Low-Frequency Quantum Sensing

TL;DR: In this article , a quantum double-lock-in amplifier with two quantum mixers under orthogonal pulse sequences is proposed, where the two mixers act the roles of two reference signals in a classical double-locksin amplifier.

Abstract: The silicon vacancy center in Silicon Carbide (SiC) provides an optically addressable qubit at room temperature in its spin-32\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\frac{3}{2}$$\end{document} electronic state. However, optical spin initialization and readout are less efficient compared to those of spin-1 systems, such as nitrogen-vacancy centers in diamond, under non-resonant optical excitation. Spin-dependent fluorescence exhibits contrast only between ∣m=±3/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| m=\pm 3/2\left.\right\rangle$$\end{document} and ∣m=±1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| m=\pm 1/2\left.\right\rangle$$\end{document} states, and optical pumping does not create a population difference between ∣+1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| +1/2\left.\right\rangle$$\end{document} and ∣−1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| -1/2\left.\right\rangle$$\end{document} states. Thus, operating one qubit (e.g., ∣+3/2,∣+1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left\{| +3/2\left.\right\rangle ,| +1/2\left.\right\rangle \right\}$$\end{document} states) leaves the population in the remaining state (∣−1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| -1/2\left.\right\rangle$$\end{document}) unaffected, contributing to background in optical readout. To mitigate this problem, we propose a sensing scheme based on duplex qubit operation in the quartet, using microwave pulses with two resonant frequencies to simultaneously operate ∣+3/2,∣+1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left\{| +3/2\left.\right\rangle ,| +1/2\left.\right\rangle \right\}$$\end{document} and ∣−1/2,∣−3/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left\{| -1/2\left.\right\rangle ,| -3/2\left.\right\rangle \right\}$$\end{document}. Experimental results demonstrate that this approach doubles signal contrast in optical readout and improves sensitivity in AC magnetometry compared to simplex operation.

TL;DR: In this paper, the use of diamond impurity centres as magnetic field sensors is explored, promising a new approach to single-spin detection and magnetic-field imaging at the nanoscale.

TL;DR: In this article, the fluorescence of individual nitrogen-vacancy defect centers in diamond was observed with room-temperature scanning confocal optical microscopy, and the centers were photostable, showing no detectable change in their fluorescence emission spectrum as a function of time.

TL;DR: The physical principles that allow for magnetic field detection with NV centres are presented and first applications of NV magnetometers that have been demonstrated in the context of nano magnetism, mesoscopic physics and the life sciences are discussed.

TL;DR: In this paper, a new molecular beam resonance method using separated oscillating fields at the incident and emergent ends of the homogeneous field region is theoretically investigated and an expression is obtained for the quantum mechanical transition probability of a system between two states when the system is subjected to such separated oscillators.