阅读说明：本技术 一种基于非线性分束器的连续变量强纠缠相干性增强装置 (Continuous variable strong entanglement coherence enhancing device based on nonlinear beam splitter ) 是由 张胜利 于 2021-09-01 设计创作，主要内容包括：本申请提供一种基于非线性分束器的连续变量强纠缠相干性增强装置,包括：光源单元,包括EPR强纠缠光源和EPR第一弱纠缠光源,EPR强纠缠光源设有输出端A,EPR第一弱纠缠光源设有第一输出端和第二输出端；第一光子探测器与第一输出端连接；第一自由空间光学通道具有输入端M1和输出端N1,输入端M1与输出端A连接；第一光学反射镜,具有输入端P1和输出端Q1,输入端P1与第二输出端连接；第一光学非线性分束器,具有输入端X1、输入端X2、输出端Y1、输出端Y2,输入端X1与输出端N1连接,输入端X2与输出端Q1连接,其中,输出端Y2用于输出两模纠缠态的其中一个模式；第三光子探测器,与输出端Y1连接。(The application provides a continuous variable strong entanglement coherence enhancing device based on nonlinear beam splitter, including: the light source unit comprises an EPR strong entanglement light source and an EPR first weak entanglement light source, the EPR strong entanglement light source is provided with an output end A, and the EPR first weak entanglement light source is provided with a first output end and a second output end; the first photon detector is connected with the first output end; the first free-space optical channel has an input end M1 and an output end N1, the input end M1 being connected to the output end a; a first optical mirror having an input end P1 and an output end Q1, the input end P1 being connected to the second output end; a first optical nonlinear beam splitter having an input X1, an input X2, an output Y1, an output Y2, an input X1 connected to an output N1, an input X2 connected to an output Q1, wherein the output Y2 is configured to output one mode of the two-mode entangled state; and the third photon detector is connected with the output end Y1.)

1. A continuous variable strong entanglement coherence enhancer based on a non-linear beam splitter, comprising:

the light source unit comprises an EPR strong entanglement light source and an EPR first weak entanglement light source, wherein the EPR strong entanglement light source is provided with an output end A, and the EPR first weak entanglement light source is provided with a first output end and a second output end;

the first photon detector is connected with the first output end;

a first free-space optical channel having an input end M1 and an output end N1, the input end M1 being connected to the output end a;

a first optical mirror having an input end P1 and an output end Q1, the input end P1 being connected to the second output end;

a first optical nonlinear beam splitter having an input X1, an input X2, an output Y1, an output Y2, an input X1 connected to an output N1, an input X2 connected to an output Q1, wherein the output Y2 is configured to output one mode of the two-mode entangled state;

and the third photon detector is connected with the output end Y1.

2. The continuous variable strong entanglement coherence enhancer based on the nonlinear beam splitter as claimed in claim 1, wherein the light source unit further comprises an EPR second weak entanglement light source, the EPR second weak entanglement light source is provided with a third output end and a fourth output end, the EPR strong entanglement light source is provided with an output end a and an output end B, correspondingly, the continuous variable strong entanglement coherence enhancer based on the nonlinear beam splitter further comprises:

the second photon detector is connected with the third output end;

a second free-space optical channel having an input end M2 and an output end N2, the input end M2 being connected to the output end B;

a second optical mirror having an input end P2 and an output end Q2, the input end P2 being connected to the fourth output end;

a second optical nonlinear beam splitter having an input X3, an input X4, an output Y3, an output Y4, an input X3 connected to an output N2, and an input X4 connected to an output Q2, wherein the output Y4 is configured to output one mode of the two-mode entangled state;

and the fourth photon detector is connected with the output end Y3.

3. The non-linear beam splitter based continuously variable strongly entangled coherence enhancer according to claim 1, characterized in that the EPR strongly entangled light source has a degree of compression of 15 dB.

4. The non-linear beam splitter based continuously variable strong-entanglement coherence enhancing apparatus according to claim 2, wherein the degree of compression of the EPR first and second weakly-entangled light sources is 0.43 dB.

5. The non-linear beam splitter based continuously variable strong entanglement coherence enhancing device according to claim 2, wherein the parameters of the first and second optically non-linear beam splitters are 0.43-0.86 dB.

6. The non-linear beam splitter-based continuously variable strong entanglement coherence enhancing apparatus according to claim 2, wherein the first photon detector and the second photon detector are both photon number-resolvable photon detectors, the third photon detector is a photon number-resolvable photon detector or a photon number-indistinguishable photon detector, and the fourth photon detector is a photon number-resolvable photon detector or a photon number-indistinguishable photon detector.

7. A method for determining continuous variable strong-entanglement coherence enhancement, which is applied to the non-linear splitter-based continuous variable strong-entanglement coherence enhancing apparatus according to claim 1, and comprises:

acquiring a first detection result of the first photon detector and a third detection result of the third photon detector;

if the photon number of the first detection result is 1 and the photon number of the third detection result is 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful;

and if the photon number of the first detection result is not 1 or the photon number of the third detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

8. A method for determining continuous variable strong-entanglement coherence enhancement, which is applied to the non-linear beam splitter-based continuous variable strong-entanglement coherence enhancing apparatus according to any one of claims 2 to 6, and comprises:

acquiring a first detection result of the first photon detector, a second detection result of the second photon detector, a third detection result of the third photon detector and a fourth detection result of the fourth photon detector;

if the photon number of the first detection result and the photon number of the second detection result are both 1, and the photon number of the third detection result and the photon number of the fourth detection result are both 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful;

and if the photon number of the first detection result or the photon number of the second detection result is not 1, or the photon number of the third detection result or the photon number of the fourth detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

Technical Field

The application relates to the technical field of continuous variable entanglement control, in particular to a continuous variable strong entanglement coherence enhancing device based on a nonlinear beam splitter.

Background

Quantum entanglement is an important resource in quantum information. Quantum entanglement, of interest today, can be divided into discrete variable quantum entanglement and continuous variable quantum entanglement. Discrete variable quantum entanglement is more pronounced in quantum entanglement of minority-level quantum systems, including atom entanglement and photon entanglement. And the continuous variable quantum entanglement is a new quantum state entanglement form taking the regular coordinate component and the regular momentum component of the quantum light field as main bodies. The continuous variable quantum entangled state has important application in precise measurement and high speed and high capacity continuous variable quantum communication system. The quantum coherence of quantum entanglement is an important index of quantum entanglement, is an important resource of a quantum system, and is an important basis for breaking through the limit of traditional information processing by quantum information processing such as quantum computation, quantum precision measurement and the like.

The quantum coherence for continuously improving the entanglement of the continuous variable quantum has important significance in specific quantum information processing. The team of the inventor proposes a coherence promotion scheme for weak entanglement of continuous variables in 2018 (Photon catalysis as noise amplification and matters application in coherence enhancement, Phys. Rev. A.97.043830 (2018)). However, this solution cannot cope with the problem of multi-photon population in the future of strong entanglement input due to the limitation in photon number processing, and cannot handle the coherency control under the strong entanglement condition. Meanwhile, at present, no report on the improvement of the strong entanglement coherence exists at home and abroad.

Disclosure of Invention

The embodiment of the application aims to provide a continuous variable strong-entanglement coherence enhancing device based on a nonlinear beam splitter, so as to overcome the defects in the prior art, and provide the continuous variable strong-entanglement coherence enhancing device which is simple in principle, good in reliability and easy to realize.

In order to achieve the above object, embodiments of the present application are implemented as follows:

in a first aspect, an embodiment of the present application provides a continuous variable strong entanglement coherence enhancing apparatus based on a nonlinear beam splitter, including: the light source unit comprises an EPR strong entanglement light source and an EPR first weak entanglement light source, wherein the EPR strong entanglement light source is provided with an output end A, and the EPR first weak entanglement light source is provided with a first output end and a second output end; the first photon detector is connected with the first output end; a first free-space optical channel having an input end M1 and an output end N1, the input end M1 being connected to the output end a; a first optical mirror having an input end P1 and an output end Q1, the input end P1 being connected to the second output end; a first optical nonlinear beam splitter having an input X1, an input X2, an output Y1, an output Y2, an input X1 connected to an output N1, an input X2 connected to an output Q1, wherein the output Y2 is configured to output one mode of the two-mode entangled state; and the third photon detector is connected with the output end Y1.

In the embodiment of the application, the non-linear beam splitter-based continuous variable strong entanglement coherence enhancement device is provided, so that the coherence enhancement operation belongs to a markable operation, and whether the coherence enhancement operation succeeds or fails can be marked through the counting of a photon counter. Thus, there is no need to re-prepare a continuous variable strong entanglement for coherence enhancement multiple times. Secondly, the scheme does not need a balanced homodyne detection system, and only utilizes mature commercial photon number detection technology, including a single photon detector or a switch-type photon detector. And the scheme can improve the coherence quality of continuous variable strong entanglement. Moreover, the scheme can overcome the amplitude attenuation noise of a continuous variable strong entangled light field in the transmission process and can also overcome the additional noise introduced by the traditional entangled distillation; the coherence can be further improved on the basis of the existing strong entanglement coherence. In addition, the continuous variable strong entanglement with the enhanced coherence prepared by the scheme can be used for quantum precision measurement and continuous variable quantum calculation based on continuous variables, and can also be applied to quantum secret communication. Therefore, the scheme provides the coherence enhancing device with strong entanglement of continuous variables, which has simple principle, good reliability and easy realization.

Combine the first aspect, in the first possible implementation of the first aspect, the light source unit still includes the EPR second light source that entangles weakly, the EPR second light source that entangles weakly is equipped with third output and fourth output, the EPR light source that entangles strongly is equipped with output A and output B, and is corresponding, the continuous variable coherence enhancer based on nonlinear beam splitter still includes: the second photon detector is connected with the third output end; a second free-space optical channel having an input end M2 and an output end N2, the input end M2 being connected to the output end B; a second optical mirror having an input end P2 and an output end Q2, the input end P2 being connected to the fourth output end; a second optical nonlinear beam splitter having an input X3, an input X4, an output Y3, an output Y4, an input X3 connected to an output N2, and an input X4 connected to an output Q2, wherein the output Y4 is configured to output one mode of the two-mode entangled state; and the fourth photon detector is connected with the output end Y3.

With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the compression degree of the EPR strong-entanglement light source is 15 dB.

With reference to the first possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the compression degree of the EPR first weakly-entangled light source and the EPR second weakly-entangled light source is 0.43 dB.

With reference to the first possible implementation manner of the first aspect, in a fourth possible implementation manner of the first aspect, the parameters of the first optical nonlinear beam splitter and the second optical nonlinear beam splitter are 0.43 to 0.86 dB.

With reference to the first possible implementation manner of the first aspect, in a fifth possible implementation manner of the first aspect, the first photon detector and the second photon detector are both photon-number-resolvable photon detectors, the third photon detector is a photon-number-resolvable photon detector or a photon-number-indistinguishable photon detector, and the fourth photon detector is a photon-number-resolvable photon detector or a photon-number-indistinguishable photon detector.

In a second aspect, an embodiment of the present application provides a method for determining continuous variable strong-entanglement coherence enhancement, which is applied to the nonlinear beam splitter-based continuous variable strong-entanglement coherence enhancement apparatus in the first aspect, and the method includes: acquiring a first detection result of the first photon detector and a third detection result of the third photon detector; if the photon number of the first detection result is 1 and the photon number of the third detection result is 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful; and if the photon number of the first detection result is not 1 or the photon number of the third detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

In a third aspect, an embodiment of the present application provides a method for determining continuous variable strong-entanglement coherence enhancement, which is applied to the device for enhancing continuous variable strong-entanglement coherence based on a non-linear beam splitter according to any one of the first to fifth possible implementation manners of the first aspect, where the method includes: acquiring a first detection result of the first photon detector, a second detection result of the second photon detector, a third detection result of the third photon detector and a fourth detection result of the fourth photon detector; if the photon number of the first detection result and the photon number of the second detection result are both 1, and the photon number of the third detection result and the photon number of the fourth detection result are both 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful; and if the photon number of the first detection result or the photon number of the second detection result is not 1, or the photon number of the third detection result or the photon number of the fourth detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

Fig. 1 is a schematic diagram of a first continuous variable strong-entanglement coherence enhancing apparatus based on a non-linear beam splitter according to an embodiment of the present application.

Fig. 2 is a schematic structural diagram of a light source unit in a first continuous variable strong entanglement coherence enhancing apparatus based on a nonlinear beam splitter according to an embodiment of the present application.

Fig. 3 is a flowchart of a first method for determining strong entanglement coherence enhancement of continuous variables according to an embodiment of the present disclosure.

Fig. 4 is a diagram illustrating the effect of the first continuous variable strong entanglement coherence enhancing apparatus based on the non-linear beam splitter.

Fig. 5 is a schematic diagram of a second continuous variable strong-entanglement coherence enhancing apparatus based on a non-linear beam splitter according to an embodiment of the present application.

Fig. 6 is a schematic structural diagram of a light source unit in a second continuous variable strong entanglement coherence enhancing apparatus based on a nonlinear beam splitter according to an embodiment of the present application.

Fig. 7 is a flowchart of a second method for determining strong entanglement coherence enhancement of continuous variables according to an embodiment of the present application.

Fig. 8 is a diagram illustrating the effect of the second continuous variable strong entanglement coherence enhancing apparatus based on the non-linear beam splitter.

Icon: 100-continuous variable strong entanglement coherence enhancing device; 110-a light source unit; 111-EPR strong entangled light source; 112-EPR first weakly entangled light source; 113-EPR second weakly entangled light source; 121-a first photon detector; 122-a second photon detector; 123-a third photon detector; 124-a fourth photon detector; 131-a first free-space optical channel; 132-a second free-space optical channel; 141-a first optical mirror; 142-a second optical mirror; 151-a first optical nonlinear beam splitter; 152-a second optical non-linear beam splitter.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

Referring to fig. 1, fig. 1 is a schematic diagram of a first continuous variable strong entanglement coherence enhancing apparatus 100 based on a non-linear beam splitter according to an embodiment of the present disclosure.

In this embodiment, the non-linear beam splitter based continuously variable strong entanglement coherence enhancing apparatus 100 may include a light source unit 110, a first photon detector 121, a first free space optical channel 131, a first optical mirror 141, a first optical non-linear beam splitter 151, a third photon detector 123.

Referring to fig. 2, fig. 2 is a schematic structural diagram of a light source unit 110 in a first non-linear beam splitter-based continuous variable strong entanglement coherence enhancing apparatus 100 according to an embodiment of the present disclosure.

Exemplarily, the light source unit 110 may include an EPR strong entanglement light source 111 and an EPR first weak entanglement light source 112, the EPR strong entanglement light source 111 is provided with an output a, and the EPR first weak entanglement light source 112 is provided with a first output and a second output. Here, the EPR entanglement light source refers to Einstein-bodoski-Rosen (Einstein-podlsky-Rosen) entanglement light source.

Illustratively, the first photon detector 121 may be connected to the first output terminal for detecting whether the first output terminal outputs photons.

Illustratively, the first free-space optical channel 131 has an input end M1 and an output end N1, the input end M1 being connected to the output end a.

Illustratively, the first optical mirror 141 has an input end P1 and an output end Q1, the input end P1 being connected to the second output end.

Illustratively, the first optical nonlinear beam splitter 151 has an input X1, an input X2, an output Y1, an output Y2, the input X1 is connected to the output N1, and the input X2 is connected to the output Q1, wherein the output Y2 is configured to output one mode of the two-mode entangled state.

Illustratively, the third photon detector 123 is connected to the output terminal Y1.

The first output end of the EPR first weak entanglement light source 112 is connected to the first photon detector 121, and when the first photon detector 121 detects a photon, the light source unit 110 completes preparation of a required quantum state light field.

In this embodiment, the compression degree of the EPR strong entanglement light source 111 is 15dB, the compression degree of the EPR first weak entanglement light source 112 is 0.43dB, and the parameters of the first optical nonlinear beam splitter 151 and the second optical nonlinear beam splitter 152 are 0.43-0.86 dB.

In the present embodiment, the first photon detector 121 is a photon-number-resolvable photon detector, and the third photon detector 123 is a photon-number-resolvable photon detector or a photon-number-indistinguishable photon detector.

Based on the first non-linear splitter-based continuous variable strong entanglement coherence enhancing apparatus 100, the success or failure of continuous variable strong entanglement coherence enhancement can be determined by using the first continuous variable strong entanglement coherence enhancing determination method.

Here, the first method for determining strong entanglement coherence of continuous variables may include step S11, step S12, and step S13.

Step S11: a first detection result of the first photon detector and a third detection result of the third photon detector are obtained.

Step S12: and if the photon number of the first detection result is 1 and the photon number of the third detection result is 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful.

Step S13: and if the photon number of the first detection result is not 1 or the photon number of the third detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

Referring to fig. 3, fig. 3 is a flowchart of a first method for determining strong entanglement coherence enhancement for continuous variables according to an embodiment of the present application. If and only if the first photon detector 121 detects 1 photon and the third photon detector 123 detects 0 photon, EPR strong entanglement coherence enhancement succeeds (i.e., continuous variable strong entanglement coherence enhancement succeeds); other cases correspond to failure of coherence enhancement. For the first continuous variable strong-entanglement coherence enhancing device 100 based on the nonlinear beam splitter, the success or failure of the continuous variable strong-entanglement coherence enhancement can be quickly and reliably judged by adopting the judging process, and the continuous variable strong-entanglement for coherence enhancement does not need to be prepared again for many times.

The coherence of a quantum state is an important quantum resource, and is defined as the difference between the entropy of a quantum state on a diagonal and the entropy of the quantum state itself. The larger the difference, the greater the coherence of the quantum state. The hot state is a state where only diagonal elements are non-zero, and its coherence is zero. The entropy of a quantum pure state, such as a coherent state, is zero, and the entropy of the corresponding diagonal element is the magnitude of the quantum coherence.

Referring to fig. 4, fig. 4 is a diagram illustrating the effect of the first continuous variable strong entanglement coherence enhancing apparatus 100 based on the non-linear beam splitter. The curve marked with an asterisk gives the magnitude C of the quantum coherence at strong compression input. The curve marked with circles shows the quantum coherence size C after passing through the coherence enhancing device when the parameter of the first optical nonlinear beam splitter 151 is 0.43-0.86 dB. By adopting the 0.43-0.86 dB optical nonlinear beam splitter, the continuous variable strong entanglement coherence enhancer 100 (the first type) can increase the coherence size C.

Referring to fig. 5, fig. 5 is a schematic diagram of a second continuous variable strong entanglement coherence enhancing apparatus 100 based on a non-linear beam splitter according to an embodiment of the present application.

In the present embodiment, the second continuous variable strong entanglement coherence enhancer 100 based on the non-linear beam splitter is further modified based on the first continuous variable strong entanglement coherence enhancer 100 based on the non-linear beam splitter.

Referring to fig. 6, fig. 6 is a schematic structural diagram of a light source unit 110 in a second non-linear beam splitter-based continuous variable strong entanglement coherence enhancing apparatus 100 according to an embodiment of the present application.

In this embodiment, the second continuous variable strong entanglement coherence enhancing apparatus 100 based on a nonlinear beam splitter further includes an EPR second weak entanglement light source 113, the EPR second weak entanglement light source 113 is provided with a third output terminal and a fourth output terminal, and the EPR strong entanglement light source 111 in this light source unit 110 is provided with an output terminal a and an output terminal B.

On this basis, the second non-linear beam splitter based continuously variable strong entanglement coherence enhancing apparatus 100 further comprises a second photon detector 122, a second free space optical channel 132, a second optical mirror 142, a second optical non-linear beam splitter 152 and a fourth photon detector 124.

Illustratively, the second photon detector 122 may be connected to the third output.

Illustratively, the second free-space optical channel 132 has an input end M2 and an output end N2, the input end M2 being connected to the output end B.

Illustratively, the second optical mirror 142 has an input end P2 and an output end Q2, the input end P2 being connected to the fourth output end.

Illustratively, the second optical nonlinear beam splitter 152 has an input X3, an input X4, an output Y3, an output Y4, the input X3 is connected to the output N2, and the input X4 is connected to the output Q2, wherein the output Y4 is configured to output one mode of the two-mode entangled state.

Illustratively, the fourth photon detector 124 may be connected to the output terminal Y3.

A first output of the EPR first weakly entangled light source 112 is connected to the first photon detector 121 and a third output of the EPR second weakly entangled light source 113 is connected to the second photon detector 122. When both the first photon detector 121 and the second photon detector 122 detect a photon, the light source unit 110 completes preparation of a desired quantum state light field.

In the present embodiment, the compression degree of the EPR strong-entanglement light source 111 is 15dB, the compression degree of the EPR first weak-entanglement light source 112 and the EPR second weak-entanglement light source 113 is 0.43dB, and the parameters of the first optical nonlinear beam splitter 151 and the second optical nonlinear beam splitter 152 are 0.43-0.86 dB.

In this embodiment, the first photon detector 121 and the second photon detector 122 are both photon number-resolvable photon detectors, the third photon detector 123 is a photon number-resolvable photon detector or a photon number-indistinguishable photon detector, and the fourth photon detector 124 is a photon number-resolvable photon detector or a photon number-indistinguishable photon detector.

Based on the second continuous variable strong entanglement coherence enhancer 100 based on the nonlinear beam splitter, the success or failure of the continuous variable strong entanglement coherence enhancement can be determined by adopting a second determination method of the continuous variable strong entanglement coherence enhancement.

Here, the second continuous variable strong entanglement coherence enhancement determining method may include step S21, step S22, and step S23.

Step S21: and acquiring a first detection result of the first photon detector, a second detection result of the second photon detector, a third detection result of the third photon detector and a fourth detection result of the fourth photon detector.

Step S22: and if the photon number of the first detection result and the photon number of the second detection result are both 1, and the photon number of the third detection result and the photon number of the fourth detection result are both 0, determining that the enhancement of the strong entanglement coherence of the continuous variables is successful.

Step S23: and if the photon number of the first detection result or the photon number of the second detection result is not 1, or the photon number of the third detection result or the photon number of the fourth detection result is not 0, determining that the enhancement of the strong entanglement coherence of the continuous variables fails.

Referring to fig. 7, fig. 7 is a flowchart of a second method for determining strong entanglement coherence enhancement for continuous variables according to an embodiment of the present application. If and only if the first and second photon detectors 121 and 122 both detect 1 photon, and the third and fourth photon detectors 123 and 124 detect 0 photon, the EPR strong entanglement coherence enhancement is successful (i.e., the continuous variable strong entanglement coherence enhancement is successful); other cases correspond to failure of coherence enhancement. For the second continuous variable strong entanglement coherence enhancing device 100 based on the nonlinear beam splitter, the success or failure of the continuous variable strong entanglement coherence enhancement can be rapidly and reliably judged by adopting the judging process, and the continuous variable strong entanglement for coherence enhancement does not need to be prepared again for many times.

Referring to fig. 8, fig. 8 is a diagram illustrating the effect of the second continuous variable strong entanglement coherence enhancing apparatus 100 based on the non-linear beam splitter. The curve marked with an asterisk in FIG. 8 gives the magnitude of quantum coherence C at strongly compressed inputs; the curve marked with circles gives the magnitude C of the quantum coherence after such a continuously variable strong entanglement coherence enhancing device 100 when the parameters of the optical nonlinear beam splitters (the first optical nonlinear beam splitter 151 and the second optical nonlinear beam splitter 152) are 0.43-0.86 dB. By adopting the 0.43-0.86 dB optical nonlinear beam splitter, the continuous variable strong entanglement coherence enhancer 100 (second type) in the scheme can realize the increase of the coherence size C.

In summary, the embodiment of the present application provides a continuous variable strong entanglement coherence enhancing apparatus 100 based on a non-linear beam splitter, so that the coherence enhancing operation belongs to a markable operation, and the count of the photon counter can mark whether the coherence enhancing operation is successful or failed. Thus, there is no need to re-prepare a continuous variable strong entanglement for coherence enhancement multiple times. Secondly, the scheme does not need a balanced homodyne detection system, and only utilizes mature commercial photon number detection technology, including a single photon detector or a switch-type photon detector. And the scheme can improve the coherence quality of continuous variable strong entanglement. Moreover, the scheme can overcome the amplitude attenuation noise of a continuous variable strong entangled light field in the transmission process and can also overcome the additional noise introduced by the traditional entangled distillation; the coherence can be further improved on the basis of the existing strong entanglement coherence. In addition, the continuous variable strong entanglement with the enhanced coherence prepared by the scheme can be used for quantum precision measurement and continuous variable quantum calculation based on continuous variables, and can also be applied to quantum secret communication. Therefore, the scheme provides the coherence enhancing device with strong entanglement of continuous variables, which has simple principle, good reliability and easy realization.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.