Precise control over the position of a single quantum object is important for many experiments in quantum science and nanotechnology. We report on a technique for high-accuracy positioning of individual diamond nanocrystals. The positioning is done with a home-built nanomanipulator under real-time scanning electron imaging, yielding an accuracy of a few nanometers. This technique is applied to pick up, move, and position a single nitrogen-vacancy ͑NV͒ defect center contained in a diamond nanocrystal. We verify that the unique optical and spin properties of the NV center are conserved by the positioning process. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3120558͔The coupling of a single quantum object to degrees of freedom in its environment is a central theme in quantum science and engineering. Examples are the coupling of a single-photon source to an optical resonator 1,2 or to a plasmonic waveguide, 3 and the coupling of a single spin to surrounding spins. 4,5 Studying and engineering such couplings is not only of fundamental interest, but may also lead to dramatic improvements in fluorescence detection efficiency, 6 ultrasensitive magnetometry, 7-11 and applications in quantum information processing.2,12,13 Controlled and precise positioning of the quantum object under study is essential for many of these experiments.Examples of well-studied single-photon emitters in a solid-state environment are quantum dots, fluorescing dye molecules, and nitrogen-vacancy ͑NV͒ centers in diamond. In particular NV centers, which consist of a substitutional nitrogen atom next to an adjacent vacancy in the diamond lattice, are extremely stable sources of single photons.14,15 In addition, they have the unique property of a paramagnetic spin whose quantum state can be read out optically using fluorescence microscopy 16 and be coherently controlled using magnetic resonance. 17 Crucially, all these properties are retained under ambient conditions. Since NV centers can form in nanocrystals as small as 10 nm, 18 their position can in principle be controlled with an accuracy of a few nanometers.The potential of NV centers for quantum optical experiments is underlined by recent reports demonstrating coupling to confined optical modes of a microsphere 19,20 and a microdisk cavity. 21 In these experiments, however, the positioning accuracy of the diamond nanocrystals was determined by the resolution of the optical setup ͑ϳ500 nm͒, whereas subwavelength resolution is desired.Here, we demonstrate a versatile technique to position a single NV center contained in a diamond nanocrystal to an arbitrary location. We locate and characterize diamond nanocrystals with single NV centers using a scanning confocal microscope. Subsequently, we use a home-built nanomanipulator, consisting of a sharp probe mounted on a piezoelectrically controlled system inside a scanning electron microscope ͑SEM͒, for picking up and positioning the nanocrystal with nanometer precision. This technique is directly applicable to studies of the coupling of a s...
We implement a strong optical nonlinearity using electromagnetically-induced transparency in cold atoms, and measure the resulting nonlinear phase shift for postselected photons. We believe that this represents the first direct measurement of the cross-phase shift due to individual photons.
Electromagnetically-induced transparency (EIT) has been proposed as a way to greatly enhance cross-phase modulation, with the possibility of leading to few-photon-level optical nonlinearities. This enhancement grows as the transparency window width, ∆EIT , is narrowed. Decreasing ∆EIT , however, increases the response time of the effect, suggesting that for pulses of a given duration, there could be a fundamental limit to the strength of the nonlinearity. We show that in the regimes of most practical interest -narrow EIT windows perturbed by short signal pulses-the enhancement offered by EIT is not only in the magnitude of the nonlinear phase shift but in fact also in its increased duration. That is, for the case of signal pulses much shorter (temporally) than the inverse EIT bandwidth, the narrow window serves to prolong the effect of the passing signal pulse, leading to an integrated phase shift that grows linearly with 1/∆EIT even though the peak phase shift may saturate; the continued growth of the integrated phase shift improves the detectability of the phase shift, in principle without bound. For many purposes, it is this detectability which is of interest, more than the absolute magnitude of the peak phase shift. We present analytical expressions based on a linear time-invariant model that accounts for the temporal behavior of the cross-phase modulation for several parameter ranges of interest. We conclude that in order to optimize the detectability of the EIT-based cross-phase shift, one should use the narrowest possible EIT window, and a signal pulse that is as broadband as the excited state linewidth and detuned by half a linewidth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.