Detecting Initial Correlations via Correlated Spectroscopy in Hybrid Quantum Systems

Generic mesoscopic quantum systems that interact with their environment tend to display appreciable correlations with environment that often play an important role in the physical properties of the system. However, the experimental methods needed to characterize such systems either ignore the role of initial correlations or scale unfavourably with system dimensions. Here, we present a technique that is agnostic to system-environment correlations and can be potentially implemented experimentally. Under a specific set of constraints, we demonstrate the ability to detect and measure specific correlations. We apply the technique on a hybrid quantum system of Nitrogen Vacancy Centers (NV) coupled to an optical cavity with initial correlations. We extract the interaction strength and effective number of interacting NVs from the initial correlations using our technique.Comment: 15 pages, comments welcom

High-Performance Silicon-Based Multiple Wavelength Source

We demonstrate a stable CMOS-compatible on-chip multiple-wavelength source by filtering and modulating individual lines from a frequency comb generated by a microring resonator optical parametric oscillator.. We show comb operation in a low-noise state that is stable and usable for many hours. Bit-error rate measurements demonstrate negligible power penalty from six independent frequencies when compared to a tunable diode laser baseline. Open eye diagrams confirm the fidelity of the 10 Gb/s data transmitted at the comb frequencies and the suitability of this device for use as a fully integrated silicon-based WDM source.Comment: 3 pages, 3 figure

Decoupling Nuclear Spins via Interaction-Induced Freezing in Nitrogen Vacancy Centers in Diamond

Nitrogen Vacancy (NV) centers in diamonds provide an ideal room-temperature platform for emulating a wide range of quantum phenomena. The ability to initialize, control, and readout proximal nuclear spins using the NV center's electron spin make it possible to emulate more complex features. A recent proposal based on Rydberg atoms presented a novel effect in the strong-interaction regime, named Rydberg-biased freezing, where the dynamics of a Rydberg atom freezes when two strongly interacting Rydberg atoms are driven by laser fields with very different Rabi frequencies. We simulate an analogous interaction-induced freezing phenomenon in an NV center system where the state dynamics of the NV center's intrinsic nuclear spin freezes when the electron and nuclear spins are simultaneously driven with unequal Rabi frequencies. We develop on this idea and show that the NV nuclear spin can also be effectively shielded from strong drive or noise fields in the frozen regime. Further, we present the evolution of quantum correlations in the electron-nuclear spin system by measuring its quantum discord and observe a clear suppression of quantum correlations in this regime. We conclude that the interaction-induced freezing phenomenon can decouple nuclear spins from stray fields and minimize their correlation with the NV electron spin. This can be instrumental in extending the storage times of NV nuclear-spin-based quantum memories in hybrid quantum systems

Enhanced Two-Photon Absorption in a Hollow-Core Photonic Bandgap Fiber

We show that two-photon absorption (TPA) in Rubidium atoms can be greatly enhanced by the use of a hollow-core photonic bandgap fiber. We investigate off-resonant, degenerate Doppler-free TPA on the 5S1/2 - 5D5/2 transition and observe 1% absorption of a pump beam with a total power of only 1 mW in the fiber. These results are verified by measuring the amount of emitted blue fluorescence and are consistent with the theoretical predictions which indicate that transit time effects play an important role in determining the two-photon absorption cross-section in a confined geometry.Comment: 5 pages, 6 figure

Optothermal Trapping of Fluorescent Nanodiamonds using a Drop-casted Gold Nanoparticle

Deterministic optical manipulation of fluorescent nanodiamonds (FNDs) in a fluid environment has emerged as an experimental challenge in multimodal biological imaging. The design and development of nano-optical trapping strategies to serve this purpose is an important task. In this letter, we show how a drop-casted gold nanoparticle (Au np) can facilitate optothermal potential to trap individual entities of FNDs using a low power density illumination (532nm laser, 0.1 mW/$\mu$m$^2$). We utilize the same trapping excitation source to capture the spectral signatures of single FNDs and track their position. Furthermore, by tracking the dynamics of FND, we measure the trapping stiffness as a function of laser power and surfactant concentration and emphasize their relevance as vital parameters for nano-manipulation. Our trapping configuration combines the thermoplasmonic fields generated by individual gold nanoparticles and the optothermoelectric effect facilitated by surfactants to realize a nano-optical trap down to a single FND 120 nm in size. We envisage that our drop-casting platform can be extrapolated to perform targeted, low-power trapping, manipulation, and multimodal imaging of FNDs inside biological systems such as cells.Comment: 17 pages, 4 figures, 3 tables. Supplementary videos may be found at: https://drive.google.com/drive/folders/1gkW9g5Z7Fhl4i3ZQUOBQYuUYAPrHykzY?usp=sharin