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arXiv:1608.02168

Quantum Zeno effect in a nitrogen-vacancy center embedded in a spin bath

Zhi-Sheng Yang, Wen Yang, Mei Zhang, Qing Ai, Fu‐Guo Deng

Published Aug 7, 2016• 0 citations
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Abstract

We study the longitudinal relaxation of a nitrogen-vacancy (NV) center surrounded by a $^{13}$C nuclear spin bath in diamond. By means of cluster-correlation expansion (CCE), we numerically demonstrate the decay process of electronic state induced by cross relaxation at low temperature. It is shown that the CCE method is not only capable of describing pure-dephasing effect at large-detuning regime, but it can also simulate the quantum dynamics of populations in the nearly resonant regime. We present a proposal to slow down the decay of NV center via implementing quantum Zeno effect (QZE). The numerical result shows that QZE can effectively inhibit the decay of NV center.

DOI
10.48550/arxiv.1608.02168

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We study the longitudinal relaxation of a nitrogen-vacancy (NV) center surrounded by a 13^{13}13C nuclear spin bath in diamond. By means of cluster-correlation expansion (CCE), we numerically demonstrate the decay process of electronic state induced by cross relaxation at low temperature. It is shown that the CCE method is not only capable of describing pure-dephasing effect at large-detuning regime, but it can also simulate the quantum dynamics of populations in the nearly resonant regime. We present a proposal to slow down the decay of NV center via implementing quantum Zeno effect (QZE). The numerical result shows that QZE can effectively inhibit the decay of NV center.
We theoretically investigate spin decoherence of a single nitrogen-vacancy (NV) center in diamond. Using the spin coherent-state PPP-representation method, we simulate coherence evolution of the NV center coupled to surrounding nitrogen electron (N) spins. In the system, the strength of N-N coupling is the same order as that of NV-N coupling (the strong intrabath coupling regime). We find that spin decoherence time as well as free-induction decay of the NV center depend on the spatial configuration of N spins. Both the spin decoherence rate (1/T21/{T}_{2}1/T2​) and dephasing rate (1/T2∗)1/{T}_{2}^{*})1/T2∗​) of the NV center increase linearly with the concentration of the N spins. Using the PPP-representation method, we also demonstrate extracting the noise spectrum of the N spin bath. The capability to calculate the noise spectrum will provide promising pathways to suppress decoherence of spin systems in the strong intrabath coupling regime.
Decoherence is the biggest bottleneck in all quantum technologies. For nitrogen-vacancy (NV) centers in diamond, the loss of coherence is caused by the electron and nuclear spin bath of the diamond lattice. Here, we demonstrate that the spin bath - that typically causes decoherence - entangles the spin states of the NV electron and the host 14^{14}14N nucleus. The many-body interaction between the 14^{14}14N nucleus - electron - bath spins at an energy level anti-crossing occurring for an applied magnetic field orientation perpendicular to the NV axis is responsible for this effect. This is observed experimentally in NV ensembles via electron spin-echo measurements, where the echo envelope is modulated at the frequency of a 14^{14}14N nuclear spin transition. Using numerical simulations, we show that the spin bath coupling to the NV centers is essential for observing this modulation. Due to the zero first-order Zeeman effect at the anti-crossing, the observed oscillations have long spin-echo coherence times, 2--3 times those at the parallel magnetic field orientation. The oscillation frequency is highly stable and robust against environmental fluctuations. These findings provide new opportunities for fundamental studies of many-body physics and quantum sensing.
We investigate nitrogen-vacancy center (NV) ensembles in diamond under the influence of strongly correlated electron-spin baths. We thoroughly calculate the decoherence properties of the NV central spin for bath concentrations of 0.1–1000.1\text{--}1000.1–100 ppm using the cluster-correlation expansion (CCE) method. We systematically analyze possible origins of the significant deviations in the values of the T2{T}_{2}T2​ coherence time reported in the literature. We demonstrate that significant variations can originate from the choice of averaging and fitting procedures used for the ensemble average and we point out the respective aspects that need to be considered when comparing the various theoretical studies. Our study may inspire readers to perform reliable simulations on the central spin problem. It provides an understanding and interpretation of the outcome parameters describing the dynamics of the local bath spins.
Abstract Nitrogen-vacancy (NV) centers in diamond have been developed into essential hardware units for a wide range of solid-state-based quantum technology applications. While such applications require the long spin coherence times of the NV centers, they are often limited due to decoherence. In this study, we theoretically investigate the decoherence of NV-spin ensembles induced by nitrogen impurities (P1 centers), which are one of the most dominant and inevitable magnetic field noise sources in diamond. We combined cluster correlation expansion and density functional theory to compute the Hahn-echo spin-coherence time of the NV centers for a broad range of P1 concentrations. Results indicate a clear linear dependence of T2 on P1 concentrations on a log scale with a slope of −1.06, which is in excellent agreement with previous experimental results. The interplay between the Jahn–Teller effect and the hyperfine interaction in the P1 center plays a critical role in determining the bath dynamics and the resulting NV decoherence. Our results provide a theoretical upper bound for the NV-spin T2 over a wide range of P1 densities, serving as a key reference for materials optimization and spin bath characterization to develop highly coherent NV-based devices for quantum information technology.
ABSTRACT The negatively charged nitrogen‐vacancy (NV) center in diamond has emerged as a leading qubit platform. One of the key challenges for NV‐based quantum applications is building an accurate model to predict their decoherence properties. In this study, a combination of theory and experiment is used to investigate NV decoherence dynamics in the presence of P1 center baths. A cluster‐correlation expansion method to compute the decoherence under the Hahn‐echo and CPMG pulse sequences at various P1 concentrations from 1 to 300 ppm is employed. Notably, we find that the coherence time ( T 2 ) scales quadratically as a function of the pulse number, on a logarithmic scale, as opposed to the linear scaling predicted by widely accepted semi‐classical theories. In this experiment, the CPMG signal for two diamond samples with high P1 concentrations of 0.8 and 13 ppm is measured. It is demonstrated that the T 2 scaling is indeed quadratic, thus confirming our theoretical predictions. These results show that the quantum bath model combined with the CCE method can accurately capture the quantum nature of the P1‐driven NV decoherence. This study opens a new avenue for developing a complete noise model that can be used to optimize the performance of NV‐based quantum devices.