High-quality optical communication wavelength quantum light source generated in atomic vapor cell and method for achieving quantum light source

Abstract

Disclosed are a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell and a method for achieving the quantum light source. The high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to one example of the present invention comprises: an atomic vapor cell containing rubidium (87Rb) atoms; and a processor for propagating a 780 nm pump laser and a 1,529 nm coupling laser in opposite directions with respect to the atomic vapor cell, wherein the atomic vapor cell generates a photon pair of a signal and an idler, and can output the signal, generated in association with the coupling laser, from a first surface on which the pump laser is incident, and output the idler, generated in association with the pump laser, from a second surface on which the coupling laser is incident.

Description

A high-quality optical communication wavelength quantum light source generated in an atomic vapor cell and a method for implementing a quantum light source

[0001] The present invention, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D5 / 2 A high-quality optical communication wavelength quantum light source and a method for implementing a quantum light source generated in an atomic vapor cell for generating high signal-to-noise ratio (SNR) time-correlated photon pairs using a spontaneous four-wavelength combination (sFWM) process through transition are disclosed.

[0002] Registration No. 10-2441594 (September 2, 2022), "High-efficiency quantum light source and entangled photon pair generation method based on multi-wavelength coupling using arrayed 0-type ppKTP crystals."

[0003] Registration No. 10-2441594 discloses a quantum light source including a quantum light source generation unit that divides a pump beam into a plurality of channels and generates a plurality of signals and a plurality of idlers using nonlinear crystals positioned in the optical paths of each of the plurality of channels, and an entangled photon pair coupling unit that combines the plurality of signals to output an enhanced signal and combines the plurality of idlers to output an enhanced idler.

[0004] International Publication WO 90 / 03054 (1990.03.22), “WAVELENGTH STABILIZED SOURCE OF LIGHT”

[0005] International Publication No. WO 90 / 03054 discloses a light source in which a diode (101) emits a 1.56 μm laser beam, a harmonic generator (105) generates harmonic emission of the laser beam, the harmonic light enters a resonator (102) having 87Rb atoms, a phase-modulated microwave is irradiated to the resonator (102), and the resonator (102) generates a double resonance signal when the wavelength of the harmonic light is the same as the resonance wavelength of 87Rb and the frequency of the microwave is the same as the transition frequency of 87Rb.

[0006] Publication No. 10-2021-0154364 (December 21, 2021), "Entanglement Generator for Quantum Operators"

[0007] Publication number 10-2021-0154364 discloses an entanglement operation generation device including a first interferometer having at least two optical paths of different lengths; a second interferometer having at least two optical paths of different lengths; a photon pair source inputting a pair of photons into the first interferometer and the second interferometer; an operator positioned on the optical paths of the first interferometer and the second interferometer; a photon detection and sensing unit detecting photons output from the first interferometer and the second interferometer, respectively; and a control unit selectively detecting signals simultaneously output from the first interferometer and the second interferometer among signals output from the photon detection and sensing unit.

[0008] The development of stable, high-yield quantum light sources is crucial for realizing long-distance quantum communication and quantum networks.

[0009] In particular, quantum light sources in the optical communication band are very essential for practical purposes in the field of long-distance quantum communications.

[0010] A quantum network can be composed of spatially separated nodes that store and process quantum information from photons.

[0011] Nodes that make up a quantum network can be connected through channels such as optical fibers or free-space links.

[0012] In the case of wired quantum communication, quantum light sources are very important for long-distance quantum information transmission because they can transmit photons with minimal loss inside the optical fiber.

[0013] Quantum light sources have been developed in various forms operating at optical communication wavelengths over the past few decades, and significant progress has been made in the technology.

[0014] Meanwhile, in recent years, the feasibility of quantum repeater protocols utilizing quantum memory based on atom-photon interactions in the field of quantum communication has become a crucial issue for long-distance quantum communication.

[0015] Moreover, to implement effective quantum entanglement exchange protocols for long-distance quantum communication and quantum networks, the development of high-quality, independent quantum light sources that are indistinguishable from each other is crucial.

[0016] Previous technologies have mainly focused on the development of quantum light sources that include optical communication wavelengths due to nonlinear phenomena such as spontaneous parametric conversion in materials such as nonlinear crystals and optical waveguides.

[0017] However, it was difficult to say that the light sources of the prior art were completely independent quantum light sources because the characteristics of the photons generated varied depending on various external environments such as temperature and device characteristics.

[0018] Additionally, conventional light sources have limitations in using atom-based quantum memory due to the problem of wide photon linewidth.

[0019] Quantum light sources generated from atomic ensembles have wavelengths and optical bandwidths that are fundamentally suitable for the atom-photon interactions that generate the photons.

[0020] In addition, photons generated from atoms have important characteristics that can have the same properties as photons, and thus can solve the problems of the above-described conventional technology.

[0021] Research on quantum light sources, including optical communication wavelengths generated from atoms, has been actively pursued since Clauser developed a quantum light source using the emission chain of mercury atoms, and the generation of correlated photon pairs in ensembles in various atomic systems has been actively pursued.

[0022] Meanwhile, it has been reported that photon pairs can be generated in the telecom wavelength range of 1.3–1.5 μm in cooled atomic systems or warm atomic vapor cells by exploiting the transition of ladder atomic structures in atomic ensembles.

[0023] However, although cooled atomic systems are effective in realizing narrow bandwidth and high signal-to-noise ratio (SNR) photon pair sources, they typically have a low generation rate of 102 pairs / s because they require complex laser manipulation and optical frequency conversion in experimental devices to prepare for generating photon pairs in the atomic medium.

[0024] Compared to complex experimental devices using cooled atomic media, quantum light sources for long-distance quantum communication and quantum networks generated in atomic vapor cells can be implemented with very simple devices.

[0025] Quantum light sources in atomic vapor cells have the advantages of being relatively simple, miniaturizable, stable, and inexpensive.

[0026] In this respect, quantum light sources in atomic vapor cells have similar advantages to quantum light sources using conventional nonlinear crystals.

[0027] To address the above-described problems, there is an urgent need for improved models that implement quantum light sources that generate photon pairs capable of long-distance quantum communication through a simple, warm atomic medium.

[0028] An embodiment of the present invention is 87 Using the warm atomic ensemble and ladder-type atomic system of the Rb atomic vapor cell, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2The purpose of this invention is to provide a high-quality optical communication wavelength quantum light source and a method for implementing a quantum light source generated in an atomic vapor cell, which generates high signal-to-noise ratio (SNR) time-correlated photon pairs using a spontaneous four-wavelength combination (sFWM) process through transition.

[0029] In addition, an embodiment of the present invention aims to overcome the disadvantage of low SNR of two-photon cross-correlation due to the Doppler effect caused by the velocity distribution of a warm atomic ensemble, and to provide a quantum light source that generates high signal-to-noise ratio (SNR) time-correlated photon pairs.

[0030] In addition, the embodiment of the present invention aims to secure the stability of the frequency with a precision corresponding to the transition line of an atom, and to robustly generate all four Bell states with very high stability by applying the unique correlation generated in the atomic system of the ladder structure without using an interferometer configuration.

[0031] In addition, the embodiment of the present invention aims to enable the development of a light source of entangled photon pairs with a high production rate using a low pump power.

[0032] According to one embodiment of the present invention, a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell is a rubidium ( 87 An atomic vapor cell containing Rb atoms; and a processor for radiating a 780 nm pump laser and a 1529 nm coupling laser in opposite directions based on the atomic vapor cell, wherein the atomic vapor cell generates a photon pair of a signal and an idler, and outputs the signal generated in association with the coupling laser on a first surface into which the pump laser is input, and outputs the idler generated in association with the pump laser on a second surface into which the coupling laser is input.

[0033] In addition, a method for implementing a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to an embodiment of the present invention may be configured to include the steps of: in a processor, radiating a 780 nm pump laser and a 1529 nm coupling laser in opposite directions based on an atomic vapor cell containing rubidium (87Rb) atoms; and, in the atomic vapor cell, generating a photon pair of a signal and an idler, outputting the signal generated in association with the coupling laser on a first surface into which the pump laser is input, and outputting the idler generated in association with the pump laser on a second surface into which the coupling laser is input.

[0034] According to one embodiment of the present invention, 87 Using the warm atomic ensemble and ladder-type atomic system of the Rb atomic vapor cell, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2 A high-quality optical communication wavelength quantum light source and a method for implementing a quantum light source generated in an atomic vapor cell using a spontaneous four-wavelength combination (sFWM) process through transition to generate high signal-to-noise ratio (SNR) time-correlated photon pairs can be provided.

[0035] In addition, according to one embodiment of the present invention, it is possible to provide a quantum light source that overcomes the disadvantage of low SNR of two-photon cross-correlation due to the Doppler effect caused by the velocity distribution of a warm atomic ensemble, and generates a high signal-to-noise ratio (SNR) time-correlated photon pair.

[0036] Furthermore, according to one embodiment of the present invention, the stability of the frequency is secured with a precision corresponding to the transition line of the atom, and all four Bell states with very high stability can be strongly generated by applying the unique correlation generated in the atomic system of the ladder structure without using an interferometer configuration.

[0037] In addition, according to one embodiment of the present invention, it is possible to develop a light source of entangled photon pairs with a high production rate using a low pump power.

[0038] FIG. 1 is a block diagram illustrating the configuration of a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to one embodiment of the present invention.

[0039] Figure 2 is a diagram illustrating the generation of spontaneous four-wavelength combinations (sFWM) in a trapezoidal atomic configuration.

[0040] Figure 3 is a diagram for explaining photon pairs output from an atomic vapor cell.

[0041] Figure 4 is a diagram showing an example of determining θi and θs.

[0042] Figure 5 is a diagram illustrating an experimental setup of a high-quality optical communication wavelength quantum light source.

[0043] Fig. 6 is a diagram showing the transmission signal of the pump field in the presence of a coupling field.

[0044] Figure 7a or 7b is a diagram showing the temporal statistical characteristic spectrum for the entangled mode of the generated photon pair.

[0045] Figures 8a to 8e are diagrams showing the performance of the developed photon pair.

[0046] Figures 9a to 9c are diagrams for explaining photon generation and characteristics according to the temperature of an atomic vapor cell.

[0047] Fig. 10 is a diagram for explaining a quantum repeater using a high-quality optical communication wavelength quantum light source of the present invention.

[0048] FIG. 11 is a flowchart illustrating a method for implementing a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to one embodiment of the present invention.

[0049] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, the embodiments may be modified in various ways, and the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or alternatives to the embodiments are included within the scope of the patent application.

[0050] The terms used in the examples are for illustrative purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0051] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments pertain. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0052] In addition, when describing with reference to the attached drawings, identical components will be assigned the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing embodiments, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

[0053] FIG. 1 is a block diagram illustrating the configuration of a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to one embodiment of the present invention.

[0054] Referring to FIG. 1, a high-quality optical communication wavelength quantum light source (hereinafter, abbreviated as 'high-quality optical communication wavelength quantum light source', 100) generated in an atomic vapor cell according to an embodiment of the present invention may be configured to include an atomic vapor cell (110), a processor (120) including a pump laser (122) and a coupling laser (124).

[0055] First, the atomic vapor cell (110) is made of rubidium ( 87 Rb) atoms are contained. That is, the atomic vapor cell (110) can serve to seal and maintain the gas of rubidium atoms.

[0056] The atomic vapor cell (110) can be manufactured as a glass tube filled with rubidium atoms having an atomic number of 37 in a vacuum. The rubidium atoms in the atomic vapor cell (110) can be manipulated (capturing, pumping, etc.) by a coupling laser (124) and a pump laser (122) described later, thereby generating two photons. At this time, the two generated photons (photon pairs) can be quantum entangled with each other.

[0057] In one embodiment, the atomic vapor cell (110) comprises rubidium ( 87 Rb) may be a glass-shaped cell that keeps the atomic vapor warm. By using a warm atomic medium, the atomic vapor cell (110) of the present invention can produce more stable photon pairs with a simple device compared to conventional atomic medium.

[0058] In one embodiment, the temperature of the atomic vapor cell (110) can be designed to be relatively high, from 99 degrees to 115 degrees. That is, the atomic vapor cell (110) is designed to be warm rubidium (from 99 degrees to 115 degrees). 87Rb) can be filled with atoms.

[0059] The processor (120) operates a 780 nm pump laser (122) and a 1529 nm coupling laser (124) in opposite directions with respect to the atomic vapor cell (110). That is, the processor (120) is configured to include a coupling laser (124) and a pump laser (122), and can generate photon pairs through manipulation by the coupling laser (124) and the pump laser (122), which operate in opposite directions, with respect to rubidium atoms in the atomic vapor cell (110).

[0060] Here, the coupling laser (124) may be a 1529 nm laser, and the pump laser (122) may be a 780 nm laser.

[0061] Under the condition that the above 780 nm pump laser (122) and the above 1529 nm combined laser (124) enter, the atomic vapor cell (110) can generate a photon pair of a signal (124-p) and an idler (122-p).

[0062] The atomic vapor cell (110) has a first surface into which the pump laser (122) is input, and a second surface into which the combination laser (124) is input.

[0063] The atomic vapor cell (110) can output the signal (124-p) generated in association with the coupling laser (124) on the first side to which the pump laser (122) is input.

[0064] On the other hand, the atomic vapor cell (110) can output the idler (122-p) generated in association with the pump laser (122) on the second side into which the combined laser (124) is input.

[0065] That is, the atomic vapor cell (110) can output an idler (122-p) generated in the direction in which the pump laser (122) enters, and output a signal (124-p) generated in the direction in which the coupling laser (124) enters.

[0066] In particular, the high-quality optical communication wavelength quantum light source (100) of the present invention may have a cascade structure in which the idler (122-p) is generated at 780 nm, the same as the pump laser (122), and the signal (124-p) is generated at 1529 nm, the same as the coupling laser (124). That is, the high-quality optical communication wavelength quantum light source (100) may be configured with a cascade structure in which the wavelength of the signal (124-p) generated in association with the coupling laser (124) is generated to be identical to the wavelength (1529 nm) of the coupling laser (124), and the wavelength of the idler (122-p) generated in association with the pump laser (122) is generated to be identical to the wavelength (780 nm) of the pump laser (122).

[0067] A high-quality optical communication wavelength quantum light source (100) may further include an idler (122-p) and a mirror for adjusting the angle at which a signal (124-p) is output from an atomic vapor cell (110), so as to simultaneously achieve a high Maximum value (correlation maximum value) and a large number of photons (Nc).

[0068] That is, the mirror can adjust the angle θs at which the signal is output on the first surface based on the virtual line into which the pump laser (122) is input, and the angle θi at which the idler is output on the second surface based on the virtual line into which the combined laser is input.

[0069] θs and θi are correlated with each other so that a high Maximum value (correlation maximum value) and many photons (Nc) can be achieved simultaneously, so that when one of θs and θi is fixed, the other must have a value determined according to the fixed value.

[0070] For example, if the above θs is fixed to 1.5 degrees, the mirror can simultaneously achieve a high Maximum value (correlation maximum value) and many photons (Nc) by adjusting the above θi to 1.1 degrees in consideration of the fixed θs of 1.5 degrees.

[0071] In addition, the mirror can adjust the θi to 0.8 degrees by considering the fixed θs of 1.0 degrees when the θs is fixed to 1.0 degrees.

[0072] In an embodiment, the virtual line into which the pump laser (122) is input may be the same line as the virtual line into which the combined laser is input.

[0073] That is, the combined laser (124) and the pump laser (122) can simultaneously advance along the same virtual line in opposite directions toward the atomic vapor cell (110) at respective locations spaced at the same distance from the atomic vapor cell (110).

[0074] That is, the combined laser (124) and the pump laser (122) travel in the same virtual line in opposite directions, and reach the atomic vapor cell (110) at the same time, enabling manipulation of rubidium atoms.

[0075] The atomic vapor cell (110) generates a signal (124-p) and an idler (122-p) through manipulation of rubidium atoms, and can output the signal (124-p) and the idler (122-p) generated with set θs and θi from the first and second surfaces according to the adjustment of the mirror.

[0076] According to an embodiment, the atomic vapor cell (110) can generate the photon pairs through spontaneous four wave mixing (sFWM) in a ladder-shaped atomic configuration.

[0077] Here, sFWM may refer to a structure in which a light source structure is formed by four signals, namely, a pump laser (122), a coupling laser (124), a signal (124-p), and an idler (122-p), in which the signal (124-p) generated in connection with the coupling laser (124) outputs light while spontaneously dropping from the highest potential position reached by the coupling laser (124), and also in which the idler (122-p) generated in connection with the pump laser (122) outputs light while spontaneously dropping from the highest potential position reached by the pump laser (122).

[0078] The optical path along which the pump laser (122) and the combination laser (124) advance to the atomic vapor cell (110) can be formed by nano-antireflection coating so that the photon pairs of the signal (124-p) and the idler (122-p) can be generated without scattering. That is, the optical path is formed by nano-antireflection coating so that the pump laser (122) and the combination laser (124) that advance can be input to the atomic vapor cell (110) without reflection along the path, so that the photon pairs of the signal (124-p) and the idler (122-p) can be generated in an optimal state.

[0079] At this time, the optical depth of the optical path is designed to be 100 to 120, so as to increase the absorption rate of the pump laser (122) and the combined laser (124).

[0080] According to one embodiment of the present invention, 87 Using the warm atomic ensemble and ladder-type atomic system of the Rb atomic vapor cell, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2A high-quality optical communication wavelength quantum light source and a method for implementing a quantum light source generated in an atomic vapor cell using a spontaneous four-wavelength combination (sFWM) process through transition to generate high signal-to-noise ratio (SNR) time-correlated photon pairs can be provided.

[0081] In addition, according to one embodiment of the present invention, it is possible to provide a quantum light source that overcomes the disadvantage of low SNR of two-photon cross-correlation due to the Doppler effect caused by the velocity distribution of a warm atomic ensemble, and generates a high signal-to-noise ratio (SNR) time-correlated photon pair.

[0082] Furthermore, according to one embodiment of the present invention, the stability of the frequency is secured with a precision corresponding to the transition line of the atom, and all four Bell states with very high stability can be strongly generated by applying the unique correlation generated in the atomic system of the ladder structure without using an interferometer configuration.

[0083] In addition, according to one embodiment of the present invention, it is possible to develop a light source of entangled photon pairs with a high production rate using a low pump power.

[0084] Figure 2 is a diagram illustrating the generation of spontaneous four-wavelength combinations (sFWM) in a trapezoidal atomic configuration.

[0085] Figure 2 shows the process of generating quantum entangled photon pairs through spontaneous four wave mixing (sFWM) in a ladder-shaped atomic structure.

[0086] sFWM of Fig. 2 is rubidium ( 87 5S of Rb) atoms 1 / 2 -5P 3 / 2 -4D5 / 2 It's about transition.

[0087] As shown in Fig. 2, in the high-quality optical communication wavelength quantum light source (100) of the present invention, a 780 nm laser for pumping and a 1529 nm laser for coupling are used, and rubidium (87 Quantum entangled photon pairs can be generated by irradiating an atomic vapor cell containing Rb atoms.

[0088] The generated quantum entangled photon pairs can be an idler of 780 nm associated with the pump and a signal of 1529 nm associated with the coupling.

[0089] The quantum entangled photon pair, idler and signal, can have frequencies related to each level, and the ideal level-specific frequencies are idler 156.9 MHz and signal 52.1 MHz at level F=2.

[0090] At this time, the high-quality optical communication wavelength quantum light source (100) is formed by a pump laser and a coupling laser. 87 Rb atomic ensemble 5S 1 / 2 - 5P 3 / 2 - 4D 5 / 2 Strong two-photon coherence can be formed between the transition lines. To reduce uncorrelated photons generated by undesired single-photon resonance, a high-quality optical communication wavelength quantum light source (100) can be implemented by fixing the laser frequency at +1 GHz outside the Doppler broadening region.

[0091] The two-photon combination of spontaneous light waves generated by strong two-photon coherence between the initial Zeeman sub-state and the laser-excited Zeeman sub-state gives rise to strong quantum entanglement correlations.

[0092] The high-quality optical communication wavelength quantum light source (100) of the present invention can obtain photon pairs having a vertical quantum relationship by using a pump laser and a coupling laser.

[0093] Figure 3 is a diagram for explaining photon pairs output from an atomic vapor cell.

[0094] In Figure 3, we show the generation of correlated photon pairs interacting with the pump and coupling lasers traveling in opposite directions to the Doppler-broadened atomic ensemble.

[0095] As shown in Fig. 3, the atomic vapor cell receives a pump laser (kp) and a coupling laser (kc) from opposite directions, respectively, through a virtual line passing through the center.

[0096] The atomic vapor cell can output a signal (ks) at an angle θs on the first surface based on a virtual line into which a pump laser (kp) is input, and can output an idler (ki) at an angle θi on the second surface based on a virtual line into which a coupling laser (Kc) is input, through adjustment of the mirrors.

[0097] The high-quality optical communication wavelength quantum light source (100) of the present invention is rubidium ( 87 By propagating a pump laser (Kp) and a coupling laser (Kc) in opposite directions in an atomic vapor cell containing Rb atoms, a photon pair of a quantum entangled signal (ks) and an idler (ki) can be generated.

[0098] The photon pairs generated can be an idler photon (ki) emitted at θi and a signal photon (Ks) emitted at θs based on the virtual line of the atomic vapor cell.

[0099] A high-quality optical communication wavelength quantum light source (100) is rubidium ( 87 An atomic vapor cell containing Rb atoms can be used. The atomic vapor cell is filled with pure rubidium atomic gas in a glass chamber measuring 12 mm in length and 25 mm in radius.

[0100] A high-quality optical communication wavelength quantum light source (100) can use a second-order cross-correlation function to confirm the temporal correlation between photon pairs.

[0101] Figure 4 is a diagram showing an example of determining θi and θs.

[0102] Figure 4 shows the sFWM process and the phase matching results in the ladder-type atomic system.

[0103] In Fig. 4, the relationship between the emission angle θi of idler photons (ki) emitted from the atomic vapor cell and the emission angle θs of signal photons (Ks) is shown.

[0104] As shown in Fig. 4, the high-quality optical communication wavelength quantum light source (100) can set the ideal θi to 0.75 degrees when θs is set to 1 degree, and can also set the ideal θi to 1.1 degrees when θs is set to 1.5 degrees.

[0105] In addition, the high-quality optical communication wavelength quantum light source (100) can set the ideal θi to 1.5 degrees when θs is set to 2 degrees, and can also set the ideal θi to 1.8 degrees when θs is set to 2.5 degrees.

[0106] 87 Rb's 5S 1 / 2 -5P 3 / 2 -4D 5 / 2 In the transition, the collective biphoton coherence of the atoms can be reduced due to the large wavelength difference between the signal (1529 nm) and idle (780 nm) photons, caused by the Doppler spreading effect of the warm atomic ensemble within the atomic vapor cell.

[0107] Additionally, the Doppler effect due to the velocity distribution of the warm atomic ensemble can overcome the disadvantage of low SNR of biphoton cross-correlation.

[0108] The high-quality optical communication wavelength quantum light source (100) of the present invention is 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2 High signal-to-noise ratio (SNR) time-correlated photon pairs can be generated using the spontaneous four-wave combination (sFWM) process via transitions.

[0109] In particular, a high-quality optical communication wavelength quantum light source (100) is 87 The generation rate of photon pairs, including photons in the optical communication wavelength band, can be achieved at the best possible level in an Rb atomic vapor cell.

[0110] Table 1 lists the maximum value (correlation maximum value) and the generation status of photons (Nc) in quantum light sources of various structures.

[0111] [Table 1]

[0112]

[0113] In Table 1, the cold atoms and hot atoms of the atomic system are distinguished by the temperature of the atoms filling the atomic cell, and the hot atoms have a temperature of 99 to 115 degrees.

[0114] In Table 1, Cascade and Diamond of Configuration are distinguished by whether the wavelength of the photons generated in the sFWM structure is equivalent to that of the laser. In the case of Cascade, the idler can be generated at 780 nm, the same as the pump laser, and the signal can be generated at 1529 nm, the same as the coupling laser.

[0115] The high-quality optical communication wavelength quantum light source (100) of the present invention can simultaneously achieve a relatively high Maximum value (correlation maximum value) of '44' and a relatively large number of photons (Nc) of '76' by combining a hot atom and a cascade.

[0116] Table 1 compares the characteristics of photon pair sources from cooled atomic ensembles and warm atomic ensembles in an atomic vapor cell in terms of the correlation of generated photon pairs and the SNR of photon pair generation.

[0117] Table 1 distinguishes two configurations for the sFWM process.

[0118] In a cascade configuration, each wavelength of the photon pair source is the same as the wavelength of the pump and coupling lasers to obtain two-photon coherence.

[0119] In the diamond configuration, the wavelength of the two-photon coherence laser and the wavelength of the photon pair photons can be made different to effectively separate the pump and coupling lasers from the photon pair.

[0120] The high-quality optical communication wavelength quantum light source (100) of the present invention can overcome the disadvantage of low SNR of photon pairs while maintaining a high photon pair production rate by using a cascade configuration and a high-density atomic density medium.

[0121] According to the present invention, 87 It can provide a high-quality telecom wavelength quantum light source generated from an Rb atomic vapor cell.

[0122] According to the present invention, a time-correlated photon pair, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2 It can be generated through a spontaneous photon combination process via transfer.

[0123] According to the present invention, the maximum value (maximum correlation value) of photon pairs generated under high-density atomic medium conditions can be achieved as 44.

[0124] According to the present invention, the laser frequency can be stabilized while the two-photon absorption spectrum width of the cascade is about 300 MHz, and the photon pair generation rate can be set to about 38,000 cps / mW.

[0125] The present invention enables the development of long-distance quantum networks and practical quantum repeaters based on atom-photon interactions as high-quality light sources generated from atomic ensembles containing optical communication wavelengths.

[0126] Figure 5 is a diagram illustrating an experimental setup of a high-quality optical communication wavelength quantum light source.

[0127] In Fig. 5, hot 87 The experimental setup and setup for the generation of correlated photon pairs from Rb atomic vapor is illustrated.

[0128] As shown in Fig. 5, a high-quality optical communication wavelength quantum light source (100) can detect and verify photon pairs generated in an atomic vapor cell.

[0129] For this purpose, a high-quality optical communication wavelength quantum light source (100) can be configured to include a prism mirror, a quarter-wave plate (QWP), a half-wave plate (HWP), and a polarizer.

[0130] The prism mirror can separate the paths of the generated photon pairs from those of the coupling laser and the pump laser. In other words, the prism mirror can guide the photon pairs generated in the atomic vapor cell to proceed in a direction distinct from that of the coupling laser and the pump laser.

[0131] HWP and QWP can control the bell state for the photon pair. That is, HWP and QWP can adjust the bell state for the photon pair satisfying the phase matching condition through their respective phase delays.

[0132] The polarizer can determine the Bell state according to polarization for the photon pair whose Bell state is controlled. That is, the polarizer can determine whether the Bell state is controlled according to the specified standard state, based on the polarization applied to the coupling laser and the pump laser.

[0133] Through this, the high-quality optical communication wavelength quantum light source (100) can be used as a light source by recognizing only photon pairs whose bell state is judged to be a standard state by the polarizer as valid photon pairs.

[0134] Fig. 6 is a diagram showing the transmission signal of the pump field in the presence of a coupling field.

[0135] The transmission signal in Fig. 6 is represented by the change in the TPA spectrum according to pump detuning.

[0136] The TPA curve in Fig. 6 is 87 5S in Rb vapor cell 1 / 2 (F = 2)-4D 5 / 2 It may be a two-photon absorption spectrum of the transition.

[0137] The TPA curve is 5P under experimental conditions. 3 / 2 (F'= 3)-4D 5 / 2 It was measured under coupling detuning conditions of +1.2 GHz from (F″= 4).

[0138] The transmission signal in Fig. 6 has a locking point at pump detuning '-1200 MHz'.

[0139] Figure 7a or 7b is a diagram showing the temporal statistical characteristic spectrum for the entangled mode of the generated photon pair.

[0140] In Fig. 7a, a histogram of the number of simultaneously measured photons is shown when the pump is 2 uW and the coupling is 2 mW.

[0141] In Fig. 7b, a histogram of the number of simultaneously measured photons is shown when the pump is 15 uW and the coupling is 5 mW.

[0142] The difference between the maximum values ​​in Figures 7a and 7b is caused by the difference in the scattered laser components between the two modes.

[0143] The results of the temporal statistical characteristic measurements of the generated photon pairs show that the maximum correlation value of the photon pairs generated under high-density atomic medium conditions is achieved at 44.

[0144] Figures 8a to 8e are diagrams showing the performance of the developed photon pair.

[0145] Figure 8a shows the single count rate (Ns) of the signal.

[0146] Figure 8b shows the single counting rate (Ni) of the idler.

[0147] Figure 8c shows the coincidence counting rate (Nc) of the biphoton as a function of the pump and coupling powers.

[0148] Figure 8d shows the maximum value of the normalized correlation function as a function of pump power and coupling power.

[0149] Figure 8e shows the characteristics over the entire parameter range for the maximum value of the function of Nc.

[0150] Figures 9a to 9c are diagrams for explaining photon generation and characteristics according to the temperature of an atomic vapor cell.

[0151] In Figures 9a to 9c, the photon pairs generated in the atomic vapor cell are represented as a Pump of 2 μW (780 nm, -1.5 GHz detuning) and a Coupling of 2 mW (1529 nm +1.5 GHz detuning) propagate in opposite directions into the atomic vapor cell.

[0152] Figure 9a is a time correlation graph of two photons generated at temperatures of 99 degrees, 105 degrees, 113 degrees, and 122 degrees in an atomic vapor cell.

[0153] As shown in Fig. 9a, the temporal correlation of two photons is highest when the temperature is 113 degrees.

[0154] Figure 9b is a graph showing the maximum temporal correlation in Figure 9a. The higher the maximum value, the better the photon pair correlation and the better the quantum light source's characteristics. As shown in Figure 9b, the quantum light source's characteristics are best at an optical depth of 116.

[0155] Figure 9c shows the results of measuring the photon pair production rate. The higher the temperature of the atomic vapor cell, the higher the photon production rate. However, as shown in Figure 9a, the time correlation actually decreases at higher temperatures, above 113°C. Therefore, the temperature at which photon pairs are produced can be flexibly determined depending on the application in quantum science and technology.

[0156] Fig. 10 is a diagram for explaining a quantum repeater using a high-quality optical communication wavelength quantum light source of the present invention.

[0157] In Fig. 10, a quantum repeater equipped with quantum memory is illustrated.

[0158] Quantum repeaters can maintain quantum coherence and generate and distribute entanglement through quantum memory.

[0159] Quantum repeaters can interconnect quanta through Bell State Measurement.

[0160] Quantum repeaters can support optical interactions between quantum entangled photons and atoms (medium).

[0161] Hereinafter, FIG. 11 describes in detail the implementation flow of a high-quality optical communication wavelength quantum light source (100) according to embodiments of the present invention.

[0162] FIG. 11 is a flowchart illustrating a method for implementing a high-quality optical communication wavelength quantum light source generated in an atomic vapor cell according to one embodiment of the present invention.

[0163] First, in the processor of the high-quality optical communication wavelength quantum light source (100), rubidium ( 87Based on the atomic vapor cell containing Rb atoms, a 780 nm pump laser and a 1529 nm coupling laser are directed in opposite directions (1110). Step (1110) may be a process of generating photon pairs by manipulating the coupling laser and the pump laser, which are directed in opposite directions, with respect to rubidium atoms in the atomic vapor cell, by a processor.

[0164] An atomic vapor cell can contain and maintain a gas of rubidium atoms.

[0165] An atomic vapor cell can be constructed from a glass tube filled with rubidium atoms, atomic number 37, in a vacuum. The rubidium atoms within the atomic vapor cell can be manipulated (capturing, pumping, etc.) by a coupling laser and a pump laser, generating two photons. The two photons (photon pairs) thus generated can become quantum entangled with each other.

[0166] In one embodiment, the atomic vapor cell comprises rubidium ( 87 Rb) may be a glass-shaped cell that keeps the atomic vapor warm. By using a warm atomic medium, the atomic vapor cell of the present invention enables the generation of more stable photon pairs with a simple device compared to conventional atomic mediums.

[0167] In one embodiment, the temperature of the atomic vapor cell can be designed to be relatively high, from 99 degrees to 115 degrees. That is, the atomic vapor cell can be designed to be warm rubidium (from 99 degrees to 115 degrees). 87 Rb) can be filled with atoms.

[0168] Here, the coupling laser may be a 1529 nm laser and the pump laser may be a 780 nm laser.

[0169] In addition, the high-quality optical communication wavelength quantum light source (100) generates a photon pair of a signal and an idler in the atomic vapor cell under the condition that the 780 nm pump laser and the 1529 nm combined laser enter (1120).

[0170] The atomic vapor cell has a first surface into which the pump laser is input and a second surface into which the coupling laser is input.

[0171] The atomic vapor cell can output the signal generated in association with the coupling laser on the first side to which the pump laser is input.

[0172] On the other hand, the atomic vapor cell can output the idler generated in association with the pump laser on the second side into which the coupling laser is input.

[0173] That is, step (1120) may be a process of outputting an idler generated in the direction in which the pump laser enters by the atomic vapor cell and outputting a signal generated in the direction in which the combined laser enters.

[0174] In particular, the high-quality optical communication wavelength quantum light source (100) of the present invention may have a cascade structure in which the idler is generated at 780 nm, the same as the pump laser, and the signal is generated at 1529 nm, the same as the coupling laser. That is, the high-quality optical communication wavelength quantum light source (100) may be configured with a cascade structure in which the wavelength of the signal generated in relation to the coupling laser is generated to be identical to the wavelength (1529 nm) of the coupling laser, and the wavelength of the idler generated in relation to the pump laser is generated to be identical to the wavelength (780 nm) of the pump laser.

[0175] In the mirror of a high-quality optical communication wavelength quantum light source (100), the angle at which the idler and signal are output from the atomic vapor cell can be adjusted so that a high Maximum value (correlation maximum value) and many photons (Nc) are achieved simultaneously.

[0176] That is, the mirror can adjust the angle θs at which the signal is output on the first surface based on the virtual line into which the pump laser is input, and the angle θi at which the idler is output on the second surface based on the virtual line into which the combined laser is input.

[0177] In order to achieve a high Maximum value (correlation maximum value) and many photons (Nc) simultaneously, θs and θi are correlated with each other, so that when one of θs and θi is fixed, the other must have a value determined according to the fixed value.

[0178] For example, if the above θs is fixed to 1.5 degrees, the mirror can simultaneously achieve a high Maximum value (correlation maximum value) and many photons (Nc) by adjusting the above θi to 1.1 degrees in consideration of the fixed θs of 1.5 degrees.

[0179] In addition, the mirror can adjust the θi to 0.8 degrees by considering the fixed θs of 1.0 degrees when the θs is fixed to 1.0 degrees.

[0180] In an embodiment, the virtual line into which the pump laser is input may be the same line as the virtual line into which the combined laser is input.

[0181] That is, the combined laser and the pump laser can simultaneously advance along the same virtual line in opposite directions toward the atomic vapor cell at respective locations spaced at the same distance from the atomic vapor cell.

[0182] That is, the combined laser and the pump laser travel along the same virtual line in opposite directions, reach the atomic vapor cell at the same time, and enable manipulation of rubidium atoms.

[0183] The atomic vapor cell generates a signal and an idler by manipulating rubidium atoms, and can output the signal and the idler generated at set θs and θi from the first and second surfaces according to the adjustment of the mirrors.

[0184] In some embodiments, the atomic vapor cell can generate photon pairs through spontaneous four wave mixing (sFWM) in a ladder-shaped atomic configuration.

[0185] Here, sFWM may refer to a structure in which a light source structure is formed by four signals: a pump laser, a coupling laser, a signal, and an idler, and the signal generated in connection with the coupling laser is output while spontaneously dropping from the highest potential position reached by the coupling laser, and also the idler generated in connection with the pump laser is output while spontaneously dropping from the highest potential position reached by the pump laser.

[0186] The optical path along which the pump laser and the coupling laser advance to the atomic vapor cell can be coated with a nano-antireflection coating so that the photon pairs of the signal and the idler can be generated without scattering. That is, the optical path is manufactured with a nano-antireflection coating so that the pump laser and the coupling laser that advance can be input into the atomic vapor cell without reflection along the path, thereby allowing the photon pairs of the signal and the idler to be generated in an optimal state.

[0187] At this time, the optical depth of the optical path is designed to be 100 to 120, so as to increase the absorption rate of the pump laser and the combined laser.

[0188] According to one embodiment of the present invention,87 Using the warm atomic ensemble and ladder-type atomic system of the Rb atomic vapor cell, 87 Rb's cascade-type 5S 1 / 2 -5P 3 / 2 -4D 5 / 2 A high-quality optical communication wavelength quantum light source and a method for implementing a quantum light source generated in an atomic vapor cell using a spontaneous four-wavelength combination (sFWM) process through transition to generate high signal-to-noise ratio (SNR) time-correlated photon pairs can be provided.

[0189] In addition, according to one embodiment of the present invention, it is possible to provide a quantum light source that overcomes the disadvantage of low SNR of two-photon cross-correlation due to the Doppler effect caused by the velocity distribution of a warm atomic ensemble, and generates a high signal-to-noise ratio (SNR) time-correlated photon pair.

[0190] Furthermore, according to one embodiment of the present invention, the stability of the frequency is secured with a precision corresponding to the transition line of the atom, and all four Bell states with very high stability can be strongly generated by applying the unique correlation generated in the atomic system of the ladder structure without using an interferometer configuration.

[0191] In addition, according to one embodiment of the present invention, it is possible to develop a light source of entangled photon pairs with a high production rate using a low pump power.

[0192] The method according to the embodiment may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiment or may be those known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands, such as ROMs, RAMs, and flash memories. Examples of the program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

[0193] Software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing device to perform a desired operation or may, independently or collectively, command the processing device. The software and / or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, computer storage medium or device, or transmitted signal wave, for interpretation by the processing device or for providing instructions or data to the processing device. The software may also be distributed over networked computer systems and stored or executed in a distributed manner. The software and data may be stored on one or more computer-readable recording media.

[0194] Although the embodiments described above have been described with limited drawings, those skilled in the art will appreciate that various technical modifications and variations can be applied based on the above. For example, appropriate results can still be achieved even if the described techniques are performed in a different order than described, and / or components of the described systems, structures, devices, circuits, etc. are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents.

[0195] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

Claims

1. Rubidium ( 87 Rb) an atomic vapor cell containing atoms; and A processor that operates a 780 nm pump laser and a 1529 nm coupling laser in opposite directions based on the above atomic vapor cell. Including, The above atomic vapor cell is, Generate a photon pair of signal and idler, On the first side where the pump laser is input, the signal generated in relation to the combined laser is output, On the second side where the combined laser is input, the idler generated in connection with the pump laser is output, High-quality optical communication wavelength quantum light source.

2. In paragraph 1, The above high-quality optical communication wavelength quantum light source is, The above idler has a cascade structure in which the above idler is generated at 780 nm, the same as the pump laser, and the above signal is generated at 1529 nm, the same as the combination laser. High-quality optical communication wavelength quantum light source.

3. In paragraph 1, The above atomic vapor cell is, Warm rubidium at 99 to 115 degrees ( 87 Rb) filled with atoms, High-quality optical communication wavelength quantum light source.

4. In paragraph 1, A mirror that adjusts the angle θs at which the signal is output on the first surface based on the virtual line into which the pump laser is input, and the angle θi at which the idler is output on the second surface based on the virtual line into which the combined laser is input. A high-quality optical communication wavelength quantum light source, which further includes:

5. In paragraph 4, The above mirror, If the above θs is fixed at 1.5 degrees, Considering the above fixed θs of 1.5 degrees, adjust the above θi to 1.1 degrees. High-quality optical communication wavelength quantum light source.

6. In paragraph 4, The above combined laser and the pump laser, At each location equidistant from the atomic vapor cell, moving simultaneously along the same virtual line in opposite directions toward the atomic vapor cell, High-quality optical communication wavelength quantum light source.

7. In paragraph 1, The above atomic vapor cell is, Generating the photon pairs through spontaneous four wave mixing (sFWM) in a ladder-shaped atomic structure. High-quality optical communication wavelength quantum light source.

8. In paragraph 1, The optical path of the above pump laser and the above combined laser to the atomic vapor cell is: By applying a nano anti-reflection coating, the photon pairs of the signal and the idler are generated without scattering. High-quality optical communication wavelength quantum light source.

9. In paragraph 8, The optical depth of the above optical path is 100 to 120 people, High-quality optical communication wavelength quantum light source.

10. In the processor, rubidium ( 87 Rb) A step of emitting a 780 nm pump laser and a 1529 nm coupling laser in opposite directions based on an atomic vapor cell containing atoms; and In the above atomic vapor cell, a step of generating a photon pair of a signal and an idler, outputting the signal generated in association with the coupling laser on the first side into which the pump laser is input, and outputting the idler generated in association with the pump laser on the second side into which the coupling laser is input A method for implementing a high-quality optical communication wavelength quantum light source, comprising:

11. In paragraph 10, A step of implementing a high-quality optical communication wavelength quantum light source having a cascade structure in which the idler is generated at 780 nm, like the pump laser, and the signal is generated at 1529 nm, like the coupling laser. A method for implementing a high-quality optical communication wavelength quantum light source, which further includes:

12. In paragraph 10, The above atomic vapor cell is, Warm rubidium at 99 to 115 degrees ( 87 Rb) filled with atoms, Method for implementing a high-quality optical communication wavelength quantum light source.

13. In paragraph 10, In the mirror, a step of adjusting the angle θs at which the signal is output on the first surface based on the virtual line into which the pump laser is input, and the angle θi at which the idler is output on the second surface based on the virtual line into which the combined laser is input A method for implementing a high-quality optical communication wavelength quantum light source, which further includes:

14. In paragraph 13, The above adjustment steps are: When the above θs is fixed to 1.5 degrees, a step of adjusting the above θi to 1.1 degrees in consideration of the fixed θs of 1.5 degrees in the above mirror. A method for implementing a high-quality optical communication wavelength quantum light source, which further includes:

15. In paragraph 13, The above combined laser and the pump laser, At each location equidistant from the atomic vapor cell, moving simultaneously along the same virtual line in opposite directions toward the atomic vapor cell, Method for implementing a high-quality optical communication wavelength quantum light source.

16. In paragraph 10, In the above atomic vapor cell, a step of generating the photon pair through spontaneous four wave mixing (sFWM) in a ladder-shaped atomic structure. A method for implementing a high-quality optical communication wavelength quantum light source, which further includes:

17. In paragraph 10, The optical path of the above pump laser and the above combined laser to the atomic vapor cell is: By applying a nano anti-reflection coating, the photon pairs of the signal and the idler are generated without scattering. Method for implementing a high-quality optical communication wavelength quantum light source.

18. In paragraph 17, The optical depth of the above optical path is 100 to 120 people, Method for implementing a high-quality optical communication wavelength quantum light source.

19. A computer-readable recording medium recording a program for executing the method of Article 10.

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