High-fidelity projective readout of a solid-state spin quantum register

TL;DR

This paper demonstrates high-fidelity, single-shot readout of a multi-spin quantum register in a solid-state system, enabling advanced quantum information processing tasks like error correction and quantum teleportation.

Contribution

It introduces a resonant optical excitation technique for multi-spin readout in a solid-state system, extending single-shot detection to multiple coupled spins.

Findings

Achieved high-fidelity single-shot readout of a single NV center's electronic spin.

Projected and measured states of up to three nuclear spins.

Demonstrated initialization, coherent manipulation, and readout of a two-qubit register.

Abstract

Initialization and readout of coupled quantum systems are essential ingredients for the implementation of quantum algorithms. If the state of a multi-qubit register can be read out in a single shot, this enables further key resources such as quantum error correction and deterministic quantum teleportation, as well as direct investigation of quantum correlations (entanglement). While spins in solids are attractive candidates for scalable quantum information processing, thus far single-shot detection has only been achieved for isolated qubits. Here, we demonstrate preparation and measurement of a multi-spin quantum register by implementing resonant optical excitation techniques originally developed in atomic physics. We achieve high-fidelity readout of the electronic spin associated with a single nitrogen-vacancy (NV) centre in diamond at low temperature, and exploit this readout to project up to three nearby nuclear spin qubits onto a well-defined state. Conversely, we can distinguish the state of the nuclear spins in a single shot by mapping it onto and subsequently measuring the electronic spin. Finally, we show compatibility with qubit control by demonstrating initialization, coherent manipulation, and single-shot readout in a single experiment on a two-qubit register, using techniques suitable for extension to larger registers. These results pave the way for the first test of Bell's inequalities on solid-state spins and the implementation of measurement-based quantum information protocols.