CN116149108A - Quantum entanglement light source analysis structure and analysis system - Google Patents

Abstract

An analytical structure and analytical system of a quantum entangled light source, including a polarization beam splitter, two 1×2 optical switches, a first 2×2 coupler, a second 2×2 coupler, two 2×1 optical splitters, The first optical path, the second optical path, and the third 2×2 coupler, the input end of the polarization beam splitter is configured to receive the quantum entanglement light source, and the first optical path includes the third 1×2 optical switch to form different delays Two branches; at least one of the first optical path and the second optical path includes a second phase shifter. The structure of the analysis structure is simple and the performance is stable.

Description

Quantum Entangled Light Source Analysis Structure and Analysis System

technical field

Embodiments of the present disclosure relate to an analytical structure and an analytical system for a quantum entangled light source.

Background technique

Quantum entanglement is a core tool in quantum information science, which is suitable for quantum key distribution, quantum computing and ultra-dense coding. As a carrier of quantum states, photons are relatively easy to achieve simultaneous multi-degree-of-freedom entanglement. By applying multi-degree-of-freedom entanglement (also known as super entanglement), the dimension of Hilbert space can be greatly increased, thereby effectively increasing the quantum information carried by the transmitted photons. At present, for the generation of super sources, nonlinear optical crystals, such as periodically poled lithium niobate waveguides and Sagnac ring optical path structures, can be realized. However, for the analysis of super entangled sources, due to the large number of entanglement degrees of freedom, discrete optical devices are used to build , there will be characteristics such as complex optical path and poor stability, which makes the performance evaluation of super entanglement source more difficult, and it is also not conducive to improving the performance of high-dimensional quantum key distribution (QKD, Quantum Key Distribution) protocol.

Contents of the invention

At least one embodiment of the present disclosure provides an analytical structure of a quantum entangled light source, including a polarization beam splitter, two 1×2 optical switches, a first 2×2 coupler, a second 2×2 coupler, two 2×1 An optical splitter, a first optical path and a second optical path, the input end of the polarization beam splitter is configured to receive a quantum entanglement light source, and the two output ends are respectively coupled to the input ends of the two 1×2 optical switches, the Each of the two 1×2 optical switches has an output end connected to the input end of the first 2×2 coupler, and the other output end is respectively connected to an input end of the two 2×1 optical splitters; The other input ends of the two 2×1 optical splitters are respectively connected to the output ends of the first 2×2 coupler; the output ends of at least one of the two 2×1 optical splitters pass through the first The phase shifter is coupled to the second 2×2 coupler, and the two output ends of the second 2×2 coupler are respectively coupled to the first optical path and the second optical path; the first optical path and the The second optical path is respectively coupled to the two input ends of the third 2×2 coupler for output; the first optical path includes a third 1×2 optical switch to form two branches with different delays; the second optical path At least one of the first optical path and the second optical path includes a second phase shifter.

In some examples, two output terminals of the third 1×2 optical switch are respectively connected to the two branches, and a delay waveguide is arranged on one branch.

In some examples, the second optical path includes an adjustable attenuator.

In some examples, the first optical path includes the second phase shifter, and the two branches are connected to the second phase shifter through a third 2×1 optical splitter.

In some examples, the first optical path and the second optical path are connected to two output optical ports through a third 2×2 coupler.

In some examples, the 2×1 optical splitter is a 2×1 coupler or a 2×1 optical switch.

In some examples, the polarization beam splitter is a polarization beam splitter rotator.

In some examples, when the optical path between the polarization beam splitter and the two 2×1 optical splitters is turned on, the delay between the second 2×2 coupler and the two branches The shorter branch conducts.

In some examples, when the optical path between the polarization beam splitter and the first 2×2 optical coupler is turned on, the second 2×2 coupler and the two branches are delayed The optical paths between the longer branches are conducted.

At least one embodiment of the present disclosure also provides a quantum entanglement light source analysis system, including two quantum entanglement light source analysis structures provided by any of the above embodiments, and the polarization beam splitters of the two quantum entanglement light source analysis structures are respectively configured to receive Entangling the two photons in a photon pair.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings that need to be used in the embodiments or related technical descriptions. Obviously, the drawings in the following description only relate to some implementations of the present disclosure example, not a limitation of the present disclosure.

FIG. 1 is a schematic structural diagram of an analytical structure of a quantum entangled light source provided by at least one implementation of the present disclosure;

FIG. 2 and FIG. 3 are respectively schematic structural diagrams of the quantum entanglement light source analysis system provided by at least one embodiment of the present disclosure in two degrees of freedom analysis modes.

Detailed ways

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Referring to the non-limiting exemplary embodiments shown in the accompanying drawings and detailed in the following description, the examples of the present disclosure will be more fully described. Embodiments and their various features and advantageous details. It should be noted that the features shown in the figures are not necessarily drawn to scale. The present disclosure omits descriptions of well-known materials, components, and process techniques so as not to obscure the example embodiments of the present disclosure. The examples given are only intended to facilitate understanding of the implementation of the example embodiments of the present disclosure and to further enable those skilled in the art to practice the example embodiments. Accordingly, these examples should not be construed as limiting the scope of the embodiments of the present disclosure.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by those skilled in the art to which the present disclosure belongs. "First", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Comprising" or "comprising" and similar words mean that the elements or items appearing before the word include the elements or items listed after the word and their equivalents, without excluding other elements or items. "Up", "Down", "Left", "Right" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. In the case of no conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

At least one embodiment of the present disclosure provides an analytical structure of a quantum entangled light source, including a polarization beam splitter, two 1×2 optical switches, a second 2×2 coupler, a first 2×2 coupler, two 2×1 Optical splitter, first optical path and second optical path. The input end of the polarization beam splitter is configured to receive a quantum entanglement light source, and the two output ends are respectively coupled to the input ends of the two 1×2 optical switches, and each of the two 1×2 optical switches has an output end connected to the input end of the first 2×2 coupler, and the other output end is respectively connected to each input end of the two 2×1 optical splitters; the other of the two 2×1 optical splitters One input port is respectively connected to the output port of the first 2×2 coupler; the output port of at least one of the two 2×1 optical splitters is coupled to the second 2×2 optical splitter through the first phase shifter A coupler, the two output ends of the second 2×2 coupler are respectively coupled with the first optical path and the second optical path; the first optical path and the second optical path are respectively connected with the third 2×2 The two input terminals of the coupler are coupled for output; the first optical path includes a third 1×2 optical switch to form two branches with different delays; at least one of the first optical path and the second optical path includes the first Binary phase shifter.

In the analysis structure of the quantum entangled light source provided by at least one embodiment of the present disclosure, through the above configuration, the device can be multiplexed to analyze the multi-degree-of-freedom entangled light source, avoiding the cumbersome problem of optical path recombination in the characterization of different degrees of freedom entangled light sources . For example, by selecting the states of two 1×2 optical switches and selecting two branches with different delays, the polarization degree of freedom or energy time degree of freedom can be analyzed for quantum entangled light sources. For example, the measurement base vector can be selected by setting and adjusting the second phase shifter, and on this basis, the phase scanning of the first phase shifter can be performed to analyze the polarization degree of freedom of the quantum entangled light source. For example, by scanning the second phase shifter, the energy-time degree of freedom of the quantum entangled light source can be analyzed. The optical signal is output by the intensity modulator composed of the second 2×2 coupler, the third 2×2 coupler and the second phase shifter between them, and the analytical entanglement can be achieved by observing the optical signals at the two output ports The purpose of the light source. In addition, when analyzing the energy-time degree of freedom, the first phase shifter can be adjusted, thereby adjusting the first 2×2 coupler, the second 2×2 coupler and the first phase shifter between them. The intensity modulator is used to adjust the optical power of the two output ends of the second 2×2 coupler, which helps to balance the optical power of the first optical path and the second optical path, thereby improving the resolution accuracy.

For example, the polarization beam splitter is a polarization beam splitting rotator, which can unify the TE wave and TM wave in the light source into a TE wave or TM wave with higher transmission efficiency according to the waveguide performance, thereby reducing the transmission loss and improving the transmission efficiency .

For example, the 2×2 coupler may be a 2×2 multimode interference coupler.

For example, the 2×1 optical splitter may be a 2×1 coupler, such as a 2×1 multimode interference coupler. In some other examples, the 2×1 optical splitter may also be a 2×1 optical switch.

For example, the couplers referred to in this disclosure are all 50:50 couplers.

FIG. 1 provides an analytical structure of a quantum entanglement light source according to at least one embodiment of the present disclosure. As shown in Figure 1, the analytical structure of the quantum entangled light source includes a polarization beam splitting rotator, and two 1×2 optical switches (1×2 optical switch -1 and 1×2 optical switch-2), a 2×2 multimode interference coupler-1 coupled with each output end of the two 1×2 optical switches (one of the first 2×2 couplers of the present disclosure Example) Two 2×1 multimode interference couplers (that is, 2×1 multimode interference coupler-1 and 2×1 multimode interference coupler-2), 2×2 multimode interference coupler-2 (this An example of a second 2×2 coupler is disclosed), and a first optical path and a second optical path respectively coupled to the two output ends of the 2×2 multimode interference coupler-2, the first optical path and the second optical path are respectively coupled to two input terminals of a 2×2 multimode interference coupler-3 (an example of the third 2×2 coupler of the present disclosure) for output.

For example, the input end of the polarization beam splitting rotator is configured to be connected to the input optical port to receive the quantum entanglement light source. For example, the quantum entanglement light source is a photon in a quantum entangled photon pair.

An output end of the 1×2 optical switch-1 (such as port E in FIG. 1 ) and an output end of the 2×2 multimode interference coupler-1 are respectively coupled to the 2×1 multimode interference coupler-1 Two input ends, the other output end of the 1×2 optical switch-1 (as shown in Figure 1 port G) is coupled to an input end of the 2×2 multimode interference coupler-1; the 1×2 optical switch- One output end of 2 (as shown in port F in Figure 1) and the other output end of the 2×2 multimode interference coupler-1 are respectively coupled to the two input ends of the 2×1 multimode interference coupler-2, the The other output terminal of the 1×2 optical switch-2 (eg, port H in FIG. 1 ) is coupled to the other input terminal of the 2×2 multimode interference coupler-1.

At least one of the two 2x1 multimode interference couplers is coupled to 2x2 multimode interference coupler-2 through a phase shifter. As shown in Figure 1, the two 2×1 multimode interference couplers are respectively coupled to the 2×2 multimode interference coupler-2 through a phase shifter (phase shifter-1 and phase shifter-2). two inputs. This helps to balance the optical losses on the two optical paths.

The first optical path includes a 1×2 optical switch-3 (an example of the third 1×2 optical switch in the present disclosure), and the input terminal I of the 1×2 optical switch-3 is connected to the 2×2 multimode interference coupler- One output end of 2 is coupled, and the two output ends J and K are respectively connected to two branches, one of which is provided with a delay waveguide, so that the delay on this branch is longer than that on the other branch.

The two branches are coupled to one optical path through a 2×1 multimode interference coupler-3 (an example of the third optical splitter of the present disclosure).

At least one of the first optical path and the second optical path includes a phase shifter for selecting a measurement basis when performing polarization degree of freedom resolution.

For example, the first optical path includes a phase shifter, and the two branches are connected to the second phase shifter through a third 2×1 optical splitter. In some other examples, the phase shifter may also be located between the 2×2 multimode interference coupler-2 and the 1×2 optical switch-3.

As shown in Figure 1, the first optical path and the second optical path are phase shifter-3 and phase shifter-4 respectively, that is, phase shifters are all arranged on the two optical paths, which helps to balance the phase shifters on the two optical paths. light loss. The two branches in the first optical path are coupled with the phase shifter-3 through the 2×1 multimode interference coupler-3.

The second optical path also includes an adjustable attenuator, which can balance the Delayed waveguide losses.

For example, the first optical path and the second optical path are connected to two output optical ports through a third 2×2 coupler. By observing the optical signals of the two output optical ports, the purpose of analyzing the entangled light source can be achieved. For example, the two output optical ports 2 and 3 are respectively connected to a single photon detector. For example, the single photon detector is a single photon avalanche photodiode (SPAD).

The analytical structure of the quantum entangled light source can realize the analysis of the multi-degree-of-freedom entangled light source. When the optical path between the polarization beam splitter and the 2×1 multimode interference coupler-1 and 2×1 multimode interference coupler-2 is conducted, the 2×2 multimode interference coupler-2 and the two branches The branch with shorter delay in the path is turned on, which can analyze the polarization degree of freedom of the quantum entangled light source. When the optical path between the polarization beam splitter and the 2×2 multimode interference coupler-1 is turned on, the 2×2 multimode interference coupler-2 is turned on with the branch with a longer delay among the two branches , which can analyze the energy-time degree of freedom of the quantum entangled light source.

For example, in the above optical path structure, the connections or couplings between the components are all waveguide connections or couplings, except for the time-delayed waveguides, the others are all non-delayed waveguides.

All components in the above-mentioned optical path structure can be integrated on one chip, and the structure is simple, the performance is stable, and it is beneficial to save costs. For example, based on silicon photonics integration technology, using the existing silicon photonics design kit (PDK, processdesign kit), on-chip super entanglement source resolution can be realized.

At least one embodiment of the present disclosure also provides a quantum entanglement light source analysis system, the quantum entanglement light source analysis system includes two quantum entanglement light source analysis structures, and the polarization beam splitters of the two quantum entanglement light source analysis structures are respectively configured to receive entangled photons Two photons in a pair. The visibility of the two-photon interference is observed by observing the output light port for signal detection, so as to determine the fidelity of the entangled source in each degree of freedom, thereby evaluating the quality of the entangled photon pair source. For example, when two-photon interference is more than 81% visible, this source of entanglement can be used in quantum key distribution (QKD) protocols, enabling two-party communication. For example, the analytical structures of the two quantum entangled light sources are the same.

The following is an example of the quantum entangled light source analysis system provided by at least one embodiment of the present disclosure, taking the analytical structure of the quantum entangled light source shown in FIG. It is not intended to limit the disclosure.

As shown in FIG. 2 , the quantum entanglement light source analysis system includes two quantum entanglement light source analysis structures shown in FIG. 1 . The analytical structures of the two quantum entangled light sources are respectively located at two ends of the communication, such as the Alice end and the Bob end. The analytical structures of the two quantum entangled light sources are both in the polarization degree of freedom analytical mode, the input terminal C of the 1×2 optical switch-1 is connected to the output terminal E, and the input terminal D of the 1×2 optical switch-2 is connected to the output terminal F, The input terminal I and the output terminal K of the 1×2 optical switch-3 are connected, so that the optical path guide between the polarization beam splitting rotator and the 2×1 multimode interference coupler-1 and 2×1 multimode interference coupler-2 Pass, the optical path between the 2×2 multimode interference coupler-2 and the delay waveguide.

For example, the signal light is input from optical port 1 and optical port 1' respectively, and after passing through the polarization split-speed rotator, the TE mode light in the signal light is output from the output port A, and the TM mode light in the signal light is converted into TE mode from the output port B output. Adjust the phase shifter-3 or phase shifter-4 of the analytical structure at both ends of Alice and Bob, select the measurement base vector of the polarization state (such as the HV base vector or AD base vector), and adjust the phase shifter-1 or phase shifter-4 at either end Phase shifter-2 performs phase scanning, and observes output optical port 2 and output optical port 2', or output optical port 2 and output optical port 3', or output optical port 3 and output optical port 2', or output optical port 3 The single-photon coincidence counting between the output port 3' and the visibility of the two-photon interference are measured to determine the fidelity of the polarization entanglement source and realize the analysis of the polarization degree of freedom.

As shown in Figure 3, the analytical structures of the two quantum entangled light sources are both in the energy-time degree of freedom analytical mode, the input end C of the 1×2 optical switch-1 is connected to the output end G, and the input end of the 1×2 optical switch-2 D is connected to the output terminal H, and the input terminal I of the 1×2 optical switch-3 is connected to the output terminal J, so that the optical path between the polarization beam splitting rotator and the 2×2 multimode interference coupler-1 is conducted, and the 2×2 optical switch-3 2 The multimode interference coupler-2 conducts with the branch with the shorter delay among the two branches.

The signal light is input from optical port 1 and optical port 1' respectively, and after passing through the polarization split-speed rotator, the TE mode light in the signal light is output from A port, and the TM mode light is converted into TE mode and output from B port. Adjust the phase shifter-1 or phase shifter-2 of the analytic structure at both ends of Alice and Bob, so that the optical power of the two input ports of the 2×2 multimode interference coupler-3 is balanced, thereby reducing the delay caused by the waveguide The influence of the unbalanced optical power on the first optical path and the second optical path. Phase scan the phase shifter-3 or phase shifter-4 at either end, observe the output optical port 2 and the output optical port 2', or the output optical port 2 and the output optical port 3', or the output optical port 3 and the output Optical port 2', or single-photon coincidence counting between output optical port 3 and output optical port 3', by measuring the visibility of two-photon interference, to determine the fidelity of the energy-time entanglement source and realize energy-time degree of freedom analysis.

In some other embodiments, the quantum entanglement light source analysis system may also include three or more quantum entanglement light source analysis structures, so as to realize the communication of the quantum network based on multi-photon entanglement source distribution.

The above descriptions are only exemplary implementations of the present disclosure, and are not intended to limit the protection scope of the present disclosure, which is determined by the appended claims.

Claims (10)

1. A quantum entangled light source analysis structure comprises a polarization beam splitter, two 1×2 optical switches, a first 2×2 coupler, a second 2×2 coupler, two 2×1 optical splitters, a first optical path and a second optical path, and a third 2×2 coupler,

wherein the input end of the polarization beam splitter is configured to receive a quantum entanglement light source, and the two output ends are respectively coupled to the input ends of the two 1 x 2 optical switches; one output end of each of the two 1×2 optical switches is connected with the input end of the first 2×2 coupler, and the other output end of each of the two 1×2 optical switches is connected with one input end of each of the two 2×1 optical distributors;

the other input ends of the two 2X 1 optical distributors are respectively connected with the output ends of the first 2X 2 coupler; the output end of the 2 x 1 optical splitter of at least one of the two 2 x 1 optical splitters is coupled to the second 2 x 2 coupler through a first phase shifter, and the two output ends of the second 2 x 2 coupler are respectively coupled with the first optical path and the second optical path;

the first optical path and the second optical path are respectively coupled with two input ends of the third 2×2 coupler to output;

the first optical path comprises a third 1 multiplied by 2 optical switch to form two branches with different delays; at least one of the first optical path and the second optical path includes a second phase shifter.

2. The quantum entanglement light source resolution structure according to claim 1, wherein two output ends of the third 1 x 2 optical switch are respectively connected with the two branches, and a delay waveguide is arranged on one branch.

3. The quantum entangled light source parsing structure of claim 2 wherein the second light path includes an adjustable attenuator.

4. The quantum entangled light source resolution structure of claim 1 wherein the first light path includes the second phase shifter, the two branches being connected to the second phase shifter by a third 2 x 1 optical splitter.

5. The quantum entangled light source parsing structure of claim 1 wherein the first light path and the second light path are connected to two output light ports through the third 2 x 2 coupler.

6. The quantum entangled light source parsing structure of claim 1 wherein the 2 x 1 optical splitter is a 2 x 1 coupler or a 2 x 1 optical switch.

7. The quantum entangled light source resolution structure of claim 1 wherein the polarizing beam splitter is a polarizing beam splitting rotator.

8. The quantum entangled light source parsing structure of any one of claims 1-7 wherein when the optical path between the polarizing beam splitter and the two 2 x 1 optical splitters is conductive, the second 2 x 2 coupler is conductive with the shorter delay branch of the two branches.

9. The quantum entangled light source parsing structure of any one of claims 1-7, wherein when an optical path between the polarizing beam splitter and the first 2 x 2 optical coupler is conductive, the second 2 x 2 coupler is conductive with an optical path between a longer-delay branch of the two branches.

10. A quantum entangled light source resolution system comprising two quantum entangled light source resolution structures as defined in any one of claims 1-9, wherein the polarizing beam splitters of the two quantum entangled light source resolution structures are each configured to receive two photons of an entangled photon pair.

Images