Repetitive Readout of a Single Electronic Spin via Quantum Logic with Nuclear Spin Ancillae

TLDR

Robust measurement of single quantum bits is essential for quantum computation, communication, metrology, and sensing. The authors propose a two‑level, concatenated procedure using a pair of nuclear spin ancillae to enhance electronic‑spin readout, advancing robust quantum information processors. They employ quantum‑logic operations on an electronic spin coupled to multiple proximal nuclear spin ancillae, enabling repetitive readout and full quantum control of up to three spins. The technique yields a ten‑fold increase in electronic‑spin readout signal, demonstrates full control of a three‑spin system in a nitrogen‑vacancy center, and improves the sensitivity and speed of nanoscale diamond magnetometers.

Abstract

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers.