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Quantum gate teleportation between separated qubits in a trapped-ion processor
Yong Wan, Daniel Kienzler, Stephen D. Erickson, Karl H. Mayer, Ting Rei Tan, Jenny J. Wu, Hilma M. Vasconcelos, Scott Glancy, Emanuel Knill, David J. Wineland, Andrew C. Wilson, Dietrich Leibfried
TL;DR
The experiment is performed in a multi-layer segmented linear Paul trap and evaluates the resulting process using maximum-likelihood estimation. The estimated entanglement fidelity is bounded by 95% confidence intervals, while Rabi-rate drifts impose an engineering requirement for future ion traps.
Problem
The experiment concerns implementing and evaluating quantum operations in a multi-layer segmented linear Paul trap.
Method
The process is analyzed using observed outcome frequencies and maximum-likelihood estimation of probability distributions.
Results
The 95% confidence interval for dataset 2 entanglement fidelity is [0.845, 0.872].
Takeaways & Limitations
Future ion traps face a significant engineering requirement associated with the measured systematic error.
Takeaways & Limitations
Drifts of Rabi rates for single-qubit operations are a known systematic error in the experiment.
Abstract
from arXiv · showhide
Large-scale quantum computers will require quantum gate operations between widely separated qubits. A method for implementing such operations, known as quantum gate teleportation (QGT), requires only local operations, classical communication, and shared entanglement. We demonstrate QGT in a scalable architecture by deterministically teleporting a controlled-NOT (CNOT) gate between two qubits in spatially separated locations in an ion trap. The entanglement fidelity of our teleported CNOT is in the interval [0.845, 0.872] at the 95% confidence level. The implementation combines ion shuttling with individually-addressed single-qubit rotations and detections, same- and mixedspecies two-qubit gates, and real-time conditional operations, thereby demonstrating essential tools for scaling trapped-ion quantum computers combined in a single device.
List of Supplementary Materials
The supplementary materials include figures documenting the QGT circuit, shuttling sequence, and process characterization.
- Figure 1 documents the proposed and experiment-specific circuits for teleporting a CNOT between B1 and B2.It identifies entanglement, classical communication, basis mapping, and tomography operations.
- Figure 2 documents the ion-shuttling sequence used to split, translate, address, and detect the B-and-M ion pairs.The sequence begins with Bell-state preparation and moves ions into and out of the local interaction zone.
- Figure 3 visualizes experimental, ideal-CNOT, and difference Pauli transfer matrices for process characterization.The figure also reports a 95% confidence interval of [0.845, 0.872] for entanglement fidelity.
Supplementary Text
The supplementary methods combine trapped-ion control, shuttling, state preparation, detection, calibration, and process estimation to implement and evaluate the teleported gate. The measured entanglement fidelities are supported by confidence intervals, while calibration drifts and rotation-angle variations remain important error sources.
- Trap operations and control: The experiment combines a segmented linear Paul trap, separated ion pairs, local two-qubit operations, individually addressed rotations and detection, and measurement-conditioned operations.The ion chain is separated into B1–M1 and M2–B2 before the pairs are transported to the laser interaction zone.
- Process estimation and fidelity: 0.858 and 0.851 are the maximum-likelihood entanglement fidelities for datasets 1 and 2, respectively.
- Calibration and error sources: The simplified depolarizing model captures major error sources, but drifting experimental parameters are not included and can contribute to approximately 1% process-fidelity underestimation.