Background and Purpose Silicon vacancies (VSi) in silicon carbide (SiC) have attracted great attention because we can measure magnetic field and temperature in some devices by fabricating VSi in the devices1,2. Simultaneous measurement of magnetic field and temperature using SiC-VSi quantum sensor requires simultaneous Optically Detected Magnetic Resonance (ODMR) measurement of the ground and excited states. However, the ODMR contrast (= sensitivity) of the excited state is about one order of magnitude smaller than that of the ground state. So, the temperature measurement is time-consuming. To solve this problem, we have proposed and demonstrated a new temperature measurement method, Simultaneous Resonance (SR) ODMR, which based on the modulation of the ODMR contrast of the ground state by simultaneous resonance of the ground and excited states3. This method converts part of the contrast of the ground state into that of the excited state. In order to perform magnetic field and temperature measurements with high sensitivity, it is necessary to optimize the RF power ratio which is related to the contrast ratio between the ground and excited states to minimize the measurement time. Therefore, the purpose of our study is to optimize the power ratio of the RF using the simultaneous measurement by SR ODMR. Methods and Results VSi dots were fabricated on p-type 4H-SiC epitaxial thin film (5.6 µm) using a particle beam writing (ion species: He, Energy: 0.5 MeV, irradiation dose: 3×105 /dots). The size and depth of the dots are 5×5 µm2 and ~1 µm, respectively. Three signal generators were used for the measurements, one fixed at the resonance frequency of the ground state (70 MHz) for SR, and the others swept near those of the ground and excited states (20-170, 300-600 MHz) for the ground state and SR ODMR measurements, respectively. Figure 1 shows the spectra of ground and SR excited states by ODMR simultaneous measurements. Signal intensities indicated by red and blue arrows are observed. The former is a resonance of the ground state, and the latter is that of the excited states. We can find that another dip indicated by green arrow around 500 MHz exists. The sweep condition indicates that this frequency corresponds to 70 MHz of the ground state measurement. This suggests that the resonance of the ground state occurs in both the ground state and SR ODMR measurements. As a result of their competition, the dip appears at around the 500 MHz on the SR ODMR side. We measured the changing of ODMR contrast of the ground and excited states when we change the RF power of signal generators. The signal intensity was almost the same at the RF power ratio of 1:9 for SR and ground state ODMR. At this condition, the contrast of SR is more than four times that of traditional excited state measurement. This suggests that we achieved faster measurement than conventional simultaneous ground and excited states measurement.
【要約】 量子力学におけるデコヒーレンス理論は、従来、対象系と無限の自由度を持つ外部環境とのエンタングルメントに依存して説明されてきた。しかし、このアプローチは全宇宙のような閉鎖系に適用できず、古典的観測値への境界(ハイゼンベルク切断)の物理的実体を提示できないという根本的な課題を抱えている。 本研究では、時空そのものが持つ情報キャリアの有限性に着目し、最小解像度スケール を持つガウス窓関数を用いた離散サンプリング写像モデルを提案する。連続波動関数から格子上の有効密度行列への変換を解析的に計算した結果、空間的に距離 離れた非対角項(コヒーレンス)が幾何学的抑制因子 によって指数関数的に減衰し、マクロスケール( )において自動的に消滅することが厳密に示された。 さらに、ナイキスト限界を超える高周波成分は基本帯域へエイリアシングとして射影され、激しい自己位相干渉によって熱化(位相キャンセレーション)を引き起こす。これにより、環境系への情報の散逸を仮定することなく、純粋な情報幾何学的制約のみから「客観的な波束の収縮」と「ボルン規則に基づく対角項の保存」が必然的な数理的帰結として導かれる。本モデルは、主観的な観測者やアドホックな境界線を必要とせず、ミクロとマクロの力学を単一の枠組みでシームレスに統合する新たな基盤を提供する。 I. INTRODUCTIONThe quantum measurement problem remains one ofthe deepest foundational issues in physics. Whileenvironment-induced decoherence successfully explainsthe rapid diagonalization of reduced density matrices foropen quantum systems, it suffers from severe limitationswhen applied to the entire universe as a closed system,where no external environment exists.Objective collapse models, such as the Ghirardi-Rimini-Weber (GRW) and Continuous Spontaneous Lo-calization (CSL) frameworks, introduce ad-hoc stochasticjumps or classical white noise fields to restore macroreal-ism. However, these mechanisms introduce non-unitaryphenomenological parameters without geometric origin.In this work, we propose that objective decoherence isa natural consequence of the finite information-carryingcapacity and spatial resolution of background spacetime.By utilizing Shannon-Nyquist sampling theory and har-monic analysis, we show that classicality emerges deter-ministically from geometric projections onto discrete lat-tice representations.
For high-bias operation devices such as silicon carbide (SiC) power devices, early detection of failure mechanisms is essential to ensure reliability. This requires a method to map high electric fields with high spatial resolution, which has not been realized until now. Here we report that the silicon vacancy (Vsi) in SiC has outstanding characteristics for detecting electric fields applied in various directions within a high-biased SiC device. Vsi exhibits an equivalent response to electric field components parallel (Epara) and perpendicular (Eperp) to the c-axis, a feature unique among quantum sensors, and the responsiveness to Epara and Eperp enables detection of arbitrary electric fields encountered in cutting-edge SiC power devices. We confirmed high electric field detection of ~2.3 MV/cm, which is ~90% of the breakdown electric field of a 4H-SiC with typical carrier concentration. Selectively formed Vsi enables high-resolution mapping of electric field distribution. Vsi-based quantum sensors bring data-driven research and development methodologies as well as device degradation diagnosis.
We highlight our work [1] on nanophotonic integration of color centers in semiconductor silicon carbide (SiC). We show ion-assisted implantation and waveguide-integration of silicon vacancy centers (VSi) in 4H-SiC with nearly lifetime limited optical lines and record spin coherence times. We further show controlled coupling to nearby nuclear spin qubits. Our experiments can be performed at high temperatures (T=20 K), thus enabling fast and direct nuclear spin control. Our work shows that VSi centers in SiC are attractive for developing next-generation quantum (computational) networks based on optically interconnected spin-based qubit clusters. [1] Babin et al, Nature Materials, to appear (2021)