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Physical Review Applied

Electrical Control for Extending the Ramsey Spin Coherence Time of Ion-Implanted Nitrogen-Vacancy Centers in Diamond

Satoshi Kobayashi, Yuichiro Matsuzaki, Hiroki Morishita, Shinji Miwa, Yoshishige Suzuki, Masanori Fujiwara, Norikazu Mizuochi

Published Oct 19, 2020• 12 citations
Publisher

Abstract

The extension of spin coherence times is a crucial issue for quantum information and quantum sensing. In solid-state systems, suppressing noise through various techniques has been demonstrated. On the other hand, an electrical control for suppression is important toward individual controls of on-chip quantum-information devices. Here, we show electrical control for extension of the spin coherence times of 40-nm-deep ion-implanted single-nitrogen-vacancy center spins in diamond by suppressing magnetic noise. We apply 120 V dc across two contacts spaced by 10 \ensuremath{\mu}m. The spin coherence times, estimated from a free-induction decay and a Hahn-echo decay, are increased up to about 10 times (reaching 10 \ensuremath{\mu}s) and 1.4 times (reaching 150 \ensuremath{\mu}s), respectively. From the quantitative analysis, the dominant decoherence source, depending on the applied static electric field, is elucidated. Electrical control for extension can deliver a sensitivity enhancement to the dc sensing of temperature, pressure, and electric (but not magnetic) fields, opening up an alternative technique in solid-state quantum-information devices.

DOI
10.1103/physrevapplied.14.044033

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The extension of spin coherence times is a crucial issue for quantum information and quantum sensing. In solid-state systems, suppressing noise through various techniques has been demonstrated. On the other hand, an electrical control for suppression is important toward individual controls of on-chip quantum-information devices. Here, we show electrical control for extension of the spin coherence times of 40-nm-deep ion-implanted single-nitrogen-vacancy center spins in diamond by suppressing magnetic noise. We apply 120 V dc across two contacts spaced by 10 \ensuremath{\mu}m. The spin coherence times, estimated from a free-induction decay and a Hahn-echo decay, are increased up to about 10 times (reaching 10 \ensuremath{\mu}s) and 1.4 times (reaching 150 \ensuremath{\mu}s), respectively. From the quantitative analysis, the dominant decoherence source, depending on the applied static electric field, is elucidated. Electrical control for extension can deliver a sensitivity enhancement to the dc sensing of temperature, pressure, and electric (but not magnetic) fields, opening up an alternative technique in solid-state quantum-information devices.
The extension of the spin coherence times is a crucial issue for quantum information and quantum sensing. In solid state systems, suppressing noises with various techniques have been demonstrated. On the other hand, an electrical control for suppression is important toward individual controls of on-chip quantum information devices. Here we show the electrical control for extension of the spin coherence times of 40 nm-deep ion-implanted single nitrogen vacancy center spins in diamond by suppressing magnetic noises. We applied 120 V DC across two contacts spaced by 10 micrometers. The spin coherence times, estimated from a free-induction-decay and a Hahn-echo decay, were increased up to about 10 times (reaching 10 microseconds) and 1.4 times (reaching 150 microseconds), respectively. From the quantitative analysis, the dominant decoherence source depending on the applied static electric field was elucidated. The electrical control for extension can deliver a sensitivity enhancement to the DC sensing of temperature, pressure and electric (but not magnetic) fields, opening a new technique in solid-state quantum information devices.
Nitrogen-vacancy (NV) centers in diamond are a leading competitor for quantum sensing. The resolution of DC magnetic field sensing is limited by dephasing of the NV electron spin, with the main dephasing source being the thermal and quantum noise from the 13C^{13}\mathrm{C}13C nuclear spin bath. In this work, we propose an effective method to extend the dephasing time of a single NV electron spin by suppressing the nuclear spin noise. On the one hand, we improve the technique of bath driving to accommodate nuclear spin bath decoupling, and extend the dephasing time from 2.6 to 10.2 $\textmu{}\mathrm{s}$ at a magnetic field of 455 G. On the other hand, our method enables decoupling the quantum noise by inserting $\ensuremath{\pi}$ rotations around the ZZZ axis of the nuclear spin bath into the free evolution. By suppressing both the thermal and quantum noise, the dephasing time is extended by more than four times at 100 G. Our results provide a new route to explore strategies of suppressing the thermal noise and quantum noise in quantum information processing, and can be applied to other solid-state defects.
High spatial resolution quantum sensing of near-surface nitrogen vacancy (NV) centers in diamond has enabled detection of magnetic, electrical, and thermal signals at the nanoscale. At depths of just a few nanometers, NV centers serve as localized quantum probes for external spins or low-dimensional materials, but their proximity to the surface also enhances decoherence caused by fluctuating nuclear spins. While advances in surface engineering have stabilized the charge state of NV centers at depths of tens of nanometers, achieving both ultra-shallow implantation (0.5-2 nm) and long-term spin coherence remains a central challenge. In this work, we show using first-principles modeling that, by exploiting the interaction of surface-induced strain and weak dc magnetic fields, the spin coherence times of 1-nm-deep NV centers can be greatly improved near the spin-phonon-confined regime at room temperature in 12C-rich diamonds. We also demonstrate that this protocol benefits ~ 10-nm-deep NV centers in natural diamond, enabling vector magnetometry at the nanoscale. Shallow NV centers in diamond are advantageous for quantum sensing but suffer from surface magnetic noise. Using first-principles simulations supported by experiments, the authors show that a combination of small magnetic fields and surface strain can significantly enhance spin coherence of 1 nm-deep NV centers.
Spin qubit coherence is a fundamental resource for the realization of quantum technologies. For solid-state platforms, spin decoherence is dominated by the magneto-active environment in the lattice, limiting their applicability. While standard dynamical decoupling techniques, such as the Hahn echo, extend central spin coherence, they fail to suppress the fast noise arising from strong dipolar interactions within the bath. Here, we present a decoupling mechanism, Hybrid-LG, that suppresses intra-bath dipolar interactions -- thus, fast noise acting on spin qubits- and demonstrate its effectiveness in extending spin coherence through efficient in-house CCE simulations. Specifically, we investigate one of the most widely exploited solid-state quantum platforms: an ensemble of nitrogen-vacancy (NV) centers in diamond coupled to a large and dense bath of substitutional nitrogen paramagnetic impurities (P1 centers). Our results reveal at least a twofold enhancement in NV coherence time relative to standard techniques including P1 center driving, without requiring additional control power.
Nitrogen-vacancy (NV) centers in diamond are promising candidates for solid-state qubits owing to their excellent spin coherence properties. Scaling up NV-based quantum information systems requires reducing the spacing between neighboring qubits. However, optical techniques are fundamentally limited by diffraction, making individual qubit addressing increasingly challenging at short distances. Electrical detection of NV spin states using ferromagnetic electrodes would provide an attractive route toward scalable qubit architectures. In this work, we investigate the feasibility of electrically detecting NV spin states through spin-dependent tunneling. Diamond substrates with NV centers (~2 nm deep) were fabricated via N-ion implantation and coupled with a 10-nm Co film. PL measurements show positive bias converts NV- to NV0 (electron extraction), while negative bias restores NV-. This enables electrical NV charge-state control toward spin-dependent tunneling detection.
Photoelectrical readout of the electronic spin state of the nitrogen-vacancy (NV) center in diamond is attracting significant interest due to the numerous advantages it possesses compared with conventional fluorescence readout. The higher charge carrier rate compared to the photon rate and the integration of the detection scheme on a chip can significantly advance quantum sensing and computing with color centers in diamond. Until now, photoelectric readout has been performed on ensembles of NV centers or single NV centers deep in ultrapure diamond substrates. However, many applications require the artificial creation and precise placement of shallow NV centers, and photoelectric detection of such centers has been challenging. Here we demonstrate photoelectrical readout and coherent control of the electronic spin of implanted shallow ($\sim$10 nm) NV centers buried by diamond overgrowth. The photoelectrically measured Ramsey T2∗T_2^*T2∗​ agrees with conventional fluorescence readout and shows no measurable dependence on the readout photocurrent, for both shallow implanted and deep ingrown NV centers. We further find that overgrowth improves photoelectric readout by suppressing the background photocurrent. These results establish photoelectric readout as a viable route to chip-integrated, electrically detected nanoscale sensing and to spin registers based on engineered shallow NV centers.