Methods for fabricating a nanofiber cavity with a degenerate Bragg grating in polarization and a system comprising a quantum computer and a repeater cell system

Abstract

A method for fabricating a polarization-degenerate Bragg grating nanofiber cavity for quantum computing or quantum repeaters. The method involves transmitting electromagnetic radiation with wavelengths from 150 nm to 400 nm and longer through a phase-shifting mask pattern to diffract the electromagnetic radiation and form an interference pattern. The pattern is illuminated onto the core of one end of a fiber optic cable region. In one example, the method forms a Bragg grating on the core of the fiber optic cable region by changing the refractive index of the core using electromagnetic radiation while rotating the fiber optic cable around a defined axis along the length of the fiber optic cable region. Figure for the abstract: Figure 1a

Description

Title of the invention: Methods for manufacturing a nanofiber cavity with a degenerate Bragg grating in polarization and a system comprising a quantum computer and a repeater cell system. FIELD OF THE INVENTION

[0001] The present invention relates to methods of manufacturing a nanofiber cavity with a polarization-degenerate Bragg grating and to a system comprising a quantum computer and a repeater cell system.

[0002] The present invention proposes techniques generally related to quantum computing and quantum repeaters. In particular, the present invention proposes a fabrication method and a resulting device for a nanofiber-based quantum computing system comprising an optical cavity configured with a pair of Bragg gratings. By way of example, the invention can be applied to a variety of applications such as cryptography, drug discovery, optimization, machine learning and artificial intelligence, finance, weather forecasting, chemistry, mechanics, electricity, civil engineering, nuclear fusion and fission, economics, materials science, and any other complex human or non-human matter. technological BACKGROUND

[0003] Various techniques have been developed for manufacturing quantum computers. Superconducting qubits have been implemented using superconducting circuits that can exhibit quantum behavior. These superconducting circuits are generally made using thin films of superconducting materials and require extremely low temperatures (close to absolute zero) to operate. Superconducting qubits have demonstrated relatively long coherence times, enabling complex computations. They can be fabricated using existing semiconductor fabrication techniques. Unfortunately, the low-temperature requirement and the need for complex cooling systems make their operation more difficult. The coherence of qubits can be sensitive to ambient noise, which limits scalability.

[0004] Another technique involves using trapped ionic qubits. These trapped ionic qubits use individual ions trapped in an electromagnetic field to store and manipulate quantum information.

[0005] Ions are manipulated using laser beams to create the basic operations of a qubit. Trapped ion qubits have shown exceptional coherence properties and long lifetimes. They can be individually controlled with high precision. However, scaling up trapped ion systems has proven difficult due to the complexity of manipulating individual ions. Furthermore, the need for high-quality vacuum systems and precise laser control adds to the complexity and cost of implementation.

[0006] Another technique uses topological qubits, which are based on the manipulation of quasiparticles called "anyons". Anyons appear in exotic states of matter, such as topological superconductors.

[0007] Anyons store and process quantum information in a topologically protected manner, making them less susceptible to errors caused by ambient noise. Topological qubits have proven robust to certain types of errors, making them potentially useful for error-resistant quantum computing. However, there are drawbacks. Indeed, topological qubits are still in the early stages of development, and practical implementations face challenges related to the creation and control of topological states. Realizing the necessary exotic materials and stable conditions is technically demanding.

[0008] In addition, photonic qubits have been studied. These photonic qubits use photons (i.e., particles of light) to encode and manipulate quantum information. Quantum gates are implemented using optical elements such as beam splitters, wave plates, and detectors. Photonic qubits can be easily manipulated with existing optical technologies. They are inherently insensitive to certain types of noise and can be transmitted over long distances. Unfortunately, photonic qubits have difficulty interacting efficiently with photons, and it is challenging to create, store, and measure them on demand. Integrating a large number of qubits is currently difficult.

[0009] The following documents describe such approaches: S. Kato and T. Aoki, "Single-frequency fiber Fabry-Perot Brillouin laser", Opt. Lett. 47, 5000 (2022). And Maxime Joos, Alberto Bramati, and Quentin Glorieux, "Completed polarization control for a nanofiber waveguide using the scattering properties", Opt. Lett. 27, 18818 (2019).

[0010] Each of the aforementioned approaches presents its own set of advantages and challenges, and the field of quantum computing is actively exploring these technologies. Unfortunately, these techniques also have drawbacks. These drawbacks include difficulties in terms of scalability, reliability, and qubit consistency. Summary of the invention

[0011] Thus, the invention relates to a method for manufacturing a nanofiber cavity with a degenerate Bragg grating in polarization for quantum computing or a quantum repeater, the method comprising: transmitting electromagnetic radiation characterized by a wavelength between 150 nm and 400 nm and more through a pattern of a phase-shift mask in order to diffract the electromagnetic radiation to form an interference pattern to be illuminated on the core of a first end of a region of optical fiber cable, the region of optical fiber cable having a first end opposite a second end, and a nanofiber cavity region defined between the first end and the second end; induce the formation of a first Bragg grating on the core of the fiber optic cable region by modifying the refractive index of the core of the fiber optic cable region using electromagnetic radiation while rotating the fiber optic cable region around a defined axis along the fiber optic cable region to form the first Bragg grating configured with a plurality of azimutally symmetrical patterns of a plurality of refractive index modulations at an angle of 360 degrees around a core of the fiber optic cable region and along a longitudinal region normal to a cross-section of the fiber optic cable region; and form a second Bragg grating at a second end of the optical fiber cable region, the second Bragg grating being configured with a plurality of symmetrical azimuthal patterns of a plurality of modulations of the refractive index at 360 degrees angle around a core of the optical fiber cable region.

[0012] According to one embodiment, the region of the nanofiber cavity configured with the first Bragg grating and the second Bragg grating is characterized by a degenerate cavity mode in polarization which is adapted to any arbitrary polarization state of light without causing one or more different resonance frequencies.

[0013] According to one embodiment, the nanofiber cavity region is characterized as a degenerate polarization Bragg grating nanofiber cavity, such that all arbitrary polarization states of light are free from any different resonance frequency.

[0014] According to one embodiment, the first Bragg grating or the second Bragg grating characterized by azimuthal symmetry refractive index modulation patterns is configured by a modulation period along the fiber axis of a dimension between 200 nm and 1 micron.

[0015] According to one embodiment, the first Bragg grating or the second Bragg grating characterized by the azimutally symmetrical patterns of modulations of the refractive index has a cross-section ranging from 1 micrometer to 10 micrometers and more in dimension.

[0016] According to one embodiment, the electromagnetic radiation is characterized by an exposure time of between 10 seconds and 100 minutes, the exposure time being controlled by monitoring the maximum reflectivity of the first Bragg grating or the second Bragg grating in real time for an electromagnetic radiation power of between 10 mW and 1 W and an electromagnetic radiation diameter of between 3 micrometers and 1 mm.

[0017] According to one embodiment, the first Bragg grating and the second Bragg grating are each arranged in space on a region of optical fiber cable with a spatial distance between the first Bragg grating and the second Bragg grating, ranging from 100 micrometers to 10 centimeters and more.

[0018] According to one embodiment, the first Bragg grating and the second Bragg grating are configured on each side of a conical region coupled to a region of nanofibers.

[0019] According to one embodiment, the first Bragg grating and the second Bragg grating are characterized by a plurality of patterns printed on a silicon dioxide material in the region of the optical fiber cable.

[0020] According to one embodiment, the rotation of the fiber along the fiber axis is characterized by a rotation speed to cause the formation of symmetrical azimuthal patterns of the refractive index modulation where a rotation speed is faster than the inverse of a UV exposure time so that a transversely anisotropic pattern of a refractive index modulation is averaged over an azimuthal direction.

[0021] In yet another example, the invention proposes a related system and other methods, in particular the formation of a first Bragg grating in a spatial region of an optical fiber cable, the rotation of the cable by a predetermined value and the formation of a second Bragg grating.

[0022] In particular, the invention relates to a method for manufacturing a nanofiber cavity with a degenerate Bragg grating in polarization for quantum computing, the method comprising: providing a region of fiber optic cable comprising a first end, a second end and a region of nanofibers between the first end and the second end; transmit electromagnetic radiation characterized by a wavelength of 150 nm to 400 nm and more through a phase-shifting mask to diffract the electromagnetic radiation in order to form an interference pattern to be illuminated on a core at one end of the region of the fiber optic cable; to induce the formation of a first Bragg grating on the core of a first end of a fiber optic cable region by modifying the refractive index of the core of the fiber optic cable region using electromagnetic radiation without rotating the fiber to create an additional spatial region of the fiber optic cable region such that the first Bragg grating exhibits a plurality of azimuthal anisotropic patterns of a plurality of modulations of the refractive index around the core of the fiber optic cable region and along a longitudinal region normal to a cross-section of the fiber optic cable region: rotate the region of the fiber optic cable around a defined axis over a length of the region of the fiber optic cable at an angle of 90 degrees; form a second Bragg grating on a core of a second end of the optical fiber cable region without rotating the fiber such that the first Bragg grating and the second Bragg grating are characterized by respective transverse anisotropies of refractive index modulations shifted by 90 degrees angle, causing a polarization degeneracy cavity from a cancellation of the transverse anisotropy.

[0023] According to one embodiment, the nanofiber region configured with the first Bragg grating and the second Bragg grating forms a degenerate polarized Bragg grating nanofiber cavity, such that any arbitrary polarization state of the light does not result in different resonance frequencies.

[0024] According to one embodiment, the nanofiber region is characterized by a degenerate polarization cavity mode, adapted to support any arbitrary polarization state of light without causing different resonance frequencies or other different properties.

[0025] According to one embodiment, the first Bragg grating is characterized by birefringence and the second Bragg grating is configured with a shift angle of 90 degrees along the axis such that one or more cavity modes formed by the first Bragg grating and the second Bragg grating are degenerate into polarization due to the cancellation of the birefringence of the first Bragg grating and the second Bragg grating.

[0026] The invention also relates to a system comprising a quantum computer and a repeater cell system, comprising: a region of fibre optic cable comprising a first end region and a second end region, the first end region comprising a first end and the second end region comprising a second end, the optical fiber cable region comprising a silicon dioxide material with a dopant material entity distributed within a central region; a first fiber Bragg grating comprising a plurality of first patterns on the first end region, configured over 360 degrees around a periphery of the first end region, and extending laterally over a length of the first end region; a second fiber Bragg grating comprising a plurality of second patterns on the second end region, configured over 360 degrees around a periphery of the second end region, and extending laterally over a length of the second end region; a nanofiber region configured from a central portion of the optical fiber cable and coupled between the first end region and the second end region, the nanofiber region having a transmission greater than or equal to 95%, the nanofiber region having a diameter between 300 nanometers and 1.5 micrometers, the nanofiber region having a length between 10 micrometers and 10 centimeters; a first conical region configured from a first part of the nanofiber region near the first fiber Bragg grating; a second conical region configured from a second part of the nanofiber region near the second fiber Bragg grating; a cavity formed between the first fiber Bragg grating and the second fiber Bragg grating, including the conical regions and the nanofiber region; a plurality of atoms including an alkali metal atom, an alkaline earth metal, an alkaline earth type atom or other laser-coolable atoms, such that the number of atoms is between one and 100,000, and which are evanescently coupled to the nanofiber region between the first Bragg lattice and the second Bragg lattice.

[0027] According to one embodiment, each of the first plurality of motifs and of the second plurality of motifs is characterized by a line width of 200 nm to 1 micrometer.

[0028] According to one embodiment, each of the first plurality of motifs and of the second plurality of motifs is characterized by a length between 100 micrometers and 10 centimeters.

[0029] According to one embodiment, each of the first Bragg grating and the second Bragg grating has the plurality of patterns printed on the core of the region of the optical fiber cable.

[0030] According to one embodiment, the first Bragg grating and the second Bragg grating form a degenerate polarization cavity which supports arbitrary polarization states of light without subjecting them to different resonance frequencies.

[0031] The present invention can provide one or more of these advantages and / or benefits. In one example, the present invention provides an efficient quantum computing system based on a novel nanofiber-based optical cavity. In other words, the present invention offers a quantum computing device using a nanofiber region configured with a pair of reflectors to form a cavity for quantum computing and a repeater. In one example, the device uses conventional optical techniques and is compact and efficient. In another example, the present invention offers the advantage of generating manufacturable optical cavities that are reliable and efficient. These advantages, as well as others, can be obtained through the present device and the corresponding methods. Further details on these advantages can be found in this specification and more particularly below. Brief description of the drawings

[0032] Embodiments of the invention will be described below with reference to the drawings, briefly described below:

[0033] [Fig. 1a] Fig. 1a is a simplified diagram illustrating a manufacturing method of an azimuthal-symmetric optical fiber Bragg grating along the fiber axis in a top-view example of the present invention.

[0034] [Fig.lb] The [Fig. la] the same simplified diagram illustrating a method of manufacturing an optical fiber Bragg grating with azimuthal symmetry along the fiber axis in a side view example of the present invention.

[0035] [Fig.2] Fig.2 is a simplified diagram illustrating a manufacturing method of a fiber Bragg grating cavity with arbitrary polarization at each mode of the cavity by rotating a fiber around a fiber axis during the fabrication of the two fiber Bragg gratings in an example of the present invention.

[0036] [Fig.3] Fig.3 is a simplified diagram illustrating another method of fabrication of a fiber Bragg grating cavity with arbitrary polarization at each mode of the cavity also fabricated by the sequential formation of a fiber Bragg grating with a 90-degree offset angle along the fiber axis in an example of the present invention.

[0037] [Fig.4] Fig.4 is a simplified diagram illustrating a method of control and characterization of the polarization of a cavity mode by monitoring the scattering from a region of nanofibers in an example of the present invention.

[0038] [Fig. 5] Fig. 5 is an exemplary diagram illustrating the applications of the use of a circularly polarized cavity mode for atom-photon entanglement and non-destructive polarization rotation imaging in an example of the present invention.

[0039] In the drawings, identical references designate identical or similar objects. DETAILED DESCRIPTION

[0040] The present invention provides techniques generally related to quantum computing and fabrication methods. In particular, the present invention provides a fabrication method and a resulting device for a nanofiber-based quantum computing system comprising an optical cavity configured with a pair of Bragg gratings. By way of example, the invention can be applied to a variety of applications such as cryptography, drug discovery, optimization, machine learning and artificial intelligence, finance, weather forecasting, chemistry, mechanics, electricity, civil engineering, nuclear fusion and fission, economics, materials science, and any other complex matter, whether human or non-human. In an exemplary case, the present invention provides a method for fabricating a degenerate polarization cavity for quantum computing.

[0041] A polarization-degenerate cavity is an optical cavity that can support arbitrary polarization states of light without these states having different resonant frequencies or other different properties. In other words, the cavity structure allows light waves with differently oriented electric fields to resonate at the same frequency. Conventional optical cavities have been designed to preferentially support a specific polarization state or inevitably support only one specific polarization, because mirrors can exhibit polarization dependence due to material impurities, anisotropic stresses induced by surrounding structures, and other types of sources that cause polarization dependence. However, according to the present example, it is advantageous for the cavity to be able to support arbitrary polarization states without discrimination.In a degenerate polarization cavity, light waves with different polarizations (e.g., horizontal and vertical, or right-handed and left-handed circular) can resonate with the same efficiency and at the same frequency. A degenerate polarization cavity ensures that variations in the polarization state do not negatively affect the performance of the optical system by causing, for example, differences in resonance frequencies for different polarizations.

[0042] Polarization-degenerate cavities have played an important role in various fields, particularly in optics and photonics, due to their ability to simultaneously support arbitrary polarization states. In lasers, a polarization-degenerate cavity can improve output power and the Stability. The ability to support arbitrary polarizations can be beneficial for achieving greater efficiency and more stable laser operation. In fiber optic communications, the ability to manipulate the polarization state of light is crucial. Polarization degeneracy cavities can be used in devices such as modulators, where the polarization of light can be controlled to encode information. By using different polarization states, it is possible to increase the capacity of communication channels. This is achieved by multiplexing signals into different polarizations, allowing more data to be transmitted over the same medium without increasing bandwidth. In optical sensors, the ability to support and analyze different polarization states can improve sensor sensitivity and specificity.For example, by examining changes in polarization states, one can detect changes in the physical or chemical properties of the material being analyzed. Polarization degeneracy cavities can be used in spectroscopy and microscopy to study the properties of materials. By examining how a material affects the polarization state of light, one can obtain information about its structure and composition.

[0043] Polarization-degenerate cavities often have compact structures, making them ideal for integration into small-footprint photonic devices. This is particularly important in the context of the increasing demands for miniaturization and integration in modern electronics and photonics. When a cavity is polarization-degenerate, it is often more resistant to external perturbations that could otherwise cause polarization state drift. These cavities are therefore well-suited to applications where stability and reliability are important. In quantum technologies, polarization-degenerate cavities are desirable for manipulating and storing quantum information. They can help generate atom-photon entanglement and entangled photon pairs, which is crucial for quantum communication and computing.Consequently, degenerate cavities are an important element of modern optics, photonics, and quantum technologies because of their ability to handle arbitrary polarization states, which is desirable for improving the performance, capacity, and functionality of various systems and devices.

[0044] However, creating a high-fineness, polarization-degenerate fiber Bragg grating cavity is challenging due to several factors that must be carefully controlled to ensure both high fineness and polarization degeneracy. Here are some of the reasons for this difficulty:

[0045] Birefringence: Most optical materials are naturally birefringent to some extent, meaning they have different refractive indices for different polarizations of light. Even a small amount of birefringence can cause the cavity to have different resonant frequencies for different polarizations, which is the inverse of what is required for polarization degeneracy.

[0046] Fiber Bragg Grating (FBG) mirror: Low-loss Bragg grating-based cavity mirrors are important for achieving high finesse. However, the reflectivity of FBGs can also be polarization-dependent, based on a standard manufacturing procedure. Creating FBGs that have both high reflectivity and are polarization-independent is a challenge.

[0047] Stress-induced birefringence: Mechanical stress, whether from the assembly or the fiber placement, can induce birefringence in the FBG. This stress-induced birefringence can cause different polarizations to resonate at different frequencies.

[0048] Design and manufacturing complexity: Achieving polarization degeneracy requires a high level of control over material properties, FBG fabrication, and proper fiber assembly. This design and manufacturing complexity can make the production of high-finesse cavities with polarization degeneracy difficult and costly.

[0049] Because of these difficulties, the creation of high-finesse cavities degenerated by polarization often requires careful design, precision manufacturing, and meticulous alignment and stabilization.

[0050] The present method and system have made it possible to overcome these difficulties and others, as we shall see later.

[0051] The fiber-based cavity is composed of two fiber Bragg grating (FBG) mirrors that act as high reflectors for the cavity modes. The FBG is a passive optical component used to filter and reflect specific wavelengths of light. The FBG is fabricated by introducing a periodic variation in the refractive index in a small section of an optical fiber. An optical fiber consists of a core surrounded by a cladding, both composed of dielectric materials, but with slightly different refractive indices. In the case of a Bragg grating, a series of periodic changes in the refractive index is created in the fiber core. Various methods can be used, such as exposing the fiber core to an ultraviolet light interference pattern, which changes the core's refractive index. When light passes through the optical fiber, most wavelengths are unaffected.However, . A specific wavelength that meets the Bragg condition will be reflected. The Bragg condition is met when twice the period of the refractive index variation in the fiber is equal to the wavelength of the light. Mathematically, it is given by λB = 2 * n * A, where λB is the Bragg wavelength, n is the effective refractive index of the core, and A is the grating period. All other wavelengths that do not meet the Bragg condition continue to travel through the fiber.

[0052] Figures 1a and 1b are a simplified diagram illustrating a method for fabricating a polarization-degenerate fiber optic Bragg grating (FBG) mirror in an embodiment of the present invention. The phase mask method is a common technique for fabricating fiber optic Bragg gratings. A phase mask, which has a binary pattern alternating transparent and opaque regions, is designed to diffract light equally and maximally in the plus-prime and minus-prime orders. Self-interference between the two orders creates an interference pattern with half the period of the phase mask, necessary for grating formation. An ultraviolet (UV) laser beam passes through the phase mask, and the resulting interference pattern is imprinted on the fiber core.The core of the fiber optic cable is composed of a UV-sensitive material commonly used for photosensitization and UV exposure in fiber-gathering cables (FBGs): germanium-doped silica glass. Germanium-doped fiber exhibits increased photosensitivity compared to standard optical fibers and / or hydrogen-filled fibers. Hydrogen doping is a process often used to enhance the photosensitivity of optical fibers, making them more suitable for fiber manufacturing. Both germanium-doped silica and hydrogen-filled fibers allow for controlled modification of the refractive index when exposed to UV light. Using a UV laser, the germanium-doped silica fiber is exposed to create a periodic variation in the refractive index, forming the Bragg grating structure. This structure reflects a specific wavelength of light, known as the Bragg wavelength.

[0053] Conventional UV light is focused onto an optical fiber cable from a fixed direction, so the intensity distribution in the fiber's cross-section is not azimuthally symmetrical along the fiber axis. Consequently, the modulation of the inscribed refractive index is not azimuthally symmetrical in the cross-section of an optical fiber cable. Therefore, the Bragg wavelength depends on the polarization of the light in the optical fiber cable, since the modulation of the refractive index for polarization parallel to the direction of UV exposure is different from that for polarization perpendicular to the direction of UV exposure, resulting in birefringence for the polarizations of the light in indifferent directions, parallel and perpendicular to the direction of propagation of UV light.

[0054] In the present invention, by rotating the optical fiber cable along the fiber axis during UV exposure, the average intensity of the UV exposure is azimuthally symmetrical in the cross-section of the optical fiber cable. In one example, the UV exposure time varies from a few tens of seconds to 10 minutes or more.

[0055] In one example, the rotation period must be much shorter than the UV exposure time, for example, much less than half the exposure time. This rapid rotation during UV exposure creates an azimuthal-symmetric modulation of the refractive index in the cross-section of the optical fiber cable, leading to a polarization-independent FBG where the Bragg wavelength does not depend on the polarization.

[0056] Figure 2 is a simplified diagram illustrating a method for fabricating a degenerate polarized FBG cavity where two orthogonal modes of light polarization are frequency degenerate by the continuous rotation of a fiber around a fiber axis during the two FBG fabrications in an embodiment of the present invention. Two FBGs are fabricated sequentially by scanning the UV light source along the fiber axis. After the fabrication of the first FBG, the UV light source is turned off by a mechanical shutter, an acousto-optic modulator, an electro-optic modulator, and / or other types of intensity modulators. Then, the UV light source is exposed to the fiber again to fabricate the second FBG. The extinction time and the scanning speed of the UV light source determine the cavity length with near MHz frequency accuracy.This scanning method for cavity fabrication allows the creation of nearly identical FBGs in terms of Bragg wavelength, maximum reflectivity, and reflection bandwidth, which is essential for generating a birefringence-free cavity in addition to fabricating azimuthal-symmetric FBGs. Because each FBG is birefringent, the resonance frequencies of the two cavity modes with two orthogonal polarizations are identical. Examples of orthogonal polarizations include two linear polarizations in the horizontal and vertical directions, two circular polarizations where the rotation can be clockwise and counterclockwise, and other pairs of orthogonal polarizations.

[0057] Figure 3 is a simplified diagram illustrating another method of fabricating a degenerate polarization FBG cavity where two orthogonal modes of light polarization are frequency degenerate by the sequential formation of a Bragg grating with a 90-degree offset angle along the axis of a fiber in an embodiment of the present invention. In this method, the first FBG is The first FBG is fabricated without rotating the fiber during UV exposure, resulting in a birefringent FBG where the modulation of the refractive index depends on the polarization state. Before fabricating the second FBG, the fiber is rotated 90 degrees and then exposed to UV light without rotation, so the birefringence of the second FBG is also rotated 90 degrees. Consequently, the birefringence of the first and second FBGs cancels each other out, so the cavity formed by the first and second FBGs supports two orthogonal polarizations at the same resonant frequency.

[0058] Figure 4 is a simplified diagram illustrating a method for characterizing and controlling the polarization state of a cavity mode at the level of the nanofiber region by monitoring the scattering from a region of the nanofiber in an example of the present invention. The characterization consists of determining the polarization state, which can be linear, circular, or elliptical.

[0059] Information on the polarization state of the cavity mode is extracted from the polarization state of the light scattered in the nanofiber region. This scattering from an optical nanofiber refers to the phenomenon whereby light guided inside the nanofiber interacts with the fiber material and structure and is redirected in different directions instead of being guided along the fiber. In nanofibers, this scattering occurs when the size of the impurities and / or defects is much smaller than the wavelength of the light, so that the polarization state of the scattered light represents the local polarization of the cavity mode.Therefore, the polarization state of scattered light is characterized by a polarimeter, which generally consists of a set of wave plates and polarizers, and which allows the measurement of Stokes parameters, which fully characterize the polarization state. To create a desired input polarization state that is coupled within the cavity, polarizers, wave plates, and other types of polarization-sensitive optics are used and evaluated by the polarimeter for scattered light.

[0060] With reference to the figure, in one example, the present invention also includes a quantum computer and a repeater cell system. As illustrated, the system comprises a fiber optic cable region with a first end region and a second end region. The first end region has a first end and the second end region has a second end. In one example, the fiber optic cable region comprises a silicon dioxide material with a dopant material entity distributed within a central region. The system includes a first Bragg grating comprising a plurality of first patterns on the first end region, configured at 360 degrees around a periphery of the first end region and extending laterally along a length of the first end region, and a second Bragg grating comprising a plurality of second patterns on the second end region, configured at 360 degrees around a periphery of the second end region and extending laterally along a length of the second end region.

[0061] In one example, the system comprises a nanofiber region configured from a central portion of the optical fiber cable and coupled between the first end region and the second end region. The nanofiber region has a transmission of 95% or more. The nanofiber region has a diameter ranging from 300 nanometers to 1.5 micrometers and other values. The length of the nanofiber region ranges from 10 micrometers to 10 centimeters, among other values. The system comprises a first conical region configured from a first portion of the nanofiber region near the first Bragg grating and a second conical region configured from a second portion of the nanofiber region near the second Bragg grating.

[0062] In one example, the system comprises a cavity formed between the first fiber Bragg grating and the second fiber Bragg grating, including the conical regions and the nanofiber region. A plurality of atoms, including an alkali metal atom, an alkaline earth metal atom, an alkaline earth-type atom, or other laser-coolable atoms, such that the number of atoms is from one to 100,000, are evanescently coupled to the nanofiber region between the first and second Bragg gratings. Further details of the present system and the associated methods can be found throughout this specification and particularly below.

[0063] Figure 5 is an exemplary diagram illustrating the applications of a polarization-degenerate cavity for atom-photon entanglement and non-destructive polarization rotation imaging in an example of the present invention. The creation of atom-photon entanglement generally involves the atom-photon interaction process, where the quantum states of the atom and the photon become correlated or entangled. In this example, the atom-photon interaction is facilitated by the cavity where one or more atomic transitions are strongly coupled to the modes of the cavity, so that the single emitted photon is efficiently coupled to the cavity mode and then extracted from the cavity for the atom-photon entanglement distribution.

[0064] Here is an overview of atom-photon entanglement generation: First, a single atom is initialized in a well-defined quantum state, usually the ground state or a specific excited state. This can be achieved using laser cooling and optical pumping techniques and / or other suitable methods. Then, for an example of an entanglement generation protocol, a single atom is coupled to an optical cavity mode and pumped from its initial state to the excited state. by applying a laser. The excited atom then preferably emits a single photon in the cavity mode with two orthogonal circular polarizations where the rotations are right-handed and left-handed. Consequently, the internal states of the single atom and the polarization states of the single photon become entangled, and the photon is efficiently extracted from the cavity for subsequent applications, including long-distance communication based on entanglement. This entanglement generation protocol requires that the cavity mode support right-handed and left-handed circular polarizations with the same resonant frequencies as those achievable by the present invention described above.

[0065] The second application consists of generating the Faraday interaction and its applications to the engineering of spin-spin interactions between a plurality of atoms. The Faraday interaction with a double lambda system refers to the interaction of light with a quantum system that exhibits a specific energy level structure known as the double lambda configuration. This configuration consists of two pairs of closely spaced energy levels, resembling the Greek letter "lambda". In a double lambda system, there are generally two ground states, for example, denoted by -jg^- and |g2) and two excited states je1)- and je2}, in [Fig. 5].

[0066] When a magnetic field is applied perpendicular to the direction of light propagation, the energy levels of the double lambda system undergo Zeeman splitting due to the interaction between the magnetic field and the atomic magnetic moments. This splitting results in differences in the transition frequencies for right- and left-hand circularly polarized light. The Faraday effect comes into play when the double lambda system is illuminated by linearly polarized control light in the presence of a magnetic field. The magnetic field induces a differential phase shift between the two orthogonal components of the linearly polarized light due to the frequency difference caused by the Zeeman splitting. This phase shift results in a rotation of the plane of polarization of the transmitted or reflected light.

[0067] By analyzing the rotation of the polarization plane, information can be extracted about the intensity of the magnetic field or other relevant properties of the system. The Faraday interaction with a double lambda system is widely used in applications such as magnetometry, optical isolators, and quantum information processing.

[0068] Furthermore, Faraday interactions can be applied to create efficient spin-spin interactions, which constitutes a tool for manipulating and controlling quantum systems and can enable the implementation of various technologies Quantum. Spin-exchange interactions are generated by the exchange of virtual photons between atoms dispersively coupled to the cavity mode. The basic element is a Raman process in which an atom changes its internal state by absorbing a photon from a control field and emitting it in a cavity mode. When a control field is detuned from the Raman resonance, the virtual emission in the cavity can induce a spin-flipping process, in which a second atom changes its spin by absorbing the virtual photon in the cavity mode and re-emitting a real photon in the control field mode.

[0069] In one example, the present invention proposes a method for fabricating a nanofiber cavity with a polarization-degenerate Bragg grating for quantum computing or quantum repeaters. The method comprises transmitting electromagnetic radiation characterized by a wavelength of 150 nm to 400 nm and above through a phase-shifting mask pattern to diffract the electromagnetic radiation and form an interference pattern. The pattern is illuminated on the core of a first end of a fiber optic cable region. The first end is positioned opposite a second end, and a nanofiber cavity region is defined between the first and second ends.

[0070] In one example, the method includes the formation of a first Bragg grating on the core of the optical fiber cable region by modifying the refractive index of the core of the optical fiber cable region using electromagnetic radiation while rotating the optical fiber cable around a defined axis along the optical fiber cable region to form the first Bragg grating configured with a plurality of azimutally symmetric patterns of a plurality of modulations of the refractive index of 360 degrees angle around a core of the optical fiber cable and along a longitudinal region normal to a cross section of the optical fiber cable region.The method involves forming a second Bragg grating at a second end of the optical fiber cable region and configuring this second Bragg grating with a plurality of azimuthalally symmetric patterns of a plurality of refractive index modulations at 360-degree angles around a core of the optical fiber cable. In one example, the second Bragg grating is formed using similar radiation through the phase-shift mask.

[0071] In one example, the nanofiber cavity configured with the first Bragg grating and the second Bragg grating is characterized by a polarization-degenerate cavity mode that is suitable for any arbitrary polarization state of the light without causing one or more different resonance frequencies. In one example, the nanofiber cavity is characterized as a polarization-degenerate Bragg grating nanofiber cavity, such that any arbitrary polarization state of the light is free from any different resonant frequencies. In one example, the nanofiber cavity ranges from 100 micrometers to 1 cm and more.

[0072] In one example, the first or second fiber Bragg grating, characterized by azimuthal-symmetric refractive index modulation patterns, is configured by a modulation period along the fiber axis with a dimension ranging from 200 nm to 1 micron, or other. In one example, the first or second Bragg grating, characterized by azimuthal-symmetric refractive index modulation patterns, has a cross-section with a dimension ranging from 1 micron to 10 microns or more. In one example, the first or second Bragg grating has a length ranging from 50 microns to 10 centimeters or more.

[0073] In one example, the electromagnetic radiation is characterized by an exposure time of between 10 seconds and 100 minutes. In a preferred example, the exposure time is controlled by monitoring the maximum reflectivity of the first Bragg grating or the second Bragg grating in real time for an electromagnetic radiation power of between 10 mW and 1 W and an electromagnetic radiation diameter of between 30 microns and 1 mm.

[0074] In one example, the first Bragg grating and the second Bragg grating are arranged in space on an optical fiber cable with a spatial distance between the first and second Bragg gratings ranging from 100 microns to 10 cm and more. In another example, the first and second Bragg gratings are configured on either side of a conical region coupled to a nanofiber region. In yet another example, the first and second Bragg gratings are characterized by a plurality of patterns printed on a silicon dioxide material in the region of the optical fiber cable.

[0075] In one example, the rotation of the fiber along the fiber axis is characterized by a rotation speed that causes the formation of symmetrical azimuthal patterns of the refractive index modulation, the rotation speed being faster than the inverse of the UV exposure time, so that an anisotropic transverse pattern of a refractive index modulation is averaged over an azimuthal direction.

[0076] In another example, the present invention proposes a method for fabricating a degenerate polarized Bragg grating nanofiber cavity for quantum computing or repeaters. In one example, the method consists of providing an optical fiber cable comprising a first end, a second end, and a region of nanofibers between the first and second ends. The method includes transmitting electromagnetic radiation characterized by a wavelength of 150 nm to 400 nm and above through a phase-shifting mask to diffract the electromagnetic radiation in order to form an interference pattern to be illuminated on the core of one end of the fiber optic cable.

[0077] In one example, the method includes the formation of a first Bragg grating on the core of a first end of a fiber optic cable region by modifying the refractive index of the core of the fiber optic cable region using electromagnetic radiation without rotating the fiber to create an additional spatial region of the fiber optic cable region such that the first Bragg grating exhibits a plurality of azimuthal anisotropic patterns of a plurality of modulations of the refractive index around the core of the fiber optic cable and along a longitudinal region normal to a cross-section of the fiber optic cable region.

[0078] In one example, the method includes rotating the optical fiber cable about an axis (or rotating the light source) defined over a length of the optical fiber cable region by 90 degrees or some other angle. The method consists of forming a second Bragg grating on a core at a second end of the optical cable without rotating the fiber such that the first and second Bragg gratings are characterized by respective transverse anisotropies of refractive index modulations shifted by 90 degrees, which causes a polarization degeneracy cavity from a cancellation of the transverse anisotropy.

[0079] In one example, the nanofiber region configured with the first Bragg grating and the second Bragg grating forms a degenerate polarized Bragg grating nanofiber cavity, such that any arbitrary polarization state of light does not result in different resonance frequencies. In one example, the nanofiber region ranges from 100 micrometers to 1 cm and larger. In another example, the nanofiber region is characterized by a degenerate polarization cavity mode adapted to support any arbitrary polarization state of light without causing different resonance frequencies or other different properties.In one example, the first Bragg grating is characterized by birefringence and the second Bragg grating is configured with a 90-degree offset angle along the axis such that one or more cavity modes formed by the first and second Bragg gratings are degenerate into polarization due to the cancellation of the birefringence of the first and second Bragg gratings.

[0080] Although the foregoing constitutes a complete description of the specific examples, various modifications, alternative constructions, and equivalents may be used. By way of example, the device may comprise any combination of elements described above, as well as those outside this specification. Furthermore, the terms first, second, third, and last do not imply any order in a particular order. several of the examples presented herein. As used herein, the terms "rear face" and / or "front face" do not denote a specific location, but are simply used with reference to other elements of the claim. Therefore, the above description and illustrations should not be construed as limiting the scope of the present invention.

Claims

Claims

1. A method of manufacturing a polarization-degenerate Bragg grating nanofiber fiber cavity for quantum computing or a quantum repeater, the method comprising: transmitting electromagnetic radiation characterized by a wavelength of between 150 nm and 400 nm and above through a pattern of a phase shift mask to diffract the electromagnetic radiation to form an interference pattern to be illuminated on the core of a first end of a fiber optic cable region, the fiber optic cable region having a first end opposite a second end, and a nanofiber cavity region defined between the first end and the second end;causing a first Bragg grating to form on the core of the fiber optic cable region by changing the refractive index of the core of the fiber optic cable region using the electromagnetic radiation while rotating the fiber optic cable region about an axis defined along the fiber optic cable region to form the first Bragg grating configured with a plurality of azimuthally symmetric patterns of a plurality of modulations of the refractive index by an angle of 360 degrees about a core of the fiber optic cable region and along a longitudinal region normal to a cross-section of the fiber optic cable region;and forming a second Bragg grating at a second end of the fiber optic cable region, the second Bragg grating being configured with a plurality of symmetrical azimuthal patterns of a plurality of refractive index modulations at 360 degrees of angle around a core of the fiber optic cable region.;

2. The method of claim 1 wherein the cavity region of the nanofiber configured with the first Bragg grating and the second Bragg grating is characterized by a polarization-degenerate cavity mode that is adapted to any arbitrary polarization state of light without causing one or more different resonant frequencies.

3. The method of claim 1 or 2, wherein the region of the nanofiber cavity is characterized as a nanofiber cavity. with degenerate polarization Bragg grating, so that all arbitrary polarization states of light are free from any different resonance frequency.

4. A method according to any one of claims 1 to 3, wherein the first Bragg grating or the second Bragg grating characterized by azimuthally symmetric refractive index modulation patterns is configured by a modulation period along the fiber axis of a dimension between 200 nm and 1 micron.

5. A method according to any one of claims 1 to 4, wherein the first Bragg grating or the second Bragg grating characterized by the azimuthally symmetric patterns of refractive index modulations has a cross-section ranging from 1 micrometer to 10 micrometers and more in dimension.

6. A method according to any one of claims 1 to 5, wherein the electromagnetic radiation is characterized by an exposure time of between 10 seconds and 100 minutes, the exposure time being controlled by monitoring the maximum reflectivity of the first Bragg grating or the second Bragg grating in real time for an electromagnetic radiation power of between 10 mW and 1 W and an electromagnetic radiation diameter of between 3 micrometers and 1 millimeter.

7. A method according to one of claims 1 to 6, wherein the first Bragg grating and the second Bragg grating are each spatially arranged on a region of optical fiber cable with a spatial distance between the first Bragg grating and the second Bragg grating ranging from 100 micrometers to 10 centimeters and more.

8. The method of one of claims 1 to 7, wherein the first Bragg grating and the second Bragg grating are configured on either side of a tapered region coupled to a nanofiber region.

9. A method according to one of claims 1 to 8, wherein the first Bragg grating and the second Bragg grating are characterized by a plurality of patterns printed on a silicon dioxide material of the region of the fiber optic cable.

10. A method according to any one of claims 1 to 9, wherein the rotation of the fiber along the fiber axis is characterized by a rotational speed to cause the formation of azimuthal symmetrical patterns of the refractive index modulation.

11.

12. where a rotation rate is faster than the inverse of a UV exposure time so that a transversely anisotropic pattern of a refractive index modulation is averaged over an azimuthal direction. A method of fabricating a polarization-degenerate Bragg grating nanofiber fiber cavity for quantum computing, the method comprising: providing a fiber optic cable region comprising a first end, a second end, and a nanofiber region between the first end and the second end; transmitting electromagnetic radiation characterized by a wavelength of 150 nm to 400 nm and above through a phase shift mask to diffract the electromagnetic radiation to form an interference pattern to be illuminated on a core of a first end of the fiber optic cable region; causing a first Bragg grating to form on the core of a first end of a fiber optic cable region by changing the refractive index of the core of the fiber optic cable region using electromagnetic radiation without rotating the fiber to create an additional spatial region of the fiber optic cable region such that the first Bragg grating has a plurality of azimuthal anisotropic patterns of a plurality of refractive index modulations around the core of the fiber optic cable region and along a longitudinal region normal to a cross-section of the fiber optic cable region: rotating the region of the fiber optic cable about an axis defined over a length of the region of the fiber optic cable by an angle of 90 degrees; forming a second Bragg grating on a core of a second end of the fiber optic cable region without rotating the fiber such that the first Bragg grating and the second Bragg grating are characterized by respective transverse anisotropies of refractive index modulations offset by 90 degrees of angle, causing a polarization degeneracy cavity from a cancellation of the transverse anisotropy. The method of claim 11, wherein the nanofiber region configured with the first Bragg grating and the second Bragg grating forms a polarization-degenerate Bragg grating nanofiber cavity, so that any arbitrary polarization state of light does not result in different resonant frequencies.

13. A method according to either of claims 11 or 12, wherein the nanofiber region is characterized by a polarization-degenerate cavity mode, adapted to support any arbitrary polarization state of light without causing different resonant frequencies or other different properties.

14. A method according to one of claims 11 to 13, wherein the first Bragg grating is characterized by birefringence and the second Bragg grating is configured with an offset angle of 90 degrees along the axis such that one or more cavity modes formed by the first Bragg grating and the second Bragg grating are polarization degenerate due to cancellation of the birefringence of the first Bragg grating and the second Bragg grating.

15. A system comprising a quantum computer and a repeater cell system, comprising: a fiber optic cable region having a first end region and a second end region, the first end region having a first end and the second end region having a second end, the fiber optic cable region comprising a silicon dioxide material with a dopant material entity distributed within a central region; a first fiber Bragg grating comprising a plurality of first patterns on the first end region, configured 360 degrees around a periphery of the first end region, and extending laterally along a length of the first end region;a second fiber Bragg grating comprising a plurality of second patterns on the second end region, configured 360 degrees around a periphery of the second end region, and extending laterally along a length of the second end region; a nanofiber region configured from a central portion of the fiber optic cable and coupled between the first end region; and the second end region, the nanofiber region having a transmission greater than or equal to 95%, the nanofiber region having a diameter between 300 nanometers and 1.5 micrometers, the nanofiber region having a length between 10 micrometers and 10 centimeters; a first tapered region configured from a first portion of the nanofiber region proximate the first fiber Bragg grating; a second tapered region configured from a second portion of the nanofiber region proximate the second fiber Bragg grating; a cavity formed between the first fiber Bragg grating and the second fiber Bragg grating, including the tapered regions and the nanofiber region;a plurality of atoms comprising an alkali metal atom, an alkaline earth metal, an alkaline earth type atom, or other laser-coolable atoms, such that the number of atoms is between one and 100,000, and which are evanescently coupled to the region of the nanofiber between the first Bragg grating and the second Bragg grating.;

16. The system of claim 15, wherein each of the first plurality of patterns and the second plurality of patterns is characterized by a line width of 200 nm to 1 micrometer.

17. The system of claim 15 or 16, wherein each of the first plurality of patterns and the second plurality of patterns is characterized by a length of between 100 micrometers and 10 centimeters.

18. The system of one of claims 15 to 17, wherein each of the first Bragg grating and the second Bragg grating has the plurality of patterns printed on the core region of the fiber optic cable.

19. The system of any one of claims 15 to 18, wherein the first Bragg grating and the second Bragg grating form a degenerate polarization cavity that supports arbitrary polarization states of light without subjecting them to different resonant frequencies.

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