Optical excitation of electron spin coherence in nitrogen vacancy (NV) centers is currently being explored for building solid-state optical devices for quantum information processing. This is possible due to the long coherence time of spin in the NV color centers in diamond. Optical systems that can address isolated electron spins in individual color centers and color center ensembles are significantly important for quantum information storage, entanglement generation, and single photon nonlinear interaction. In this project, the team plans to develop an instrument that will interface color centers in diamond nanocrystals with laser excitations to study quantum phenomena both at room and low (~70K) temperatures. In addition to a confocal optical system, a subsystem consisting of tapered fiber-coupled nanocrystals will be used. This takes advantage of the wave guiding property of tapered fibers to optically address the color center ensemble. Both of these instruments will provide single photon detection and measurement capabilities for doing quantum measurements. These will be used to explore coherence properties of nanocrystals for quantum information storage/retrieval, and single photon nonlinear interactions. The instruments will be extensively used in research-related education and training for a large number of underrepresented minority students engaged in STEM research at Delaware State University. The instruments will also be used in extending advanced physics, material science and quantum optics laboratory experiences for undergraduate and graduate students in the Physics & Pre-Engineering department.
Layman Summary: Nitrogen vacancy color centers in diamond are generally considered as defects. Laser excitation of electron spins in a nitrogen vacancy in crystalline diamond exhibits quantum phenomena. This is promising to build solid-state devices for quantum information processing and communication. Single nitrogen vacancy defects can easily be formed in diamond nanocrystals as opposed to a bulk diamond sample. In this project, the team plans to develop instruments that can interface a single as well as a collection of individual nitrogen vacancy defects with laser excitation to build quantum systems. These instruments will be equipped with single photon detection and measurement capabilities to perform quantum measurements. As a specific goal, the team will demonstrate a quantum memory using these instruments as an integral quantum subsystem. Additionally, the instruments will be extensively used to provide research training and education to a large number of underrepresented undergraduate and graduate minority students at Delaware State University. The team plans to incorporate the instruments with several laboratory sessions in graduate courses in Optics. The effort will combine research with broad educational activities involving students and will significantly impact physics and optics-related education at Delaware State.
Normal 0 false false false EN-US X-NONE X-NONE Nitrogen vacancy (NV) defects in diamond nanomaterials produce bright, stable, broadband and anti-bunched fluorescence under optical excitation. NV defect has the unique property that it can be spin polarized by optical excitation, and the spin-state of a single NV defect can be read out optically. These properties create exciting possibilities in nanoscale detection, sensing and imaging applications. In this project, we have developed instruments to study basic properties of NV centers in nanodiamond using laser excitation. Our goal in this effort is to investigate quantum-optical phenomena in diamond impurity spin for constructing novel physical systems for quantum information processing applications. Project Outcomes 1. Our efforts are concentrated in designing and developing systems for performing laser excitations and photon-counting measurements in diamond nanocrystals. Systems with two different laser excitation modalities are developed. i. A free-space confocal optical system with single photon detection and measurement capabilities has been designed. This system is designed to achieve high sensitivity and high resolution by using a high numerical aperture objective lens. Currently, this system is used in our research to investigate laser excitation and optical-addressing of single impurity spin NV center in nanodiamond. The instrument serves as an invaluable tool for exploring fundamental aspects of single NV defects, namely, microwave- and photon-mediated spin polarization, fluorescence inhibited imaging, and isolated single-spin dynamics for creating novel sensing paradigms. ii. A fiber-coupled diamond nanoemitter system has been designed. In this fiber-integrated system, optical excitation in diamond nanoparticles (attached to a tapered fiber surface) is performed by sending the laser either through the fiber or by focusing it from outside the fiber. A flame heating and fiber pulling system has been designed to fabricate tapered optical fiber for this purpose (fig. 1). Unlike its free-space counterpart, the fiber-coupled diamond nanoemitter system has the potential to achieve high coupling efficiency from fluorescent nanodiamonds. We are currently exploring a plasmonic tapered fiber in our system for achieving enhanced sensitivity in particle sensing using single-photon spectroscopy. 2. Different types of nanodiamonds containing NV defects were characterized using spectroscopic techniques. These studies include measurements of bulk absorption and fluorescence properties of nanodiamonds suspended in aqueous solutions. The main objective of these studies is to identify the charge states of NV defects in commercially available samples keeping in mind that negatively-charged NV defects are only suitable for our applications. We have also modified our confocal instrument using an imaging spectrograph to measure the fluorescent properties of an isolated nanocrystal (fig. 2). This instrument generates fluorescence spectrum with high spectral resolution that will allow us to determine the ratio of charged NV defects in the nanocrystal by measuring the intensity ratio for their respective zero-phonon lines (fig. 3). The instrument can also allow us to estimate the concentration of NV centers in a given crystal by directly measuring the fluorescence yield from the nanocrystal. A single NV defect in the nanocrystal is ensured by measuring the second-order intensity correlation function by fiber-delivering the fluorescence output from this system to photon-counting detectors. 3. We have developed a versatile photon detection, counting and measurement capability for exploring various types of quantum-optical phenomena in NV centers in nanodiamond. The measurement and processing capabilities of these single-photon devices and electronic instruments were studied and tested by conducting a basic quantum imaging experiment using a heralded single-photon source. The study facilitated our understanding in conducting quantum measurements using entangled photon pairs and resulted in a research study for completing the M.S. thesis for one of our graduate students. 4. We have successfully used these instruments to provide research training to a number of our students at Delaware State University. The instrument building efforts have had a significant impact on our students in giving them new technical knowledge and knowhow in this field, and helping them in conducting innovative research. The investigators are continuing to use these instruments to carry out their research under a recently awarded NSF CREST subproject entitled ‘Spin Polarization Spectroscopy in Nanodiamond for Nanoscale Sensing and Imaging’. The instruments developed with the support of this NSF MRI award is helping us in forging our research ahead. We will acknowledge this NSF-MRI support in all our future works and publications.
