Quantum Coherence at Room Temperature: The Physics and Mathematics of Nitrogen-Vacancy Center Quantum Computing

Mo Chen, David Layden, Paola Cappellaro

Junfeng Wang, Fei-Fei Yan, Qiang Li +12 more

Solid-state color centers with manipulatable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which telecom-wavelength emission is detected. We increase the NV concentration sixfold through optimization of implantation conditions. Hence, coherent control of NV center spins is achieved at room temperature, and the coherence time T_{2} can be reached to around 17.1 μs. Furthermore, an investigation of fluorescence properties of single NV centers shows that they are room-temperature photostable single-photon sources at telecom range. Taking advantage of technologically mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising platforms for large-scale integrated quantum photonics and long-distance quantum networks.

Daniel S. Saraga, Daniel Loss

Gang‐Qin Liu, Jian Ping Xing, Wen-Long Ma +7 more

Single-shot readout of qubits is required for scalable quantum computing. Nuclear spins are superb quantum memories due to their long coherence time, but are difficult to be read out in a single shot due to their weak interaction with probes. Here we demonstrate single-shot readout of a weakly coupled ^{13}C nuclear spin at room temperature, which is unresolvable in traditional protocols. States of the weakly coupled nuclear spin are trapped and read out projectively by sequential weak measurements, which are implemented by dynamical decoupling pulses. A nuclear spin coupled to the nitrogen-vacancy (NV) center with strength 330 kHz is read out in 200 ms with a fidelity of 95.5%. This work provides a general protocol for single-shot readout of weakly coupled qubits at room temperature and therefore largely extends the range of physical systems for scalable quantum computing.

David Peter Divincenzo, Daniel Loss

Mutsuko Hatano

Nitrogen-vacancy (NV) centers consisting of a nitrogen atom and a lattice vacancy in diamond have superior physical properties, and their quantum coherence is preserved even at room temperature. To achieve an ideal quantum sensor for scalable applications, the technical challenges in the material and the quantum control techniques are discussed. Moreover, sensor systems of biomagnetic field and EV battery monitoring are introduced.