here, we devise methods to implement scalable and parallel entangling gates by using engineered localized phonon modes. We propose to tailor such localized modes by tuning the local potential of individual ions with programmable optical tweezers. Localized modes of small subsets of qubits form the basis to perform entangling gates on these subsets in parallel. We demonstrate the inherent scalability of this approach by presenting analytical and numerical results for long 1D ion chains and even for infinite chains of uniformly spaced ions. Furthermore, we show that combining our methods with optimal coherent control techniques allows to realize maximally dense universal parallelized quantum circuits.
Highlights
Trapped atomic ions are a leading platform for quantuminformation processing [1,2,3,4,5,6,7,8,9]
High-fidelity gate operations, qubit initialization and readout, as well as long coherence times have been demonstrated in trapped-ion quantum computers, which consist of tens of individually addressable qubits [10,11,12,13,14]
The spectrum of phonon modes becomes dense for long ion crystals [16,17], and, gate operations that rely on using a single phonon mode become slow due to the necessity to spectrally resolve this mode
Summary
Trapped atomic ions are a leading platform for quantuminformation processing [1,2,3,4,5,6,7,8,9]. Solving optimal control problems [18,19,20,21,22,23,24,25,26], which become exceedingly complex, in particular, when gates should be performed on many qubits in parallel [23,24] This additional complication to implement parallel gates is due to the collective and nonlocal nature of phonon modes, which stands in contrast to the goal of effecting two-qubit entangling operations that locally address individual pairs of ions. We discuss different ways to minimize crosstalk between parallel two-qubit entangling gates based on optimal control of time-modulated laser-pulse amplitudes as developed by Duan et al [17] This enables the implementation of dense “brick-wall circuits.”.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
