WO2021043201A1 - Multi-photon entangled light source - Google Patents

Abstract

The present application provides a multi-photon entangled light source, comprising a laser. A working substance of the laser has a parity. The laser comprises an optical resonant cavity. The optical resonant cavity is a parallel plane standing wave cavity, and comprises a laser output end and a total reflection end opposite to the laser output end. The working substance is subjected to stimulated radiation in the optical resonant cavity to generate a laser in a two-photon entangled state. The laser in the two-photon entangled state propagates back and forth in the optical resonant cavity and is amplified to generate a multi-photon entangled laser. The total reflection end totally reflects the multi-photon entangled laser incident thereon, so that a macro-scale multi-photon entangled laser in a single entangled state is emitted from the laser output end. The multi-photon entangled light source provided by the present application can enable the multi-photon entangled laser output from the laser output end to have a single entangled state, and therefore can be applied in applications such as quantum computing, quantum detection, and quantum communication without performing corresponding processing.

Description

Multiphoton entangled light source

Cross-references to related applications

This application claims the priority of the Chinese patent application with the application number 2019108308140 and the invention title of "Multiphoton Entangled Light Source" filed with the Chinese Patent Office on September 4, 2019, the entire content of which is incorporated into this application by reference.

Technical field

This application relates to the field of optics, in particular to a multiphoton entangled light source.

Background technique

Quantum information science combines quantum mechanics and information science. In quantum information science, quantum entanglement is one of its main characteristics that distinguish it from classical informatics. It has an extremely important position in the field of basic quantum physics research, and it plays an important role in quantum cryptography, quantum communication, quantum computing and other applications. Important role. The optical quantum information processing method is a quantum information processing method, and the photon entangled state is a recent research hotspot in the field of quantum optics.

At present, the team of Chinese scientist Pan Jianwei has achieved a photon entanglement state of ten orders of magnitude, which is currently the highest level in the world publicly reported. The ten-order photon entangled state of Pan Jianwei’s team uses a nonlinear crystal as a parameter, and uses an ultraviolet pulse laser to pump the nonlinear crystal, converts and generates 5 pairs of independent two-photon entangled states, and then obtains ten entangled states through multiphoton interference. An order of magnitude multiphoton entangled state. However, the photon entanglement scheme of Pan Jianwei's team is difficult to expand the number of entangled photons. In applications such as quantum computing, quantum detection and quantum communication, it is necessary to increase the number of photons in an entangled state in order to increase the signal-to-noise ratio of quantum detection and weaken the effect of quantum decoherence.

The prior art discloses a multi-photon entangled light source, which can generate a multi-photon entangled laser with a macro-scale (the number of entangled photons reaches a trillion, on the order of ten trillion). However, the multi-photon entangled light source can only achieve bidirectional output of macro-scale multi-dimensional multi-photon entangled lasers, cannot achieve unidirectional output of macro-scale multi-photon entangled lasers, and cannot directly generate single-entangled multi-photon entangled lasers. In specific applications (for example, quantum computing, quantum lighting, quantum radar, etc.), a unidirectional output light source is usually used, and a single-entangled multi-photon entangled laser is usually used. Therefore, the multi-photon entangled light source in the prior art There are many inconveniences in specific applications.

Summary of the invention

This application provides a multi-photon entangled light source.

A multiphoton entangled light source, comprising a laser, the working substance of the laser is a substance with a parity, the laser comprises an optical resonant cavity, the optical resonant cavity is a parallel plane standing wave cavity, and the optical resonant cavity comprises a laser The output end and the total reflection end opposite to the laser output end, the working substance generates a two-photon entangled laser light by stimulated radiation in the optical resonant cavity, and the two-photon entangled laser light propagates back and forth in the optical resonant cavity And amplify to generate a macro-scale multi-photon entangled laser, the total reflection end performs total reflection on the multi-photon entangled laser incident thereon, so that the macro-scale single-entangled multi-photon entangled laser is emitted from the laser output end Shoot out.

In an embodiment, the laser is a gas laser, a solid laser or a semiconductor laser.

In an embodiment, the gas laser is a helium-neon laser, an argon ion laser, a carbon dioxide laser, or a nitrogen molecular laser.

In an embodiment, the total reflection end includes a first end mirror, and the first end mirror is a total reflection mirror.

In an embodiment, the laser output end includes a second end mirror, and the single-entangled multi-photon entangled laser is emitted from the second end mirror.

In one embodiment, the working substance is an atom, an ion, a molecule with a symmetry center or a crystal with inversion symmetry.

In one embodiment, the multi-photon entangled light source further includes an adjustment component, the adjustment component being arranged on a side of the laser output end away from the total reflection end and located on the light path of the laser. The component is used to adjust the beam area of the laser to be smaller than its coherence area.

In an embodiment, the adjustment component includes a first lens, a second lens, an aperture stop, and an interference filter arranged along the laser emission direction, the first lens has a first focal length, and the first lens has a first focal length. The two lenses have a second focal length value, and the first focal length value is smaller than the second focal length value, and the distance between the first lens and the center of the laser is the second focal length value; The distance between the second lens is the sum of the first focal length value and the second focal length value; the distance between the aperture stop and the second lens is the second focal length value.

In an embodiment, the single entangled state is a polarization entangled state.

In an embodiment, the multiphoton entangled light source further includes a half mirror, the half mirror is arranged on the light path of the laser and located on the side of the adjustment component away from the laser .

In an embodiment, the multi-photon entangled light source further includes a polarizer, and the polarizer is arranged on the light path of the laser and located between the adjustment component and the half mirror.

In an embodiment, the single entangled state is a translational entangled state.

In an embodiment, the multiphoton entangled light source further includes an electromagnetic shielding cover, the electromagnetic shielding cover being arranged outside the laser.

Description of the drawings

In order to better describe and illustrate the embodiments or examples of the present application, one or more drawings may be referred to. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments and examples, and the best mode of these applications currently understood.

FIG. 1 is a schematic diagram of the structure of a multi-photon entangled light source provided by an embodiment of the application;

2 is a schematic structural diagram of a multi-photon entangled light source provided by another embodiment of the application;

FIG. 3 is a schematic structural diagram of a multi-photon entangled light source capable of outputting multi-dimensional multi-photon entanglement provided by the application;

FIG. 4 is a schematic structural diagram of a multi-photon entangled light source provided by another embodiment of the application.

detailed description

In order to make the purpose, technical solutions, and advantages of the application more clear, the application will be described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described here are only used to explain the application, and should not be considered as a limitation to the application.

Please refer to FIG. 1, the multi-photon entangled light source 10 provided by the first embodiment of the present application is used to output a single entangled multi-photon laser on a macro scale. In this article, the macro-scale refers to the number of entangled photons reaching hundreds of millions of orders of magnitude.

The multiphoton entangled light source 10 includes a laser 11. The laser 11 may be a gas laser, a solid laser, a semiconductor laser, or the like. In this embodiment, the laser 11 is a gas laser.

The laser 11 includes an optical resonant cavity 111. In this embodiment, the optical resonant cavity 111 is a parallel plane standing wave cavity. The optical resonant cavity 111 includes a total reflection end 112 and a laser output end 113 disposed opposite to the total reflection end 112. The total reflection end 112 can totally reflect the laser light incident thereon, so that the laser light is output from the laser output end 113. The total reflection end 112 includes a first end mirror 1121. In this embodiment, the first end mirror 1121 is a total reflection mirror.

The working substance in the laser 11 is a substance having a parity. Substances with parity can be, for example, atoms, ions, molecules with symmetry centers, crystals with inversion symmetry, and the like. In this embodiment, gas lasers corresponding to substances with parity include helium-neon lasers, argon ion lasers, carbon dioxide lasers, nitrogen molecular lasers, and the like.

The electronic state and wave function of a substance with a parity all have a parity. Both the spontaneous emission process and the stimulated emission process of a substance with a parity obey the law of conservation of parity. The photon state generated by the spontaneous radiation of the substance with parity in the optical resonant cavity 111 has a parity, the photon state generated by stimulated radiation also has a parity, and the photon state with a parity is a quantum superposition state. A matter with a parity is stimulated by radiation to produce a two-photon entangled state.

Using a parallel plane standing wave cavity as an optical resonant cavity can make the two-photon entangled state generated by the stimulated radiation of a parity substance propagate and amplify back and forth in the optical resonant cavity, thereby generating a multiphoton entangled state. The multiphoton entangled state in the parallel plane standing wave cavity can be expressed as:

When (2.1) and (2.2) occur simultaneously, then:

|Ф _2n > ₀ can be expressed as a 2n plane polarization entangled state:

Among them, |Ф _2n > represents a multiphoton entangled state, and the sign of its subscript corresponds to the sign of ΔJ. When the entangled states represented by equations (2.1) and (2.2) occur at the same time, the subscript is 0; 2n represents The number of photons; J is the total angular momentum of the electronic state, |η ₊ >=|z, K _Z >, |η _- >=|-z, -K _Z > is the translational state along the laser axis (z axis), K _Z is the wave loss of the photon; |R ₊ > is the right circular polarization state, the corresponding photon’s spin angular momentum m=1, |R ₊ >=R _y (π)|R ₊ >, spin angular momentum m=- 1; |L ₊ > is the left circular polarization state, the corresponding spin angular momentum m=-1, |L _- >=R _y (π)|L ₊ >, spin angular momentum m=1; R _y (π) Rotate 180 degrees around the y-axis of the system's measurement coordinates. It can be seen from the above that the two states of the quantum superposition state in the parallel plane standing wave cavity are mirror symmetric to each other, and the mirror symmetry superposition state is emitted along the two symmetric directions of the laser axis, including the translational entangled state and the polarization entangled state. It is a multi-dimensional multi-photon entangled state.

The total reflection end 112 causes the parity to be destroyed, the entangled state of the translation state disappears, and the entangled state of the multiphoton entangled laser output through the laser output end 113 only leaves the entangled state of the polarization state (single entangled state). The expression of the entangled state can be expressed as:

The plane polarization entangled state corresponding to the entangled state of polarization is:

Because the total reflection end 112 destroys the parity, only the translation state η ₊ along the laser axis is left in the translation state, the translation state η _- along the laser axis disappears, and the entangled state of the translation state is destroyed. Therefore, the entangled state of the translation state disappears. _{The η + in} equations (3.1) and (3.2) represents the translational state of the photon, not the entangled translational state of the photon.

It can be understood that, in this embodiment, the laser output end 113 may include a second end mirror 1131. The second end mirror 1131 is arranged in parallel with the first end mirror 1121, and is used to cooperate with the first end mirror 1121 to make the two-photon entangled state generated by the stimulated radiation of the parity substance propagate back and forth in the parallel plane standing wave cavity and enlarge , And then produce macro-scale multi-photon entangled laser. The sum of the reflectance and the transmittance of the second end mirror 1131 is 1, and the transmittance of the second end mirror is greater than zero. Exemplarily, when the laser 11 is a helium-neon laser, the transmittance of the second end mirror 1131 is greater than 0 and less than 1%, and correspondingly, the reflectivity of the second end mirror 1131 is greater than 99% and less than 1. The transmittance of the second end mirror 1131 can be, for example, 0.9%, 0.7%, 0.5%, 0.3%, 0.1%, or any value between the two. Accordingly, the reflectivity of the second end mirror 1131 can be 99.1%, 99.3%, 99.5%, 99.7%, 99.9% or any value in between. In this embodiment, the reflectance of the second end mirror 1131 is 99.7%, and the transmittance is 0.3%. It can be understood that the specific values of the transmittance and reflectance of the second end mirror 1131 here are only an example when the laser 11 is a helium-neon laser, and it is not limited to this, as long as the second end mirror 1131 can achieve the same value as the first end mirror 1131. The end mirror 1121 cooperates to make the two-photon entangled state generated by the stimulated radiation of the parity substance propagate and amplify back and forth in the parallel plane standing wave cavity, thereby generating a macro-scale multi-photon entangled laser, which passes through the first end mirror 1121 The multiphoton entangled light in a single entangled state obtained by performing total reflection to break the parity can be emitted from the second end mirror 1131.

It can be understood that, in this embodiment, the parallel plane standing wave cavity is not provided with an optical element, such as a polarizing element, that destroys the multi-photon entanglement state.

In the multiphoton entangled light source provided by the first embodiment of the present application, the working substance of the laser has a parity and the optical resonant cavity of the laser is a parallel plane standing wave cavity, and the working substance with a parity is generated by stimulated radiation in the parallel plane standing wave cavity Two-photon entangled laser, the two-photon entangled laser propagates back and forth in the optical resonator and amplifies the multi-photon entangled laser that can produce macro-scale (the number of entangled photons is on the order of trillions), while the parallel plane standing wave cavity The total reflection end performs total reflection on the multi-photon entangled laser incident on the total reflection end, so that the multi-photon entangled laser output from the laser output end can be a single-entangled multi-photon entangled laser. Therefore, a unidirectional output can be realized. Large-scale multi-photon entangled laser, and the output laser is a single entangled multi-photon entangled laser, which can be used in quantum computing, quantum detection, quantum communication and other applications without corresponding processing.

It can be understood that in other embodiments, the multi-photon entangled light source 10 further includes an electromagnetic shielding cover provided outside the laser 11 to prevent external magnetic fields from destroying the multi-photon entangled state in the optical resonator 111 of the laser 11.

It can be understood that the multi-photon entangled light source further includes an environment isolation component, and the environment isolation component is used to isolate the light source from the environment, thereby realizing the anti-decoherence effect.

It can be understood that in other embodiments, the laser 11 may take power stabilization measures, including power stabilizing devices.

Referring to FIG. 2, the multi-photon entangled light source provided in the second embodiment of the present application is substantially the same as the multi-photon entangled light source provided in the first embodiment of the present application. The difference is that an adjustment component 12 is provided on the light exiting path of the laser. .

The coherence volume of the laser beam output by the laser 11 can be expressed as:

V=c ³ /[v ² ·Δv·(Δθ) ² ]

Where c is the speed of light, v is the frequency of the laser output by the laser 11, Δv is the half-width of the spectrum line of the laser output by the laser 11, c/Δv is the coherence length of the laser source, and Δθ is the laser beam output by the laser 11 Divergence angle.

In this embodiment, it can be derived from ^{V=c 3} /[v ² ·Δv·(Δθ) ^{2 ]:}

V=(c ² /v ² )·(c/Δv)·[1/(Δθ) ² ],

Among them, (c ² /v ² ) is λ ² , from this we can see that in the above formula (c ² /v ² )·[1/(Δθ) ² ]=(λ/Δθ) ² , so we can get

V=(c/Δv)·(λ/Δθ) ² ,

Among them, (c/Δv) is the calculation formula of the coherence length, and as we can see from the following, (λ/Δθ) ² is the calculation formula of the coherence area, so it can be concluded that the coherence volume is the product of the coherence length and the coherence area.

The coherence area can be expressed as:

S=(λ/Δθ) ²

Among them, S is the coherent area;

λ is the wavelength of the laser light output by the laser 11;

Δθ is the divergence angle of the laser beam output by the laser 11.

Because the photons located in the coherence volume and in the coherence area are homomorphic photons with the same quantum state (momentum and polarization state are the same), and the homomorphic photons are coherent photons. If the divergence angle of the laser beam output by the laser 11 or the half width of the laser spectrum line is large, the coherence volume and the coherence area of the corresponding laser beam will be small, and the multiphoton entangled laser output by the laser 11 will be impure (that is, not All are homomorphic photons). The adjustment component 12 is used to adjust the beam area of the laser beam output by the laser 11 to be smaller than its coherence area, so that the multiphoton entangled light source including the adjustment component 12 can obtain a single entangled state of pure multiphoton entangled light. In this embodiment, the beam area of the laser beam refers to the cross-sectional area of the laser beam.

In this embodiment, the adjustment assembly 12 includes a first lens 121, a second lens 123, an aperture stop 125, and an interference filter 127 that are arranged along the laser emission direction. The first lens 121 has a first focal length value. The second lens 123 has a second focal length value. The first focal length value is smaller than the second focal length value. The distance between the first lens 121 and the center of the laser 11 is the second focal length value. The distance between the first lens 121 and the second lens 123 is the sum of the first focal length value and the second focal length value. The distance between the aperture stop 127 and the second lens 123 is the second focal length value. In this embodiment, both the first lens 121 and the second lens 123 are convex lenses. The interference filter 127 is an ultra-narrowband interference filter.

In this embodiment, the first focal length value is 25mm, the second focal length value is 400mm, the diameter of the aperture stop 127 is 1-7 mm, the divergence angle of the laser output from the aperture stop Δθ=0.02 milliradian, the corresponding coherence area (λ/Δθ) ² =909.83mm2. It can be understood that the description here is only an example, and is not limited thereto.

In this embodiment, the laser 11 is a helium-neon laser. The cavity length of the optical resonant cavity 111 is 150 mm. The laser wavelength λ output by laser 11 is

The laser power is 0.1mw, and the emission angle is in the range of 2.5 to 3.5 milliradians. It can be understood that the description here is only an example, and is not limited thereto.

3, this application provides a unidirectional laser-based multi-photon entangled light source capable of outputting multi-dimensional multi-photon entanglement. Its structure is roughly the same as that of the multi-photon entangled light source provided in the second embodiment of this application, but is different The point is that the half mirror 13 is also included. The half mirror 13 is arranged on the light path of the laser 11 and is located on the side of the adjustment component 12 away from the laser 11. The half mirror 13 can adjust the multi-photon entangled laser in a single entangled state (polarized state entangled state) emitted by the adjusted component 12 to obtain a multi-dimensional multi-photon entangled laser including a translational state and a polarization state.

The regained multi-dimensional entangled state (that is, the entangled state of translation and the entangled state of polarization) multi-photon entangled state satisfies the expression:

Among them, η _∥ and η _⊥ represent the horizontal translation state and the vertical translation state, respectively.

Please refer to FIG. 4, the multi-photon entangled light source provided by the third embodiment of the present application is used to output a macro-scale single-entangled multi-photon entangled laser. Based on the structure shown in FIG. 3, it further includes a polarizer 14. The polarizer 14 is arranged on the light path of the laser 11 and between the adjustment component 12 and the half mirror 13. Since the polarizer 14 is arranged between the adjustment component 12 and the half mirror 13, the laser light emitted by the half mirror 13 can be a multiphoton entangled laser with only a translational entangled state (single entangled state). . The entangled state of the multiphoton entangled laser of the translational entangled state satisfies the following expression:

or

Among them, |ξ _2n > represents the entangled state of the translation state.

In this embodiment, the polarizer 14 can achieve polarization in the X-axis direction or polarization in the Y-axis direction.

The multiphoton light source provided in this embodiment adds a half mirror and a polarizer to the embodiment shown in FIG. 2 so that the output light source is a multiphoton entangled laser in a single entangled state (translational entangled state).

The various technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation manners of the present application, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Industrial applicability

In the multiphoton entangled light source provided in the present application, the working substance of the laser has a parity and the optical resonant cavity of the laser is a parallel plane standing wave cavity, and the working substance with a parity generates a two-photon entangled state in the parallel plane standing wave cavity by stimulated radiation The laser in the two-photon entangled state propagates back and forth in the optical resonator and amplifies the multi-photon entangled laser that can produce macro-scale (the number of entangled photons is in the order of trillions), and the total reflection end of the parallel plane standing wave cavity is The multi-photon entangled laser incident on the total reflection end is totally reflected, which can make the multi-photon entangled laser output from the laser output end a single-entangled multi-photon entangled laser. Therefore, a unidirectional output of macro-scale multi-photon can be achieved. Entangled laser, and the output laser is a single entangled multiphoton entangled laser, which can be used in quantum computing, quantum detection and quantum communication applications without corresponding processing.

Claims (13)

1. A multiphoton entangled light source, comprising a laser, the working substance of the laser is a substance with a parity, the laser comprises an optical resonant cavity, the optical resonant cavity is a parallel plane standing wave cavity, and the optical resonant cavity comprises a laser The output end and the total reflection end opposite to the laser output end, the working substance generates a two-photon entangled laser light by stimulated radiation in the optical resonant cavity, and the two-photon entangled laser light propagates back and forth in the optical resonant cavity And amplify and generate a macro-scale multi-photon entangled laser, the total reflection end performs total reflection on the multi-photon entangled laser incident thereon, so that a macro-scale single entangled multi-photon entangled laser is emitted from the laser output end .
2. The multiphoton entangled light source according to claim 1, wherein the laser is a gas laser, a solid laser or a semiconductor laser.
3. The multiphoton entanglement light source according to claim 2, wherein the gas laser is a helium-neon laser, an argon ion laser, a carbon dioxide laser, or a nitrogen molecular laser.
4. The multiphoton entangled light source according to claim 1, wherein the total reflection end comprises a first end mirror, and the first end mirror is a total reflection mirror.
5. 4. The multi-photon entangled light source according to claim 4, wherein the laser output end comprises a second end mirror, and the single-entangled multi-photon entangled laser is emitted from the second end mirror.
6. The multiphoton entangled light source according to claim 1, wherein the working substance is an atom, an ion, a molecule with a symmetry center or a crystal with inversion symmetry.
7. The multi-photon entangled light source according to claim 1, wherein the multi-photon entangled light source further comprises an adjustment component disposed on a side of the laser output end away from the total reflection end and located at the laser The adjustment component is used to adjust the beam area of the laser to be smaller than its coherence area.
8. The multiphoton entangled light source according to claim 7, wherein the adjustment component comprises a first lens, a second lens, an aperture stop and an interference filter arranged along the laser emission direction, and the first lens has A first focal length value, the second lens has a second focal length value, and the first focal length value is smaller than the second focal length value, and the distance between the first lens and the center of the laser is the second focal length value The distance between the first lens and the second lens is the sum of the first focal length value and the second focal length value; the distance between the aperture stop and the second lens is the second focal length value.
9. The multiphoton entangled light source according to any one of claims 1 to 8, wherein the single entangled state is a polarization entangled state.
10. The multi-photon entangled light source according to claim 7, wherein the multi-photon entangled light source further comprises a half mirror, the half mirror is arranged on the light path of the laser, and is located in the adjustment The side of the component away from the laser.
11. The multi-photon entangled light source according to claim 10, wherein the multi-photon entangled light source further comprises a polarizer, the polarizer is arranged on the light path of the laser, and is located between the adjusting component and the semi-transparent Between half mirrors.
12. The multi-photon entangled light source according to claim 11, wherein the single entangled state is a translational entangled state.
13. The multi-photon entangled light source according to claim 1, wherein the multi-photon entangled light source further comprises an electromagnetic shielding cover, and the electromagnetic shielding cover is arranged outside the laser.

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