Dual-species, multi-qubit logic primitives for Ca+/Sr+ trapped-ion crystals

Abstract

We demonstrate key multi-qubit quantum logic primitives in a dual-species trapped-ion system based on 40 Ca + and 88 Sr + ions, using two optical qubits with quantum-logic-control frequencies in the red to near-infrared range. With all ionization, cooling, and control wavelengths in a wavelength band similar for the two species and centered in the visible, and with a favorable mass ratio for sympathetic cooling, this pair is a promising candidate for scalable quantum information processing. Same-species and dual-species two-qubit gates, based on the Mølmer-Sørensen interaction and performed in a cryogenic surface-electrode trap, are characterized via the fidelity of generated entangled states; we achieve fidelities of 98.8(2)% and 97.5(2)% in Ca + -Ca + and Sr + -Sr + gates, respectively. For a similar Ca + -Sr + gate, we achieve a fidelity of 94.3(3)%, and carrying out a Sr + -Sr + gate performed with a Ca + sympathetic cooling ion in a Sr + -Ca + -Sr + crystal configuration, we achieve a fidelity of 95.7(3)%. These primitives form a set of trapped-ion capabilities for logic with sympathetic cooling and ancilla readout or state transfer for general quantum computing and communication applications.

Engineering of microfabricated ion traps and integration of advanced on-chip features

“…Some of the optical technologies discussed in this Technical Review will perform optimally only at certain wavelengths. Integrating many of these optical components could therefore require multi-species schemes to best take advantage of these technologies [182]- [186]. With a large variety of technologies being simultaneously integrated, unforeseen consequences will be a likely occurrence, hence full integration will remain a tremendous engineering challenge.…”

Velocity distribution of 43Ca+ion cloud in the low temperature limit in a quadrupole Penning Trap

“…43 Ca + ion has only one valence electron and has simple energy level structure, has long-lived D-states, therefore it can be used for quantum computation [1,2,3], for building an ion clock [4] and also for laser cooling. The large fine-structure splitting of ∆ν FS = 6.7T Hz between the P 1/2 and P 3/2 states in 43 Ca + ion as shown in Figure 1 allows a large detuning of the Raman light fields from the P− levels and thus high fidelity gate operations, as spontaneous emission processes are largely suppressed, which is requirement for ion trap quantum computation.…”

Significant-loophole-free test of Kochen-Specker contextuality using two species of atomic-ions

“…For this aim, we choose a composite system of two different ions [41][42][43][44][45][46], one 171 Yb + ion and one 138 Ba + ion. This dual-species system allows us performing sequential repeatable highly efficient single-shot fluorescence measurements on each of the ions.…”