Quantum computing system and operation method thereof

Abstract

A quantum computing device for generating a plurality of qubits according to an embodiment of the present invention comprises: a bar which is disposed in a space formed by a magnet and is configured to be divided into a plurality of regions by an inner wall; an original gradient coil disposed in the space and configured to apply an original gradient to the bar; a reverse gradient coil disposed in the space and configured to apply a reverse gradient to the bar; and at least one radio frequency (RF) coil disposed between the bar and the original gradient coil and configured to apply RF pulses to the bar, wherein a uniform magnetic field is applied to each of the plurality of regions by the original gradient and the reverse gradient, and a plurality of qubits corresponding to the plurality of regions are generated by the applied magnetic field and RF pulses matching the applied magnetic field.

Description

Quantum computing system and its operation method

[0001] The present invention relates to a quantum computing system, and more particularly, to a quantum computing system for performing quantum operations using qubits generated based on magnetic field compensation, and an operating method thereof.

[0002] A quantum computer is a computer that processes data using phenomena related to quantum mechanics, such as quantum entanglement and quantum superposition. Quantum computers use quantum bits, or qubits, as the smallest basic unit of information for data processing using phenomena related to quantum mechanics. Quantum computers may be needed to solve problems that cannot be solved with the limited computational power of modern computers, such as neuroscience, which deals with hundreds of billions to trillions of neurons. Quantum computers can demonstrate quantum supremacy in various fields that modern computers cannot solve, such as optimizing models of atomic and molecular interactions, making new scientific discoveries about nature at the microscopic and macroscopic scales, developing new materials, developing new pharmaceuticals, optimizing logistics, finance, communications, and security, and optimizing artificial intelligence algorithms.

[0003] Quantum entanglement refers to the quantum connection between two or more spin states of two or more qubits, such that each spin state cannot be treated separately. Quantum superposition refers to the probability that multiple measurable spin states of a single qubit can exist simultaneously before the qubit is measured (or observed).

[0004] The driving mechanism for generating multiple qubits for quantum computation is referred to as the quantum computer platform. The quantum computer platform can be selected from a variety of driving mechanisms, including superconductors, semiconductors, magnets, diamonds, atoms, and ions.

[0005] A quantum computing platform may include a magnet having a space formed inside, a material inserted into the magnet capable of state transition, and a gradient coil provided inside the magnet to generate a gradient magnetic field inside the magnet. The material may include a nucleus having a nuclear spin of 1 / 2. The material may include a hydrogen nucleus. The material may include ¹H, ¹³H, ³¹P, etc. Nuclear spin may refer to all angular momentum of an atomic nucleus. Nuclear spin may be formed by the combination of the spin and orbital angular momentum of all nucleons. Nucleons may be elementary particles that constitute an atomic nucleus. Nucleons may include protons and / or neutrons. A nucleus may be an atomic nucleus or a type of atom with a unique atomic number and mass number. An atomic nucleus may refer to a positively charged portion located at the center of an atom. An atom may refer to an elementary particle that constitutes matter.

[0006] A gradient coil can generate a gradient magnetic field whose strength varies linearly along the z-axis. In this case, the field strength can increase linearly along the z-axis. Therefore, atomic nuclei contained in the material within the magnet, positioned relative to the z-axis, can generate signals of different frequencies.

[0007] However, a uniformly strong magnetic field needs to be applied to the area inside the gradient coil corresponding to the area where the qubit is generated. In other words, in order for each of the multiple qubits to have a single frequency, a uniform magnetic field needs to be applied to the area where each qubit is generated within the quantum computer platform. If the magnetic field is not uniform in the area where the qubit is generated, the RF signal for changing the spin state of the qubit may not be properly applied. This is because the strength of the applied magnetic field directly affects the resonant frequency of the radio frequency (RF) signal that changes the spin state of the qubit. More information regarding the quantum computing platform can be obtained, for example, from KR 10-2022-0093630, which is incorporated herein by reference.

[0008] A quantum computing platform may include one or more RF coils positioned between a bar and a gradient coil. The one or more RF coils can apply one or more RF pulses to the inside of the magnet (more specifically, to hydrogen protons contained in the bar). That is, by applying one or more RF pulses to the spin of a qubit, which is a collection of hydrogen protons, the spin state of the qubit can be changed. In this way, multiple spin states that probabilistically exist simultaneously within a single qubit can be measured, thereby measuring a single spin state and thereby measuring an MR signal with the largest magnitude.

[0009] However, as time passes after one or more RF pulses are applied to the spin of a qubit, the spin signal magnitude may decrease as the spin of the qubit dephasing occurs. In this case, it may be difficult to measure the spin states of the qubit to measure the MR signal with the maximum magnitude, and it may be difficult to perform quantum computations on two or more qubits using the detected spin signal values. More information on the application of one or more RF pulses can be obtained, for example, from KR 10-2022-0093630, which is incorporated herein by reference.

[0010] Therefore, in order to create a qubit that is a collection of multiple hydrogen protons rather than a single particle and to perform quantum operations using two or more qubits, a quantum computing system that can apply a uniform magnetic field to the area where the qubits are created and detect spin signal values ​​from the qubits as much as possible may be required.

[0011] Related prior art documents include Korean Patent Publication No. 10-2022-0093690 (published on November 30, 2023) and Korean Patent Publication No. 10-2022-0031998 (published on March 15, 2022).

[0012] An object of the present invention is to provide a quantum computing system and an operating method thereof capable of generating a plurality of qubits based on magnetic field compensation and determining a quantum state for a target qubit using control pulses generated based on detected spin values ​​of the qubits.

[0013] The present invention relates to the generation of quantum bits (qubits) based on a new MRI (Magnetic Resonance Imaging, hereinafter referred to as magnetic resonance imaging) technique, unlike the generation of qubits based on nuclear magnetic resonance spectroscopy techniques such as 13C-NMR (Nuclear Magnetic Resonance, hereinafter referred to as nuclear magnetic resonance) using conventional trichlorothene (C2HCl3) and (2,3)-dibromothiophene.

[0014] This novel technique allows for the creation of multiple qubits using magnetic resonance imaging-based gradient techniques, with the additional benefit of local reverse gradient fields. This configuration allows for the creation of multiple local magnetic fields, each capable of generating multiple qubits with a single frequency.

[0015] When using existing nuclear magnetic resonance techniques, it can be difficult to obtain qubits in a high-purity state because they are fundamentally based on the ensemble or bulk properties of nuclear spins, each with "spin ½" under a strong magnetic field.

[0016] That is, while it may be impossible to generate a sufficient number of qubits using conventional nuclear magnetic resonance techniques and difficult to generate qubits in a high-purity state that can be used for quantum computation, the present invention can generate multiple qubits in a “pure or quasi-pure” state with bulk and ensemble properties that can be used for quantum computation by utilizing MRI pulse sequences.

[0017] In addition, the present invention can provide a quantum computing system and its operating method that provides a "qubit" that does not require a special low-temperature environment, such as a superconducting qubit, a superconducting transmon, or a superconducting transistor, i.e., that can operate at ordinary room temperature and environment.

[0018] Meanwhile, the technical tasks to be achieved by the platform and operating method according to the technical idea of ​​the technology disclosed in this specification are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0019] A quantum computing device for generating a plurality of qubits according to an embodiment of the present invention includes a bar arranged in a space formed by a magnet and configured to be divided into a plurality of regions by an inner wall, an original gradient coil arranged in the space and configured to apply an original gradient to the bar, a reverse gradient coil arranged in the space and configured to apply a reverse gradient to the bar, and at least one RF coil arranged between the bar and the gradient coil and configured to apply RF pulses to the bar, wherein a uniform magnetic field is applied to each of the plurality of regions by the gradient magnetic field and the reverse gradient magnetic field, and a plurality of qubits corresponding to the plurality of regions are generated by the applied magnetic field and the RF pulses matching the applied magnetic field.

[0020] As an example, the plurality of qubits have Larmor frequencies of different values, and each of the plurality of qubits has a Larmor frequency of one value.

[0021] As an example, the gradient magnetic coil is divided into a plurality of magnetic field fields corresponding to a plurality of areas formed on the bar, and the reverse gradient magnetic coil includes a plurality of coils corresponding to a plurality of magnetic field fields.

[0022] As an example, each of the plurality of regions is applied with a magnetic field having a strength corresponding to the sum of the difference between the magnetic field by the magnet and the gradient magnetic field and the counter-gradient magnetic field generated in the magnetic field.

[0023] As an embodiment, at least one RF coil includes a first RF coil configured to apply a first RF pulse in a first direction and a second RF coil configured to apply a second RF pulse in a second direction different from the first direction.

[0024] As an example, the first RF pulse is a pulse applied to the bar to rotate the spin of the qubit by an angle of 90 degrees in the first direction, and the second RF pulse is a pulse applied to the bar to rotate the spin of the qubit by an angle of 180 degrees in the second direction.

[0025] A quantum computing system according to an embodiment of the present invention includes a quantum computing device, and a controller configured to control the quantum computing device to generate a plurality of qubits and to perform quantum operations using at least two qubits among the generated plurality of qubits, wherein the controller detects spin signals from qubits generated by applying RF+ pulses, operates on the spin signals to generate control pulses, and applies at least some of the control pulses and RF pulses to a target qubit to determine a quantum state of the target qubit, wherein at least some of the control pulses to be applied are determined according to the quantum state of the qubit.

[0026] As an example, the spin signals include a first spin signal and a second spin signal, and the controller generates a first control pulse by adding values ​​of the first and second spin signals, and generates a second control pulse by adding values ​​of the first spin signal and an inverted second spin signal.

[0027] As an example, the first control pulse is a double pulse that rotates the spin of the target qubit twice, and the second control pulse is a single pulse that rotates the spin of the target qubit once.

[0028] As an example, when the quantum state of the qubit is the first state, the controller determines the quantum state of the target qubit by applying the first control pulse and RF pulses.

[0029] As an example, when the quantum state of the qubit is a second state, the controller determines the quantum state of the target qubit by applying a second control pulse and RF pulses.

[0030] As an example, when the second control pulse and RF pulses are applied to the target qubit, the changed quantum state is determined as the quantum state of the target qubit.

[0031] As an example, the RF pulses include a pulse that rotates the spin of the qubit by 90 degrees in a first direction, a pulse that rotates the spin of the qubit by 180 degrees in a second direction different from the first direction, and a pulse that rotates the spin of the qubit by 90 degrees in a third direction different from the first and second directions.

[0032] A method of operating a quantum computing system including a quantum computing device according to an embodiment of the present invention includes detecting spin signals from qubits generated by applying RF pulses, generating control pulses by operating the spin signals, and applying at least some of the control pulses and RF pulses to a target qubit to determine a quantum state of the target qubit, wherein at least some of the control pulses to be applied are determined according to the quantum state of the qubit.

[0033] A computer program stored on a non-transitory computer-readable recording medium according to an embodiment of the present invention includes commands, which when executed by a computer implement a method of operating a quantum computing system.

[0034] According to an embodiment of the present invention, by arranging the reverse-gradient magnetic field coils corresponding to the region where qubits are generated, local non-uniformity of the magnetic field applied to the region where qubits are generated can be minimized. In this case, a uniform magnetic field can be applied to the region where one qubit is generated, and different magnetic fields can be applied to each region where qubits are generated. Accordingly, quantum operations on two or more qubits can be performed in parallel on multiple qubits, thereby reducing the time required for quantum operations.

[0035] Furthermore, according to an embodiment of the present invention, a single qubit can be created in which a pure spin state of 0 or 1 is observed for multiple hydrogen protons supplied to an area where a uniform magnetic field is applied through magnetic field compensation. Accordingly, a magnetic resonance (MR) signal can be measured by analyzing the spin signal detected from a single qubit. Furthermore, the performance of a quantum computing system that processes quantum information through quantum operations with a target qubit can be improved by utilizing the spin values ​​detected from the qubit.

[0036] Meanwhile, these effects are merely exemplary, and effects predicted or expected from the detailed configuration of the present invention from the perspective of those skilled in the art may also be added to the inherent effects of the present invention.

[0037] FIG. 1 is a block diagram of a quantum computing system according to an embodiment of the present invention.

[0038] Figure 2 is a schematic diagram of a quantum computing device included in the quantum computing system of Figure 1.

[0039] Figures 3a to 3d are a first example of a change in spin state when an RF signal is applied to a local area.

[0040] Figures 4a to 4d are a second example of a change in spin state when an RF signal is applied to a local area.

[0041] Figures 5a to 5c are a third embodiment of a change in spin state when an RF signal is applied to a local area.

[0042] Figures 6a to 6c are a fourth embodiment of a change in spin state when an RF signal is applied to a local area.

[0043] Fig. 7 is a block diagram of a signal conversion unit that generates control pulses by calculating spin signals for the superimposed spin states in Fig. 6c.

[0044] Figures 8a and 8b are a first embodiment showing the spin state of a target qubit determined by quantum entanglement.

[0045] Figures 9a and 9b are a second embodiment showing the spin state of a target qubit determined by quantum entanglement.

[0046] Figures 10a and 10b are a third embodiment showing the spin state of a target qubit determined by quantum entanglement.

[0047] Figures 11a and 11b are a fourth embodiment showing the spin state of a target qubit determined by quantum entanglement.

[0048] FIG. 12 is a first flowchart of an operation method of a quantum computing system for generating a qubit according to an embodiment of the present invention.

[0049] FIG. 13 is a second flowchart of a method of operating a quantum computing system for generating and storing control pulses according to an embodiment of the present invention.

[0050] FIG. 14 is a third flowchart of an operating method of a quantum computing system for determining a quantum state of a target qubit according to an embodiment of the present invention.

[0051] Hereinafter, embodiments of the present invention will be described clearly and in detail to the extent that a person having ordinary skill in the art can easily practice the present invention.

[0052] In connection with the description of this specification, it should be understood that terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used solely for the purpose of distinguishing one component from another. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that terms such as "comprises" or "has" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0053] Although the present disclosure has been illustrated and described in detail in the drawings and the foregoing description, it is to be understood that the present disclosure is to be considered in an illustrative rather than a restrictive sense, and that only certain embodiments have been illustrated and described, and that all changes and modifications falling within the spirit of the present disclosure are intended to be protected.

[0054] The quantum computing system mentioned herein may be a quantum information processing technology intended to implement quantum computing. Quantum computing is a new concept of computing that utilizes quantum properties such as quantum superposition and quantum entanglement to enable ultra-fast parallel computation. It can be categorized into algorithms, simulators, and general-purpose quantum computers. Quantum information processing technology may be a technology that determines quantum states based on interacting qubits, controls changes in these states, measures them, and analyzes them.

[0055] The qubits mentioned herein can simultaneously represent multiple bits using a quantum superposition state. For example, each qubit can be represented by a probability, such as "0 with a 20% probability and 1 with an 80% probability." When observed, the qubit can be determined as a single quantum state, as the quantum superposition state is released.

[0056] FIG. 1 is a block diagram of a quantum computing system (100) according to an embodiment of the present invention.

[0057] Referring to FIG. 1, a quantum computing system (100) may include a quantum computing device (200) configured to generate a plurality of qubits and a controller (300) configured to control components of the quantum computing device (200) so that the quantum computing device (200) generates a plurality of qubits.

[0058] For example, the quantum computing device (200) may include a shielded room (or chamber). The quantum computing device (200) may include an environment in which various noises that may arise from the external environment during signal measurement are blocked. A detailed description of the quantum computing device (200) is described below with reference to FIG. 2.

[0059] The controller (300) may include a magnetic field application control unit (310), an RF signal application unit (320), a spin signal analysis unit (330), a signal conversion unit (340), a data management unit (350), a quantum entanglement processing unit (360), a temperature management unit (370), a power management unit (380), and a control logic (390).

[0060] The controller (300) may control the quantum computing device (200) to generate a plurality of qubits by some of the components included therein, and perform quantum operations on the generated plurality of qubits. Alternatively, the controller (300) may control the quantum computing device (200) to generate a plurality of qubits by all of the components included therein and additional components not shown, and perform quantum operations on the generated plurality of qubits.

[0061] All or part of the components included in the controller (300) may be implemented in the form of software, hardware, or a combination thereof. For example, the software may be machine code, firmware, embedded code, and application software. For example, the hardware may include electrical circuits, electronic circuits, processors, computers, integrated circuits, integrated circuit cores, pressure sensors, inertial sensors, MEMS (MicroElectroMechanical Systems), passive components, or a combination thereof.

[0062] The magnetic field application control unit (310) may refer to all devices and means for supplying current and / or voltage to the quantum computing device (200) so that a magnetic field or gradient magnetic field is generated within the quantum computing device (200).

[0063] The radio frequency (RF) signal application unit (320) may refer to any device or means for applying an RF signal having a corresponding resonant frequency to a quantum computing device (200). The RF signal may be applied to a qubit having a frequency matching its resonant frequency. Accordingly, the quantum state of the hydrogen proton spin of the qubit may be controlled independently from all other qubits.

[0064] The spin signal analysis unit (330) may refer to all devices and means for observing (measuring) the spin state (or quantum state) of a qubit and analyzing a single measured spin state. A qubit is a quantum superposition state that can be simultaneously expressed as a value corresponding to multiple bits, but when observed by the spin signal analysis unit (330), the quantum superposition state is resolved and can be determined as a single spin state.

[0065] The signal conversion unit (340) may refer to any device or means for calculating the spin signals of a qubit to create another quantum superposition state expressed as a linear sum of two or more different distinct states. Alternatively, the signal conversion unit (340) may refer to any device or means for converting the spin signals of such another quantum superposition state into control pulses.

[0066] The transformed control pulse can be applied to other qubits, either neighboring or spatially distant. That is, once the quantum state of one qubit is determined (the control pulse to be applied is determined), the control pulse can be applied to another entangled qubit (the target qubit, described later) to determine the quantum state of the other qubit.

[0067] The data management unit (350) may refer to all devices and means for storing and managing information about control pulses generated for a single qubit. Alternatively, the data management unit (350) may refer to all devices and means for storing and managing information about the quantum state of a qubit observed and analyzed by the spin signal analysis unit (330).

[0068] The quantum entanglement processing unit (360) may be a quantum algorithm implemented to enable parallel operations on two or more qubits for multiple qubits by utilizing the quantum characteristics of quantum entanglement.

[0069] The quantum entanglement processing unit (360) may be configured to control the quantum state change of the target qubit so that a quantum algorithm can be implemented. However, the quantum state change of the target qubit may also be controlled by controlling the RF signal application unit (320) by the control logic (390) included in the controller (300). In this case, the quantum entanglement processing unit (360) may perform its function within the control logic (390).

[0070] The temperature management unit (370) may include all devices and means (e.g., a heater or temperature control device) for controlling and managing the temperature inside the quantum computing device (200).

[0071] The permanent magnet (see magnet (210) of FIG. 2) provided in the quantum computing device (200) may lose its magnetic performance at a rate determined by the size, shape, grade, usage method, etc. of the magnet whenever the temperature rises by 1 degree Celsius. Therefore, the temperature management unit (370) may further include a temperature sensor (not shown) for measuring the temperature of the permanent magnet in order to maintain the temperature at a constant temperature of about 5 degrees Celsius higher than the maximum temperature expected at the time and place where the product to which the permanent magnet is applied is operated.

[0072] The power management unit (380) may refer to all devices and means for supplying and managing power (e.g., battery, current, voltage) to components of the quantum computing device (200).

[0073] The control logic (390) may be configured to control the operations of all or part of the components of the controller (300). For example, the controller (300) may control the operations of the magnetic field application control unit (310), the RF signal application unit (320), the spin signal analysis unit (330), the signal conversion unit (340), the data management unit (350), and the quantum entanglement processing unit (360) through the control logic (390) to enable parallel operations on two or more qubits for multiple qubits by utilizing quantum characteristics such as quantum superposition and quantum entanglement.

[0074] Fig. 2 is a schematic diagram of a quantum computing device (200) included in the quantum computing system (100) of Fig. 1. The internal temperature of the quantum computing device (200) can be maintained constant by a temperature management unit (370).

[0075] Referring to FIGS. 1 and 2, a quantum computing device (200) may include a magnet (210), a bar (220), a gradient coil (230), a reverse-gradient coil (240), a first RF coil (250), and a second RF coil (260).

[0076] The configuration of the quantum computing device (200) illustrated in FIG. 1 is merely a simplified cross-sectional example. In one embodiment of the present invention, the quantum computing device (200) may further include other components for generating a plurality of qubits, and only some of the disclosed components may constitute the quantum computing device (200).

[0077] The magnet (210) is an object that generates a magnetic field (Bo), and may be arranged so that a space (or chamber) is formed inside the quantum computing device (200). For example, the magnet (210) may have a cylindrical shape and may be arranged in a longitudinal direction (e.g., in the z-axis direction). A bar (220), a gradient magnetic field coil (230), a reverse gradient magnetic field coil (240), a first RF coil (250), and a second RF coil (260) may be provided inside the magnet (210).

[0078] The interior of the magnet (210) may be filled with air or be in a vacuum. However, the shape of the magnet (210) is not limited thereto and may have various shapes. The magnet (210) may be one of a permanent magnet, a superconducting magnet, and a high-temperature superconducting magnet. However, the type of the magnet (210) is not limited thereto and may include various objects that generate a magnetic field (Bo).

[0079] The magnetic flux density of the magnet (210) may range from 1.0 T to 20 T. The corresponding frequency may range from 150 MHz to 500 MHz. However, the magnetic flux density and frequency of the magnet (210) are not limited thereto, and the magnet (210) may have various magnetic flux densities and frequencies.

[0080] The magnetic field application control unit (310) can generate a magnetic field in a space (or chamber) within the quantum computing device (200) by supplying current and / or voltage to the magnet (210).

[0081] If the bar (220) is rod-shaped, it may be formed of a material capable of state transition. If it is hollow and tubular, it may contain a material capable of state transition within it. For example, the bar (220) may refer to a tube through which water is supplied to provide hydrogen protons. However, the shape of the bar (220) is not limited thereto and may take various forms.

[0082] The bar (220) can be inserted in the longitudinal direction of the magnet (210) (e.g., along the z-axis) and placed inside the magnet (210). The bar (220) can rotate or not rotate around the longitudinal axis (e.g., along the z-axis). The bar (220) can be divided into a plurality of regions by walls provided inside. Water can be supplied to each of the plurality of regions so that hydrogen protons are provided.

[0083] The gradient coil (230) is provided inside the magnet (210) and can generate a gradient magnetic field (Original Gradient, OG) inside the magnet (210). For example, the gradient coil (230) can be located on the upper part of the inner wall of the magnet (210).

[0084] An OG can be calculated as the change in magnetic field divided by the change in distance. An OG can be generated when there are different magnetic fields of different magnitudes and directions between two points.

[0085] The gradient coil (230) can generate a gradient magnetic field (OG) in which the strength of the magnetic field linearly changes along at least one axis among the x-axis, the y-axis, and the z-axis. As illustrated in FIG. 2, the gradient magnetic field coil (230) can be a coil for generating a gradient magnetic field (OG) along the z-axis. In this case, the strength of the magnetic field can linearly increase along the z-axis.

[0086] The gradient magnetic coil (230) can be divided into a plurality of magnetic field fields (F1 to Fn) to correspond to a plurality of areas provided in the bar (220), and the intensity of the magnetic field for each of the plurality of magnetic field fields (F1 to Fn) can increase linearly in the z-axis.

[0087] Hydrogen protons contained in water supplied to a bar (220) located inside a magnet (210) can generate signals of different frequencies when such a gradient magnetic field is applied. However, if multiple hydrogen protons within a single region generate signals of different frequencies, it may be difficult to collectively or entirely change the spin state of a single qubit that may be generated in response to a single region.

[0088] This may be because the applied magnetic field strength directly affects the resonant frequency of the RF signal that changes the spin state of a qubit. That is, to change the spin state of a qubit globally or collectively, it is necessary to ensure that a qubit has a single frequency, and thus, a uniform magnetic field must be applied to the region where a qubit is generated.

[0089] Accordingly, a reverse gradient coil (240) may be provided inside the magnet (210) to generate a reverse gradient (RG) inside the magnet (210). For example, the reverse gradient coil (240) may include a plurality of coils positioned on the upper side of the inner side of the gradient coil (230).

[0090] The reverse-gradient coil (240) can generate a reverse-gradient magnetic field (RG) that varies linearly in the z-axis. For example, the intensity of the reverse-gradient magnetic field (RG) can decrease linearly in the z-axis. Through the reverse-gradient magnetic field coil (240), the reverse-gradient magnetic field (RG) can be applied to the corresponding magnetic field field of the gradient magnetic field coil (230).

[0091] For example, a first reverse-gradient magnetic field (RG) can be applied to a first magnetic field (F1) by a first reverse-gradient magnetic field coil. A second reverse-gradient magnetic field (RG) can be applied to a second magnetic field (F2) by a second reverse-gradient magnetic field coil. A third reverse-gradient magnetic field (RG) can be applied to a third magnetic field (F3) by a third reverse-gradient magnetic field coil.

[0092] In this case, not only a gradient magnetic field but also a counter-gradient magnetic field (RG) that decreases linearly in the z-axis can be applied to each region where a qubit is created.

[0093] Therefore, the strength of the corresponding magnetic fields (B1 to Bn) in each of the plurality of magnetic fields (F1 to Fn) can be uniform. This can be expressed by the following formula.

[0094]

[0095] Here, Bo can represent the magnetic field strength by the magnet (210).

[0096] Here, G(zn) may represent a gradient magnetic field by a gradient magnetic field coil (230). For example, G(z1) may represent a gradient magnetic field in a first magnetic field field (F1). G(z2) may represent a gradient magnetic field in a second magnetic field field (F2). G(z3) may represent a gradient magnetic field in a third magnetic field field (F3).

[0097] Here, Gn(zn) may represent a reverse-gradient magnetic field by a reverse-gradient magnetic field coil (240). For example, G1(z1) may represent a reverse-gradient magnetic field in a first magnetic field field (F1). G2(z2) may represent a reverse-gradient magnetic field in a second magnetic field field (F2). G3(z3) may represent a reverse-gradient magnetic field in a third magnetic field field (F3).

[0098] Here, Bn(zn) can represent the sum of the magnetic field strengths for each magnetic field. For example, B1(z1) can represent the sum of the magnetic field strengths in the first magnetic field field (F1). B2(z2) can represent the sum of the magnetic field strengths in the second magnetic field field (F2). B3(z3) can represent the sum of the magnetic field strengths in the third magnetic field field (F3).

[0099] In this case, multiple qubits having different frequencies (w1 to wn, hereinafter referred to as Larmor frequencies) can be generated in multiple areas provided in the bar (220). This can be expressed by the following formula.

[0100]

[0101] Here, γ may be the gyromagnetic ratio of hydrogen protons.

[0102] Here, wn may represent the Larmor frequency of the qubit. For example, w1 may be the Larmor frequency of the first qubit (QB1) generated in the first region (the first local region) of the bar (220). w2 may be the Larmor frequency of the second qubit (QB2) generated in the second region (the second local region) of the bar (220). w3 may be the Larmor frequency of the third qubit (QB3) generated in the third region (the third local region) of the bar (220).

[0103] The first RF coil (250) is placed between the bar (220) and the gradient magnetic coil (230), and may be made of a metal (e.g., copper) for applying a first RF pulse to the interior of the magnet (210). However, the material of the first RF coil (250) is not limited thereto. The first RF coil (250) may be composed of a single coil, but is not limited thereto.

[0104] The shape of the first RF coil (250) may be spiral. However, the shape of the first RF coil (250) is not limited thereto, and may have various shapes for applying the first RF pulse to the bar (220). A detailed description of the configuration for applying the first RF pulse through the first RF coil (250) will be described later.

[0105] The second RF coil (260) may be a metal (e.g., copper) disposed between the bar (220) and the first RF coil (250) to apply a second RF pulse to the interior of the magnet (210). However, the material of the second RF coil (260) is not limited thereto. The second RF coil (260) may include a plurality of RF coils disposed spaced apart from each other.

[0106] The shape of the second RF coil (260) may be a ring shape. Accordingly, the second RF coil (260) may be a shape that surrounds the outer surface of the bar (220). However, the shape of the second RF coil (260) is not limited thereto, and may have various shapes for applying the second RF pulse to the bar (220). A detailed description of the configuration for applying the second RF pulse through the second RF coil (260) will be described later.

[0107] The second RF coils (260) may be spaced apart from each other to correspond to a predetermined distance (e.g., 10 cm, 20 cm, etc.). The predetermined distance may be determined in advance based on the number of second RF coils and the length of the bar (220).

[0108] A plurality of qubits (QB1 to QBn) can be generated using hydrogen protons provided through the bar (220) based on RF pulses (RF signals) applied through the first RF coil (250) and the second RF coil (260). For example, a number of qubits equal to the number of second RF coils (260) can be generated, but the number of qubits generated is not limited thereto.

[0109] That is, since the strength of the magnetic field applied to each of the multiple regions is different and a uniform magnetic field is applied to each of the multiple regions, when RF pulses having a resonance frequency matching the magnetic field and the frequency of the magnetic field are applied to the bar, multiple qubits having different Larmor frequencies corresponding to the multiple regions can be generated.

[0110] FIGS. 3A to 3D are a first embodiment of a change in spin state when an RF signal is applied to a local region. For example, FIGS. 3A to 3D show an embodiment of applying an RF signal (or RF pulse) to a qubit so as to rotate the spin of the qubit by 90 degrees around the y-axis. In FIG. 3A, t0- is a time point immediately before the RF pulse is applied, t0+ is a time point immediately after the RF pulse is applied, and t0++ may mean a time point at which a sufficient amount of time has passed after the RF pulse is applied and the spin of the qubit is dephasing.

[0111] Fig. 3a is a diagram showing the timing of application of an RF pulse. Fig. 3b is a diagram showing the spin trajectory when the spin of a qubit is rotated 90 degrees around the y-axis. Fig. 3c is a diagram showing the changed quantum state of a qubit immediately after application of an RF pulse. Fig. 3d is a diagram showing the state in which the spin signals of a qubit are dephased over time after application of an RF pulse.

[0112] For reference, the information of a qubit can be represented as two ground states (or vectors) using the bra-ket notation |0> and |1>. A pure qubit state is a linear quantum superposition of these two states, and therefore the state of any qubit can be expressed as a linear combination of |0> and |1>, as |ψ=α|0>+β|1>. Here, α and β are complex probability amplitudes that can satisfy |α|^2 +|β^2 = 1. In this case, the probability that the qubit will be measured in the |0> state is α^2 and the probability that it will be measured in the |1> state is β^2, so the total probability of being measured in these two states can be 1. When observed, the qubit can be determined as a single quantum state by releasing the quantum superposition state.

[0113] In FIGS. 3A to 6C, the explanation is made assuming that the quantum state of the qubit before the RF pulse is applied is |0>. The contents to be explained in FIGS. 3A to 6C can also be applied to the case where the quantum state of the qubit before the RF pulse is applied is |1>.

[0114] Referring to FIGS. 1 to 3D, the controller (300) can control the RF signal application unit (320) to apply an RF pulse to a qubit in the |0> state through the first RF coil (250) or the second RF coil (260).

[0115] As described above, since a uniform magnetic field is applied to the qubit so that the qubit has a single Larmor frequency, when an RF pulse having a resonant frequency matching the single Larmor frequency is applied to the qubit, the spin can be moved globally or collectively for the qubit, which is a collection of several hydrogen protons.

[0116] The controller (300) can rotate the spin of the qubit within an angle range of 0 to 360 degrees around the y-axis through the first RF coil (250). For example, as illustrated in FIGS. 3A and 3B, the controller (300) can apply an RF pulse (Ry(90)) that rotates the spin of the qubit 90 degrees around the y-axis through the first RF coil (250).

[0117] In this case, the spin trajectory of the qubit can occur from the +z-axis spin (|0>) to the +x-axis spin (|ψ+x>). Although not shown, if the quantum state of the qubit before the RF pulse (Ry(90)) is the |1> state, the spin trajectory of the qubit can occur from the -z-axis spin (|1>) to the -x-axis spin (|ψ-x>). The +x-axis spin (|ψ+x>) and the -x-axis spin (|ψ-x>) can be expressed by the following formulas.

[0118]

[0119]

[0120] However, if a sufficient amount of time has passed since the RF pulse (Ry(90)) is applied through the first RF coil (250), the spin of the qubit may be dephased. In this case, the spin of the qubit may be dephased on the xy plane, and the spin signals may move from the +x-axis to the +y-axis and -y-axis.

[0121] FIGS. 4A to 4D illustrate a second embodiment of a change in spin state when an RF signal is applied to a local region. By way of example, FIGS. 4A to 4D illustrate an embodiment of applying an RF signal (or RF pulse) to a qubit so as to rotate the spin of the qubit 180 degrees around the x-axis. Detailed descriptions of the same content as in FIGS. 3A to 3D are omitted.

[0122] Fig. 4a is a diagram showing the timing of application of an RF pulse. Fig. 4b is a diagram showing the spin trajectory when the spin of a qubit is rotated 180 degrees around the x-axis. Fig. 4c is a diagram showing the changed quantum state of a qubit immediately after application of an RF pulse. Fig. 4d is a diagram showing the state in which the spin of a qubit is dephased as time passes after application of an RF pulse.

[0123] Referring to FIGS. 1 to 4d, the controller (300) can cause the spin of the qubit to rotate around the x-axis at an angle within a range of 0 to 360 degrees through the second RF coil (260). For example, as illustrated in FIGS. 4a and 4b, the controller (300) can apply an RF pulse (Rx (180)) that causes the spin of the qubit to rotate 180 degrees around the x-axis through the second RF coil (260).

[0124] In this case, the spin trajectory of the qubit can occur from +z-axis spin (|0>) to -z-axis spin (|1>). Although not shown, if the quantum state of the qubit before the RF pulse (Rx(180)) is |1>, the spin trajectory of the qubit can occur from -z-axis spin (|1>) to +z-axis spin (|0>).

[0125] However, if a sufficient amount of time has passed since the RF pulse (Rx (180)) is applied through the second RF coil (260), the spin of the qubit may be dephased. In this case, the spin of the qubit may be dephased on the yz plane, so that the spin signals may move from the -z axis to the +y axis and the -y axis.

[0126] FIGS. 5A to 5C are a third embodiment of a change in spin state when an RF signal is applied to a local region. For example, FIGS. 5A to 5C show an embodiment of applying RF signals (or RF pulses) to a qubit so as to rotate the quantum state of the qubit 90 degrees around the y-axis and 180 degrees around the x-axis at the same time. In FIG. 5C, tE may denote the point in time when the spin of the qubit is re-phased. Detailed descriptions of the same content as in FIGS. 3A to 3D are omitted.

[0127] Fig. 5a is a diagram showing the application timing of RF pulses. Fig. 5b is a diagram showing the spin trajectory when the spin of a qubit is rotated 90 degrees around the y-axis and 180 degrees around the x-axis simultaneously. Fig. 5c is a diagram showing the changed quantum state of a qubit after the RF pulses are applied.

[0128] Referring to FIGS. 1 to 5C, the controller (300) can rotate the spin of the qubit around the y-axis and the x-axis at an angle within a range of 0 to 360 degrees through the first RF coil (250) and / or the second RF coil (260). For example, as illustrated in FIGS. 5A and 5B, the controller (300) can apply an RF pulse (Ry (90)) that rotates the spin of the qubit around the y-axis by 90 degrees while simultaneously applying an RF pulse (Rx (180)) that rotates the spin of the qubit around the x-axis by 180 degrees.

[0129] In this case, the spin trajectory of the qubit can occur from the +z-axis spin (|0>) to the +x-axis spin (|ψ+x>). Although not shown, if the quantum state of the qubit before the RF pulses (Ry(90), Rx(180)) are applied is the |1> state, the spin trajectory of the qubit can occur from the -z-axis spin (|1>) to the -x-axis spin (|ψ-x>).

[0130] However, when the spin of the qubit is rotated simultaneously around the y-axis and the x-axis, the quantum state of the qubit can be rephased to +x-axis spin (|ψ+x>) when RF pulses (Ry(90), Rx(180)) are applied. Although not shown, if the quantum state of the qubit before the RF pulses (Ry(90), Rx(180)) are applied is |1>, the quantum state of the qubit can be rephased to -x-axis spin (|ψ-x>).

[0131] The re-phased signal is referred to as a spin echo. In this case, the qubit may be a signal generated by a spin echo phenomenon that occurs when a second RF pulse at a different angle from the first RF pulse is applied to the bar (220) from the second RF coil (260).

[0132] Spin echo, in the spin magnetic resonance of electrons or nuclei, can refer to an echo signal generated after a certain amount of time has elapsed when pulses at different angles are applied to the spins. In this case, the echo signal can be detected to obtain a magnetic resonance imaging (MRI) signal.

[0133] FIGS. 6A to 6C illustrate a fourth embodiment of a change in spin state when an RF signal is applied to a local region. By way of example, FIGS. 6A to 6C illustrate an embodiment in which RF signals (or RF pulses) are applied to simultaneously rotate the quantum state of a qubit around the y-axis and the x-axis, and then rotate it once more around the y-axis. Detailed descriptions of the overlapping content with FIGS. 3A to 5C are omitted.

[0134] Fig. 6a is a diagram showing the changed quantum state of a qubit when the spin of the qubit is rotated 90 degrees around the y-axis and 180 degrees around the x-axis at the same time. Fig. 6b is a diagram showing the state in which the spin of the qubit is dephased in the xy plane over time. Fig. 6c is a diagram showing the spin signals of the qubit after the spin signals of the dephased qubit are rotated -90 degrees around the y-axis.

[0135] Here, a rotation of -90 degrees around the y-axis can mean a rotation of 90 degrees clockwise or counterclockwise around the y-axis. In this specification, if a rotation of 90 degrees around the y-axis means a rotation of 90 degrees clockwise around the y-axis, a rotation of -90 degrees can mean a rotation of 90 degrees counterclockwise around the y-axis, and vice versa.

[0136] Referring to FIGS. 1 to 6c, when the spin of the qubit is simultaneously rotated about the y-axis and the x-axis, when RF pulses (Ry(90), Rx(180)) are applied, the quantum state of the qubit can be rephased to +x-axis spin (|ψ+x>). Although not shown, if the quantum state of the qubit before the RF pulses (Ry(90), Rx(180)) are applied is |1>, the quantum state of the qubit can be rephased to -x-axis spin (|ψ-x>). The product of the RF pulses (Ry(90), Rx(180)) can be defined by the rotation operator ε0, which is a unit operator, as follows.

[0137]

[0138] Rx(π) can mean that the RF pulse (Rx(180)) is expressed as a rotation operator with a unit operator. Ry(π / 2) can mean that the RF pulse (Ry(90)) is expressed as a rotation operator with a unit operator.

[0139] However, if a sufficient amount of time has passed since RF pulses (Ry (90), Rx (180)) are applied through the first RF coil (250) and the second RF coil (260), the spin of the qubit may be dephased on the xy plane. When the spin of the qubit is dephased, the spin on the +x axis may move to the +y axis and the -y axis to form a spin trajectory. Forming a spin trajectory by dephasing can be defined by a rotation operator ε1, which is a unit operator. When a spin trajectory is formed, the quantum state of the qubit can be expressed by the following equation.

[0140]

[0141] The quantum state of the qubit is rephased to +x-axis spin (|ψ+x>) and then dephased over sufficient time to form a spin trajectory on the xy-plane, which can be expressed as ε1*ε0.

[0142] In this case, as the spin of the qubit is dephased on the xy plane, the signal size also decreases, which may reduce the detection accuracy when trying to detect an MRI signal.

[0143] Therefore, as illustrated in Fig. 6c, an RF pulse (Ry(-90)) can be applied (line selected) to the qubit through the first RF coil (250) to rotate the spin signals of the qubit by -90 degrees around the y-axis. The RF pulse (Ry(-90)) can be defined as a rotation operator ε2, which is a unit operator, as follows.

[0144]

[0145] Ry(-π / 2) can mean that the RF pulse (Ry(-90)) is expressed as a rotation operator with the unit operator.

[0146] When an RF pulse (Ry(-90)) is applied to a qubit to rotate the qubit's spin trajectory by -90 degrees around the y-axis, the quantum state of the qubit can be expressed by the following formula.

[0147]

[0148] In this case, the spin signals of the qubit can move from the xy plane to the yz plane, and the controller (300) can control the spin signal analysis unit (330) to detect the y-axis or -y-axis spin signal through the spin signal analysis unit (330).

[0149] The quantum state of the qubit is rephased to +x-axis spin (|ψ+x>), and then dephased over sufficient time to form a spin trajectory on the xy plane, and the spin trajectory rotates -90 degrees around the y-axis, which can be expressed as ε2*ε1*ε0.

[0150] A combination of y-axis or -y-axis spin signals detected from a qubit can be referred to as a pseudo-pure qubit state. That is, unlike a pure qubit state, which is expressed as a linear combination of +z-axis spin (|0>) and -z-axis spin (|1>), a pseudo-pure qubit state can be expressed as a linear combination of +y-axis spin (|ψ+y>) and -y-axis spin (|ψ-y>).

[0151] That is, just like a pure qubit state, a pseudo-pure qubit state can also be a quantum superposition state in which multiple spin states that can be measured for a single qubit probabilistically exist simultaneously within a single qubit. +y-axis spin (|ψ+y>) and -y-axis spin (|ψ-y>) can be expressed by the following formulas.

[0152]

[0153]

[0154] In addition, the spin signal value observed in the pseudo-pure qubit state may be smaller than the spin signal value observed in the pure qubit state. When a qubit in a pseudo-pure state is observed, the quantum superposition state can be resolved to one of the spin states of the y-axis spin (|ψ+y>) and the -y-axis spin (|ψ-y>). The pseudo-pure qubit state can be defined by the following formula, which is the unit transformation of the density matrix.

[0155]

[0156] Here, N can denote the spin number of hydrogen protons of the qubit. |ψ> and <ψ| can denote pure qubit states. ρ can denote the density matrix defined by the ensemble in which most of the water molecules constituting the qubit are in purely statistically distributed states. U'(t) and U'(t) -1 may mean unit operators for unit transformation of density matrices.

[0157] FIG. 7 is a block diagram of a signal conversion unit (340) that generates control pulses by calculating spin signals for the superimposed spin states in FIG. 6c.

[0158] Referring to FIGS. 1 to 7, the signal conversion unit (340) may include a first operation unit (341), a second operation unit (342), a first pulse generation unit (343), and a second pulse generation unit (344).

[0159] The signal conversion unit (340) can receive signals of a pseudo pure qubit state (+y-axis spin (|ψ+y>) and -y-axis spin (|ψ-y>)) from the quantum computing device (200) to generate control pulses. The signal conversion unit (340) can calculate a +z-axis spin (|0>) value or a -z-axis spin (|1>) value using the signals of the pseudo pure qubit state (+y-axis spin (|ψ+y>) and -y-axis spin (|ψ-y>)). The signal conversion unit (340) can generate control pulses based on the +z-axis spin (|0>) value or the -z-axis spin (|1>) value. The control pulses can be temporarily or permanently stored in the data management unit (350).

[0160] The first operation unit (341) may include a quantum algorithm for adding signals of pseudo-pure qubit states (+y-axis spin (|ψ+y>) and -y-axis spin (|ψ-y>)). The first operation unit (341) may be any electronic circuit including a quantum algorithm. In this case, the signal value for +z-axis spin (|0>) may be detected as a current value by the spin signal analysis unit (330). This may be expressed by the following equation with reference to Equations 8 to 10.

[0161]

[0162] The second operation unit (342) may include a quantum algorithm for adding the y-axis spin (|ψ+y>) and the -y-axis spin (-|ψ-y>) inverted by the inverter (Inv). The second operation unit (342) may be any electronic circuit including a quantum algorithm. In this case, the signal value for the -z-axis spin (|1>) may be detected as a current value by the spin signal analysis unit (330). This may be expressed by the following equation with reference to Equations 8 to 10.

[0163]

[0164] The first pulse generator (343) can generate a first control pulse based on a signal value for the +z-axis spin (|0>). The first pulse generator (343) can be any electronic circuit for generating the first control pulse. The first control pulse can be a double pulse.

[0165] The second pulse generator (344) can generate a second control pulse based on a signal value for the -z-axis spin (|1>). The second pulse generator (344) can be any electronic circuit for generating the second control pulse. The second control pulse can be a single pulse. The control pulses generated by the first and second pulse generators (343, 344) can be used for quantum operations utilizing the quantum entanglement phenomenon. A detailed description thereof will be described later with reference to FIGS. 8A to 11B.

[0166] FIGS. 8A to 11B show examples in which control pulses generated based on RF pulses being applied to a qubit are applied to a target qubit.

[0167] The region (or local region) where a qubit is created and the region (or local region) where the target qubit is created can be adjacent regions, or they can be distant regions with one or more regions between them. However, regardless of the distance between these regions, the qubit and the target qubit can be quantum entangled with each other.

[0168] As explained above, the information of the target qubit can be expressed as a linear quantum combination of |0> and |1> using the bra-ket notation, as |ψα|0>+β, with two ground states (or vectors). In other words, the target qubit can be in a quantum superposition state where multiple spin states that can be measured probabilistically exist simultaneously within the target qubit. When observed, the target qubit can be determined to be in one of the quantum states of 0 or 1 as the quantum superposition state is released.

[0169] When quantum operations are performed using qubits and target qubits by the quantum entanglement processing unit (360), quantum entanglement can be implemented using the generated control pulses and RF pulses. Accordingly, four Bell states can be formed with two qubits. This can be expressed by the following equations.

[0170]

[0171] Here, |υ1> can refer to a linear quantum combination of qubits, and |υ2> can refer to a linear quantum combination of target qubits. H can refer to a rotation operator, which is an unit operator, such as ε2*ε1*ε0 or ε0. C can refer to a CNOT operation, which is a quantum entanglement operation. |Ф1>, |Ф2>, |Ф3>, |Ф4> can refer to the respective Bell states.

[0172] |Ф1> can be the first Bell state generated by the CNOT operation when the quantum state of the qubit is |0> and the quantum state of the target qubit is |0>.

[0173] |Ф2> can be the second Bell state generated by the CNOT operation when the quantum state of the qubit is |1> and the quantum state of the target qubit is |0>.

[0174] |Ф3> can be a third Bell state generated by the CNOT operation when the quantum state of the qubit is |0> and the quantum state of the target qubit is |1>.

[0175] |Ф4> can be the fourth Bell state generated by the CNOT operation when the quantum state of the qubit is |1> and the quantum state of the target qubit is |1>.

[0176] The CNOT operation may include applying control pulses generated from a qubit and RF pulses to a target qubit. That is, the CNOT operation may include applying control pulses generated by applying a rotation operator H to the quantum state of the qubit and determined to be applied differently when the quantum state of the qubit is |0> or |1> to the target qubit.

[0177] FIGS. 8A and 8B are a first embodiment showing the spin state of a target qubit determined by quantum entanglement. For example, in FIGS. 8A and 8B, the quantum state of the qubit is |0>, and a first control pulse (B+) can be applied to the target qubit (A+) whose quantum state is |0> or whose spin when observed is |0>. At least a portion of the first Bell state is illustrated in FIGS. 8A and 8B.

[0178] Fig. 8a is a diagram showing the application timing of the first control pulse (B+) and RF pulses applied to the target qubit (A+). Fig. 8b is a diagram showing the spin trajectory when the spin of the target qubit (A+) is rotated around the x-axis, y-axis, and z-axis.

[0179] Referring to FIGS. 1, 7, and 8a and 8b, the first control pulse (B+) may be a dual pulse that rotates the spin of the target qubit (A+) twice 180 degrees around the z-axis. The first control pulse (B+) may be applied through the first RF coil (250) or the second RF coil (260), or may be applied through any component within the quantum computing device (200) that is not shown.

[0180] At time t1, an RF pulse that rotates the spin of the target qubit (A+) 90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a +z-axis spin state (|0>) to a +x-axis spin state (|ψ+x>).

[0181] At time t2, an RF pulse that rotates the spin of the target qubit (A+) 180 degrees around the x-axis and a first control pulse (B+) that rotates the spin of the target qubit 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a +x-axis spin state (|ψ+x>) to a -x-axis spin state (|ψ-x>).

[0182] At time t3, an RF pulse that rotates the spin of the target qubit (A+) 180 degrees around the x-axis and a first control pulse (B+) that rotates the spin of the target qubit 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a -x-axis spin state (|ψ-x>) to a +x-axis spin state (|ψ+x>).

[0183] At time t4, an RF pulse that rotates the spin of the target qubit (A+) by -90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a +x-axis spin state (|ψ+x>) to a +z-axis spin state (|0>).

[0184] As a result, when the first control pulse (B+) and RF pulses are applied to the target qubit (A+), the quantum state of the target qubit (A+) before applying the first control pulse (B+) and RF pulses can be determined as the quantum state of the target qubit (A+). In other words, the combination of the quantum states of the qubit and the target qubit can be maintained from |00> to |00>.

[0185] FIGS. 9A and 9B are a second embodiment showing the spin state of a target qubit determined by quantum entanglement. For example, in FIGS. 9A and 9B, the quantum state of the qubit is |1>, and a second control pulse (B-) can be applied to the target qubit (A+), which is in the quantum state |0> or whose spin when observed is |0>. At least a portion of the second Bell state is illustrated in FIGS. 9A and 9B.

[0186] Fig. 9a is a diagram showing the application timing of the second control pulse (B-) and RF pulses applied to the target qubit (A+). Fig. 9b is a diagram showing the spin trajectory when the spin of the target qubit (A+) is rotated around the x-axis, y-axis, and z-axis.

[0187] Referring to FIGS. 1, 7, and 9a and 9b, the second control pulse (B-) may be a single pulse that rotates the spin of the target qubit (A+) 180 degrees about the z-axis. The second control pulse (B-) may be applied through the first RF coil (250) or the second RF coil (260), or may be applied through any component within the quantum computing device (200) that is not shown.

[0188] At time t1, an RF pulse that rotates the spin of the target qubit (A+) 90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a +z-axis spin state (|0>) to a +x-axis spin state (|ψ+x>).

[0189] At time t2, an RF pulse that rotates the spin of the target qubit (A+) 180 degrees around the x-axis and a second control pulse (B-) that rotates the spin of the target qubit 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a +x-axis spin state (|ψ+x>) to a -x-axis spin state (|ψ-x>).

[0190] At time t3, only an RF pulse that rotates the spin of the target qubit (A+) by 180 degrees around the x-axis can be applied by the controller (300). That is, unlike the first control pulse (B+) of FIGS. 8A and 8B, the second control pulse (B-) described in FIGS. 9A and 9B is a single pulse and thus may not be applied to the target qubit (A+) at time t3. In this case, the quantum state of the target qubit (A+) may not change from the -x-axis spin state (|ψ-x>).

[0191] At time t4, an RF pulse that rotates the spin of the target qubit (A+) by -90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A+) can change from a -x-axis spin state (|ψ-x>) to a -z-axis spin state (|1>).

[0192] As a result, when the second control pulse (B-) and RF pulses are applied to the target qubit (A+), the quantum state changed to the -z-axis spin state (|1>) can be determined as the quantum state of the target qubit (A+). In other words, the combination of the quantum states of the qubit and the target qubit can change from |10> to |11>.

[0193] FIGS. 10A and 10B are third embodiments showing the spin state of a target qubit determined by quantum entanglement. For example, in FIGS. 10A and 10B, the quantum state of the qubit is |0>, and a first control pulse (B+) can be applied to the target qubit (A-) whose quantum state is |1> or whose spin when observed is |1>. At least a portion of the third Bell state is illustrated in FIGS. 10A and 10B.

[0194] Fig. 10a is a diagram showing the application timing of the first control pulse (B+) and RF pulses applied to the target qubit (A-). Fig. 10b is a diagram showing the spin trajectory when the spin of the target qubit (A-) is rotated around the x-axis, y-axis, and z-axis. Detailed descriptions of the overlapping contents of Figs. 8a and 8b are omitted.

[0195] Referring to FIGS. 1, 7, and 10a and 10b, at time t1, an RF pulse that rotates the spin of the target qubit (A-) by 90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from a -z-axis spin state (|1>) to a -x-axis spin state (|ψ-x>).

[0196] At time t2, an RF pulse that rotates the spin of the target qubit (A-) by 180 degrees around the x-axis and a first control pulse (B+) that rotates the spin of the target qubit (A-) by 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from a -x-axis spin state (|ψ-x>) to a +x-axis spin state (|ψ+x>).

[0197] At time t3, an RF pulse that rotates the spin of the target qubit (A-) by 180 degrees around the x-axis and a first control pulse (B+) that rotates the spin of the target qubit (A-) by 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from the +x-axis spin state (|ψ+x>) to the -x-axis spin state (|ψ-x>).

[0198] At time t4, an RF pulse that rotates the spin of the target qubit (A-) by -90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from the -x-axis spin state (|ψ-x>) to the -z-axis spin state (|1>).

[0199] As a result, when the first control pulse (B+) and RF pulses are applied to the target qubit (A-), the quantum state of the target qubit (A-) before applying the first control pulse (B+) and RF pulses can be determined as the quantum state of the target qubit (A-). In other words, the combination of the quantum states of the qubit and the target qubit can be maintained from |01> to |01>.

[0200] FIGS. 11A and 11B are a fourth embodiment showing the spin state of a target qubit determined by quantum entanglement. For example, in FIGS. 11A and 11B, the quantum state of the qubit is |1>, and a second control pulse (B-) can be applied to the target qubit (A-) whose quantum state is |1> or whose spin when observed is |1>. At least a part of the fourth Bell state is illustrated in FIGS. 11A and 11B.

[0201] Fig. 11a is a diagram showing the application timing of the second control pulse (B-) and RF pulses applied to the target qubit (A-). Fig. 11b is a diagram showing the spin trajectory when the spin of the target qubit (A-) is rotated around the x-axis, y-axis, and z-axis. Detailed descriptions of the overlapping contents with Figs. 8a and 8b are omitted.

[0202] Referring to FIGS. 1, 7, and 11a and 11b, at time t1, an RF pulse that rotates the spin of the target qubit (A-) by 90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from a -z-axis spin state (|1>) to a -x-axis spin state (|ψ-x>).

[0203] At time t2, an RF pulse that rotates the spin of the target qubit (A-) 180 degrees around the x-axis and a second control pulse (B-) that rotates the spin of the target qubit (A-) 180 degrees around the z-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from a -x-axis spin state (|ψ-x>) to a +x-axis spin state (|ψ+x>).

[0204] At time t3, only an RF pulse that rotates the spin of the target qubit (A-) by 180 degrees around the x-axis can be applied to the target qubit (A-) by the controller (300). That is, unlike the first control pulse (B+) of FIGS. 10A and 10B, the second control pulse (B-) described in FIGS. 11A and 11B is a single pulse and thus may not be applied to the target qubit (A-) at time t3. In this case, the quantum state of the target qubit (A-) may not change from the +x-axis spin state (|ψ+x>).

[0205] At time t4, an RF pulse that rotates the spin of the target qubit (A-) by -90 degrees around the y-axis can be applied by the controller (300). In this case, the quantum state of the target qubit (A-) can change from a +x-axis spin state (|ψ+x>) to a +z-axis spin state (|0>).

[0206] As a result, when the second control pulse (B-) and RF pulses are applied to the target qubit (A-), the quantum state changed to the +z-axis spin state (|0>) can be determined as the quantum state of the target qubit (A-). That is, the combination of the quantum states of the qubit and the target qubit can be changed from |11> to |10>.

[0207] As described in FIGS. 8A to 11B , once the quantum state of a qubit is determined and the control pulse to be applied to the target qubit is determined, the quantum state of the target qubit generated in a neighboring or distant region (or local region) can be immediately determined. Accordingly, the performance of a quantum computing system that processes quantum information by utilizing the quantum entanglement relationship between the qubit and the target qubit can be improved.

[0208] FIG. 12 is a first flowchart of an operation method of a quantum computing system for generating a qubit according to an embodiment of the present invention.

[0209] Referring to FIGS. 1, 2, and 12, at step S110, the quantum computing system can apply a magnetic field to multiple local regions via a gradient coil. That is, the quantum computing system can apply a gradient magnetic field to each local region to generate a qubit in the local region.

[0210] At step S120, the quantum computing system can apply magnetic fields to multiple corresponding local regions via multiple local reverse-gradient magnetic field coils. That is, the quantum computing system can apply reverse-gradient magnetic fields to multiple local regions, thereby performing magnetic field compensation so that the magnetic field is uniform within a single local region, while applying magnetic fields of different strengths to different local regions.

[0211] At step S130, the quantum computing system can apply an RF pulse in a first direction or a second direction through the RF coil. The RF coil can apply the RF pulse to the qubit in the first direction (e.g., a direction rotating around the y-axis) and / or can apply the RF pulse to the qubit in the second direction (e.g., a direction rotating around the x-axis).

[0212] At step S140, the quantum computing system can generate qubits for each of the multiple local regions. That is, the quantum computing system can generate n qubits for n local regions. Since magnetic fields of different strengths are applied to the n local regions (i.e., magnetic fields of different frequencies are applied to the n local regions), the n qubits can have different frequencies (Lamor frequencies).

[0213] FIG. 13 is a second flowchart of a method of operating a quantum computing system for generating and storing control pulses according to an embodiment of the present invention.

[0214] Referring to FIGS. 1 to 7 and 13, in step S210, the quantum computing system can apply RF pulses through the RF coil to simultaneously rotate the spin of the qubit 90 degrees in a first direction and 180 degrees in a second direction. The quantum state of the qubit can be represented by a linear combination of |0> and |1>, and when observed, the quantum superposition state can be resolved and determined to be one of 0 and 1 quantum states. That is, the spin of the qubit can be a spin in the +z-axis direction (|0>) or a spin in the -z-axis direction (|1>).

[0215] When the spin of the observed qubit is the spin in the +z direction (|0>), the quantum state of the qubit can change in the +x direction (|ψ+x>). When the spin of the observed qubit is the spin in the -z direction (|1>), the quantum state of the qubit can change in the -x direction (|ψ-x>).

[0216] After the RF pulses are applied, if enough time has passed, the spin signals of the qubits can be dephased and moved along the xy plane. In this case, the spin of the qubit that was on the +x-axis or -x-axis can move to the +y-axis and -y-axis, forming a spin trajectory.

[0217] At step S220, the quantum computing system can apply RF pulses through the RF coil to rotate the spin signals of the qubits on the xy plane by -90 degrees in the first direction. In this case, the spin signals of the qubits on the xy plane can be moved to the yz plane.

[0218] At step S230, the quantum computing system can detect spin signals in the +y-axis direction and -y-axis direction among the spin signals of the qubits on the yz plane. In this way, the quantum state of the qubit expressed as a linear combination of the spin in the y-axis direction (|ψ+y>) and the spin in the -y-axis direction (|ψ-y>) can be defined as a pseudo-pure qubit state.

[0219] At step S240, the quantum computing system can perform calculations on the detected spin signals to measure spin signal values ​​on the +z-axis and -z-axis.

[0220] A quantum computing system can measure the spin signal value on the +z-axis as a current value by adding the spin value in the y-axis direction (|ψ+y>) and the spin value in the -y-axis direction (|ψ-y>).

[0221] A quantum computing system can measure the spin signal value on the -z axis as a current value by adding the spin value in the y-axis direction (|ψ+y>) and the inverted spin value in the -y-axis direction (-|ψ-y>).

[0222] At step S250, the quantum computing system can generate control pulses based on the measured spin signal values. That is, the quantum computing system can convert the spin signal value on the +z-axis into a first control pulse, which is a double pulse. Furthermore, the quantum computing system can convert the spin signal value on the -z-axis into a second control pulse, which is a single pulse.

[0223] At step S260, the quantum computing system can store first and second control pulses. In a quantum operation utilizing quantum entanglement between the qubit that is the target of the control pulses and the target qubit, once the quantum state of the qubit is determined, one of the stored control pulses can be applied to the target qubit.

[0224] FIG. 14 is a third flowchart of an operating method of a quantum computing system for determining a quantum state of a target qubit according to an embodiment of the present invention.

[0225] Referring to FIGS. 1 to 14, in step S310, the quantum computing system can detect the quantum state of the target qubit by observing the target qubit. Similar to the quantum state of the qubit, the quantum state of the target qubit can be represented as a linear combination of |0> and |1>, and when observed, the quantum superposition state can be resolved and determined as one of the quantum states of 0 and 1. That is, the spin of the target qubit can be a spin in the +z-axis direction (|0>) or a spin in the -z-axis direction (|1>).

[0226] In step S320, the quantum computing system may apply a first control pulse or a second control pulse, and RF pulses to the target qubit via the RF coil. Alternatively, the quantum computing system may apply RF pulses to the target qubit via the RF coil, and apply the first control pulse or the second control pulse to the target qubit via any component other than the RF coil. The first control pulse and the second control pulse may be pulses that rotate the spin of the target qubit about the z-axis.

[0227] In step S330, when the first control pulse and RF pulses are applied to the target qubit, the quantum computing system can determine the quantum state of the target qubit detected before the first control pulse and RF pulses are applied as the quantum state of the target qubit.

[0228] At step S340, when the second control pulse and RF pulses are applied to the target qubit, the quantum computing system can determine the changed quantum state of the target qubit as the quantum state of the target qubit.

[0229] The systems and methods described above may be implemented using hardware components, software components, and / or a combination of hardware components and software components. For example, the components described in the embodiments may be implemented using one or more general-purpose computers or special-purpose computers, such as a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing instructions and responding to them. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing device is sometimes described as being used singly; however, those skilled in the art will appreciate that the processing device may include multiple processing elements and / or multiple types of processing elements. For example, the processing device may include multiple processors, or one processor and one controller. Additionally, other processing configurations, such as parallel processors, are also possible.

[0230] Software may include computer programs, code, instructions, or a combination of one or more of these, and may configure a processing device to perform a desired operation or, independently or in combination, command the processing device. The software and / or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual device, computer storage medium, or device for interpretation by the processing device or for providing instructions or data to the processing device. The software may also be distributed across networked computer systems and stored or executed in a distributed manner. The software and data may be stored on one or more computer-readable recording media.

[0231] The method according to the embodiment may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiment or may be those known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands, such as ROMs, RAMs, and flash memories. Examples of the program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

[0232] Although the embodiments have been described with limited examples and drawings, those skilled in the art will appreciate that various modifications and variations are possible based on the above description. For example, appropriate results can be achieved even if the described techniques are performed in a different order than described, and / or components of the described systems, structures, devices, circuits, etc. are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents.

[0233] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

Claims

1. A quantum computing device for generating multiple qubits, A bar arranged in a space formed by a magnet and configured to be divided into multiple areas by an inner wall; An original gradient coil arranged in the above space and configured to apply an original gradient to the bar; A reverse gradient coil arranged in the above space and configured to apply a reverse gradient to the bar; and At least one RF coil disposed between the bar and the gradient coil and configured to apply RF pulses to the bar, By the above gradient magnetic field and the above reverse gradient magnetic field, a uniform magnetic field is applied to each of the plurality of regions, A plurality of qubits corresponding to the plurality of regions are generated by the applied magnetic field and RF pulses matching the applied magnetic field. Quantum computing device.

2. In paragraph 1, The plurality of qubits have Larmor frequencies of different values, and each of the plurality of qubits has a Larmor frequency of one value. Quantum computing device.

3. In paragraph 1, The above gradient magnetic field coil is divided into a plurality of magnetic field fields corresponding to the plurality of areas formed on the bar, The above-mentioned reverse-magnetic field coil includes a plurality of coils corresponding to the plurality of magnetic field fields, Quantum computing device.

4. In paragraph 3, In each of the above multiple regions, a magnetic field of a strength corresponding to the sum of the difference between the magnetic field by the magnet and the gradient magnetic field and the counter-gradient magnetic field generated in the magnetic field is applied. Quantum computing device.

5. In paragraph 1, The at least one RF coil comprises a first RF coil configured to apply a first RF pulse in a first direction and a second RF coil configured to apply a second RF pulse in a second direction different from the first direction. Quantum computing device.

6. In paragraph 5, The first RF pulse is a pulse applied to the bar to rotate the spin of the qubit by an angle of 90 degrees in the first direction, The second RF pulse is a pulse applied to the bar to rotate the spin of the qubit by an angle of 180 degrees in the second direction. Quantum computing device.

7. A quantum computing device according to any one of paragraphs 1 to 6; and A controller configured to control the quantum computing device to generate a plurality of qubits and to perform a quantum operation using at least two qubits among the generated plurality of qubits, The above controller: Detecting spin signals from qubits generated by applying RF pulses, generating control pulses by operating on the spin signals, and applying at least some of the control pulses and the RF pulses to a target qubit to determine a quantum state of the target qubit, At least some of the control pulses to be applied are determined according to the quantum state of the qubit, Quantum computing system.

8. In paragraph 7, The above spin signals include a first spin signal and a second spin signal, The above controller: Generating a first control pulse by adding the values ​​of the first and second spin signals, Generating a second control pulse by adding the values ​​of the first spin signal and the inverted values ​​of the second spin signal, Quantum computing system.

9. In paragraph 8, The first control pulse is a double pulse that rotates the spin of the target qubit twice, The second control pulse is a single pulse that rotates the spin of the target qubit once. Quantum computing system.

10. In paragraph 8, When the quantum state of the qubit is the first state, the controller determines the quantum state of the target qubit by applying the first control pulse and the RF pulses. Quantum computing system.

11. In paragraph 8, When the quantum state of the qubit is a second state, the controller determines the quantum state of the target qubit by applying the second control pulse and the RF pulses. Quantum computing system.

12. In paragraph 11, When the second control pulse and the RF pulses are applied to the target qubit, the changed quantum state is determined as the quantum state of the target qubit. Quantum computing system.

13. In paragraph 7, The RF pulses include a pulse that rotates the spin of the qubit by 90 degrees in a first direction, a pulse that rotates the spin of the qubit by 180 degrees in a second direction different from the first direction, and a pulse that rotates the spin of the qubit by 90 degrees in a third direction different from the first and second directions. Quantum computing system.

14. A method of operating a quantum computing system including a quantum computing device according to any one of claims 1 to 6, A step of detecting spin signals from a qubit generated by applying RF pulses; A step of generating control pulses by calculating the above spin signals; and A step of applying at least some of the control pulses and the RF pulses to the target qubit to determine the quantum state of the target qubit, At least some of the control pulses to be applied are determined according to the quantum state of the qubit, How quantum computing systems work.

15. A computer program stored in a non-transitory computer-readable recording medium, wherein the computer program includes commands, and the commands, when executed by a computer, implement the method of claim 14.

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