arXiv subjects

Xiang-Dong Chen

Publications and source records attributed to Xiang-Dong Chen.

29 records · Page 2Linked to original sources

arXiv2018

Room-temperature Composite-pulses for Robust Diamond Magnetometry

The sensitivity of a practical quantum magnetometer is challenged by both inhomogeneous coupling between sensors and environment and errors in quantum control. Based on the physical criteria of modern quantum sensing, we present a robust and effective composite-pulse for high fidelity operation against inhomogeneous broadening of sensor and control errors via optimized modulation of control field. Such a technique is verified on nitrogen-vacancy (NV) center in diamond to keep almost perfect operation up to a detuning as larger as $110\%$. The sensitivity of the magnetometer with NV center ensemble is experimentally improved by a factor of $4$, comparing to dynamical decoupling with normal rectangular pulse. Our work marks an important step towards high trustworthy ultra-sensitive quantum sensing with imperfect quantum control in realistic systems. The used principle however, is universal and not restricted to NV center ensemble magnetometer.

quant-ph↗

arXiv2018

Non-Markovianity-assisted high-fidelity Deutsch-Jozsa algorithm in diamond

The memory effects in non-Markovian quantum dynamics can induce the revival of quantum coherence, which is believed to provide important physical resources for quantum information processing (QIP). However, no real quantum algorithms have been demonstrated with the help of such memory effects. Here, we experimentally implemented a non-Markovianity-assisted highfidelity refined Deutsch-Jozsa algorithm (RDJA) with a solid spin in diamond. The memory effects can induce pronounced nonmonotonic variations in the RDJA results, which were confirmed to follow a non-Markovian quantum process by measuring the non-Markovianity of the spin system. By applying the memory effects as physical resources with the assistance of dynamical decoupling, the probability of success of RDJA was elevated above 97% in the open quantum system. This study not only demonstrates that the non-Markovianity is an important physical resource but also presents a feasible way to employ this physical resource. It will stimulate the application of the memory effects in non-Markovian quantum dynamics to improve the performance of practical QIP.

quant-ph↗

arXiv2017

Optimal demonstration of Autler Townes splitting

The atom-light interaction in a three-level system has shown significant physical phenomena, such as electromagnetically induced transparency and Autler{Townes splitting (ATS), for broad applications in classical and quantum information techniques. Here, we optimally demonstrated the ATS with a quantum state manipulation method. The ATS in the dephasing-dominated diamond NV center system was successfully recovered by coherent microwave control, which cannot be observed with traditional method. The dynamical process of ATS was investigated in detail, revealing a nontrivial quantum interference with geometric phase modulations. Based on the quantum interference, the signal of the optimal ATS is twice as intense as those with traditional observation method.

quant-ph↗

arXiv2017

Bunching Effect and Quantum Statistics of Partially Indistinguishable Photons

The quantum statistics of particles is determined by both the spins and the indistinguishability of quantum states. Here we studied the quantum statistics of partially distinguishable photons by defining the multi-photon indistinguishability. The photon bunching co-efficient was formulated based on the properties of permutation symmetry, and a modified Bose--Einstein statistics was presented with an indistinguishability induced photon bunching effect. Moreover, the statistical transition of the photon state was studied for partially distinguishable photons, and the results shows the that indistinguishability exhibits the same role as that observed in the generation of laser. The results will fill the gap between Bose--Einstein and Poisson statistics for photons, and a formula is presented for the study of multi-photon quantum information processes.

quant-ph↗

arXiv2017

Indistinguishability-induced classical-to-nonclassical transition of photon statistics

Photon statistics is one of the key properties of the photon state for the study of quantum coherence and quantum information techniques. Here, we discuss the photon indistinguishability induced bunching effect which can significantly change photon statistics. Through the measurement of the second-order degree of coherence of a mixed photon state composed of a single-photon state and a weak coherent state, the statistical transition from a classical behavior to a nonclassical behavior is experimentally demonstrated by modifying the indistinguishability of the two-photon states. The study will help us to understand and control the photon statistics with a method for quantum optical coherence and quantum information applications. It also indicates that the photon indistinguishability is a key parameter for multipartite quantum coherence.

quant-ph↗

arXiv2016

Super-resolution quantum sensing using NV centers based on rotating linear polarized light and Monte-Carlo method

The nitrogen vacancy (NV) center in diamond has been widely applied for quantum information and sensing in last decade. Based on the laser polarization dependent excitation of fluorescence emission, we propose a super-resolution microscopy of NV center. A series of wide field images of NV centers are taken with different polarizations of the linear polarized excitation laser. The fluorescence intensity of NV center is changed with the relative angle between excitation laser polarization and the orientation of NV center dipole. The images pumped by different excitation laser polarizations are analyzed with Monte Carlo method. Then the symmetry axis and position of NV center are obtained with sub-diffraction resolution.

physics.optics↗

arXiv2016

Reviving the precision of multiple entangled probes in an open system by simple $π$-pulse sequences

Quantum metrology with entangled states in realistic noisy environments always suffers from decoherence. Therefore, the measurement precision is greatly reduced. Here we applied the dynamical decoupling method to protect the $N$-qubit quantum metrology protocol and successfully revived the scaling of the measurement precision as ${N^{-k}}$ with $k\in \left[{5/6,11/12}\right]$. The degree of the precision revival, as determined by the noise spectrum distribution, indicates that the performance of the protected protocol can be further improved by controlling the noise spectrum. Such a protected protocol is proved to be universal for entanglement-based quantum metrology in the pure dephasing and relaxation noise, which should stimulate the development of practical quantum metrology for weak signal detection of microscopic physics.

quant-ph↗

arXiv2016

Near-infrared-enhanced charge state conversion for low power optical nanoscopy with nitrogen vacancy center in diamond

The near-infrared (NIR) optical pumped photophysics of nitrogen vacancy (NV) center in diamond was experimentally studied by considering both the charge state conversion and stimulated emission. We found that the NIR laser can help to highly enhance the charge state conversion rate, which can be applied to improve the performance of charge state depletion nanoscopy. Using a doughnut-shaped visible laser beam and a Gaussian-shaped NIR laser beam for charge state manipulation, we developed a low power charge state depletion nanoscopy for NV center. A spatial resolution of 14 nm was achieved with the depletion laser intensity approximately three orders lower than that used for the stimulated emission depletion nanoscopy with NV center. With high spatial resolution and low laser power, the nanoscopy can be used for nanoscale quantum sensing with NV center. And our study on the charge state conversion can help to further optimize the NV center spin state initialization and detection.

physics.optics↗

arXiv2013

Photonic Simulation of System-Environment Interaction: Non-Markovian Process and Dynamical Decoupling

The system-environment interaction is simulated by light propagating in coupled photonic waveguides. The profile of the electromagnetic field provides intuitive physical insight to study the Markovian and non-Markovian dynamics of open quantum systems. The transition from non-Markovian to Markovian process is demonstrated by increasing the size of environment, as the energy evolution changes from oscillating to an exponential decay, and the revival period increases. Moreover, the dynamical decoupling with a sequence of phase modulations is introduced to such a photonic open system to form a band structure in time dimension, where the energy dissipation can be significantly accelerated or inhibited. It opens the possibility to tune the dissipation in photonic system, similar to the dynamic decoupling of spins.

quant-ph↗

arXiv2013

Quantum statistical imaging of particles without restriction of the diffraction limit

A practical quantum measurement method based on the quantum nature of anti-bunching photon emission has been developed to detect single particles without the restriction of the diffraction limit. By simultane- ously counting the single-photon and two-photon signals with fluorescence microscopy, the images of nearby Nitrogen-Vacancy centers in diamond at a distance of 8.5+/-2.4 nm have been successfully reconstructed. Also their axes information was optically obtained. This quantum statistical imaging technique, with a simple exper- imental setup, can also be easily generalized in the measuring and distinguishing of other physical properties with any overlapping, which shows high potential in future image and study of coupled quantum systems for quantum information techniques.

quant-ph↗

arXiv2011

Movable Fiber-Integrated Hybrid Plasmonic Waveguide on Metal Film

A waveguide structure consisting of a tapered nanofiber on a metal film is proposed and analyzed to support highly localized hybrid plasmonic modes. The hybrid plasmonic mode can be efficiently excited through the in-line tapered fiber based on adiabatic conversion and collected by the same fiber, which is very convenient in the experiment. Due to the ultrasmall mode area of plasmonic mode, the local electromagnetic field is greatly enhanced in this movable waveguide, which is potential for enhanced coherence light emitter interactions, such as waveguide quantum electrodynamics, single emitter spectrum and nonlinear optics.

physics.optics↗