arXiv subjects

Bao-Sen Shi

Publications and source records attributed to Bao-Sen Shi.

At least 145 records · Page 8Linked to original sources

arXiv2014

An optical fan for light beams for high-precision optical measurements and optical switching

The polarization and orbital angular momentum properties of light are of great importance in optical science and technology in the fields of high precision optical measurements and high capacity and high speed optical communications. Here we show, a totally new method, based on a combination of these two properties and using the thermal dispersion and electro-optical effect of birefringent crystals, the construction of a simple and robust scheme to rotate a light beam like a fan. Using a computer-based digital image processing technique, we determine the temperature and the thermal dispersion difference of the crystal with high resolution. We also use the rotation phenomenon to realize thermo-optic and electro-optic switches. The basic operating principles for measurement and switching processes are presented in detail. The methods developed here will have wide practical applicability in various fields, including remote sensing, materials science and optical communication networks.

physics.optics↗

arXiv2014

Quantum Storage of Orbital Angular Momentum Entanglement in an Atomic Ensemble

Constructing a quantum memory for a photonic entanglement is vital for realizing quantum communication and network. Besides enabling the realization of high channel capacity communication, entangled photons of high-dimensional space are of great interest because of many extended applications in quantum information and fundamental physics fields. Photons entangled in a two-dimensional space had been stored in different system, but there have been no any report on the storage of a photon pair entangled in a high-dimensional space. Here, we report the first experimental realization of storing an entangled orbital angular momentum (OAM) state through a far off-resonant two-photon transition (FORTPT) in a cold atomic ensemble. We reconstruct the matrix density of an OAM entangled state postselected in a two-dimensional subspace with a fidelity of 90.3%+/-0.8% and obtain the Clauser, Horne and Shimony and Holt inequality parameter S of 2.41+/-0.06 after a programmed storage time. All results clearly show the preservation of entanglement during the storage. Besides, we also realize the storage of a true-single-photon via FORTPT for the first time.

quant-ph↗

arXiv2013

Image cloning beyond diffraction based on coherent population trapping in a hot Rubidium vapor

Following the recent theoretical predictions given in a paper [PRA 88, 013810 (2013)], we reported on an experimental realization of an image cloning beyond usual diffraction through coherent population trapping (CPT) effect in a hot rubidium vapor. In our experiment, an alphabet image was transferred from a coupling field to a probe field based on the CPT effect. Furthermore, we demonstrated that the cloned probe field carrying the image transmitted without usual diffraction. To our best knowledge, there is no any such an experimental report about images cloning beyond diffraction. We believe this mechanism based on CPT definitely has important applications in image metrology, image processing and biological imaging.

quant-ph↗

arXiv2013

Storing High-Dimensional Quantum States in a Cold Atomic Ensemble

The reversible transfer of the quantum information between a photon, an information carrier, and a quantum memory with high fidelity and reliability is the prerequisite for realizing a long-distance quantum communication and a quantum network. Encoding photons into higher-dimensional states could significantly increase their information-carrying capability and network capacity. Moreover, the large-alphabet quantum key distribution affords a more secure flux of information. Quantum memories have been realized in different physical systems, such as atomic ensembles and solid systems etc., but to date, all quantum memories only realize the storage and retrieval of the photons lived in a two-dimensional space spanned for example by orthogonal polarizations, therefore only a quantum bit could be stored there. Here, we report on the first experimental realization of a quantum memory storing a photon lived in a three-dimensional space spanned by orbital angular momentums via electromagnetically induced transparency in a cold atomic ensemble. We reconstruct the storage process density matrix with the fidelity of 85.3% by the aid of a 4-f imaging system experimentally. The ability to store a high-dimensional quantum state with high fidelity is very promising for building a high-dimensional quantum network.

quant-ph↗

arXiv2013

Single-Photon-Level Quantum Image Memory Based on Cold Atomic Ensembles

An important step towards the successful development of network that allows the distribution of quantum information is the storage of light in a matter at the single-photon level. Encoding photons in high-dimensional photonic states can significantly increase their information-carrying capacity. So far, there is no any report on the storage of an image at true single photon level, realizing a quantum memory that can record the shape of a single photon is a challenging work. In this work, we report on the first experimental realization of storing a true single photon carrying an orbital angular momentum via electromagnetically induced transparency in a cold atomic ensemble and retrieved later after a given storage time. We experimentally not only prove the preservation of the property of the single photon, but also show very good similarity on the spatial structures of the input and the retrieved photons. More importantly, we also demonstrate the preservation of the coherence of the single photon during the storage using a Sagnac interferometer. The demonstrated capability of storing a spatial structure at single-photon-level opens the possibility to the realization of a high-dimensional quantum memory.

quant-ph↗

arXiv2013

Multimode image memory based on a cold atomic ensemble

Quantum memory is one of key ingredients consisting of quantum networks, therefore storing light at single photon level is an important step for realizing quantum networks. A photon, encoded in a high-dimensional state, can significantly increase the information capacity that a photon can carry. Furthermore, quantum memories with the ability to store multiple optical modes offer advantages in speed and robustness over single mode memories in quantum communication and computation. So far, there is no any report about the storage and retrieval of multiple mode images at single photon level. Here, we give a first experimental demonstration to our best knowledge, that two spatial probe fields at single photon level, each imprinted a real image, can be stored and retrieved with a considerable visibility and similarity through electromagnetically induced transparency in cold atomic ensemble. The accomplishment of multiple modes quantum image memory would move closer towards high dimensional quantum networks.

quant-ph↗

arXiv2013

Actively switchable non-degenerate polarization entangled photon pair distribution in a dense wave-division multiplexing

We have realized experimentally a non-degenerate polarization-entangled photon pair distribution in a commercial telecom dense wave-division multiplexing device (DWDM) with 8 channels. A promising point of this work is that the entangled photon pair is obtained via spontaneously parametric down conversion in a single type-II periodically poled KTiOPO4 crystal without usual post-selection. Another promising advantage is that we can actively control and switch the distribution of the photon pair between different channel pairs in DWDM at will. There is no crosstalk between the different channel pair because of a limited emission bandwidth of the source. High raw visibility of greater than 90% in Bell-type interference measurement in each channel pair and the CHSH inequality S parameter of 2.63+/-0.08 prove high entanglement of our source. Our work is helpful for building quantum communication networks.

quant-ph↗

arXiv2013

Ultra-broadband continuously-tunable polarization entangled photon pair source covering the C+L telecom bands based on a single type-II PPKTP crystal

In this work, we report on the preparation of an ultra-broadband continuously-tunable, highly polarization-entangled photon-pair source covering the C+L telecom bands using a single type-II phase-matched bulk PPKTP crystal. Over 60 nm turning band of the down-converted photons is achieved experimentally. The broad tuning ability is due to operating near an extended phase match point in this crystal. The S parameter value of CHSH inequality is in the range between 2.60+/-0.04 (minimum) and 2.72+/-0.07 (maximum), which clearly demonstrates the high entanglement of the source over the whole tunable range. This is the first realization of such a broadband tunable degenerate polarization entanglement pair source in the telecom band. Combined with dense wavelength-division multiplexing technique, our source could be used to improve the transmission capacity of a single communication channel in the field of quantum communication.

quant-ph↗

arXiv2013

Light storage based on four-wave mixing and electromagnetically induced transparency in cold atoms

We performed an experiment to observe the storages of an input probe field and an idler field generated through an off-axis four-wave mixing (FWM) process via a double-lambda configuration in a cold atomic ensemble. We analyzed the underlying physics in detail and found that the retrieved idler field came from two parts if there was no single-photon detuning for pump pulse: part 1 was from the collective atomic spin (the input probe field, the coupling field and the pump field combined to generate the idle field through FWM, then the idler was stored through electromagnetically induced transparency.); part 2 was from the generated new FWM process during the retrieval process (the retrieved probe field, the coupling field and the pump field combined to generate a new FWM signal). If there was single-photon detuning for pump pulse, then the retrieved idler was mainly from part 2. The retrieved two fields exhibited damped oscillations with the same oscillatory period when a homogeneous external magnetic field was applied, which was caused by the Larmor spin precession. We also experimentally realized the storage and retrieval of an image of light using FWM for the first time. In which, an image was added into the input signal. After the storage, the retrieved idler beams and input signal carried the same image. This image storage technique holds promises for application in image processing, remote sensing and quantum communication.

physics.atom-ph↗

arXiv2012

Efficient infrared upconversion via a ladder-type atomic configuration

We have demonstrated experimentally that infrared light at 1529.4nm can be converted into the visible at 780nm with 54% efficiency through a ladder-type atomic configuration in 85Rb. Specifically we theoretically analyze that high efficiency is due to the large nonlinear dispersion of the index of refraction from the off-resonant enhancement in a four-wave mixing (FWM) process. By using two perpendicular polarized pump fields, the coherence of two FWM processes in this configuration is verified.

physics.optics↗

arXiv2012

Storage and retrieval of a light in telecomband in a cold atomic ensemble

A telecom photon is a suitable information carrier in a fiber-based quantum network due to its lower transmission loss in fiber. Because of the paucity of suitable atomic system, usually the photon connecting different memories is in near infrared band, therefore the frequency conversion of the photon in and out of telecomband has to be required to realize the interface between the atomic-based memory and the photon-based carrier. In order for that, two atomic or other systems which could realize the frequency conversion have to be taken into account, and besides, one more atomic system as a storing media is need. So the ability of storing a photon in telecomband is an interesting and exciting topic. In this work, we give a first experimental proof of principle of storing a light in telecomband. The telecom light is directly stored and retrieved later through two nonlinear processes via an inverted-Y configuration in a cold atomic ensemble, therefore the interface between the memory and photon in other proposals is not needed. We believe our work may open a new avenue for long-distance quantum communication.

physics.optics↗

arXiv2012

Bichromatic field generation from double-four-wave mixing in a double-electromagnetically induced transparency system

We demonstrate the double electromagnetically induced transparency (double-EIT) and double four-wave mixing (double-FWM) based on a new scheme of non-degenerate four-wave mixing (FWM) involving five levels of a cold 85Rb atomic ensemble, in which the double-EIT windows are used to transmit the probe field and enhance the third-order nonlinear susceptibility. The phase-matching conditions for both four-wave mixings could be satisfied simultaneously. The frequency of one component of the generated bichromatic field is less than the other by the ground-state hyperfine splitting (3GHz). This specially designed experimental scheme for simultaneously generating different nonlinear wave-mixing processes is expected to find applications in quantum information processing and cross phase modulation. Our results agree well with the theoretical simulation.

physics.optics↗

arXiv2012

Multiple images storage and frequency conversion in a cold atomic ensemble

The strong demand for quantum memory, a key building block of quantum network, has inspired new methodologies and led to experimental progress for quantum storage. The use of quantum memory for spatial multimode or image storage could dramatically increase the channel bit-rate. Furthermore, quantum memory that can store multiple optical modes would lead to higher efficiencies in quantum communication and computation. Here, by using resonant tripod electromagnetically induced transparency in a cold atomic ensemble, we experimentally demonstrate multiple probes storage in frequency domain, where two probe fields have discrete wavelengths and different spatial information. In addition, by using different read-light, we realize frequency conversion of retrieved images with high efficiency. Besides, our method could be used to create a superposition of the images by realizing the function of a beamsplitter. All advantages make our method useful in many fields including quantum information, detection, imaging, sensing and even astrophysical observation.

quant-ph↗

arXiv2012

Experimental Upconversion of Images

We experimentally demonstrate the up-conversion of light carrying an image from the infrared spectrum to the visible spectrum using four-wave mixing via a ladder-type configuration in an atomic vapor. The results we obtained show the high correlation between the input image and the up-converted image. We also discuss the possible influences of experimental parameters on the resolution. Our work might be useful for research in astrophysics, night-vision technology, and chemical sensing.

physics.optics↗

arXiv2012

Linear Up-conversion of Orbital angular momentum

We experimentally demonstrated that infrared light imprinted with orbital angular momentum (OAM) was linearly converted into visible light using four-wave mixing (FWM) via a ladder-type configuration in 85Rb atoms. Simultaneously, we theoretically simulated this linear conversion process, and the theoretical analysis was in reasonable agreement with the experimental results. A large single-photon detuning process was used to reduce the absorption of the atoms to the up-converted light and to avoid pattern formation in the FWM process. The multi-mode image linear conversion process is important for applications including image communications, astrophysics and quantum information.

physics.optics↗

arXiv2012

Image Transfer through Two Sequential Four-Wave Mixing in a Hot Atomic Vapor

Efficient wavelength conversion of images has many potential applications in optical communication, sensing, imaging, and quantum information fields. In this work, we report on here the first demonstration of an image transfer between the light of wavelength 780 nm and the light of wavelength 1530 nm by performing two sequential four-wave mixing processes in two different hot atomic rubidium vapor cells. Furthermore, we confirm the persistence of coherence of the input light during this sequential process experimentally. Our results may be useful to the research fields mentioned above.

physics.optics↗

arXiv2012

Generation of non-classical correlated photon pairs via a ladder-type atomic configuration: theory and experiment

We experimentally generate a non-classical correlated two-color photon pair at 780 and 1529.4 nm in a ladder-type configuration using a hot 85Rb atomic vapor with the production rate of ~107/s. The non-classical correlation between these two photons is demonstrated by strong violation of Cauchy-Schwarz inequality by the factor R=48+-12. Besides, we experimentally investigate the relations between the correlation and some important experimental parameters such as the single-photon detuning, the powers of pumps. We also make a theoretical analysis in detail and the theoretical predictions are in reasonable agreement with our experimental results.

quant-ph↗

arXiv2011

Multipartite continuous-variable entanglement distillation using local squeezing and only one photon-subtraction operation

In this paper, we study entanglement distillation of multipartite continuous-variable Gaussian entangled states. Following Opatrný \emph{et al.}'s photon subtraction (PS) scheme, the probability of successful distillation decreases exponentially with the number of parties $N$. However, here, we shall propose an entanglement distillation scheme whose success probability scales as a constant with $N$. Our protocol employs several local squeezers, but it requires only a single PS operation. Using the logarithmic negativity as a measure of entanglement, we find that both the success probability and the distilled entanglement can be improved at the same time. Moreover, an $N$-mode transfer theorem (transferring states from phase space to Hilbert space) is presented.

quant-ph↗