28 results about "Spontaneous parametric down-conversion" patented technology

A stream of photons from an optical source at a source wavelength are converted into entangled photon pairs via a spontaneous parametric down-conversion process. This produces time-synchronized signal and idler photon pairs which share a nominal wavelength, twice the source wavelength, a common polarization. The signal and idler individually have wavelengths that are equally offset above and below their nominal wavelength. The photons segregated into two paths based on wavelength via a wavelength division multiplexer. A phase modulator in the signal path alters the phase of the signal photon, while the idler photon's phase remains unchanged. By applying a modulation signal to the phase modulator, a quantum message is encoded on the photon pair. A multi-channel wavelength division multiplexer may be used to support multiple channels, each carrying signal-idler pairs conveying a quantum encoded message.

The classical channel employs a transmit laser and classical modulator. The quantum channel employs a nonlinear medium and spontaneous parametric down conversion producing quantum entangled signal and idler photon pairs which are encoded. The classical and quantum channels are combined to define a propagated hybrid signal. The receiver splits the hybrid signal on basis of wavelength into classical and quantum channels. The quantum receiver employs optical parametric amplification, supplied with energy from a second harmonic generation device synchronized to the classical carrier wavelength. A photodetector and extracts a quantum message from the quantum signal.

A quantum entanglement system comprising a laser system, a spontaneous parametric down conversion crystal system, and a thermal management system. The laser system is configured to generate a laser beam. The spontaneous parametric down conversion crystal system comprises a spontaneous parametric down conversion crystal configured to receive the laser beam at a spontaneous parametric down conversion crystal and generate an entangled photon pair in response to the spontaneous parametric down conversion crystal receiving the laser beam. The thermal management system is configured to maintain the spontaneous parametric down conversion crystal at an annealing temperature during a generation of the entangled photon pair. A translation system is configured to move a position of the spontaneous parametric down conversion crystal. A

The invention discloses a rapid biological cell classification imaging method and system based on a quantum correlation diffraction optical neural network, and the method comprises the steps: regulating and controlling a signal photon to an orbital angular momentum state optimized by a neural network based on a time-energy correlation two-photon pair generated in a spontaneous parametric down-conversion process, and irradiating a biological cell sample; a diffractive optical neural network is utilized to construct a quantum state illumination diffractive optical processor, photons carrying cell complex amplitude information are mapped to different detection areas of a predefined image plane, and rapid and high-precision cell classification and recognition are realized through correlation imaging results of an enhanced charge coupled camera. The method has the signal-to-noise ratio and anti-interference capability exceeding the classic limit, can keep high-precision cell classification capability under high background noise, and is suitable for long-time monitoring of living cells under the condition of extremely low light intensity. The method has the characteristics of low energy consumption and high efficiency, and meets the requirements of green calculation and sustainable development. And the method can be used for rapidly classifying and identifying the living biological cells without marks and phototoxicity.

This invention proposes a multi-target detection method based on entangled photons. First, a pump light is generated using a continuous narrow-linewidth semiconductor laser, which, after polarization modulation and focusing, illuminates a PPKTP crystal. A spontaneous parametric down-conversion process generates polarization-entangled photon pairs, which are then separated into signal and reference light. These are received by a single-photon detector to obtain two time series. Second, coincidence measurements are performed on the time series in different scanning directions within the observation area to obtain a coincidence count matrix. Then, a two-dimensional constant false alarm rate (CFAR) detection algorithm is introduced, using ordered statistics to estimate background noise and adaptively adjust the detection threshold to screen candidate target points. Third, a density clustering algorithm based on correlation strength weighting is employed, combining the correlation strength and spatial distribution of entangled photon pairs to detect different targets and suppress isolated noise. Finally, the coincidence count peak points within each target cluster are selected as the final detection targets, thereby achieving multi-target detection with unknown numbers and randomly distributed locations.

The invention provides a waveguide assembly, a control method of the waveguide assembly, an optical chip and an optical quantum computer, and the waveguide assembly comprises a waveguide body which has a preset polarization period in an optical signal propagation direction; the plurality of heating devices are used for heating different areas of the waveguide body; and the controller is used for controlling the plurality of heating devices to heat the waveguide body in the corresponding area to different temperatures, so that the waveguide body is subjected to spontaneous parametric down-conversion at different frequencies, and quantum entanglement light sources of different wavebands are generated. According to the waveguide assembly, the requirement for generation of the broadband quantum entangled light source is met, meanwhile, dependence on waveguide process parameters can be reduced, and then the waveguide process manufacturing difficulty is reduced.

This invention provides a waveguide assembly, a control method for the waveguide assembly, an optical chip, and an optical quantum computer. The waveguide assembly includes: a waveguide body having a preset polarization period in the direction of optical signal propagation; multiple heating devices for heating different regions of the waveguide body; and a controller for controlling the multiple heating devices to heat corresponding regions of the waveguide body to different temperatures, enabling the waveguide body to undergo spontaneous parametric switching at different frequencies, generating quantum entangled light sources in different bands. This waveguide assembly, while meeting the requirements for generating broadband quantum entangled light sources, reduces dependence on waveguide process parameters, thereby reducing the difficulty of waveguide manufacturing.

The invention relates to a gradient polarization BBO crystal quantum entanglement source device based on a wavefront-power cooperative regulation and control method. The gradient polarization BBO crystal quantum entanglement source device is mainly applied to the fields of quantum optics and nonlinear photonics. The device breaks through the limitation of a traditional entanglement source in the aspects of wavelength tuning range and long-term stability through the cooperative regulation and control of an integrated spatial light modulator (SLM) and an electro-optical modulator (EOM) and the design of a gradient polarization crystal, and can be widely applied to the fields of quantum precision measurement, super-resolution imaging, weak signal detection and the like. A traditional BBO crystal entangled source based on spontaneous parametric down-conversion (SPDC) has the problems of narrow wavelength tuning range, thermally induced phase mismatch, group velocity mismatch (GVM) and the like. According to the invention, through dynamic wavefront-power cooperative regulation and control and gradient polarization crystal design, the generation efficiency and quality of entangled photon pairs are significantly improved. The device comprises a pump light source, a light source adjusting assembly, a BBO crystal assembly and a test assembly. The light source adjusting assembly dynamically adjusts the phase distribution of a pump light field through the SLM loading hologram, and meanwhile, the EOM adjusts the laser power in real time to suppress phase mismatch caused by environmental disturbance. The BBO crystal adopts a gradient polarization design, the pumping wavelength is dynamically adapted, the group velocity mismatch is compensated, and the time entanglement fidelity is improved to 99.3%. And the test assembly is used for evaluating the quality of the entangled photon pair and ensuring high purity and high fidelity of the entangled photon pair.

The invention discloses an efficient entangled photon pair preparation method based on a rhombic stacked two-dimensional material, and relates to the field of integrated quantum photonics and advanced nano photonic devices. According to the method, a two-dimensional material waveguide layer with periodic grooves in the light propagation direction is prepared on a substrate, pump light is coupled to a waveguide specific mode, spontaneous parametric down-conversion is completed by means of the second-order nonlinear effect of a two-dimensional material, photon pairs are generated and coupled to different modes of waveguide, and the wavelength of the pump light is changed. Quasi-phase matching is realized by utilizing the periodic grooves so as to compensate phase mismatching, and finally, polarization-coded entangled photons are output. The method is high in efficiency and compact in structure, is compatible with an existing nano photon integration process, provides support for development of an on-chip quantum light source, and is of great significance in promoting practicability of quantum communication and quantum calculation.

A quantum absorption spectroscopy system (1) includes a pump light source (11), a quantum interferometer (21), and a spectroscope (31). The pump light source (11) emits pump light. The quantum interferometer (21) causes quantum interference between a plurality of physical processes in which a quantum entanglement photon pair of a signal photon and an idler photon is generated through spontaneous parametric down-conversion of the pump light, a sample being arranged on a propagation path of the idler photon. The spectroscope (31) detects a signal photon from the quantum interferometer (21). The quantum interferometer (21) includes a single mode fiber (SMF) portion optically coupled to at least part of a propagation path of the signal photon and the propagation path of the idler photon.

The invention belongs to the technical field of quantum optics and quantum information devices, and discloses a near-infrared-mid-infrared dual-wavelength quantum polarization entangled source generating device which comprises a mounting seat, and a near-infrared light source, a mid-infrared light source, a first entangled crystal, a second entangled crystal, a core crystal module, a polarization controller and a generator are mounted and connected above the mounting seat. High-coherence pump light is output through a near-infrared light source, and the high-coherence pump light is shaped into parallel light beams through an aspheric collimating lens group and then is coupled to a first entangled crystal; under a quasi-phase matching condition, the pump light is converted into a near-infrared entangled photon pair of a communication band of 1.5-1.7 [mu] m through a spontaneous parametric down-conversion process, and then the near-infrared entangled photon pair is input into the core crystal module along a preset optical axis; a mid-infrared light source outputs mid-infrared pump light, linear polarization direction locking and polarization state fine regulation and control are completed through a polarization controller, and interference of pump light polarization fluctuation on subsequent entanglement state generation is eliminated; the regulated and controlled mid-infrared pump light is coupled to the second entangled crystal, mid-infrared entangled photon pairs in the atmosphere window wave band of 3.5-4.0 microns are generated through spontaneous parametric down-conversion, the mid-infrared entangled photon pairs are synchronously input into the core crystal module along the optical axis, and actual application and operation are facilitated.

The present invention relates to a design and preparation method for an on-chip entangled source based on an X-cut periodically poled lithium niobate film, comprising: (1) preparing a first set of electrodes and a second set of electrodes with different polarization periods on the lithium niobate film; (2) polarizing the first set of electrodes and the second set of electrodes respectively; (3) applying a voltage to cause domain inversion of the lithium niobate between the electrodes, and directly etching the lithium niobate in the domain inversion region to prepare a lithium niobate waveguide, thereby obtaining a periodically poled lithium niobate waveguide; (4) generating two sets of photon pairs with perpendicular polarization directions through a spontaneous parametric down-conversion process between the first set of electrodes and the second set of electrodes, and preparing a polarization entangled source when the length of the lithium niobate waveguide is less than the coherence length of the pump light; and (5) separating the photon pairs. The design and preparation method for the on-chip entangled source provided in the present application provides a stable and highly integrated on-chip polarization entangled source generation solution that meets the requirements of high integration.

This invention provides a self-calibrated low-light radiance meter and measurement method based on 355nm pumping, including self-calibration and radiation observation. In self-calibration mode, the multiplexed optical path module periodically imports spontaneous parametric downconversion correlated photons, and the photon counting and coincidence detection modules calibrate the absolute quantum efficiency of the three channels. In radiation observation mode, the multiplexed optical path module imports the low-light target radiation, and simultaneously acquires the absolute spectral radiance of the observed target in the 460nm–1550nm band. The calibration coefficients obtained in the self-calibration mode are used to correct the observation results. This invention starts from the basic principle of calibrating the quantum efficiency of single-photon detectors based on the correlated photon method of spontaneous parametric downconversion, realizing high-precision observation of low-light spectral radiance in the visible to near-infrared bands. It solves the scientific problem of traceability of low-light observation instruments on space platforms and plays an important role in climate monitoring, low-light radiation metrology, and single-photon source radiance measurement.

This invention provides a waveguide assembly, a control method for the waveguide assembly, an optical chip, and an optical quantum computer. The waveguide assembly includes: a waveguide body having a preset polarization period in the direction of optical signal propagation; multiple heating devices for heating different regions of the waveguide body; and a controller for controlling the multiple heating devices to heat corresponding regions of the waveguide body to different temperatures, enabling the waveguide body to undergo spontaneous parametric switching at different frequencies, generating quantum entangled light sources in different bands. This waveguide assembly, while meeting the requirements for generating broadband quantum entangled light sources, reduces dependence on waveguide process parameters, thereby reducing the difficulty of waveguide manufacturing.

The present invention discloses a method for generating an ultra-wideband energy-time entangled two-photon state. By preparing a straight waveguide structure, and then the pump light is incident perpendicularly into the straight waveguide from the convex part of the trapezoidal cross-section of the straight waveguide structure for propagation. The mismatch amount in the spontaneous parametric down-conversion process in the straight waveguide, after the spontaneous parametric down-conversion process occurs in the straight waveguide structure, a pump light photon with a frequency of w P is converted by the nonlinear photonic crystal into a signal light photon with a frequency of w S and an idler light photon with a frequency of w I . The cross-section of the nonlinear straight waveguide provided by the present invention is trapezoidal. This cross-section structure can adjust the dispersion relation of the straight waveguide, change the spatial mode matching of the pump light, the signal light and the idler light, and realize a wider-band spectrum of the signal light and the idler light.

A polarization entangled light source, comprising: an interference mechanism for obtaining a first pump laser beam and a second pump laser beam with the same polarization direction and different propagation directions from an initial laser; a resonant cavity adapted to receive the first pump laser beam and the second pump laser beam; a nonlinear optical crystal disposed in the resonant cavity, the two pump laser beams entering the resonant cavity pass through the nonlinear optical crystal from different directions, and under the action of the nonlinear optical crystal, photons of the first pump laser beam undergo spontaneous parametric down-conversion to obtain two first down-conversion photons, and photons of the second pump laser beam undergo spontaneous parametric down-conversion to obtain two second down-conversion photons; the interference mechanism is also adapted to ensure that the first target down-conversion photons and the second target down-conversion photons can produce quantum coherent superposition to obtain polarization entangled photon pairs.

The invention discloses a continuous variable quantum relay method and system based on all-optical entanglement swapping. According to the disclosed scheme, a transmitting end prepares a hyper-entangled photon pair with continuous variable entanglement association on orthogonal amplitude-phase degree of freedom and time-energy degree of freedom at the same time, keeps one group of photons, and transmits the other group of photons to a relay node; at a relay node, quantum purification is firstly implemented based on T-E degree of freedom; then, all-optical entanglement exchange is carried out on the purified photons and photons locally prepared by a relay, and transfer of the X-P degree-of-freedom continuous variable entanglement relation is achieved; reconstructing T-E degree-of-freedom entanglement for the photons after entanglement exchange through a non-degenerate spontaneous parametric down-conversion process; and the plurality of relay nodes are repeatedly executed until the Bob end receives the photon sequence. Probabilistic non-Gaussian measurement is not needed, the structure is simple, the problems that a traditional continuous variable quantum relay is low in generation rate and poor in cascading performance are solved, and the continuous variable quantum relay is suitable for a long-distance continuous variable quantum communication network.

The invention relates to an on-chip entangled photon source based on thin film lithium niobate, which comprises a coupled semiconductor laser, an on-chip beam splitter, a thin film lithium niobate photon chip formed by a first PPLN waveguide, a second PPLN waveguide and an on-chip beam combiner, the on-chip beam splitter outputs split beams to align to the light incident ends of the first PPLN waveguide and the second PPLN waveguide, the on-chip beam combiner inputs to align to the first PPLN waveguide and the second PPLN waveguide, the on-chip beam combiner performs polarization conversion on photon pairs entering through the second PPLN waveguide, then entangles the photon pairs entering through the first PPLN waveguide, outputs entangled photon pairs, and outputs the entangled photon pairs to the light incident ends of the first PPLN waveguide and the second PPLN waveguide. By means of the on-chip structure, the device size can be effectively reduced, beam splitting, spontaneous parametric down-conversion and polarization beam combination are formed in the chip, entangled photon pairs can be effectively and directly generated, and direct polarization entanglement is achieved on the integrated photon chip while the size of the entangled light source device is reduced.

The invention discloses a single-photon detector spectral response calibration device based on a quantum light source, and belongs to the field of quantum optics and quantum information. The device comprises a pump laser light source, a laser lens, a quantum light source module, a light source collection module, a polarization-dependent unequal-arm optical fiber interferometer, a to-be-detected single-photon detector and a time-dependent counter. A collinear spontaneous parametric down-conversion quantum light source is used as an input light source to carry out single-photon detector spectral response test, and the measurement precision can be traced to a Planck constant. The quantum light source is adopted for calibration, so that the damage risk possibly generated when strong light is input into the single-photon detector, and strong light darkening counting and post-pulse can be reduced. A dispersion compensation optical fiber is adopted as a single photon frequency domain-time domain converter, and an optical fiber polarization correlation unequal arm interferometer is adopted to calibrate the spectral response of the same detector through high-precision time counting without the help of a reference detector and a low-temperature refrigeration single photon spectrometer.

[Problem] To provide a compact structure capable of generating an entangled photon pair with high optical alignment robustness and high efficiency. [Solution] A resonator 2 having a first reflective layer 3, a laminated semiconductor layer 4, a polarization control element 5, a nonlinear crystal 6, and a second reflective layer 7 is irradiated with pump light Lp having a defined polarization state, and a high internal electric field strength generated by the standing wave of the pump light Lp is used to induce spontaneous parametric down-conversion in the nonlinear crystal 6. This increases the probability that the pump light Lp is wavelength-converted into signal light Ls and idler light Li, thereby efficiently generating an entangled photon pair Fa and Fb.

The application discloses an absolute spectral responsivity calibration system and method of an infrared detector based on an optical microcavity, and the system comprises a pump light generating device, a first photon counting module capable of being switched in an optical path, an optical microcavity module, a background light elimination module, a tentative calibration infrared detector, a second photon counting module, a current measurement module and a control and data acquisition module. The application introduces the optical microcavity technology into the spectral responsivity calibration of the infrared detector based on the spontaneous parametric down-conversion calibration principle, solves the problem that the existing spontaneous parametric down-conversion calibration method can only be implemented at a single wavelength point or a narrow waveband, and realizes the absolute calibration of the wide waveband continuous spectral responsivity of the infrared detector.

The present application relates to a kind of single channel multi-entangled photon pair generation method, device, equipment and medium, belong to nonlinear optics technical field.The method improves the method for generating entangled light in existing nonlinear crystal spontaneous parametric down-conversion, by the quasi-phase matching period of nonlinear crystal is designed specifically, based on spontaneous parametric down-conversion process, simultaneously realize the generation of high-dimensional polarization entangled photon pair of two wavelengths, reduce conversion channel, compared with the existing spontaneous parametric down-conversion generation method, the generated entangled photon pair doubles, and compared with the existing non-spontaneous parametric down-conversion generation method, then no complex optical system, reduce the multi-source of experimental error, so comprehensive compared with the existing entangled light generation method has simple, efficient, reliable and flexible design characteristics, greatly reduce the difficulty of preparation high-dimensional entangled source, can better promote quantum entangled source and the development of quantum information technology.

This invention discloses a method and system for measuring single-photon orbital angular momentum Bell states based on a diffractive optical neural network. Based on time-energy correlated photon pairs generated by a spontaneous parametric downconversion process, an interference light field is generated by passing a signal photon modulated into a single-photon orbital angular momentum Bell state through a Bell state evolution system. A diffractive optical processor is constructed using a diffractive optical neural network to map the interference light fields of different Bell states into Gaussian spots in different detection regions within the output plane. Fast and high-precision identification of single-photon orbital angular momentum Bell states is achieved by correlating the imaging results with an enhanced charge-coupled device (CCD) camera. The proposed Bell state measurement method possesses a signal-to-noise ratio and anti-interference capability exceeding the classical limit, maintaining high-precision Bell state identification capability even under high background noise. It exhibits low energy consumption and high efficiency, meeting the needs of green computing and sustainable development. It can be applied to quantum state measurement in the field of quantum information processing.

The invention provides an on-chip integrated spectral measurement method and device based on quantum induced coherence, and the method comprises the steps: introducing pump light into one or more surface waveguide channels, enabling the pump light to be subjected to spontaneous parametric down-conversion in a first nonlinear region in the corresponding surface waveguide channel, and generating first detection light and first signal light entangled with the first detection light; in the microfluidic control, the first probe light generates resonance absorption when interacting with the sample to be detected. The mixed light after interaction enters a second nonlinear region at the rear end of the surface waveguide channel through the surface waveguide channel to establish quantum coherence, and after the refractive index of each surface waveguide channel is scanned through the modulation element, a quantum interference signal representing spectral information of the detected sample is formed on the signal light detector at the outlet of each surface waveguide channel. The method not only realizes non-contact measurement of the spectrum, but also is wide in detection range and high in precision.

The invention belongs to the technical field of spectral measurement, and discloses an orbital angular momentum spectrum coincidence measurement method based on a time correlation two-photon source, which comprises the following steps of: obtaining a pair of down-conversion photons, namely signal photons and idler frequency photons, with a time correlation characteristic by utilizing a spontaneous parametric down-conversion process of a nonlinear crystal; loading orbital angular momentum information on the signal photons, and obtaining an orbital angular momentum spectrum of the signal photons by using an optical coordinate transformation method; and performing time marking and coincidence measurement on the orbital angular momentum spectrum signals of the signal photons by using the idler frequency photons. According to the invention, single-photon orbital angular momentum spiral spectrum detection is carried out by using the time correlation characteristic of two photons, and background stray light noise contained before signal light reaches a detector is suppressed by measuring correlated photon signals which reach the detector on two light paths of signal light and idler frequency light at the same time or in a short time; therefore, the detection sensitivity reaches the sensitivity threshold limit of a photoelectric detection system, namely a single photon level.

The invention discloses an experimental device and method for realizing quantum imaging by using sunlight. The device comprises a sunlight shaping system, a quantum correlation photon pair generation unit and a wide spectrum quantum imaging system, wherein the sunlight shaping system is used for shaping collected small-spot sunlight and polarizing the small-spot sunlight into a pump beam polarized in the horizontal direction, so that the pump beam can completely penetrate through the quantum correlated photon pair generation unit; the quantum correlation photon pair generation unit is used for receiving the pumping light beam and splitting the light beam to generate quantum correlation photon pairs under a wide spectrum; the polarization directions of the quantum correlation photon pair are respectively vertical polarization and horizontal polarization; a wide-spectrum quantum imaging system and the like. According to the invention, collection, transmission and shaping of sunlight can be realized, a spontaneous parametric down-conversion process is carried out on the wide-spectrum light beam nonlinear crystal, enough wide-spectrum down-conversion two-photon pairs for quantum imaging are generated, and a set of experimental device is provided for application research of sunlight in the aspect of quantum imaging.

This invention discloses an on-chip integrated beam-splitting polarization-entangled photonic array chip, belonging to the field of integrated quantum mechanics. The chip includes a pump laser input terminal, an on-chip beam-splitting structure, and a Bragg reflection waveguide array. After the pump light is coupled into the chip, it undergoes progressively uniform power distribution through a beam-splitting structure composed of multiple cascaded Y-beam splitters and is injected into multiple Bragg reflection waveguides. The Bragg reflection waveguides are constructed based on AlGaAs / GaAs materials to form a non-ideal quarter-wavelength structure, efficiently generating polarization-entangled photon pairs through a spontaneous parametric down-conversion process. This invention achieves monolithic integration of pump light beam splitting and entangled photon generation, offering advantages such as low loss, uniform splitting ratio, good output consistency, high integration density, and strong compatibility. It is suitable for applications in quantum imaging, quantum communication, and parallel quantum information processing.

A stream of photons from an optical source at a source wavelength are converted into entangled photon pairs via a spontaneous parametric down-conversion process. This produces time-synchronized signal and idler photon pairs which share a nominal wavelength, twice the source wavelength, a common polarization. The signal and idler individually have wavelengths that are equally offset above and below their nominal wavelength. The photons segregated into two paths based on wavelength via a wavelength division multiplexer. A phase modulator in the signal path alters the phase of the signal photon, while the idler photon's phase remains unchanged. By applying a modulation signal to the phase modulator, a quantum message is encoded on the photon pair. A multi-channel wavelength division multiplexer may be used to support multiple channels, each carrying signal-idler pairs conveying a quantum encoded message.