Two-mode intensity squeezed entanglement source
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- QUNNECT INC
- Filing Date
- 2026-01-28
- Publication Date
- 2026-08-06
Smart Images
Figure US2026012851_06082026_PF_FP_ABST
Abstract
Description
[0001] Attorney Docket No.: Q0074.70020WO00
[0002] TWO-MODE INTENSITY SQUEEZED ENTANGLEMENT SOURCE CROSS REFERENCE TO RELATED APPLICATIONS
[0003] This application claims the benefit under 35 U. S. C. § 119(e) to U. S. Provisional Application No. 63 / 750,736, filed January 28, 2025, under Attorney Docket No. Q0074.70020US00, titled “TWO-MODE INTENSITY SQUEEZED ENTANGLEMENT SOURCE,” which is incorporated herein by reference in its entirety.
[0004] BACKGROUND
[0005] Quantum networks facilitate the transmission of information in the form of quantum bits (“qubits”) between physically separated quantum processors or other quantum devices (e.g., quantum sensors). Quantum networks may be used to enable optical quantum communication over distances and can be implemented over standard telecommunication optical fibers through the transmission of single photons onto which information is encoded (e.g., in polarization).
[0006] SUMMARY
[0007] The following is a non-limiting summary of some embodiments of the present application. Some aspects of the present application are directed to a photon source including: an atomic vapor cell disposed within beam paths of a first laser beam, a second laser beam, and a third laser beam generated during operation of the photon source, wherein: the atomic vapor cell includes atoms of an atomic species configured to generate two optical signals by a four-wave mixing process, wherein the two optical signals are squeezed due to two-mode squeezing; the first laser beam has a first wavelength selected based on a first atomic transition of the atomic species; the second laser beam has a second wavelength selected based on a second atomic transition of the atomic species; and the third laser beam has a third wavelength selected based on a third atomic transition of the atomic species.
[0008] In some embodiments, the first wavelength is selected to have a first detuning relative to the first atomic transition of the atomic species, the second wavelength is selected to have a second detuning relative to the second atomic transition of the atomic species, and / or the third wavelength is selected to have a third detuning relative to the third atomic transition of the atomic species.
[0009] In some embodiments, the first atomic transition is between a |5S1 / 2state and a |5P3 / 2⟩ state of the atomic species, the second atomic transition is between a |5P3 / 2⟩ state and a |6S1 / 2Attorney Docket No.: Q0074.70020WO00
[0010] state of the atomic species, and / or the third atomic transition is between a |5S1 / 2) state and a |5P1 / 2) state of the atomic species.
[0011] In some embodiments, the atomic species includes an alkali metal or alkali earth metal. In some embodiments, the atomic species includes rubidium.
[0012] In some embodiments, photon pairs of the two optical signals include a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being related to a fourth atomic transition of the atomic species. In some embodiments, the fourth atomic transition is between a |6S1 / 2) state and a |5P1 / 2) state of the atomic species.
[0013] In some embodiments, the first, second, and third laser beams intersect at a location within the atomic vapor cell.
[0014] In some embodiments, the third laser beam is arranged to enter the atomic vapor cell along a first direction perpendicular to a face of the atomic vapor cell, the first laser beam is arranged to enter the atomic vapor cell along a second direction being defined by an angle greater than or equal to 0° and less than or equal to 5° between the first and second directions, and the second laser beam is arranged to enter the atomic vapor cell along a third direction defined by an angle less than or equal to 0° and greater than or equal to -5° between the first and third directions.
[0015] In some embodiments, during operation of the photon source: the first and second laser beams are operated at powers in a range from 5 mW to 50 mW, and the third laser beam is operated at a power in a range from 0.01 µW to 1 mW.
[0016] In some embodiments, during operation of the photon source: the first and / or the second laser beam is operated at a first power having a first value, and the third laser beam is operated at a power having a second value, the second value being less than the first value. In some embodiments, the second value is a factor less than the first value, the factor being in a range from 1,000 to 2,000.
[0017] In some embodiments, the first wavelength and the second wavelength have values configured to satisfy conditions for a four-wave mixing process in the atomic species.
[0018] In some embodiments, the third wavelength is compatible with telecommunications technology and the fourth wavelength is a near-infrared (NIR) wavelength.
[0019] In some embodiments, the third wavelength is in a range from 700 nm to 925 nm. In some embodiments, the third wavelength is in a range from 750 nm to 850 nm. In some embodiments, the third wavelength is approximately 795 nm or approximately 780 nm.Attorney Docket No.: Q0074.70020WO00
[0020] In some embodiments, the fourth wavelength is in a range from 1300 nm to 1600 nm. In some embodiments, the fourth wavelength is approximately 1324 nm. In some embodiments, the fourth wavelength is approximately 1324 nm, approximately 1367 nm, approximately 1476 nm, or approximately 1529 nm.
[0021] In some embodiments, the first wavelength is approximately 780 nm, the second wavelength is approximately 1367 nm, the third wavelength is approximately 795 nm, and the fourth wavelength is approximately 1324 nm.
[0022] In some embodiments, the photon source further includes a first output and a second output optically coupled to outputs of the atomic vapor cell such that a first optical signal of the two optical signals exits the photon source from the first output and a second optical signal of the two optical signals exits the photon source from the second output.
[0023] In some embodiments, the photon source further includes a polarizer between a source of the third laser beam and the atomic vapor cell, the polarizer aligned to a polarization.
[0024] In some embodiments, the photon source further includes polarizing beam splitters disposed between sources of the first and second laser beams and the atomic vapor cell, the polarizing beam splitters being configured to allow transmission of light having an polarization.
[0025] In some embodiments, the photon source further includes: a first laser configured to generate the first laser beam during operation of the photon source; a second laser configured to generate the second laser beam during operation of the photon source; and a third laser configured to generate the third laser beam during operation of the photon source.
[0026] In some embodiments, the techniques described herein relate to a method of generating two optical signals squeezed by two-mode squeezing, the method including: generating a first laser beam having a first wavelength selected based on a first atomic transition of an atomic species; generating a second laser beam having a second wavelength selected based on a second atomic transition of the atomic species; generating a third laser beam having a third wavelength selected based on a third atomic transition of the atomic species; causing a four- wave mixing process and two-mode squeezing in an atomic vapor cell containing atoms of the atomic species by passing the first laser beam, the second laser beam, and the third laser beam through the atomic vapor cell; and generating, as a result of the four-wave mixing process and the twomode squeezing, the two optical signals.
[0027] In some embodiments, the method further includes: configuring the first laser beam to have a first detuning relative to the first atomic transition of the atomic species, configuring the second wavelength to have a second detuning relative to the second atomic transition of theAttorney Docket No.: Q0074.70020WO00
[0028] atomic species, and / or configuring the third wavelength to have a third detuning relative to the third atomic transition of the atomic species.
[0029] In some embodiments, the method further includes: selecting the first wavelength based on the first atomic transition being between a |5S1 / 2) state and a |5P3 / 2) state of the atomic species, selecting the second wavelength based on the second atomic transition being between a |5P3 / 2) state and a |6S1 / 2) state of the atomic species, and / or selecting the third wavelength based on the third atomic transition being between a |5S1 / 2) state and a |5P1 / 2) state of the atomic species.
[0030] In some embodiments, the atomic species includes an alkali metal or alkali earth metal. In some embodiments, the atomic species includes rubidium.
[0031] In some embodiments, photon pairs of the two optical signals include a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being associated with a fourth atomic transition of the atomic species.
[0032] In some embodiments, the fourth atomic transition is between a |6S1 / 2) state and a |5P1 / 2) state of the atomic species.
[0033] In some embodiments, the method further includes: arranging the third laser beam to enter the atomic vapor cell along a first direction perpendicular to a face of the atomic vapor cell, arranging the first laser beam to enter the atomic vapor cell along a second direction being defined by an angle greater than or equal to 0° and less than or equal to 5° between the first and second directions, and arranging the second laser beam to enter the atomic vapor cell along a third direction defined by an angle less than or equal to 0° and greater than or equal to -5° between the first and third directions.
[0034] In some embodiments, generating the first laser beam and the second laser beam includes generating the first laser beam and the second laser beam with powers in a range from 5 mW to 50 mW, and generating the third laser beam includes generating the third laser beam with a power in a range from 0.01 µW to 1 mW.
[0035] In some embodiments, generating the first laser beam and / or the second laser beam includes generating the first laser beam and / or the second laser beam with a first power having a first value, and generating the third laser beam includes generating the third laser beam with a second power having a second value, the second value being less than the first value. In some embodiments, the second value is a factor less than the first value, the factor being in a range from 1,000 to 2,000.Attorney Docket No.: Q0074.70020WO00
[0036] In some embodiments, the first wavelength and the second wavelength have values configured to satisfy conditions for causing a four-wave mixing process in the atomic species.
[0037] In some embodiments, the third wavelength is compatible with telecommunications technology and the fourth wavelength is a near-infrared (NIR) wavelength.
[0038] In some embodiments, third wavelength is in a range from 700 nm to 925 nm. In some embodiments, the third wavelength is in a range from 750 nm to 850 nm. In some embodiments, the third wavelength is approximately 795 nm or approximately 780 nm.
[0039] In some embodiments, the fourth wavelength is in a range from 1300 nm to 1600 nm. In some embodiments, the fourth wavelength is approximately 1324 nm.
[0040] In some embodiments, the fourth wavelength is approximately 1324 nm, approximately 1367 nm, approximately 1476 nm, or approximately 1529 nm.
[0041] In some embodiments, the first wavelength is approximately 780 nm, the second wavelength is approximately 1367 nm, and the third wavelength is approximately 795 nm.
[0042] In some embodiments, photon pairs of the two optical signals include a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being associated with a fourth atomic transition of the atomic species, and the fourth wavelength is approximately 1324 nm.
[0043] The foregoing apparatus and method embodiments may be implemented with any suitable combination of embodiments, features, and acts described above or in further detail below. These and other aspects, embodiments, and features of the present teachings can be more fully understood from the following description in conjunction with the accompanying drawings.
[0044] BRIEF DESCRIPTION OF DRAWINGS
[0045] Various aspects and embodiments will be described with reference to the following figures. It should be appreciated that the figures are not necessarily drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.
[0046] FIG. 1 is a schematic diagram of a photon source 100, in accordance with some embodiments of the technology described herein.
[0047] FIG. 2 is an illustrative energy level diagram for certain atomic species, in accordance with some embodiments of the technology described herein.Attorney Docket No.: Q0074.70020WO00
[0048] FIG. 3 is a schematic diagram of a photon source 300 with beam paths arranged at incident angles relative to a face of the atomic vapor cell, in accordance with some embodiments of the technology described herein.
[0049] FIG. 4A shows measured gain as a function of detuning of a pump beam and the probe beam of the photon source, in accordance with some embodiments of the technology described herein.
[0050] FIG. 4B is a plot showing a horizontal slice (e.g., for a fixed detuning of the 1367 nm pump beam) of FIG. 4A and measured gain with only the probe beam present, in accordance with some embodiments of the technology described herein.
[0051] FIG. 5A is a plot showing measured noise including electronic noise and for squeezed and coherent output optical signals, in accordance with some embodiments of the technology described herein.
[0052] FIG. 5B is a section of the plot of FIG. 5A showing more detail of the noise measurements for squeezed and coherent output optical signals, in accordance with some embodiments of the technology described herein.
[0053] FIG. 6 is a plot showing measured gain as functions of pump and probe detunings, in accordance with some embodiments of the technology described herein.
[0054] FIG. 7 is a plot showing measured squeezing as a function of the detuning of the probe beam, in accordance with some embodiments of the technology described herein.
[0055] FIG. 8 is a flowchart describing a process 800 of generating two squeezed optical signals, in accordance with some embodiments of the technology described herein.
[0056] DETAILED DESCRIPTION
[0057] Described herein are techniques for generating two optical signals having squeezed states due to two-mode squeezing. These techniques include the use of two pump laser beams and a probe laser beam to cause four-wave mixing and two-mode squeezing in atoms of an atomic species (e.g., in an atomic vapor). The two pump laser beams interact with atoms of the atomic vapor and, through a four-wave mixing process, cause the generation of photon pairs having two wavelengths to be emitted from the atomic vapor cell. The probe laser beam “seeds” the four-wave mixing process and introduces squeezing to both of the output optical signals, causing quantum correlation of intensity fluctuations of the two optical signals. The output optical signals and their noise correlations may then be used for various applications, including secure transmission of quantum information and providing connections between sensitive sensors like magnetometers.Attorney Docket No.: Q0074.70020WO00
[0058] Quantum communication leverages the special properties of quantum mechanics in order to exponentially enhance encoding, processing and transferring information. Whether the end goal is connecting quantum computers, performing ultra-precise sensing measurements, or creating quantum- secured communication networks, all would rely on the connection of heterogeneous quantum devices. Such devices are often not intrinsically, communicatively compatible; for example, they may operate using different frequencies or spatial modes (e.g., transmitting over free space or optical fiber). For example, atomic magnetometers (AMs) use rubidium (Rb) atoms to measure magnetic fields with sensitivities better than 10 T / VHz by detecting the change in the polarization state of the magnetic fields interacting with the Rb atoms. Networking an array of AMs with a polarization-entangled photon source would be desirable for improving measurement sensitivity, similar to what has been proposed for a long-baseline telescope based on a quantum repeater. Many applications require multiple sensors that work jointly to tackle distributed sensing problems.
[0059] However, this realization still remains elusive as AMs and other atomic-based sensors typically operate at wavelengths of approximately 780-795 nm instead of 1300 nm and / or 1550nm which are commonly used for optical fiber communication. The same challenge is also faced for room temperature quantum memories and many other atomic technologies such as quantum simulators and photonic phase modulators. The communication between quantum devices is even further complicated as quantum technology transitions from static to mobile quantum devices (e.g., aero- or naval quantum nodes). To connect these mobile nodes to each other efficiently, photons with near-infrared (NIR) wavelengths (780-795 nm) have been shown to experience reduced atmospheric loss and disturbances compared to photons at optical fiber-compatible wavelengths (e.g., infrared wavelengths). There exists a significant and unmet need for devices which enable cross-device frequency compatibility in quantum- secure networks.
[0060] The inventors have also recognized and appreciated that entanglement alone cannot improve the sensitivity of these networks. Rather, entangled squeezed states can provide sufficiently improved sensitivity to quantum- secure networks. Squeezed states are quantum states that have a component with an uncertainty below that of Heisenberg’s uncertainty principle, in contrast with a normal entanglement source which is fundamentally limited by Heisenberg’s uncertainty principle. In particular, squeezed states are useful where sensitive noise measurements are desired, as squeezed states generated by two-mode squeezing exhibit quantum-correlated noise (e.g., intensity fluctuations). Comparing output photons from a two-Attorney Docket No.: Q0074.70020WO00
[0061] mode squeezed entanglement source therefore enables low-noise connections between sensors, as comparing output photons from such an optical source allows for the cancellation of all noise in the optical signals. As one example, a two-mode squeezed entanglement source could provide an input optical signal to an atomic magnetometer (e.g., a rubidium-based magnetometer), the input optical signal having reduced noise compared to a normal laser input that could be provided to the atomic magnetometer. Noise reductions due to two-mode squeezing are also useful for cybersecurity applications, as reduced signal noise can make eavesdropping more difficult (e.g., by making signal tampering more apparent).
[0062] Accordingly, the inventors have developed systems and methods for generating entangled optical signals having squeezed states and different wavelengths suitable for integration between atomic and telecommunications technologies. In some embodiments, the techniques include generating a first laser beam, a second laser beam, and a third laser beam (e.g., using suitable lasers). The first, second, and third laser beams may be directed through an atomic vapor cell containing an atomic vapor formed of atoms of an atomic species. The first and second laser beams may be pump beams having first and second wavelengths corresponding to first and second atomic transitions of the atomic species, and stimulation of the atomic vapor by the first and second laser beams may cause spontaneous four-wave mixing (SFWM) in the atomic vapor. The third laser beam may be a probe beam having a third wavelength corresponding to a third atomic transition of the atomic species, and stimulation of the atomic vapor by the third laser beam (e.g., at a same time as stimulation by the first and second laser beams) may “seed” the atomic vapor medium, thereby inducing two-mode squeezing of the output optical signals generated by the SFWM process.
[0063] Following below are more detailed descriptions of various concepts related to, and embodiments of, techniques for generating pairs of optical signals having two-mode squeezing. It should be appreciated that various aspects described herein may be implemented in any of numerous ways. Examples of specific implementations are provided herein for illustrative purposes only. In addition, the various aspects described in the embodiments below may be used alone or in any combinations and are not limited to the combinations explicitly described herein.
[0064] FIG. 1 is a schematic diagram of a photon source 100, in accordance with some embodiments of the technology described herein. The photon source 100 is configured to receive (e.g., through suitable input ports or from integrated lasers, not shown) a first laser beam 102, a second laser beam 104, and a third laser beam 106. The first laser beam 102 and the second laser beam 104 may be configured as pump beams, while the third laser beam 106Attorney Docket No.: Q0074.70020WO00
[0065] may be configured as a probe beam. The first laser beam 102, the second laser beam 104, and the third laser beam 106 may have respective different wavelengths
[0066]
[0067] d2, and d3. For example, the first laser beam 102 and the second laser beam 104 may have wavelengths selected based on first and second atomic transitions of atoms in an atomic vapor stored within an atomic vapor cell 116 located within a beam path of the first, second, and third laser beams 102, 104, and 106.
[0068] In some embodiments, atomic vapor cell 116 may contain an atomic vapor comprising atoms that may, upon receipt of pump fields (e.g., first and second laser beams 102, 104) absorb received photons of certain frequencies, go through a two-stage excitation and decay process, and re-emit photons having entangled polarization states. Additionally, upon receipt of a probe beam (e.g., third laser beam 106), which may “seed” the atomic vapor medium, the photons reemitted from the atomic vapor by the two-stage excitation and decay process may also be squeezed according to two-mode squeezing.
[0069] In some embodiments, the first and second laser beams 102, 104 (e.g., the pump beams) may be operated at higher powers than the third laser beam 106 (e.g., the probe beam). As one example, the first and second laser beams 102, 104 may be operated at powers in a range from 5 mW to 50 mW, and the third laser beam 106 may be operated at a power in a range from 0.01 µW to 1 mW. In some embodiments, the third laser beam 106 may be operated at a power having a value that is a factor in a range from 1,000 to 2,000 times less than a power of the first laser beam 102.
[0070] In some embodiments, the atomic vapor cell 116 may contain an atomic vapor of an atomic species having atomic energy transitions exhibiting a diamond shape (e.g., thereby exhibiting a two-photon resonance suitable to support spontaneous four-wave mixing processes). As one example, the atomic vapor cell 116 may contain an atomic vapor of an alkali metal or alkali earth metal. As another example, the atomic vapor cell 116 may contain an atomic vapor of rubidium (e.g.,87Rb,85Rb, or any other suitable isotope). Alternatively, in some embodiments, atomic vapor cell 116 may contain an atomic vapor of another alkali metal including but not limited to isotopes of cesium (e.g.,133Cs, or any other suitable isotope).
[0071] FIG. 2 is an illustrative energy level diagram 200 for certain atomic species exhibiting a two-photon resonance that permits generation of entangled photon pairs at two desired wavelengths. As shown in FIG. 2, such an atomic species exhibits a two-photon resonance (or four-wave mixing process) along the transitions from 1202) 1204) 1206) associated with wavelengths and d2, where reference numerals 202, 204, and 206 represent arbitrary atomicAttorney Docket No.: Q0074.70020WO00
[0072] states. As shown in the energy level diagram 200, the atomic species also exhibits a two-photon decay path along the transitions from 1206) 1208) 1202) associated with wavelengths d3and A4. That is, if the atomic species is stimulated by light having wavelengths
[0073] and d2, the atomic species will output light having wavelengths d3and d4. It should be appreciated that this process is symmetrical such that if the atomic species is stimulated by light having wavelengths d3and d4, the atomic species will output light having wavelengths
[0074]
[0075] and d2.
[0076] As one example,85Rb exhibits a two-photon resonance (or four-wave mixing process) along the transitions |
[0077]
[0078] 5S1 / 2) |5P3 / 2) |6S1 / 2) corresponding to excitations caused by received light having wavelengths of approximately
[0079]
[0080] ~ 780 nm and λ2≈ 1367 nm. This four- wave mixing process can generate entangled photons having wavelengths of approximately λ3≈ 795 nm and approximately λ4≈ 1324 nm along the two-photon decay path from |
[0081]
[0082] 6S1 / 2) |5P1 / 2) |5S1 / 2). Alternatively or additionally, a two-photon resonance in an87Rb and / or85Rb vapor may be used to generate photon pairs having wavelengths of approximately 1367 nm and 780 nm, 1476 nm and 795 nm, and / or 1529 nm and 780 nm, based on the selections of
[0083] and d2, providing a flexible photon source that may be used to generate a spectrum of wavelengths in the NIR, O, C, and / or S bands. These particular bands have a wide range of applications across quantum communications and computation. For example, the wavelengths 1324 nm (or 1367 nm), 1476 nm, and 1529 nm each respectively correspond to O, S, and C telecom bands, and are suitable wavelengths for optical fiber communications over large distances. Additionally, the wavelengths 795nm and 780nm are commonly used for quantum buffers and sensors, including but not limited to magnetometers.
[0084] This illustrative transition cycle offers few pathways for photons to spontaneously decay to the ground state, providing a higher rate of entanglement and fewer output uncorrelated photons. It should be appreciated that other similar two-photon resonances may exist in other isotopes of rubidium or other atomic systems. As additional examples, potential wavelengths of photon pairs that may be generated in87Rb and133Cs systems are provided in Tables 1 and 2, respectively. These additional illustrative wavelengths may be used to interface with some Rydberg and ion technologies such as neutral quantum computers and sensors. Table 1: Wavelengths of photon pairs that can be generated from atomic transitions in87Rb.
[0085] Transitions between the Transitions between the
[0086]
[0087] Di line and nS states D2line and nS statesAttorney Docket No.: Q0074.70020WO00
[0088] n First Second First Second Wavelength Wavelength Wavelength Wavelength (nm) (nm) (nm) (nm) 4
[0089] 5
[0090] 6 1323.88 1366.87
[0091] 7 1323.88 728.20 1366.87 741.02 8 1323.88 607.23 1366.87 616.12 9 1323.88 558.03 1366.87 565.53 10 1323.88 532.38 1366.87 539.21 11 1323.88 517.11 1366.87 523.54 12 1323.88 507.20 1366.87 513.39 13 1323.88 500.38 1366.87 506.40 14 1323.88 495.47 1366.87 501.38 15 1323.88 491.82 1366.87 497.63 16 1323.88 489.02 1366.87 494.77 17 1323.88 486.83 1366.87 492.52 18 1323.88 485.073 1366.87 490.73 19 1323.88 483.65 1366.87 489.27 20 1323.88 482.48 1366.87 488.08 n -> oo 1323.88 474 1366.87 479
[0092] Transitions between the Transitions between the Di line and nS states D2line and nS states n First Second First Second Wavelength Wavelength Wavelength Wavelength (nm) (nm) (nm) (nm) 4 1475.64 1529.26
[0093] 5 1475.64 762.10 1529.26 776.16 6 1475.64 620.80 1529.26 630.10 7 1475.64 564.93 1529.26 572.62 8 1475.64 536.42 1529.26 543.35 9 1475.64 519.68 1529.26 526.17 10 1475.64 508.94 1529.26 515.17 11 1475.64 501.62 1529.26 507.67 12 1475.64 496.38 1529.26 502.31 13 1475.64 492.51 1529.26 498.34 14 1475.64 489.56 1529.26 495.32 15 1475.64 487.25 1529.26 492.96
[0094]
[0095] Attorney Docket No.: Q0074.70020WO00
[0096] 16 1475.64 485.42 1529.26 491.08
[0097] 17 1475.64 483.93 1529.26 489.56
[0098] 18 1475.64 482.71 1529.26 488.31
[0099] 19 1475.64 481.70 1529.26 487.28
[0100] 20 1475.64 480.85 1529.26 486.41
[0101] n -> oo 1475.64 474 1529.26 479
[0102]
[0103] Table 2: Wavelengths of photon pairs that can be generated from atomic transitions in133Cs.
[0104] Transitions between the Transitions between the D1line and nS states D2line and nS states n First Second First Second Wavelength Wavelength Wavelength Wavelength (nm) (nm) (nm) (nm)
[0105] 4
[0106] 5
[0107] 6
[0108] 7 1359.20 1469.89
[0109] 8 1359.20 761.10 1469.89 794.61
[0110] 9 1359.20 635.63 1469.89 658.83
[0111] 10 1359.20 584.05 1469.89 603.58
[0112] 11 1359.20 557.00 1469.89 574.73
[0113] 12 1359.20 540.82 1469.89 557.52
[0114] 13 1359.20 530.29 1469.89 546.34
[0115] 14 1359.20 523.03 1469.89 538.64
[0116] 15 1359.20 517.79 1469.89 533.09
[0117] 16 1359.20 513.88 1469.89 528.94
[0118] 17 1359.20 510.89 1469.89 525.77
[0119] 18 1359.20 508.54 1469.89 523.28
[0120] 19 1359.20 506.66 1469.89 521.29
[0121] 20 1359.20 505.13 1469.89 519.68
[0122] n -> oo 1359.20 494 1469.89 508 Transitions between the Transitions between the Di line and nS states D2line and nS states n First Second First Second Wavelength Wavelength Wavelength Wavelength (nm) (nm) (nm) (nm)
[0123]
[0124] Attorney Docket No.: Q0074.70020WO00
[0125] 4
[0126] 5 3011.15 3614.09
[0127] 6 3011.15 876.38 3614.09 921.11 7 3011.15 672.51 3614.09 698.54 8 3011.15 601.22 3614.09 621.93 9 3011.15 566.56 3614.09 584.92 10 3011.15 546.75 3614.09 563.83 11 3011.15 534.24 3614.09 550.54 12 3011.15 525.80 3614.09 541.58 13 3011.15 519.82 3614.09 535.23 14 3011.15 515.41 3614.09 530.56 15 3011.15 512.07 3614.09 527.02 16 3011.15 509.47 3614.09 524.27 17 3011.15 507.41 3614.09 522.08 18 3011.15 505.74 3614.09 520.32 19 3011.15 504.38 3614.09 518.88 20 3011.15 503.25 3614.09 517.68 n -> oo 3011.15 494 3614.09 508
[0128]
[0129] It should be appreciated that the specific examples of laser wavelength pairs and input laser wavelength pairs provided herein are not the only wavelengths that may be used or generated, as aspects of the technology described herein are not limited in this respect. For example, in some embodiments, the laser wavelength pairs and / or the entangled photon wavelength pairs may be in a range from 700 nm to 925 nm, from 750 nm to 850 nm, or a nearinfrared (NIR) wavelength and in a range from 1300 nm to 1600 nm or compatible with telecommunications technologies. Any suitable wavelengths corresponding to the atomic species’ desired atomic transition energies may be selected from within these ranges.
[0130] For the photon source to exhibit desired values of brightness, one- and two-photon detunings of the first, second, and third laser beams 102, 104, and 106 may be implemented, in some embodiments. A lower bound on the two-photon detuning is determined by the velocity of atoms inside the atomic vapor cell 116 at different temperatures. The atomic velocity is resonantly excited at:
[0131] c8
[0132] v ~ -
[0133]
[0134] Attorney Docket No.: Q0074.70020WO00
[0135] where c is the speed of light, δ is the two-photon detuning, and ω is the energy of the double excited state (e.g., the |6S1 / 2⟩ state in the example of FIG. 2). This velocity is ideally much larger than the characteristic atomic velocity, vp:
[0136] 2kBT
[0137]
[0138] m
[0139] where m is the atomic mass of the atoms of the atomic vapor. Or, alternatively, it is desirable for 8 to have a value of:
[0140] a> 2kBT
[0141] 8 » -
[0142]
[0143] — —
[0144] c J m
[0145] For the example of85Rb, δ ≫ 2π × 2 GHz, as described below. It should be appreciated that this technique of detuning is generally applicable to atomic species exhibiting diamond, two-photon excitations.
[0146] In some embodiments, the first and second laser beams 102, 104 may be configured with detunings, Δ1and Δ2, as shown in the example of FIG. 2, relative to atomic transitions of the atomic species in the atomic vapor. In some embodiments, the detuning of the first laser beam 102 may be on the order of hundreds of MHz. In some embodiments, the detuning of the first laser beam 102 may be greater than the resonant Doppler broadening of the atomic species. For example, the detuning of the first laser beam 102 may be approximately equal to or greater than 2π × 1 GHz, 2π × 1.1 GHz, or 2π × 1.15 GHz and may be less than or equal to 2π × 10 GHz. As shown in the example of FIG. 2, the first laser beam 102 may be frequency stabilized to the85Rb transition between a first energy level 202, at the |5S1 / 2, F = 3⟩ state, to a second energy level 204, at the |5P3 / 2, F′ = 4⟩ state such that the detuning amount, Δ1, is approximately 2π × 1.1 GHz. That is, the first laser beam 102 may be blue detuned from the8
[0147]
[0148] 5Rb 15S1 / 2, F = 2) -> |5P3 / 2, F′ = 3⟩ transition.
[0149] In some embodiments, the second laser beam 104 may be configured with a detuning, A2, relative to an atomic transition between the second energy level 204 and a third energy level 206 (e.g., the |6S1 / 2⟩ state) and the first detuning, Δ1. The detuning of the second laser beam 104 may be controlled, for example, using an electro-optic modulator (EOM; not shown). In some embodiments, the detuning of the second laser beam 104 may be on the order of hundreds of MHz. In some embodiments, the detuning of the second laser beam 104 may be greater than the double-resonant Doppler broadening of the atomic species. For example, theAttorney Docket No.: Q0074.70020WO00
[0150] detuning of the second laser beam 104 may be approximately equal to or greater than 2π × 2 GHz or 2π × 2.4 GHz and less than or equal to 2π × 10 GHz.
[0151] In some embodiments, the third laser beam 106 may be configured with a detuning, A3, relative to an atomic transition between the first energy level 202 and a third energy level 208 (e.g., the |5P1 / 2⟩ state). The detuning of the third laser beam 106 may be controlled, for example, using an electro-optic modulator (EOM; not shown). In some embodiments, the detuning of the third laser beam 106 may be on the order of hundreds of MHz. In some embodiments, the detuning of the third laser beam 106 may be greater than the double-resonant Doppler broadening of the atomic species. For example, the detuning of the third laser beam 106 may be approximately equal to or greater than 2π × 2 GHz or 2π × 2.4 GHz and less than or equal to 2π × 10 GHz.
[0152] By configuring the first, second, and third laser beams 102, 104, and 106 with detunings relative to atomic transitions of the atomic species in the atomic vapor cell 114, the corresponding two-photon resonance may be used to generate two noise-correlated squeezed optical signals upon decay of the excited atomic state. In particular, the detunings may prevent reabsorption of the newly generated light having wavelength X3. It should be appreciated that in some embodiments, detunings Δ1, Δ2, and Δ3may be smaller than the values provided above or set to zero, as aspects of the technology described herein are not limited in this respect. In particular, the detunings Δ1, Δ2, and Δ3may be on the order of a few MHz or on resonance with the atomic transitions for embodiments in which the atomic vapor comprises cold atoms.
[0153] Returning to FIG. 1, in some embodiments, the first, second, and third laser beams 102, 104, and 106 may be optically coupled to the atomic vapor cell 116 by one or more optical components. As shown in the example of FIG. 1, the first laser beam 102 and the second laser beam 104 may each pass through respective bandpass filters 108a, 108b. The third laser beam 106 may be combined with the first and / or second laser beams 102 and / or 104 by way of mirrors 110. Thereafter, the first, second, and third laser beams 102, 104, and 106 may be combined by a dichroic mirror 112a such that the first, second, and third laser beams 102, 104, and 106 are co-propagating along a same beam path. The co-propagating first, second, and third laser beams 102, 104, and 106 may then pass through a polarizing beamsplitter 114. The polarizing beamsplitter 114 may be configured to cause the first, second, and third laser beams 102, 104, and 106 to be horizontally polarized (e.g., aligned with an \H) polarization).
[0154] It should be appreciated that, in some alternative embodiments, optical components between the input ports of the photon source 100 and the atomic vapor cell 116 may be disposedAttorney Docket No.: Q0074.70020WO00
[0155] in an alternative arrangement (e.g., polarizing beamsplitter 114 may be removed, and alternative polarizing beamsplitters may be disposed between the bandpass filters 108a, 108b and the dichroic mirror 112a), as aspects of this technology are not limited in this respect.
[0156] In some embodiments, the atomic vapor cell 116 includes a housing supporting a magneto-optical trap configured to confine atoms of the atomic vapor within the atomic vapor cell 116. The housing of the atomic vapor cell 116 may be hermetically sealed to prevent contamination and may include one or more optically transparent windows to allow light to enter and / or exit the atomic vapor cell 116. The atomic vapor cell 116 may have a length on the order of several millimeters (e.g., 5 mm). The atomic vapor cell 116 may be configured to confine a warm atomic vapor or a cold atomic cold, in some embodiments. In embodiments in which the atomic vapor cell 116 is configured to confine a warm atomic vapor, the atomic vapor cell 116 may be heated by one or more ceramic heaters thermally coupled to the atomic vapor cell 116. In some embodiments, the atomic vapor cell 116 may be surrounded by shielding (e.g., comprising mu-metal or other suitable shielding materials) to prevent magnetic and / or electric fields from affecting the atomic vapor within the atomic vapor cell 116.
[0157] In some embodiments, after the first, second and third laser beams 102, 104, and 106 have entered the atomic vapor cell 116, two squeezed optical signals may be generated and coupled out of the atomic vapor cell 116. Thereafter, in some embodiments, the generated squeezed optical signals and first, second, and third laser beams 102, 104, and 106 may pass through a dichroic mirror 112b configured to separate the two optical signals (e.g., based on wavelength).
[0158] In some embodiments, a first optical signal of the two squeezed optical signals may be deflected by the dichroic mirror 112b towards output 118. The first optical signal may be, for example, a photon or photons having a wavelength, d4, compatible with telecom applications (e.g., in a range from 1300-1600 nm). Prior to exiting the photon source 100, the first optical signal may further pass through a bandpass filter 108c configured to filter out photons from the first, second, and third laser beams 102, 104, and 106 such that only the first optical signal reaches the output 118.
[0159] In some embodiments, the second optical signal of the two generated squeezed optical signals may pass through the dichroic mirror 112b prior to being steered towards output 120 by mirror 110. The second optical signal may be, for example, a photon or photons having a wavelength, λ3, that is near-infrared (e.g., in a range from 700-925 nm). In some embodiments, a bandpass filter 108d may also be optically coupled between the mirror 110 and the outputAttorney Docket No.: Q0074.70020WO00
[0160] 120. The bandpass filter 108d may be configured to filter out photons from the first and second laser beams 102, 104 such that only the second optical signal reaches the output 120.
[0161] In some embodiments, additional optical components may be disposed between the dichroic mirror 112b and the outputs 118 and / or 120 that are not depicted in the example of FIG. 1. For example, one or more of a quarter waveplate, half waveplate, and / or polarizing beamsplitter may be optically coupled along the beam path between the dichroic mirror 112b and the outputs 118 and / or 120. These additional optical components, for example, may be used to select generated photons of detected polarization modes.
[0162] It should be appreciated that while the example of FIG. 1 depicts a photon source 100 that is not multiplexed, that multiplexing of the photon source 100 may be achieved by splitting the first laser beam 102 and the second laser beam 104 into multiple paths (e.g., on a two-dimensional or three-dimensional grid), as aspects of the technology are not limited in this respect. This splitting may be achieved, for example, to simultaneously excite many microscopic-sized atomic vapor cells or in hollow core fibers. The multiplexed photon outputs may then be collected into different optical fiber outputs.
[0163] In some embodiments, and in contrast to the example of FIG. 1, the incoming laser beams may be arranged to not be co-propagating. FIG. 3 shows one example of a photon source 300 with beam paths arranged at incident angles relative to a face of the atomic vapor cell, in accordance with some embodiments of the technology described herein. The photon source 300 is configured to receive (e.g., through suitable input ports or from integrated lasers, not shown) a first laser beam 102, a second laser beam 104, and a third laser beam 106. As with the example of FIG. 1, the first laser beam 102 and the second laser beam 104 may be configured as pump beams, while the third laser beam 106 may be configured as a probe beam. The first laser beam 102, the second laser beam 104, and the third laser beam 106 may have respective different wavelengths
[0164]
[0165] λ2, and λ3selected based on respective atomic transitions of atoms in an atomic vapor stored within the atomic vapor cell 116 located within a beam path of the first, second, and third laser beams 102, 104, and 106. The first, second, and third laser beams may be arranged to intersect at a location within the atomic vapor cell 116.
[0166] In some embodiments, the first and second laser beams 102, 104 may be arranged (e.g., by steering optics) to enter the atomic vapor cell 116 at respective angles 0 and relative to a beam path of the third laser beam 106. The third laser beam 106 may be arranged to enter the atomic vapor cell 116 along a direction approximately perpendicular to the face of the atomic vapor cell 116. In some embodiments, the first laser beam 102 may be arranged to enter theAttorney Docket No.: Q0074.70020WO00
[0167] atomic vapor cell along a second direction defined by the angle 0, which may be an angle greater than or equal to 0°and less than or equal to 5°. Preferably, the angle 0 may be approximately 2°. In some embodiments, the second laser beam 104 may be arranged to enter the atomic vapor cell along a third direction defined by the angle (p. which may be an angle less than or equal to 0° and greater than or equal to -5°. Preferably, the angle (p may be approximately -0.7°.
[0168] In some embodiments, additional components may be disposed between the sources of the first, second, and / or third laser beams 102, 104, and / or 106 and the atomic vapor cell 116. The first laser beam 102 may pass through one or more of a half waveplate 302, a quarter waveplate 304, a lens 306 (e.g., a 175 mm lens), a polarizing beam splitter 308 (e.g., aligned with a horizontal polarization), a bandpass filter 108a, and / or a shortpass dichroic mirror 310a before entering the atomic vapor cell 116. The second laser beam 104 may pass through one or more of a polarizing beam splitter 308 (e.g., aligned with a horizontal polarization), a lens 312 (e.g., a 500 mm lens), a bandpass filter 108b, and one or more steering mirrors 314 before entering the atomic vapor cell 116. The third laser beam 106 may pass through one or more of a polarizer 316 (e.g., aligned with a vertical polarization) and / or a lens (e.g., a 200 mm lens) before entering the atomic vapor cell 116.
[0169] In some embodiments, the first, second, and third laser beams 102, 104, and 106 may cause a four- wave mixing process with two-mode squeezing to occur within the atomic vapor cell 116, as described above in connection with the example of FIG. 1. The four-wave mixing process may cause two correlated, squeezed optical signals to exit the atomic vapor cell 116 along with photons of the first, second, and third laser beams 102, 104, and 106.
[0170] In some embodiments, photons exiting from the atomic vapor cell 116 may first pass through a dichroic mirror 310b configured to split the photons of the two optical signals having different wavelengths. The first optical signal, having wavelength λ4, of the output pair of squeezed optical signals may be steered by the dichroic mirror 310b through a lens 320 (e.g., a 150 mm lens), one or more mirrors 314, a bandpass filter 108c configured to filter out any remaining photons from the first and / or second laser beams 102 and / or 104, and / or a lens 324 (e.g., a 25 mm lens) before exiting the photon source 300 at output 118. In some embodiments, the second optical signal, having wavelength λ3, of the output pair of squeezed optical signals may be steered by mirrors 314 through a lens 321 (e.g., a 150 mm lens), another lens 326 (e.g., a 100 mm lens), and a bandpass filter 108d configured to filter out any remaining photons from the first and / or second laser beams 102 and / or 104 before exiting the photonAttorney Docket No.: Q0074.70020WO00
[0171] source 300 at output 120. In some embodiments, remaining photons of the first and second laser beams 102 and 104 that exit the atomic vapor cell 116 may be steered by mirrors 314 to one or more beam dumps 322.
[0172] FIG. 4A shows measured gain in an87Rb atomic vapor as a function of detuning of a pump beam and the probe beam of the photon source, in accordance with some embodiments of the technology described herein. FIG. 4B is a plot showing gain 402 for a fixed detuning of the 1367 nm pump beam of FIG. 4A and measured gain 404 with only the probe beam present.
[0173] The data of FIGs. 4A and 4B was gathered by addressing a warm87Rb ensemble with pump beams at 780 nm and 1367 nm and a weak 795 nm probe beam. Due to the four-wave mixing process, the 795-nm probe experiences gain, thereby increasing the power in the beam which also produces power in the conjugate 1324-nm beam generated by the87Rb ensemble.
[0174] Due to the 795 nm and 1324 nm outputs being created simultaneously as a result of four-wave mixing, their intensities are strongly correlated and display squeezing. In the absence of loss, squeezing can be tied directly to the gain measured on the 795 nm output field:
[0175] i 1 1
[0176] S = log10
[0177] L2G - 1J
[0178] where for a gain, G, of 1 (e.g., the87Rb ensemble does not amplify the 795 nm output field), then the squeezing parameter, S, is zero, and for G > 1, the squeezing parameter is negative.
[0179] For the data collected in FIGs. 4A and 4B, the87Rb ensemble was pumped with approximately 20 mW of 1367 nm light and 10 mW of 780 nm light. The probe beam was approximatley a 1 uW 795 nm probe. The 780 nm light was detuned around +1.1 GHz from the F = 2 to F' = 3 transition of87Rb. The gain spectra was acquired with the 795 nm light being at a fixed detuning while the detuning of the 1367 nm light was adjusted. Gains are seen in FIGs. 4A and 4B up to approximately a value of 3.5, which corresponds to a squeezing of approximately 8 dB.
[0180] FIGs. 5A and 5B were acquired using photon source 300, with
[0181]
[0182] ≈ 1367 nm, λ2≈ 780 nm, λ3≈ 795 nm, and λ4≈ 1324 nm. The data for FIGs. 5A and 5B was acquired using laser powers of approximately 210 mW for the 780 nm pump, 60 mW for the 1367 nm pump, and 110 pW for the 795 nm probe. The 780 nm pump beam was -1200 MHz detuned from the85Rb F = 3 to F' = 4 transition. The 1367 nm pump beam was +2000 MHz detuned from the85Rb F' = 4 to F" = 3 transition. The 795 nm probe beam was detuned +600 MHz from the85Rb F = 3 to F' = 3 transition. FIGs. 5A and 5B are plots showing measured noise including electronic noise 502, noise for a squeezed optical signal 504 (e.g., with the probe beam 106 turned on), and for a coherent optical signal 506 (e.g., without the probe beam 106), inAttorney Docket No.: Q0074.70020WO00
[0183] accordance with some embodiments of the technology described herein. FIG. 5B is a zoomedin section of the plot of FIG. 5 A, showing approximately 2 dB of squeezing for the squeezed optical signal 504.
[0184] The techniques described herein apply to a wide range of pump and probe detuning values. FIG. 6 is a plot showing measured gain as functions of pump and probe detunings, in accordance with some embodiments of the technology described herein. FIG. 6 shows that significant squeezing can be achieved for detuning pairings of the pump and probe beams across a range of 200 MHz to 1000 MHz.
[0185] FIG. 7 is a plot showing measured squeezing 702 as a function of the detuning of the probe beam for a fixed detuning of the pump beam, in accordance with some embodiments of the technology described herein. The minimum squeezing is indicated by line 704, achieving nearly -3 dB of squeezing.
[0186] FIG. 8 is a flowchart describing a process 800 of generating two squeezed optical signals, in accordance with some embodiments of the technology described herein. The process may be performed, for example, using any one of photon sources 100 and / or 300 described herein. The process 800 may begin at act 802, wherein a first laser beam is generated, the first laser beam having a first wavelength selected based on a first atomic transition of an atomic species. The atomic species may be, for example, an atomic species that exhibits spontaneous four-wave mixing processes (e.g., an atomic species having diamond-like energy level structures as described in connection with FIG. 2 herein). For example, the atomic species may be an alkali metal or an alkali earth metal (e.g., isotopes of rubidium, cesium, and / or other suitable atomic species).
[0187] In some embodiments, after act 802, the process 800 may proceed to act 804, in which a second laser beam is generated. The second laser beam has a second wavelength selected based on a second atomic transition of the atomic species. In some embodiments, the first wavelength and the second wavelength may be selected to satisfy conditions for causing the four-wave mixing process in the atomic species (e.g., the first wavelength and the second wavelength may cause two-photon excitation in the atomic species).
[0188] In some embodiments, after act 804, the process 800 may proceed to act 806, in which a third laser beam is generated. The third laser beam has a third wavelength selected based on a third atomic transition of the atomic species. For example, the third wavelength may be selected to correspond to an atomic transition that is part of a two-photon decay process associated with the four-wave mixing process in the atomic species.Attorney Docket No.: Q0074.70020WO00
[0189] In some embodiments, the first, second, and third wavelengths may be selected based on the atomic species having a two-photon resonance along the atomic transitions from |
[0190]
[0191] 5S1 / 2) 15P3 / 2) |6S1 / 2). For example, the first wavelength may be selected based on the first atomic transition being between a |5S1 / 2) state and a |5P3 / 2) state of the atomic species. The second wavelength may be selected based on the second atomic transition being between a |5P3 / 2) state and a |6S1 / 2) state of the atomic species. The third wavelength may be selected based on the third atomic transition being between a |5S1 / 2) state and a |5P1 / 2) state of the atomic species.
[0192] As one example,85Rb exhibits a two-photon resonance (or four-wave mixing process) along the transitions |
[0193]
[0194] 5S1 / 2) |5P3 / 2) |6S1 / 2) corresponding to excitations caused by received light having wavelengths of approximately
[0195]
[0196] ~ 780 nm and λ2≈ 1367 nm. This four- wave mixing process can generate entangled photons having wavelengths of approximately λ3≈ 795 nm and approximately λ4≈ 1324 nm along the two-photon decay path from |
[0197]
[0198] 6S1 / 2) |5P1 / 2) |5S1 / 2). Alternatively or additionally, a two-photon resonance in an87Rb vapor may be used to generate photon pairs having wavelengths of approximately 1367 nm and 780 nm, 1476 nm and 795 nm, and / or 1529 nm and 780 nm, based on the selections of λ1and λ2, providing a flexible photon source that may be used to generate a spectrum of wavelengths in the NIR, O, C, and / or S bands.
[0199] In some embodiments, the first and second laser beams (e.g., the pump beams) may be generated to have higher optical powers than the third laser beam (e.g., the probe beam). As one example, the first and second laser beams may be operated at powers in a range from 5 mW to 50 mW, and the third laser beam 106 may be operated at a power in a range from 0.01 µW to 1 mW. In some embodiments, the third laser beam 106 may be operated at a power having a value that is a factor in a range from 1,000 to 2,000 times less than a power of the first laser beam 102.
[0200] In some embodiments, the first, second, and / or third laser beams may be generated with detunings relative to respective atomic transitions of the atomic species in the atomic vapor. In some embodiments, the detunings of the first, second, and / or third laser beams may be on the order of hundreds of MHz. In some embodiments, the detunings of the first, second, and / or third laser beams may be greater than the resonant Doppler broadening of the atomic species. For example, the detunings of the first, second, and / or third laser beams may be approximately equal to or greater than 2π × 1 GHz, 2π × 1.1 GHz, 2π × 1.15 GHz, 2π × 2 GHz, or 2π × 2.4 GHz and may be less than or equal to 2π × 10 GHz.Attorney Docket No.: Q0074.70020WO00
[0201] In some embodiments, after act 806, the process 800 may proceed to act 808, in which a four-wave mixing process and two-mode squeezing are caused by passing the first, second, and third laser beams through an atomic vapor cell containing atoms of the atomic species. In some embodiments, the first, second, and / or third laser beams may be arranged to co-propagate along a same direction through the atomic vapor cell. In some embodiments, the first, second, and / or third laser beams may be arranged to intersect at a position within the atomic vapor cell and may enter the atomic vapor cell at different angles relative to a face of the atomic vapor cell.
[0202] In some embodiments, passing the first, second, and third laser beams through the atomic vapor cell may include arranging the third laser beam to enter the atomic vapor cell along a first direction perpendicular to a face of the atomic vapor cell. The first laser beam may be arranged to enter the atomic vapor cell along a second direction being defined by an angle greater than or equal to 0° and less than or equal to 5° between the first and second directions, and preferably at an angle of approximately 2° The second laser beam may be arranged to enter the atomic vapor cell along a third direction defined by an angle less than or equal to 0° and greater than or equal to -5° between the first and third directions, and preferably at an angle of approximately -0.7°
[0203] In some embodiments, after act 808, the process 800 may proceed to act 810, in which two optical signals (e.g., each having squeezed states) are generated as a result of the four-wave mixing process and the two-mode squeezing. In some embodiments, photon pairs of the two optical signals comprise a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being associated with a fourth atomic transition of the atomic species. For example, the fourth atomic transition may be the other atomic transition associated with the two-photon decay path of the atomic species. As another example, the fourth atomic transition may be between a |6S1 / 2state and a |5P1 / 2) state of the atomic species.
[0204] In some embodiments, the atomic species and / or the atomic transitions may be selected such that the third wavelength is compatible with telecommunications technology and the fourth wavelength is a near-infrared (NIR) wavelength. For example, the third wavelength may be in a range from 700 nm to 925 nm, in a range from 750 nm to 850 nm, may be approximately 795 nm or approximately 780 nm, or may be any suitable value within those ranges. As another example, the fourth wavelength may be in a range from 1300 nm to 1600 nm or may be approximately 1324 nm, approximately 1367 nm, approximately 1476 nm, or approximatelyAttorney Docket No.: Q0074.70020WO00
[0205] 1529 nm. In some embodiments, the first wavelength may be approximately 780 nm, the second wavelength is approximately 1367 nm, and the third wavelength is approximately 795 nm.
[0206] Various aspects of the embodiments described above may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.
[0207] Having thus described several aspects and embodiments of the technology set forth in the disclosure, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the technology described herein. For example, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the embodiments described herein. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described. In addition, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the scope of the present disclosure.
[0208] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.
[0209] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The use of “coupled” or “connected” is meant to refer to elements, or signals, that are either directly linked to one another or are linked through intermediate components. Elements that are not “coupled” or “connected” are “decoupled” or “disconnected.”Attorney Docket No.: Q0074.70020WO00
[0210] The use of “between” in a coupled signal chain is not meant to require a particular direction of signal flow in the signal chain unless stated otherwise. For instance, where element B is described as coupled between elements A and C in a signal chain, signals may flow from element A to element C through element B and / or from element C to element A through element B unless stated otherwise.
[0211] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
[0212] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
[0213] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including butAttorney Docket No.: Q0074.70020WO00
[0214] not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.
[0215] The terms “approximately” and “about” may be used to mean within ±20% of a target value in some embodiments, within ±10% of a target value in some embodiments, within ±5% of a target value in some embodiments, within ±2% of a target value in some embodiments. The terms “approximately” and “about” may include the target value.
[0216] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
Claims
Attorney Docket No.: Q0074.70020WO00CLAIMSWhat is claimed is:
1. A photon source comprising:an atomic vapor cell disposed within beam paths of a first laser beam, a second laser beam, and a third laser beam generated during operation of the photon source, wherein:the atomic vapor cell comprises atoms of an atomic species configured to generate two optical signals by a four-wave mixing process, wherein the two optical signals are squeezed due to two-mode squeezing;the first laser beam has a first wavelength selected based on a first atomic transition of the atomic species;the second laser beam has a second wavelength selected based on a second atomic transition of the atomic species; andthe third laser beam has a third wavelength selected based on a third atomic transition of the atomic species.
2. The photon source of claim 1, wherein:the first wavelength is selected to have a first detuning relative to the first atomic transition of the atomic species,the second wavelength is selected to have a second detuning relative to the second atomic transition of the atomic species, and / orthe third wavelength is selected to have a third detuning relative to the third atomic transition of the atomic species.
3. The photon source of claim 1, wherein:the first atomic transition is between a |5S1 / 2) state and a |5P3 / 2) state of the atomic species,the second atomic transition is between a |5P3 / 2) state and a |6S1 / 2) state of the atomic species, and / orthe third atomic transition is between a |5S1 / 2) state and a |5P1 / 2) state of the atomic species.Attorney Docket No.: Q0074.70020WO004. The photon source of claim 1, wherein the atomic species comprises an alkali metal or alkali earth metal.
5. The photon source of claim 4, wherein the atomic species comprises rubidium.
6. The photon source of claim 1, wherein photon pairs of the two optical signals comprise a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being related to a fourth atomic transition of the atomic species.
7. The photon source of claim 6, wherein the fourth atomic transition is between a |6S1 / 2) state and a |5P1 / 2) state of the atomic species.
8. The photon source of claim 1, wherein the first, second, and third laser beams intersect at a location within the atomic vapor cell.
9. The photon source of claim 1, wherein:the third laser beam is arranged to enter the atomic vapor cell along a first direction perpendicular to a face of the atomic vapor cell,the first laser beam is arranged to enter the atomic vapor cell along a second direction being defined by an angle greater than or equal to 0° and less than or equal to 5° between the first and second directions, andthe second laser beam is arranged to enter the atomic vapor cell along a third direction defined by an angle less than or equal to 0° and greater than or equal to -5° between the first and third directions.
10. The photon source of claim 1, wherein during operation of the photon source:the first and second laser beams are operated at powers in a range from 5 mW to 50 mW, andthe third laser beam is operated at a power in a range from 0.01 µW to 1 mW.
11. The photon source of claim 1, wherein during operation of the photon source:Attorney Docket No.: Q0074.70020WO00the first and / or the second laser beam is operated at a first power having a first value, andthe third laser beam is operated at a power having a second value, the second value being less than the first value.
12. The photon source of claim 11, wherein the second value is a factor less than the first value, the factor being in a range from 1,000 to 2,000.
13. The photon source of claim 6, wherein the first wavelength and the second wavelength have values configured to satisfy conditions for a four-wave mixing process in the atomic species.
14. The photon source of claim 13, wherein the third wavelength is compatible with telecommunications technology and the fourth wavelength is a near-infrared (NIR) wavelength.
15. The photon source of claim 14, wherein the third wavelength is in a range from 700 nm to 925 nm.
16. The photon source of claim 14, wherein the third wavelength is in a range from 750 nm to 850 nm.
17. The photon source of any one of claims 14, wherein the third wavelength is approximately 795 nm or approximately 780 nm.
18. The photon source of claim 14, wherein the fourth wavelength is in a range from 1300 nm to 1600 nm.
19. The photon source of claim 18, wherein the fourth wavelength is approximately 1324 nm.
20. The photon source of claim 18, wherein the fourth wavelength is approximately 1324 nm, approximately 1367 nm, approximately 1476 nm, or approximately 1529 nm.Attorney Docket No.: Q0074.70020WO0021. The photon source of claim 6, wherein the first wavelength is approximately 780 nm, the second wavelength is approximately 1367 nm, the third wavelength is approximately 795 nm, and the fourth wavelength is approximately 1324 nm.
22. The photon source of claim 1, further comprising a first output and a second output optically coupled to outputs of the atomic vapor cell such that a first optical signal of the two optical signals exits the photon source from the first output and a second optical signal of the two optical signals exits the photon source from the second output.
23. The photon source of claim 1, further comprising a polarizer between a source of the third laser beam and the atomic vapor cell, the polarizer aligned to a | V) polarization.
24. The photon source of claim 1, further comprising polarizing beam splitters disposed between sources of the first and second laser beams and the atomic vapor cell, the polarizing beam splitters being configured to allow transmission of light having an \H) polarization.
25. The photon source of claim 1, further comprising:a first laser configured to generate the first laser beam during operation of the photon source;a second laser configured to generate the second laser beam during operation of the photon source; anda third laser configured to generate the third laser beam during operation of the photon source.
26. A method of generating two optical signals squeezed by two-mode squeezing, the method comprising:generating a first laser beam having a first wavelength selected based on a first atomic transition of an atomic species;generating a second laser beam having a second wavelength selected based on a second atomic transition of the atomic species;generating a third laser beam having a third wavelength selected based on a third atomic transition of the atomic species;Attorney Docket No.: Q0074.70020WO00causing a four-wave mixing process and two-mode squeezing in an atomic vapor cell containing atoms of the atomic species by passing the first laser beam, the second laser beam, and the third laser beam through the atomic vapor cell; andgenerating, as a result of the four-wave mixing process and the two-mode squeezing, the two optical signals.
27. The method of claim 26, further comprising:configuring the first laser beam to have a first detuning relative to the first atomic transition of the atomic species,configuring the second wavelength to have a second detuning relative to the second atomic transition of the atomic species, and / orconfiguring the third wavelength to have a third detuning relative to the third atomic transition of the atomic species.
28. The method of claim 26, further comprising:selecting the first wavelength based on the first atomic transition being between a |5S1 / 2) state and a |5P3 / 2) state of the atomic species,selecting the second wavelength based on the second atomic transition being between a |5P3 / 2) state and a |6S1 / 2) state of the atomic species, and / orselecting the third wavelength based on the third atomic transition being between a |5S1 / 2) state and a |5P1 / 2) state of the atomic species.
29. The method of claim 26, wherein the atomic species comprises an alkali metal or alkali earth metal.
30. The method of claim 29, wherein the atomic species comprises rubidium.
31. The method of claim 26, wherein photon pairs of the two optical signals comprise a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being associated with a fourth atomic transition of the atomic species.
32. The method of claim 31, wherein the fourth atomic transition is between a |6S1 / 2) state and a |5P1 / 2) state of the atomic species.Attorney Docket No.: Q0074.70020WO0033. The method of claim 26, further comprising:arranging the third laser beam to enter the atomic vapor cell along a first direction perpendicular to a face of the atomic vapor cell,arranging the first laser beam to enter the atomic vapor cell along a second direction being defined by an angle greater than or equal to 0° and less than or equal to 5° between the first and second directions, andarranging the second laser beam to enter the atomic vapor cell along a third direction defined by an angle less than or equal to 0° and greater than or equal to -5° between the first and third directions.
34. The method of claim 26, wherein:generating the first laser beam and the second laser beam comprises generating the first laser beam and the second laser beam with powers in a range from 5 mW to 50 mW, and generating the third laser beam comprises generating the third laser beam with a power in a range from 0.01 µW to 1 mW.
35. The method of claim 26, wherein:generating the first laser beam and / or the second laser beam comprises generating the first laser beam and / or the second laser beam with a first power having a first value, and generating the third laser beam comprises generating the third laser beam with a second power having a second value, the second value being less than the first value.
36. The method of claim 35, wherein the second value is a factor less than the first value, the factor being in a range from 1,000 to 2,000.
37. The method of claim 26, wherein the first wavelength and the second wavelength have values configured to satisfy conditions for causing the four-wave mixing process in the atomic species.
38. The method of claim 31, wherein the third wavelength is compatible with telecommunications technology and the fourth wavelength is a near-infrared (NIR) wavelength.Attorney Docket No.: Q0074.70020WO0039. The method of claim 38, wherein the third wavelength is in a range from 700 nm to 925 nm.
40. The method of claim 38, wherein the third wavelength is in a range from 750 nm to 850 nm.
41. The method of claim 38, wherein the third wavelength is approximately 795 nm or approximately 780 nm.
42. The method of claim 38, wherein the fourth wavelength is in a range from 1300 nm to 1600 nm.
43. The method of claim 42, wherein the fourth wavelength is approximately 1324 nm.
44. The method of claim 42, wherein the fourth wavelength is approximately 1324 nm, approximately 1367 nm, approximately 1476 nm, or approximately 1529 nm.
45. The method of claim 26, wherein the first wavelength is approximately 780 nm, the second wavelength is approximately 1367 nm, and the third wavelength is approximately 795 nm.
46. The method of claim 45, wherein:photon pairs of the two optical signals comprise a first photon having the third wavelength and a second photon having a fourth wavelength, the fourth wavelength being associated with a fourth atomic transition of the atomic species, andthe fourth wavelength is approximately 1324 nm.