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International Conference on Communications, Circuits and Systems

Impact of Magnetic Field and Noises on Rabi Oscillation of Spin Qubit in Nitrogen-Vacancy Center in Diamond

Islam Jubaidul, Amsyar Rahim, C. Wei

Published May 23, 2025• 0 citations
Publisher

Abstract

Quantum computing holds the potential to outperform classical computing in certain complicated tasks by leveraging qubits and their manipulation through quantum gates. A compelling platform to physically realize qubits and their control is the Nitrogen-Vacancy (NV) center in diamond, where Rabi oscillation of spin qubit enables effective quantum operations. However, a significant challenge lies in mitigating qubit decoherence caused by external factors. Hence, this paper reports on the experimental demonstration of Rabi oscillation of spin qubit in NV center in diamond, focusing on investigating the impact of magnetic field and noises. Experiments conducted using CIQTEK Diamond Quantum Computer for Education (CIQTEK is a China quantum company) reveal that the magnetic field significantly impacts the resonant frequency which must align with the microwave pulse to observe clear Rabi oscillations. However, despite careful frequency tuning, noises from several sources lead to qubit decoherence, disrupting Rabi oscillations and causing them to decay over time. These results provide insights into key factors affecting qubit performance, paving the way in developing strategies to minimize decoherence.

DOI
10.1109/icccas65806.2025.11102615

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Quantum computing holds the potential to outperform classical computing in certain complicated tasks by leveraging qubits and their manipulation through quantum gates. A compelling platform to physically realize qubits and their control is the Nitrogen-Vacancy (NV) center in diamond, where Rabi oscillation of spin qubit enables effective quantum operations. However, a significant challenge lies in mitigating qubit decoherence caused by external factors. Hence, this paper reports on the experimental demonstration of Rabi oscillation of spin qubit in NV center in diamond, focusing on investigating the impact of magnetic field and noises. Experiments conducted using CIQTEK Diamond Quantum Computer for Education (CIQTEK is a China quantum company) reveal that the magnetic field significantly impacts the resonant frequency which must align with the microwave pulse to observe clear Rabi oscillations. However, despite careful frequency tuning, noises from several sources lead to qubit decoherence, disrupting Rabi oscillations and causing them to decay over time. These results provide insights into key factors affecting qubit performance, paving the way in developing strategies to minimize decoherence.
The coherent control of spin qubits forms the basis of many applications in quantum information processing and nanoscale sensing, imaging, and spectroscopy. Such control is conventionally achieved by direct driving of the qubit transition with a resonant global field, typically at microwave frequencies. Here we introduce an approach that relies on the resonant driving of nearby environment spins, whose localized magnetic field in turn drives the qubit when the environmental spin Rabi frequency matches the qubit resonance. This concept of environmentally mediated resonance (EMR) is explored experimentally using a qubit based on a single nitrogen-vacancy (NV) center in diamond, with nearby electronic spins serving as the environmental mediators. We demonstrate EMR driven coherent control of the NV spin state, including the observation of Rabi oscillations, free induction decay, and spin echo. This technique also provides a way to probe the nanoscale environment of spin qubits, which we illustrate by acquisition of electron spin resonance spectra from single NV centers in various settings.
Abstract Nitrogen vacancy (NV) centers, optically active atomic defects in diamond, have attracted tremendous interest for quantum sensing, network, and computing applications due to their excellent quantum coherence and remarkable versatility in a real, ambient environment. One of the critical challenges to develop NV-based quantum operation platforms results from the difficulty in locally addressing the quantum spin states of individual NV spins in a scalable, energy-efficient manner. Here, we report electrical control of the coherent spin rotation rate of a single-spin qubit in NV-magnet based hybrid quantum systems. By utilizing electrically generated spin currents, we are able to achieve efficient tuning of magnetic damping and the amplitude of the dipole fields generated by a micrometer-sized resonant magnet, enabling electrical control of the Rabi oscillation frequency of NV spins. Our results highlight the potential of NV centers in designing functional hybrid solid-state systems for next-generation quantum-information technologies. The demonstrated coupling between the NV centers and the propagating spin waves harbored by a magnetic insulator further points to the possibility to establish macroscale entanglement between distant spin qubits.
We investigate coherent quantum control of a nitrogen vacancy (NV) center in diamond with microwave fields generated from a nanoscale magnet that is proximal to the NV center. Our results show remarkable coherent control with high contrast Rabi oscillations using nearfield microwaves from shape anisotropic nanomagnets of lateral dimensions down to 200 nm x 180 nm, driven remotely by surface acoustic wave (SAW) excitation that is at least 400 times and potentially 4 orders of magnitude more energy efficient than generating microwaves with an antenna. Furthermore, we show that varying the acoustic power driving such nanomagnets can achieve control over Rabi frequency. We also report spin-lattice relaxation time T1 is 103 +/-0.5 micro-seconds, the spin-spin relaxation time T2 is 1.23+/-0.29 micro-seconds, and the Ramsey coherence time T2* is 218+/-27 nanoseconds measured using microwave pulses generated by such nanomagnets. The use of the nanoscale magnets to implement highly localized and energy efficient coherent quantum control can replace thermally noisy microwave circuits and demonstrate a path to scalable quantum computing and sensing with NV-defects in diamond and other spin qubits.
Abstract Decoherence of Rabi oscillation in a two-level quantum system consists of two components, a simple exponential decay and a damped oscillation. In dense-ensemble spin systems like negatively charged nitrogen-vacancy (NV−) centers in diamond, fast quantum state decoherence often obscures clear observation of the Rabi nutation. On the other hand, the simple exponential decay (or baseline decay) of the oscillation in such spin systems can be readily detected but has not been thoroughly explored in the past. This study investigates in depth the baseline decay of dense spin ensembles in diamond under continuously driving microwave (MW). It is found that the baseline decay times of NV− spins decrease with the increasing MW field strength and the MW detuning dependence of the decay times shows a Lorentzian-like spectrum. The experimental findings are in good agreement with simulations based on the Bloch formalism for a simple two-level system in the low MW power region after taking into account the effect of inhomogeneous broadening. This combined investigation provides new insight into fundamental spin relaxation processes under continuous driving electromagnetic fields and paves ways to better understanding of this underexplored phenomena using single NV− centers, which have shown promising applications in quantum computing and quantum metrology.
Abstract Owing to its remarkable optical properties and its ability to be controlled by microwave fields at room temperature, nitrogen-vacancy (NV) centre in diamond has been a promising platform for various nanotechnological applications, e.g. quantum sensing and magnetic resonance spectroscopy. The qubit associated with the NV centre ground state spin has been the key element for the realisation of such applications. Its coherence time determines the application performances, e.g. the sensitivity of the NV-qubit based quantum sensor. Due to unwanted and unavoidable interactions with noisy environment, the qubit undergoes decoherence that shortens its coherence time and hence reduces its application performance. Therefore, the investigation and mitigation of the decoherence of the NV qubit are of the utmost importance. Here, we simulate the qubit decoherence using Ornstein-Uhlenbeck process that is essential for designing a set of modulating control pulses to mitigate the effect.
Nitrogen-vacancy (NV) centers in diamond as ideally individual spin quantum systems can be coherently manipulated by microwave fields. Compared to the traditional method using the IQ (In-phase/Quadrature) mixer with a local oscillator and intermediate-frequency (IF) signals, we report an effective and technically simple method to generate the required microwave field by frequency multiplication and realize coherent manipulation of the NV center’s electron spin. After frequency multiplication, the IF signal can be directly converted to the high-frequency microwave field with adjustable pulse width, frequency, phase, and amplitude. A series of spin dynamics applications such as Rabi oscillation, free induction decay, and spin-locking are executed, which verified its performance and feasibility. Frequency multiplication can overcome the problem of clock synchronization between the local oscillator and IF signal and greatly reduce the complexity of the experimental system. The method can be easily used to realize a more complex quantum control sequence such as dynamic decoupling and extended to a wide range of spin-based quantum information applications in the future.