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arXiv:1705.00156 · New Journal of Physics

High-fidelity spin measurement on the nitrogen-vacancy center

Michael Hanks, Michael Trupke, Jörg Schmiedmayer, William J. Munro, Kae Nemoto

Published Oct 3, 2017• 20 citations
arXivHTMLPDF

Abstract

Nitrogen-vacancy (NV) centers in diamond are versatile candidates for many quantum information processing tasks, ranging from quantum imaging and sensing through to quantum communication and fault-tolerant quantum computers. Critical to almost every potential application is an efficient mechanism for the high fidelity readout of the state of the electronic and nuclear spins. Typically such readout has been achieved through an optically resonant fluorescence measurement, but the presence of decay through a meta-stable state will limit its efficiency to the order of 99%. While this is good enough for many applications, it is insufficient for large scale quantum networks and fault-tolerant computational tasks. Here we explore an alternative approach based on dipole induced transparency (state-dependent reflection) in an NV center cavity QED system, using the most recent knowledge of the NV center's parameters to determine its feasibility, including the decay channels through the meta-stable subspace and photon ionization. We find that single-shot measurements above fault-tolerant thresholds should be available in the strong coupling regime for a wide range of cavity-center cooperativities, using a majority voting approach utilizing single photon detection. Furthermore, extremely high fidelity measurements are possible using weak optical pulses.

DOI
10.1088/1367-2630/aa8085

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Nitrogen-vacancy (NV) centers in diamond are versatile candidates for many quantum information processing tasks, ranging from quantum imaging and sensing through to quantum communication and fault-tolerant quantum computers. Critical to almost every potential application is an efficient mechanism for the high fidelity readout of the state of the electronic and nuclear spins. Typically such readout has been achieved through an optically resonant fluorescence measurement, but the presence of decay through a meta-stable state will limit its efficiency to the order of 99%. While this is good enough for many applications, it is insufficient for large scale quantum networks and fault-tolerant computational tasks. Here we explore an alternative approach based on dipole induced transparency (state-dependent reflection) in an NV center cavity QED system, using the most recent knowledge of the NV center's parameters to determine its feasibility, including the decay channels through the meta-stable subspace and photon ionization. We find that single-shot measurements above fault-tolerant thresholds should be available in the strong coupling regime for a wide range of cavity-center cooperativities, using a majority voting approach utilizing single photon detection. Furthermore, extremely high fidelity measurements are possible using weak optical pulses.
Abstract High-fidelity projective readout of a qubit’s state in a single experimental repetition is a prerequisite for various quantum protocols of sensing and computing. Achieving single-shot readout is challenging for solid-state qubits. For Nitrogen-Vacancy (NV) centers in diamond, it has been realized using nuclear memories or resonant excitation at cryogenic temperature. All of these existing approaches have stringent experimental demands. In particular, they require a high efficiency of photon collection, such as immersion optics or all-diamond micro-optics. For some of the most relevant applications, such as shallow implanted NV centers in a cryogenic environment, these tools are unavailable. Here we demonstrate an all-optical spin readout scheme that achieves single-shot fidelity even if photon collection is poor (delivering less than 10 3 clicks/second). The scheme is based on spin-dependent resonant excitation at cryogenic temperature combined with spin-to-charge conversion, mapping the fragile electron spin states to the stable charge states. We prove this technique to work on shallow implanted NV centers, as they are required for sensing and scalable NV-based quantum registers.
High fidelity single-shot readout of qubits is a crucial component for fault-tolerant quantum computing and scalable quantum networks. In recent years, the nitrogen-vacancy (NV) center in diamond has risen as a leading platform for the above applications. The current single-shot readout of the NV electron spin relies on resonance fluorescence method at cryogenic temperature. However, the spin-flip process interrupts the optical cycling transition, therefore, limits the readout fidelity. Here, we introduce a spin-to-charge conversion method assisted by near-infrared (NIR) light to suppress the spin-flip error. This method leverages high spin-selectivity of cryogenic resonance excitation and flexibility of photoionization. We achieve an overall fidelity > 95% for the single-shot readout of an NV center electron spin in the presence of high strain and fast spin-flip process. With further improvements, this technique has the potential to achieve spin readout fidelity exceeding the fault-tolerant threshold, and may also find applications on integrated optoelectronic devices.
Abstract High fidelity single-shot readout of qubits is a crucial component for fault-tolerant quantum computing and scalable quantum networks. In recent years, the nitrogen-vacancy (NV) center in diamond has risen as a leading platform for the above applications. The current single-shot readout of the NV electron spin relies on resonance fluorescence method at cryogenic temperature. However, the spin-flip process interrupts the optical cycling transition, therefore, limits the readout fidelity. Here, we introduce a spin-to-charge conversion method assisted by near-infrared (NIR) light to suppress the spin-flip error. This method leverages high spin-selectivity of cryogenic resonance excitation and flexibility of photoionization. We achieve an overall fidelity > 95% for the single-shot readout of an NV center electron spin in the presence of high strain and fast spin-flip process. With further improvements, this technique has the potential to achieve spin readout fidelity exceeding the fault-tolerant threshold, and may also find applications on integrated optoelectronic devices.
The nitrogen-vacancy (NV) center in diamond is one of the advanced candidates for solid-state quantum computing at room temperature and has proven to be competitive in terms of gate fidelity and the availability of quantum error correction codes. Ambient solid-state qubits may therefore provide quantum computing architectures as an alternative to current solutions. The NV center has an associated electronic spin that is conventionally read out via photoluminescence. As an alternative, the electrical readout is not limited by the confocal resolution of quantum microscopes, which is required in the development of NV-based quantum processors to establish a scalable individual single-spin readout on the order of a few nanometers (necessary for strong dipole-dipole coupling). In this work, the performance of photoelectric readout versus traditional optical readout is investigated to perform Quantum State Tomography measurements on a single NV center. A state fidelity of 0.995 ±\pm± 0.006 is achieved using photoelectrical spin-state readout for state reconstruction, comparable to simultaneous optical measurements. We report photocurrent signal delays, which significantly slow down the photocurrent tomography. We develop a model describing their origin, and propose strategies for their mitigation.
Nitrogen-vacancy (NV) centers in diamond have been used in recent years for a wide range of applications, from nanoscale NMR to quantum computation. These applications depend strongly on the efficient readout of the NV center's spin state, which is currently limited. Here we suggest a method of reading the NV center's spin state, using the weak optical transition in the singlet manifold. We numerically calculate the number of photons collected from each spin state using this technique, and show that an order of magnitude enhancement in spin-readout signal-to-noise ratio is expected, making single-shot spin readout within reach. Thus, this method could lead to an order of magnitude enhancement in sensitivity for ubiquitous NV-based sensing applications, and remove a major obstacle from using NVs for quantum information processing.
A key step in the use of diamond nitrogen vacancy (NV) centers for quantum computational tasks is a single shot quantum non-demolition measurement of the electronic spin state. Here, we propose a high fidelity measurement of the ground state spin of a single NV center, using the effects of cavity quantum electrodynamics. The scheme we propose is based in the one-dimensional atom or Purcell regime, removing the need for high Q cavities that are challenging to fabricate. The ground state spin of the NV center has a splitting of ≈6–10 μeV, which can be resolved in a high-resolution absorption measurement. By incorporating the center in a low- Q and low volume cavity we show that it is possible to perform single shot readout of the ground state spin using a weak laser with an error rate of ≈7 × 10 −3 , when realistic experimental parameters are considered. Since very low levels of light are used to probe the state of the spin we limit the number of florescence cycles, which dramatically reduces the measurement induced decoherence approximating a non-demolition measurement of ground state spin.