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![Experimental results of universal quantum gates with fault-tolerant fidelity on an NV center in diamond. (a) Experimental results of randomized benchmarking for quantifying the average gate fidelity F a of single-qubit gates on the electron spin qubit of the NV center. Symbols are experimental results and solid lines are the fitting from which F a is derived. Inset, comparison of the error per gate (1 − F a ) of naive, SUPCODE, BB1, and BB1inC pulses. (b) Experimental results for measurement of the two-qubit CNOT gate fidelity. Symbols are experimental results and solid lines are the fitting from which the CNOT gate fidelity is derived. Inset, the measurement sequence. Note: Figures are adapted from Ref. [116].](publication/311938014/figure/fig5/AS:1023702477062147@1621081098894/Experimental-results-of-universal-quantum-gates-with-fault-tolerant-fidelity-on-an-NV.png)
Experimental results of universal quantum gates with fault-tolerant fidelity on an NV center in diamond. (a) Experimental results of randomized benchmarking for quantifying the average gate fidelity F a of single-qubit gates on the electron spin qubit of the NV center. Symbols are experimental results and solid lines are the fitting from which F a is derived. Inset, comparison of the error per gate (1 − F a ) of naive, SUPCODE, BB1, and BB1inC pulses. (b) Experimental results for measurement of the two-qubit CNOT gate fidelity. Symbols are experimental results and solid lines are the fitting from which the CNOT gate fidelity is derived. Inset, the measurement sequence. Note: Figures are adapted from Ref. [116].
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Quantum computation provides great speedup over its classical counterpart for certain tasks. Spin system is one of the most important candidates to realize quantum computations. The initialization, readout and quantum gate operations of spin-qubits can be accomplished by advanced spin resonance techniques, which include nuclear magnetic resonance,...
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... gate fidelity is experimentally quantified with the standard technique of randomized benchmarking [117]. The experimental results are shown in Figure 7(a), where the control strength is set to ω 1 = 10 MHz. An average gate fidelity of F a = 0.999952(6) is achieved for the gates realized with BB1inC. ...
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... repeatedly applying the CNOT gate and recording the dynamics of state evolution, the average fidelity of each CNOT gate can be derived. Figure 7(b) shows the experimental results of state population with repeated application of the CNOT gate. As shown in Figure 7(b), the population of state |01, P |01 , exhibits oscillatory attenuation as the number of gates increases. ...
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... 7(b) shows the experimental results of state population with repeated application of the CNOT gate. As shown in Figure 7(b), the population of state |01, P |01 , exhibits oscillatory attenuation as the number of gates increases. The decay of P |01 is mainly owing to the quasi-static fluctuation of δ and the instability of the control field, which are quantitatively characterized with additional experiments [116]. ...
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Single-qubit gates are essential components of a universal quantum computer. Without selective addressing of individual qubits, scalable implementation of quantum algorithms is extremely challenging. When the qubits are discrete points or regions on a lattice, selectively addressing magnetic spin qubits at the nanoscale remains a challenge due to t...
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... It can be initialized and read out by the optical detection magnetic resonance (ODMR) and can be controlled by the alternating magnetic field. These excellent properties make it applicable in quantum computing [3], quantum simulation [4], and quantum physics [5][6][7][8]. It has broad application prospects in physics, chemistry, and biology. ...
The nitrogen-vacancy (NV) center of the diamond has attracted widespread attention because of its high sensitivity in quantum precision measurement. The phonon piezoelectric device of the NV center is designed on the basis of the phonon-coupled regulation mechanism. The propagation characteristics and acoustic wave excitation modes of the phonon piezoelectric device are analyzed. In order to improve the performance of phonon-coupled manipulation, the influence of the structural parameters of the diamond substrate and the ZnO piezoelectric layer on the phonon propagation characteristics are analyzed. The structure of the phonon piezoelectric device of the NV center is optimized, and its Micro-Electro-Mechanical System (MEMS) implementation and characterization are carried out. Research results show that the phonon resonance manipulation method can effectively increase the NV center’s spin transition probability using the MEMS phonon piezoelectric device prepared in this paper, improving the quantum spin manipulation efficiency.
... 7 These advantages are promising for broad applications in biology and condensed matter physics. [8][9][10][11][12][13] Among these, single-molecule scale magnetic resonance (MR) spectroscopy is one of the most amazing research fields, which push the detectable sample volumes from ∼100 μl to 10 −21 l and could be applied to structural analysis and dynamic characterization of single molecules in chemistry and biology. The nanoscale nuclear magnetic resonance (NMR) spectrum, [14][15][16][17][18][19][20] single-biomolecule electron spin resonance (ESR) spectrum, 21,22 and NMR spectrum 23 have been demonstrated in the NV center system. ...
We develop a parallel optically detected magnetic resonance (PODMR) spectrometer to address, manipulate, and read out an array of single nitrogen-vacancy (NV) centers in diamond in parallel. In this spectrometer, we use an array of micro-lenses to generate a 20 × 20 laser-spot lattice (LSL) on the objective focal plane and then align the LSL with an array of single NV centers. The quantum states of NV centers are manipulated by a uniform microwave field from a Ω-shape coplanar coil. As an experimental demonstration, we observe 80 NV centers in the field of view. Among them, magnetic resonance (MR) spectra and Rabi oscillations of 18 NV centers along the external magnetic field are measured in parallel. These results can be directly used to realize parallel quantum sensing and multiple times speedup compared with the confocal technique. Regarding the nanoscale MR technique, PODMR will be crucial for a high throughput single molecular MR spectrum and imaging.
... It has been explored as an outstanding magnetic quantum sensor 4, 5 with singlespin sensitivity 6 and nanometer spatial resolution 7 . These advantages promise broad applications in biology and condensed matter physics [8][9][10][11][12][13] . Among these, single-molecule scale magnetic resonance spectroscopy is one of the most amazing research fields, which push the detectable sample volumes from ~ 100 L to 10 -21 L and could be applied to structural analysis and dynamic characterization of single molecules in chemistry and biology. ...
We develop a parallel optically detected magnetic resonance (PODMR) spectrometer to address, manipulate and read out an array of single nitrogen-vacancy (NV) centers in diamond in parallel. In this spectrometer, we use an array of micro-lens to generate 20 * 20 laser-spot lattice (LSL) on the objective focal plane, and then align the LSL with an array of single NV centers. The quantum states of NV centers are manipulated by a uniform microwave field from a {\Omega}-shape coplanar coil. As an experimental demonstration, we observe 80 NV centers in the field of view. Among them, magnetic resonance (MR) spectrums and Rabi oscillations of 18 NV centers along the external magnetic field are measured in parallel. These results can be directly used to realize parallel quantum sensing and multiple times speedup compared with the confocal technique. Regarding the nanoscale MR technique, PODMR will be crucial for high throughput single molecular MR spectrum and imaging.
... Herein, we synthesize a prototype cathode material P2-type Na 0.6 Mg 0.3 Mn 0.7 O 2 (NaMMO) with Mg 2+ and Mn 4+ in the TM layers, both of which are considered to be electrochemically inactive owing to their instability under higher valence states [25]. The cationic and anionic redox behaviors and the fading mechanisms upon cycling are systematically investigated by a combination of soft X-ray absorption spectroscopy (sXAS) and electroanalytical methods. ...
P2-type sodium layered transition metal oxides have been intensively investigated as promising cathode materials for sodium-ion batteries (SIBs) by virtue of their high specific capacity and high operating voltage. However, they suffer from problems of voltage decay, capacity fading, and structural deterioration, which hinder their practical application. Therefore, a mechanistic understanding of the cationic/anionic redox activity and capacity fading is indispensable for the further improvement of electrochemical performance. Here, a prototype cathode material of P2-type Na 0.6 Mg 0.3 Mn 0.7 O 2 is comprehensively investigated, which presents both cationic and anionic redox behaviors during the cycling process. By a combination of soft X-ray absorption spectroscopy and electroanalytical methods, we unambiguously reveal that only oxygen redox reaction is involved in the initial charge process, then both oxygen and manganese participate in the charge compensation in the following discharge process. In addition, a gradient distribution of Mn valence state from surface to bulk is disclosed, which could be mainly related to the irreversible oxygen activity during the charge process. Furthermore, we find that the average oxidation state of Mn is reduced upon extended cycles, leading to the noticeable capacity fading. Our results provide deeper insights into the intrinsic cationic/anionic redox mechanism of P2-type materials, which is vital for the rational design and optimization of advanced cathode materials for SIBs.
... In recent years, the interest in quantum technology has grown rapidly. 2 Quantum technology has grown out of quantum information theory, which relies on controllable quantum bits (qubits) as the most elementary unit of quantum information. 3 Quantum information theory is predicted to solve such complex problems by algorithms based on qubits that are otherwise intractable by classic digital computers [3][4][5][6][7][8] as well as led to the foundation of inherently secure communication based on the noclone theorem of quantum states. 9 The latter is the fundamental of quantum communication applications that are now available commercially, in particular, by the use of quantum key distribution. ...
Quantum technology has grown out of quantum information theory and now provides a valuable tool that researchers from numerous fields can add to their toolbox of research methods. To date, various systems have been exploited to promote the application of quantum information processing. The systems that can be used for quantum technology include superconducting circuits, ultracold atoms, trapped ions, semiconductor quantum dots, and solid-state spins and emitters. In this review, we will discuss the state-of-the-art of material platforms for spin-based quantum technology, with a focus on the progress in solid-state spins and emitters in several leading host materials, including diamond, silicon carbide, boron nitride, silicon, two-dimensional semiconductors, and other materials. We will highlight how first-principles calculations can serve as an exceptionally robust tool for finding novel defect qubits and single-photon emitters in solids, through detailed predictions of electronic, magnetic, and optical properties.
Quantum processors based on NMR architectures, which use nuclear spins as qubits and radio frequency pulses to implement unitary quantum gates, came into existence nearly two decades ago. Since their first proof-of-principle demonstrations as a testbed quantum processors, NMR quantum processors have contributed significantly to advances in various subareas of quantum information processing. Indian researchers have been working in this field since its inception and have continued to contribute to novel developments. This article begins by delineating the basic building blocks of an NMR quantum processor and evaluating the advantages and disadvantages of this quantum technology. Contributions of NMR quantum information processing techniques in the areas of the state initialization and quantum control, experimental implementation of quantum algorithms, entanglement detection and characterization, foundational tests of quantum mechanics, quantum state and process tomography, noise characterization and decoherence mitigation protocols, quantum simulation, and quantum thermodynamics are described. The article traces the historical development of this area, with an emphasis on Indian contributions and perspectives.
The nitrogen-vacancy (NV) center is one of the major platforms in the evolving field of quantum technologies. The inertial surveying technology based on NV centers in diamond is a developing field with both scientific and technological importance. Inertial measurement using the solid-state spin of the NV center has demonstrated potential in both high-precision and small-volume low-cost devices. In terms of rotation measurement, the geometric phase theory has provided a perspective of the rotation measurement mechanism via the solid-state spin of the NV center. A new type of gyroscope based on the solid-state spin in diamond according to the theory has attracted considerable attention. In addition, combined with the ingenious quantum mechanics manipulation and transform mechanism, acceleration measurement can be achieved through an efficient quantum detection technology of the NV center. This review summarizes the recent research progress in diamond-based inertial measurement, including sensitivity optimization methods for inertial measurement systems based on the NV center.
We present an efficient approach to optimizing pulse sequences for implementing fast entangling two-qubit gates on trapped ion quantum information processors. We employ a two-phase procedure for optimizing gate fidelity, which we demonstrate for multi-ion systems in linear Paul trap and microtrap architectures. The first phase involves a global optimization over a computationally inexpensive cost function constructed under strong approximations of the gate dynamics. The second phase involves local optimizations that utilize a more precise ordinary differential equation description of the gate dynamics, which captures the nonlinearity of the Coulomb interaction and the effects of finite laser repetition rate. We propose two gate schemes that are compatible with this approach, and we demonstrate that they outperform existing schemes in terms of achievable gate speed and fidelity for feasible laser repetition rates. In optimizing sub-microsecond gates in microtrap architectures, the proposed schemes achieve orders-of-magnitude-higher fidelities than previous proposals. Finally, we investigate the impact of pulse imperfections on gate fidelity and evaluate error bounds for a range of gate speeds.
This chapter reviews the construction, modification, and physical characteristics of two types of diamond electrodes: nanoparticle-modified diamond electrodes (NMDE) and detonation nanodiamond-based electrodes (DNDE). These particular types of diamond electrodes show great promise for improving the performance of diamond electrodes via the incorporation of nano-scale chemistry at their surfaces. The construction of both types of electrodes is reviewed, along with the resultant physical and electronic effects. The methods reviewed here are particularly applicable for electroanalytical and electrocatalytic applications of nanoparticle-based diamond electrodes. A brief review of progress on the interactions between metals and diamond at nanoparticle-based electrodes is also included. Finally, an outline of the present state-of-the art research in this field is presented.
