Decoherence-protected quantum gates for a hybrid solid-state spin register

TL;DR

This paper demonstrates decoherence-protected quantum gates in a hybrid solid-state spin system, integrating dynamical decoupling with gate operations to enhance fidelity at room temperature.

Contribution

It introduces a novel method combining dynamical decoupling with quantum gates in a hybrid electron-nuclear spin system, overcoming decoherence during multi-qubit operations.

Findings

Achieved over 90% fidelity in quantum gates exceeding electron spin dephasing time.

Successfully implemented Grover's algorithm with high fidelity at room temperature.

Demonstrated protection of qubits during gate operations comparable to idle qubits.

Abstract

Protecting the dynamics of coupled quantum systems from decoherence by the environment is a key challenge for solid-state quantum information processing. An idle qubit can be efficiently insulated from the outside world via dynamical decoupling, as has recently been demonstrated for individual solid-state qubits. However, protection of qubit coherence during a multi-qubit gate poses a non-trivial problem: in general the decoupling disrupts the inter-qubit dynamics, and hence conflicts with gate operation. This problem is particularly salient for hybrid systems, wherein different types of qubits evolve and decohere at vastly different rates. Here we present the integration of dynamical decoupling into quantum gates for a paradigmatic hybrid system, the electron-nuclear spin register. Our design harnesses the internal resonance in the coupled-spin system to resolve the conflict between gate operation and decoupling. We experimentally demonstrate these gates on a two-qubit register in diamond operating at room temperature. Quantum tomography reveals that the qubits involved in the gate operation are protected as accurately as idle qubits. We further illustrate the power of our design by executing Grover's quantum search algorithm, achieving fidelities above 90% even though the execution time exceeds the electron spin dephasing time by two orders of magnitude. Our results directly enable decoherence-protected interface gates between different types of promising solid-state qubits. Ultimately, quantum gates with integrated decoupling may enable reaching the accuracy threshold for fault-tolerant quantum information processing with solid-state devices.