All-fiber quantum information beam splitting device

Abstract

The invention discloses an all-fiber quantum information beam splitting device. The device is composed of a mode-locked fiber laser, a first wavelength division multiplexer, a first 50 / 50 beam splitter, a second 50 / 50 beam splitter, a first polarization controller, a first circulator, a second circulator, a first Sagnac fiber loop, a fourth polarization controller, a first filter, a second filter, a first linear beam splitter, a second linear beam splitter, an electro-optical modulator, a third 50 / 50 beam splitter, a fifth polarization controller, a fourth polarization controller, a fourth polarization controller, a fifth polarization controller, a fourth polarization controller, a fifth polarization controller, a fourth polarization controller and a fifth polarization controller. The system comprises a sixth polarization controller, a seventh polarization controller, a second wavelength division multiplexer, a third wavelength division multiplexer, a second polarization controller, a third polarization controller, a third circulator, a fourth circulator, a second Sagnac optical fiber ring, a ninth polarization controller, a third filter, a fourth filter, a first balance zero beat detector, a second balance zero beat detector and an eighth polarization controller. And a fourth 50 / 50 beam splitter, a third balance zero beat detector, and an electronic spectrum analyzer. According to the device disclosed by the invention, a frequency degenerate and spatial non-degenerate entangled light beam based on the Sagnac optical fiber ring is injected into a frequency degenerate and spatial non-degenerate parameter amplifier based on the Sagnac optical fiber ring, so that three paths of quantum information beam splitting is realized. The device is of an all-fiber structure, is stable and portable, and lays a foundation for the construction of a quantum information network.

Description

Technical Field

[0001] The present invention belongs to the field of quantum information processes, and particularly relates to an all-fiber quantum information beam splitter device. Background Art

[0002] The distribution of information requires the use of a beam splitter. When the information is encoded in an ideal coherent state, using a classical linear beam splitter will reduce the signal-to-noise ratio of the information after beam splitting, because the idle port of the classical linear beam splitter will introduce vacuum noise. To suppress the mixing of vacuum noise and achieve noiseless quantum information beam splitting, that is, the signal-to-noise ratio of the information output from each port is the same as that of the original information, a squeezed vacuum state can be used to fill the idle port of the linear beam splitter (see the literature: Shapiro Jeffrey H., Optical waveguide tap with infinitesimal insertion loss. [J]. Optics Letters, 1980, 5(8):351). In addition, a frequency non-degenerate parametric amplifier injected with a correlated light source can also achieve quantum information beam splitting (see the literature: Xueshi Guo, Xiaoying Li, Nannan Liu and Z. Y. Ou, Quantum information tapping using a fiber optical parametric amplifier with noise figure improved by correlated inputs [J]. Scientific Reports, 2016, 6(1):30214).

[0003] Recently, theoretical studies have shown that three-way noiseless quantum information splitting can be achieved by using a frequency-degenerate and spatially non-degenerate parametric amplifier with correlated light source injection combined with a linear beam splitter (see the literature: Liu N, Li J, Li X, et al. Three-way noiseless signal splitting in a parametric amplifier with quantum correlation[J]. Physical Review A, 2016, 93(6):063838). However, a general fiber parametric amplifier cannot directly output frequency-degenerate and spatially non-degenerate twin beams, so three-way noiseless quantum information splitting cannot be directly achieved based on this theory. According to existing research (see the literature: K. Mori, T. Morioka, and M. Saruwatari, Optical parametric loop mirror[J]. Optics Letters, 1995, 20(12):1424-1426), a nonlinear Sagnac fiber loop can be used as a nonlinear total reflector to reflect the input beam at one port and the generated in-phase scattered beam through the same port. The present invention uses a nonlinear Sagnac fiber loop structure with dual-pump two-port injection to generate frequency-degenerate and spatially non-degenerate correlated beams, and injects them into another nonlinear Sagnac fiber loop structure with dual-pump two-port injection to realize a frequency-degenerate and spatially non-degenerate parametric amplifier with correlated light source injection. Combined with two linear beam splitters, a fully fiber-optic quantum information splitting device is proposed. Summary of the Invention

[0004] The object of the present invention is to achieve noiseless splitting of coherent state encoded information and propose a fully fiber-optic quantum information splitting device.

[0005] The solution of the present invention is as follows: An all-fiber quantum information beam splitter device, characterized in that: the device is composed of a mode-locked fiber laser, a first wavelength division multiplexer, a first 50 / 50 beam splitter, a second 50 / 50 beam splitter, a first polarization controller, a first circulator, a second circulator, a first Sagnac fiber loop, a fourth polarization controller, a first filter, a second filter, a first linear beam splitter, a second linear beam splitter, an electro-optic modulator, a third 50 / 50 beam splitter, a fifth polarization controller, a sixth polarization controller, a seventh polarization controller, a second wavelength division multiplexer, a third wavelength division multiplexer, a second polarization controller, a third polarization controller, a third circulator, a fourth circulator, a second Sagnac fiber loop, a ninth polarization controller, a third filter, a fourth filter, a first balanced homodyne detector, a second balanced homodyne detector, an eighth polarization controller, a fourth 50 / 50 beam splitter, a third balanced homodyne detector, and an electronic spectrum analyzer.The positional relationship is as follows: The mode-locked fiber laser outputs a broadband laser beam, which is divided into a first laser beam, a second laser beam, and a third laser beam by a first wavelength division multiplexer; the first laser beam is divided into a first pump beam and a third pump beam by a first 50 / 50 beam splitter, and the second laser beam is divided into a second pump beam and a fourth pump beam by a second 50 / 50 beam splitter; the first pump beam enters a first Sagnac fiber loop after passing through a first polarization controller and a first circulator, and the second pump beam enters the first Sagnac fiber loop after passing through a second circulator, and a fourth polarization controller is placed in the first Sagnac fiber loop; the beam output from one port of the first Sagnac fiber loop is input to a first linear beam splitter after passing through the first circulator and a first filter, and the beam output from the other port of the first Sagnac fiber loop is input to a second linear beam splitter after passing through the second circulator and a second filter; the third laser beam output by the first wavelength division multiplexer is divided into two beams after passing through an electro-optic modulator and then through a third 50 / 50 beam splitter, one of which is input to the first linear beam splitter after passing through a fifth polarization controller, and the other is input to the second linear beam splitter after passing through a sixth polarization controller; the first linear beam splitter outputs a first signal beam and a second signal beam, and the second linear beam splitter outputs a first idler beam and a second idler beam; the first signal beam is input to a second wavelength division multiplexer after passing through a seventh polarization controller, and the first idler beam is input to a third wavelength division multiplexer; the third pump beam output by the first 50 / 50 beam splitter is input to the second wavelength division multiplexer after passing through a second polarization controller, and the fourth pump beam output by the second 50 / 50 beam splitter is input to the third wavelength division multiplexer after passing through a third polarization controller; the beam output by the second wavelength division multiplexer enters a second Sagnac fiber loop after passing through a third circulator, and the beam output by the third wavelength division multiplexer enters the second Sagnac fiber loop after passing through a fourth circulator, and a ninth polarization controller is placed in the second Sagnac fiber loop; the beam output from one port of the second Sagnac fiber loop is input to a first balanced homodyne detector after passing through the third circulator and a third filter, and the beam output from the other port of the second Sagnac fiber loop is input to a second balanced homodyne detector after passing through the fourth circulator and a fourth filter; the second signal beam output by the first linear beam splitter is input to a fourth 50 / 50 beam splitter after passing through an eighth polarization controller, and the second idler beam output by the second linear beam splitter is input to the fourth 50 / 50 beam splitter; the output beam of the fourth 50 / 50 beam splitter is input to a third balanced homodyne detector; the three signals output by the first balanced homodyne detector, the second balanced homodyne detector, and the third balanced homodyne detector are respectively input to an electronic spectrum analyzer for signal-to-noise ratio analysis.

[0006] The electro-optic modulator is a lithium niobate amplitude modulator. After being modulated by it, the amplitude of the third laser beam carries information, which is the information to be split.

[0007] The first Sagnac fiber loop and the second Sagnac fiber loop described above are both formed by welding a non-linear optical fiber and a 50 / 50 fiber beam splitter.

[0008] The first polarization controller is used to adjust the polarization of the first pump beam so that it has the same polarization as the second pump beam when entering the first Sagnac fiber loop, and a degenerate four-wave mixing process occurs to generate two beams with frequency degeneracy and entanglement characteristics. The fifth polarization controller and the sixth polarization controller are respectively used to adjust the polarization of the two beams output by the third 50 / 50 beam splitter so that they have the same polarization as the output beams of the first filter and the second filter when entering the first linear beam splitter and the second linear beam splitter respectively, and the two beams are coupled. The second polarization controller, the third polarization controller and the seventh polarization controller are respectively used to adjust the polarization of the third pump beam, the fourth pump beam and the first signal beam so that the three beams have the same polarization as the first idler beam when entering the second Sagnac fiber loop, and a degenerate four-wave mixing process occurs to amplify the input first signal beam and the first idler beam without noise. The eighth polarization controller is used to adjust the polarization of the second signal beam so that it has the same polarization as the second idler beam when entering the fourth 50 / 50 beam splitter, and the two beams are coupled. The fourth polarization controller is used to adjust the phase difference of the two-way transmission beam in the first Sagnac fiber loop to zero, so that the two beams with frequency degeneracy and entanglement characteristics in the first Sagnac fiber loop are respectively output from the two ports.

[0009] The ninth polarization controller is used to adjust the phase difference of the two-way transmission beam in the second Sagnac fiber loop to zero, so that the signal and idler beams amplified without noise in the second Sagnac fiber loop are respectively output through the two ports.

[0010] The splitting ratios of the first linear beam splitter and the second linear beam splitter are the same and adjustable.

[0011] The signals output by the first balanced homodyne detector, the second balanced homodyne detector and the third balanced homodyne detector are the signals after three-way quantum information splitting, and are respectively input into an electronic spectrum analyzer for signal-to-noise ratio analysis and compared with the signal-to-noise ratio of the information to be split.

[0012] The beneficial effects of the present invention are as follows: 1. The present invention uses a double non-linear Sagnac fiber loop and combines two linear beam splitters to achieve three-way noiseless quantum information splitting.

[0013] 2. The device of the present invention has an all-fiber structure, is stable, portable and is convenient to access the fiber optic network. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the all-fiber quantum information beam splitter device of the present invention. Detailed Embodiments

[0015] The present invention will be further described below in conjunction with embodiments and the drawings, but the protection scope of the present invention should not be limited thereby.

[0016] Please refer to Figure 1 , Figure 1 is a schematic structural diagram of an embodiment of the all-fiber quantum information beam splitter device of the present invention. The all-fiber quantum information beam splitter device in this embodiment is composed of a mode-locked fiber laser 1, a first wavelength division multiplexer 21, a first 50 / 50 beam splitter 31, a second 50 / 50 beam splitter 32, a first polarization controller 51, a first circulator 61, a second circulator 62, a first Sagnac fiber loop 71, a fourth polarization controller 54, a first filter 81, a second filter 82, a first linear beam splitter 91, a second linear beam splitter 92, an electro-optic modulator 4, a third 50 / 50 beam splitter 33, a fifth polarization controller 55, a sixth polarization controller 56, a seventh polarization controller 57, a second wavelength division multiplexer 22, a third wavelength division multiplexer 23, a second polarization controller 52, a third polarization controller 53, a third circulator 63, a fourth circulator 64, a second Sagnac fiber loop 72, a ninth polarization controller 59, a third filter 83, a fourth filter 84, a first balanced homodyne detector 101, a second balanced homodyne detector 102, an eighth polarization controller 58, a fourth 50 / 50 beam splitter 34, a third balanced homodyne detector 103, and an electronic spectrum analyzer 11.

[0017] The mode-locked fiber laser 1 outputs a broadband laser beam, which is divided by the first wavelength division multiplexer 21 into a first laser beam, a second laser beam, and a third laser beam with different central frequencies. Among them, the first laser beam is divided by the first 50 / 50 beam splitter 31 into a first pump beam and a third pump beam, and the second laser beam is divided by the second 50 / 50 beam splitter 32 into a second pump beam and a fourth pump beam. The first pump beam enters the first Sagnac fiber loop 71 after passing through the first polarization controller 51 and the first circulator 61 and transmits bidirectionally. The second pump beam enters the first Sagnac fiber loop 71 after passing through the second circulator 62 and transmits bidirectionally. The first polarization controller is used to adjust the polarization of the first pump beam so that it has the same polarization as the second pump beam when entering the first Sagnac fiber loop 71, thereby generating a degenerate four-wave mixing process and generating two beams with degenerate frequencies and entanglement characteristics. The fourth polarization controller 54 is placed in the first Sagnac fiber loop 71 and is used to adjust the phase difference of the bidirectionally transmitted beams to zero, so that the generated entangled beams are respectively output from the two ports.

[0018] The light beam output from one port of the first Sagnac fiber loop 71 is input into the first linear beam splitter 91 after passing through the first circulator 61 and the first filter 81. The light beam output from the other port of the first Sagnac fiber loop 71 is input into the second linear beam splitter 92 after passing through the second circulator 62 and the second filter 82. The central frequencies and bandwidths of the two filters are the same. The third laser beam output by the first wavelength division multiplexer 21 has its amplitude modulated by the electro-optic modulator 4 to carry information, which is the information to be beam-split. The light beam output by the electro-optic modulator 4 is split into two beams by the third 50 / 50 beam splitter 33. One of the beams is input into the first linear beam splitter 91 through the fifth polarization controller 55, and the other beam is input into the second linear beam splitter 92 through the sixth polarization controller 56. The two polarization controllers are used to adjust the polarization of the two light beams output by the third 50 / 50 beam splitter 33 so that their polarizations are the same as those of the light beams output by the first filter 81 and the second filter 82 when they are input into the first linear beam splitter and the second linear beam splitter respectively. The beam-splitting ratios of the first linear beam splitter 91 and the second linear beam splitter 92 are the same and adjustable.

[0019] The first linear beam splitter 91 outputs a first signal light beam and a second signal light beam, and the second linear beam splitter 92 outputs a first idler light beam and a second idler light beam. The first signal light beam is input into the second wavelength division multiplexer 22 after passing through the seventh polarization controller 57, and the first idler light beam is input into the third wavelength division multiplexer 23. The third pump light beam output by the first 50 / 50 beam splitter 31 is input into the second wavelength division multiplexer 22 after passing through the second polarization controller 52, and the fourth pump light beam output by the second 50 / 50 beam splitter 32 is input into the third wavelength division multiplexer 23 after passing through the third polarization controller 53. The light beam output by the second wavelength division multiplexer 22 enters the second Sagnac fiber loop 72 after passing through the third circulator 63, and the light beam output by the third wavelength division multiplexer 23 enters the second Sagnac fiber loop 72 after passing through the fourth circulator 64. The second polarization controller 52, the third polarization controller 53, and the seventh polarization controller 57 are respectively used to adjust the polarizations of the third pump light beam, the fourth pump light beam, and the first signal light beam so that the polarizations of the three light beams are the same as that of the first idler light beam when they enter the second Sagnac fiber loop 72, and a degenerate four-wave mixing process occurs to amplify the input first signal light beam and the first idler light beam without noise. The ninth polarization controller 59 is placed in the second Sagnac fiber loop 72 to adjust the phase difference of the two-way transmitted light beams in the fiber loop to zero, so that the amplified signal light beam and idler light beam without noise are respectively output from the two ports of the second Sagnac fiber loop.

[0020] The light beam output from one port of the second Sagnac fiber loop 72 is input into the first balanced homodyne detector 101 after passing through the third circulator 63 and the third filter 83. The light beam output from the other port of the second Sagnac fiber loop 72 is input into the second balanced homodyne detector 102 after passing through the fourth circulator 64 and the fourth filter 84. The center frequencies and bandwidths of the two filters are the same. The second signal light beam output from the first linear beam splitter 91 is input into the fourth 50 / 50 beam splitter 34 through the eighth polarization controller 58. The second idler light beam output from the second linear beam splitter 92 is input into the fourth 50 / 50 beam splitter 34. The eighth polarization controller 58 is used to adjust the polarization of the second signal light beam so that it has the same polarization as the second idler light beam when they are input into the fourth 50 / 50 beam splitter 34. The output light beam of the fourth 50 / 50 beam splitter 34 is input into the third balanced homodyne detector 103. The three signals output from the first balanced homodyne detector 101, the second balanced homodyne detector 102, and the third balanced homodyne detector 103 are signals after quantum information beam splitting. The three signals are respectively input into an electronic spectrum analyzer 11 for signal-to-noise ratio analysis and compared with the signal-to-noise ratio of the information to be beam split.

Claims

1. An all-fiber quantum information beam splitter device, characterized in that, The device consists of a mode-locked fiber laser (1), a first wavelength division multiplexer (21), a first 50 / 50 beam splitter (31), a second 50 / 50 beam splitter (32), a first polarization controller (51), a first circulator (61), a second circulator (62), a first Sagnac fiber loop (71), a fourth polarization controller (54), a first filter (81), a second filter (82), a first linear beam splitter (91), a second linear beam splitter (92), an electro-optic modulator (4), a third 50 / 50 beam splitter (33), a fifth polarization controller (55), a sixth polarization controller (56), a seventh polarization controller (57), a second wavelength division multiplexer (22), a third wavelength division multiplexer (23), a second polarization controller (52), a third polarization controller (53), a third circulator (63), a fourth circulator (64), a second Sagnac fiber loop (72), a ninth polarization controller (59), a third filter (83), a fourth filter (84), a first balanced homodyne detector (101), a second balanced homodyne detector (102), an eighth polarization controller (58), a fourth 50 / 50 beam splitter (34), a third balanced homodyne detector (103), and an electronic spectrum analyzer (11); their positional relationship is as follows: The mode-locked fiber laser (1) outputs a broadband laser beam, which is divided into a first laser beam, a second laser beam, and a third laser beam by the first wavelength division multiplexer (21); the first laser beam is divided into a first pump beam and a third pump beam by the first 50 / 50 beam splitter (31), and the second laser beam is divided into a second pump beam and a fourth pump beam by the second 50 / 50 beam splitter (32); the first pump beam enters the first Sagnac fiber loop (71) after passing through the first polarization controller (51) and the first circulator (61), the second pump beam enters the first Sagnac fiber loop (71) after passing through the second circulator (62), and the fourth polarization controller (54) is placed in the first Sagnac fiber loop (71); the beam output from one port of the first Sagnac fiber loop (71) is input to the first linear beam splitter (91) after passing through the first circulator (61) and the first filter (81), and the beam output from the other port of the first Sagnac fiber loop (71) is input to the second linear beam splitter (92) after passing through the second circulator (62) and the second filter (82); the third laser beam output by the first wavelength division multiplexer (21) is divided into two beams after passing through the electro-optic modulator (4) and the third 50 / 50 beam splitter (33), one of which is input to the first linear beam splitter (91) after passing through the fifth polarization controller (55), and the other is input to the second linear beam splitter (92) after passing through the sixth polarization controller (56); the first linear beam splitter (91) outputs a first signal beam and a second signal beam, and the second linear beam splitter (92) outputs a first idler beam and a second idler beam;The first signal light beam is input into the second wavelength division multiplexer (22) after passing through the seventh polarization controller (57), and the first idler light beam is input into the third wavelength division multiplexer (23); the third pump light beam output by the first 50 / 50 beam splitter (31) is input into the second wavelength division multiplexer (22) after passing through the second polarization controller (52), and the fourth pump light beam output by the second 50 / 50 beam splitter (32) is input into the third wavelength division multiplexer (23) after passing through the third polarization controller (53); the light beam output by the second wavelength division multiplexer (22) enters the second Sagnac fiber loop (72) after passing through the third circulator (63), and the light beam output by the third wavelength division multiplexer (23) enters the second Sagnac fiber loop (72) after passing through the fourth circulator (64), and the ninth polarization controller (59) is placed in the second Sagnac fiber loop (72); the light beam output from one port of the second Sagnac fiber loop (72) is input into the first balanced homodyne detector (101) after passing through the third circulator (63) and the third filter (83); the light beam output from the other port of the second Sagnac fiber loop (72) is input into the second balanced homodyne detector (102) after passing through the fourth circulator (64) and the fourth filter (84); the second signal light beam output by the first linear beam splitter (91) is input into the fourth 50 / 50 beam splitter (34) after passing through the eighth polarization controller (58), and the second idler light beam output by the second linear beam splitter (92) is input into the fourth 50 / 50 beam splitter (34); the output light beam of the fourth 50 / 50 beam splitter (34) is input into the third balanced homodyne detector (103); the three signals output by the first balanced homodyne detector (101), the second balanced homodyne detector (102), and the third balanced homodyne detector (103) are input into an electronic spectrum analyzer (11) for analysis of the information signal-to-noise ratio.; 2. A all-fiber quantum information beam splitter device applicable to that described in claim 1, characterized in that, The electro-optic modulator (4) is a lithium niobate amplitude modulator. After being modulated by it, the amplitude of the third laser beam carries information, which is the information to be split.

3. A full-fiber quantum information beam splitter device applicable to the one described in claim 1, characterized in that, The first Sagnac fiber loop (71) and the second Sagnac fiber loop (72) are both formed by welding a non-linear fiber and a 50 / 50 fiber splitter.

4. A all-fiber quantum information beam splitter device applicable to the one described in claim 1, characterized in that, The first polarization controller (51) is used to adjust the polarization of the first pump beam so that it has the same polarization as the second pump beam when entering the first Sagnac fiber loop (71); the fifth polarization controller (55) and the sixth polarization controller (56) are respectively used to adjust the polarization of the two beams output by the third 50 / 50 beam splitter (33) so that they have the same polarization as the output beams of the first filter (81) and the second filter (82) when entering the first linear beam splitter (91) and the second linear beam splitter (92); the second polarization controller (52), the third polarization controller (53) and the seventh polarization controller (57) are respectively used to adjust the polarization of the third pump beam, the fourth pump beam and the first signal beam so that the three beams have the same polarization as the first idler beam when entering the second Sagnac fiber loop (72); the eighth polarization controller (58) is used to adjust the polarization of the second signal beam so that it has the same polarization as the second idler beam when entering the fourth 50 / 50 beam splitter (34); the fourth polarization controller (54) and the ninth polarization controller (59) are respectively used to adjust the phase difference of the two-way transmission beams in the first Sagnac fiber loop (71) and the second Sagnac fiber loop (72) so that the phase difference of the two-way transmission beams is zero.

5. A all-fiber quantum information beam splitter device applicable to the one described in claim 1, characterized in that, The splitting ratios of the first linear beam splitter (91) and the second linear beam splitter (92) are the same and adjustable.

6. A all-fiber quantum information beam splitter device applicable to the one described in claim 1, characterized in that, The first pump beam and the second pump beam enter the first Sagnac fiber loop (71), and a degenerate four-wave mixing process occurs therein, generating two beams with degenerate frequencies and entanglement characteristics, which are respectively output from the two ports of the first Sagnac fiber loop (71); the third pump beam, the fourth pump beam, the first signal beam, and the first idler beam enter the second Sagnac fiber loop (72), and a degenerate four-wave mixing process occurs therein, amplifying the input first signal beam and first idler beam without noise, and outputting them from the two ports of the second Sagnac fiber loop (72) respectively.

7. A full-fiber quantum information beam splitter device applicable to the one described in claim 1, characterized in that, The signals output by the first balanced homodyne detector (101), the second balanced homodyne detector (102) and the third balanced homodyne detector (103) are three quantum information splitting signals, and the signal-to-noise ratios of the information are respectively analyzed by the electronic spectrum analyzer (11) and compared with the signal-to-noise ratio of the information to be split.

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