Speaker
Description
Universal control of multiple qubits -- the ability to entangle qubits and to perform arbitrary individual qubit operations -- is a fundamental resource for quantum computing, simulation, and networking. Qubits realized in trapped atomic ions have shown the highest-fidelity two-qubit entangling operations and single-qubit rotations to date. Universal control of trapped ion qubits has separately been demonstrated using tightly-focused laser beams or by moving ions with respect to laser beams, but at lower fidelities. Laser-free entangling methods may offer improved scalability by harnessing microwave technology developed for wireless communications, but so far their performance has lagged the best reported laser-based approaches. Here, we demonstrate high-fidelity laser-free universal control of two trapped-ion qubits by creating both symmetric and antisymmetric maximally entangled states with fidelities of $1^{+0}_{-0.0017}$ and $0.9977^{+0.0010}_{-0.0013}$, respectively (68% confidence level), corrected for initialization error. We use a new scheme based on radiofrequency magnetic field gradients combined with microwave magnetic fields that is robust against multiple sources of decoherence, usable with essentially any trapped ion species, and has the potential to perform simultaneous entangling operations on multiple pairs of ions in a large-scale trapped-ion quantum processor without increasing control signal power or complexity. Combining this technology with low-power laser light delivered via trap-integrated photonics and trap-integrated photon detectors for qubit readout offers a potential avenue for scalable, high-fidelity, fully-chip-integrated trapped-ion quantum computing.
