Quantum computing device and quantum computer

Abstract

A quantum computing device (1) is specified, comprising a permanent magnet device (2) and a space (5) within said permanent magnet device (2) for at least two trapped quantum particles (6) arranged along a first axis (7), said permanent magnet device (2) comprising a plurality of segments (3), i.e., at least four segments (3), each segment (3) having a magnetization direction (4), the magnetization directions (4) of the at least four segments (3) being different from one another, thereby establishing a magnetic field having a magnitude that varies along the first axis (7). Further, a quantum computer (8) is specified, comprising the quantum computing device (1).

Description

[Technical Field]

[0001] The present disclosure relates to quantum computing devices and quantum computers. [Background technology]

[0002] In many quantum computing processes that use quantum computing devices, the devices can be configured to trap trapped quantum particles, which must be controlled and manipulated to perform computations. For trapped quantum particles that have a charge, interactions such as Coulomb repulsion can create coupling between nearby trapped quantum particles, allowing for entanglement. Thus, to perform quantum computing processes with trapped quantum particles, the trapped quantum particles must be controllable and addressable independently of one another.

[0003] Individual addressing of multiple trapped quantum particles, e.g., qubit registers, is desirable to have negligible crosstalk. However, crosstalk between nearby trapped quantum particles is typically a difficult-to-control source of errors in quantum computing processes and can hinder the meaningful application, and hence scalability, of quantum error correction protocols. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, the problem to be solved is to specify a quantum computing device with improved controllability, and further, a quantum computer comprising such a quantum computing device is specified. [Means for solving the problem]

[0005] This object is solved by the subject matter of the independent claims. Advantageous embodiments, implementations and further developments are the subject matter of the respective dependent claims.

[0006] According to at least one embodiment, the quantum computing device includes a permanent magnet device, for example, the permanent magnet device has a first axis, the permanent magnet device has a main extension plane, and the first axis extends along the main extension plane.

[0007] The first axis is an imaginary axis. The first axis is, for example, an axis of symmetry in the main extension plane. That is, the first axis divides the permanent magnet device into two halves in a cross-section along the main extension plane, and the shapes of the two halves are essentially identical. "Essentially identical" exemplarily means that due to manufacturing tolerances of the permanent magnet device, the areas of the halves, for example the cross sections of the halves, may differ from each other by at most 5% or at most 1%.

[0008] According to at least one embodiment, a quantum computing device includes a space for at least two trapped quantum particles within a permanent magnet device, the at least two trapped quantum particles being arranged along a first axis, and illustratively the space has a principal direction of extension extending along the first axis.

[0009] For example, a permanent magnet device surrounds the space, which is defined as an area or volume enclosed by the permanent magnet device, and quantum particles are trapped during operation of the quantum computing device. Illustratively, the trapped quantum particles are linearly arranged one after the other along a first axis during operation of the quantum computing device. In particular, more than two trapped quantum particles, for example, at least 8, at least 20, or at least 100, and / or up to 1000 trapped quantum particles are arranged along the first axis during operation of the quantum computing device.

[0010] The trapped quantum particles are represented, for example, by the energy levels of an atom or molecule, by the spin, charge, magnetic flux or phase of an electron and / or atomic nucleus in a superconductor, or by the topological quantum numbers of an anyon in a topologically protected system.

[0011] For example, the space is located in a vacuum environment and / or a cryogenic environment.

[0012] Illustratively, each trapped quantum particle is trapped by a predetermined trapping potential. The trapping potential can be static or dynamic. For trapped quantum particles represented by atomic or molecular energy levels, ions are trapped by electromagnetic fields. Illustratively, ions are trapped by dynamic electric fields, particularly radio frequency fields. For trapped quantum particles represented by electron spins, the electrons are trapped in potential wells within a semiconductor system. For example, the trapped quantum particle is a charged trapped quantum particle.

[0013] According to at least one embodiment of the quantum computing device, the permanent magnet device includes a plurality of segments, i.e., at least four segments. For example, the permanent magnet device includes at least four segments, particularly at least eight segments, at least 16 segments, or at least 32 segments. Each segment includes a permanent magnet material. In particular, each of the segments includes the same permanent magnet material. Illustratively, the permanent magnet material includes a ferromagnetic material.

[0014] Each segment may, for example, be integrally formed. Alternatively, each segment may be formed from at least two sub-segments, the at least two sub-segments having the same material and / or magnetization properties.

[0015] In one preferred embodiment, the first axis extends linearly from one of the segments to another of the segments that is located diametrically opposite the one of the segments relative to the center of the permanent magnet device.

[0016] Illustratively, the permanent magnet device is a Halbach device.

[0017] According to at least one embodiment of the quantum computing device, each segment has a magnetization direction. The magnetization of each segment is defined by a vector field representing the dipole moment of the respective permanent magnetic material. That is, each permanent magnetic material exhibits a dipole moment. The vector field, and in particular the dipole moment of the permanent magnetic material, defines the respective magnetization direction. The dipole moment roughly points to the magnetization direction.

[0018] Each magnetization direction is defined relative to a first axis, i.e., each magnetization direction forms an angle with the first axis.

[0019] According to at least one embodiment of the quantum computing device, the magnetization directions of the at least four segments are different from one another, thereby establishing magnetic fields with different magnitudes for different positions on the first axis. Illustratively, the magnitude of the magnetic field varies along the first axis for different positions on the first axis. This magnitude is, for example, symmetrical about the center of the permanent magnet device along the first axis. That is, for example, there are two points on the first axis with the same magnitude.

[0020] For example, all of the magnetization directions of the segments are different from each other, i.e., each magnetization direction has a different angle with respect to the first axis, or in other words, all angles enclosed by the magnetization directions and the first axis are different from each other.

[0021] The arrangement of the segments and the respective magnetization directions of each segment are predetermined to generate a multipole magnetic field, particularly a quadrupole magnetic field, where the magnitude of the magnetic field vanishes at the center of the permanent magnet device, e.g., approximately 0 T. For a multipole magnetic field, particularly a quadrupole magnetic field, the permanent magnet device has a magnetic field magnitude along a first axis that depends on the arrangement of the segments and their respective magnetic directions.

[0022] For such permanent magnet devices, the magnitude of the magnetic field varies continuously along the first axis, i.e., for different positions on the first axis, and thus the magnitude of the magnetic field for different positions on the first axis is characteristic of a magnetic field gradient along the first axis.

[0023] The magnetic field is represented by the magnetic flux density, and the absolute value of the magnetic flux density corresponds to the magnitude of the magnetic field for a given position on the first axis.

[0024] The vectors that are components of the magnetic field can point in any direction relative to the first axis. That is, at least some of the vectors of the magnetic field for different positions on the first axis can have different angles relative to the first axis. For example, at least some of the vectors of the magnetic field can point in the radial direction of the first axis or the axial direction of the first axis.

[0025] For example, at least some of the vectors of the magnetic field point in the same radial and / or axial direction of the first axis for different positions on the first axis. Alternatively or additionally, at least some of the vectors of the magnetic field are rotated relative to each other in the radial direction of the first axis.

[0026] The distribution of the magnetic field magnitude is symmetrical about the center of the permanent magnet device along the first axis. Illustratively, the first axis is divided into two halves by the center of the permanent magnet device. That is, for every point on the first axis in one half, there is an additional point on the first axis in the other half with the same magnetic field magnitude. The magnetic field magnitude has a negative gradient in one half and a positive gradient in the other half. The magnetic field gradient increases, for example, approximately linearly along the first axis with respect to the magnetic field magnitude along the first axis starting from the center. That is, the magnetic field gradient is approximately constant along the first axis starting from the center.

[0027] If there are m segments (m is an even natural number at least 4), the magnetization directions of two directly adjacent segments are rotated by 360°·3 / m with respect to each other.

[0028] In particular, the magnitude of the magnetic field in the central region established by the permanent magnet arrangement varies by at least 0.5 T / m or at most 500 T / m, in particular by at least 50 T / m and at most 250 T / m, illustratively by 150 T / m.

[0029] In particular, it is conceivable to use a permanent magnet device in combination with the space in which the trapped quantum particles are located during operation of the quantum computing device. Different magnitudes of the magnetic field, i.e., the magnetic field gradient of the permanent magnet device, make the equilibrium position of the trapped quantum particles state-dependent. Furthermore, the resonant frequency is unique for each trapped quantum particle due to the magnetic field gradient.

[0030] That is, due to different magnitudes of magnetic fields, i.e., magnetic field gradients of permanent magnet devices, trapped quantum particles can be individually addressed in frequency space, improved multi-qubit gates can be advantageously realized, and the coupling of nearby trapped quantum particles can be controlled. Furthermore, by tuning the coupling, highly entangled cluster states can be generated that can be advantageously used for quantum computing.

[0031] For example, each trapped quantum particle is represented by a two-level quantum system. When no magnetic field is applied to the two-level quantum system, the two-level quantum system includes a first level and a second level, both of which correspond to respective eigenstates of each trapped quantum particle. For example, the first level represents the ground state of each trapped quantum particle, and the second level represents the excited state of each trapped quantum particle.

[0032] Illustratively, when a magnetic field is applied to a two-level quantum system, the degeneracy of the second level is broken and at least two, particularly at least three, sublevels are generated, which results in two, particularly three, possible transitions from each of the two, particularly three, sublevels to the first level.

[0033] When a trapped quantum particle is represented by an n-level quantum system, where n is a natural number greater than or equal to 2, each n-level quantum system contains n levels. For example, when a magnetic field is applied, at least some of the n levels correspond to sublevels. In such an n-level quantum system, multiple transitions are achievable.

[0034] Furthermore, the strength of the level splitting, as well as the strength of the sublevel splitting, depends on the applied magnetic field. For trapped quantum particles, the magnitude of the magnetic field is different for different positions, and therefore the splitting is also different for these trapped quantum particles. Therefore, a frequency difference of a particular transition between neighboring trapped quantum particles is also achieved. The frequency difference also results in different resonant frequencies for neighboring trapped quantum particles.

[0035] The total energy of each trapped quantum particle is predetermined by the trapping potential and the characteristic energies of each transition.

[0036] When a trapping potential, e.g., a harmonic trapping potential, is superimposed on the levels and sublevels of each trapped quantum particle, the equilibrium position depends on the state of each trapped quantum particle. If a trapped quantum particle in its ground state is excited to one of the excited states, e.g., by following one of the possible transitions, the equilibrium position of the trapped quantum particle changes. Due to the change in equilibrium position, an effective spin-spin coupling between the trapped quantum particle and a neighboring trapped quantum particle is achieved via Coulomb interactions. Thus, the equilibrium position depends on the state of each trapped quantum particle as well as the magnitude of the magnetic field, i.e., the magnetic field gradient.

[0037] That is, the coupling of at least two trapped quantum particles depends on the magnitude of the magnetic field, i.e., the magnetic field gradient. Because the coupling is proportional to the square of the magnetic field gradient, the magnetic field gradient must be large enough to generate sufficient coupling for high-speed computation, which can be achieved by the permanent magnet configuration described herein. That is, the magnetic field gradient must be large enough to generate coupling that is large compared to the decoherence rate. Such a relatively large gradient improves addressing, while providing lower crosstalk and stronger coupling of the trapped quantum particles. Therefore, faster quantum operations are achievable and fewer error-correction operations are required.

[0038] Advantageously, with the permanent magnet arrangement of the quantum computing devices described herein, the magnetic gradients are particularly high, while the available solid angle and distance to space of the trapped quantum particles are limited, thus allowing such quantum computing configurations to be implemented in a variety of systems.

[0039] In essence, permanent magnet devices are used to obtain large magnetic field gradients experienced by trapped charged quantum particles, generating significantly different magnetic fields seen by individual trapped quantum particles. In quantum information environments, this allows for sophisticated addressing in frequency space, thus allowing individual single-qubit rotation with low crosstalk, and for introducing coupling between charged trapped quantum particles, allowing for interactions, thus enabling multi-qubit gates. It can also be used in conjunction with radio frequency (RF) fields for qubit control; in this case, addressing by focusing radiation is not an option due to the long wavelength, but RF fields can offer advantages in terms of miniaturization and integration. To this end, large or steep magnetic field gradients are desirable, allowing for better addressing with higher fidelity and faster quantum gates. Permanent magnet devices, particularly Halbach arrays, allow for large magnetic field gradients, even when the distance between the segments of the permanent magnet array and the quantum particles is limited by technological constraints.

[0040] According to at least one embodiment of the quantum computing device, the segments surround the space in the form of a ring, or the segments surround the space in the form of a polygonal outline.

[0041] The ring or polygonal contour is of an imaginary nature. Illustratively, in a cross-sectional view along the main extension plane, each segment is located on a point, which is located on the ring or polygonal contour. These points are spaced apart from one another so that the sections do not overlap each other in the main extension plane. For example, each point represents the center of the respective segment.

[0042] If the segments are arranged on a ring, the ring may be circular or elliptical in shape. If the segments are arranged on a polygonal outline, the polygonal outline may be square, rectangular, hexagonal, or octagonal in shape.

[0043] For example, directly adjacent segments arranged on a ring or polygonal contour are in direct and immediate contact with each other and / or have a distance from each other of at most 50 mm, in particular at most 1 mm, Due to such a relatively small distance, the magnetic field advantageously resembles a smooth quadrupole field, and therefore the magnetic field gradient along the first axis is also particularly linear.

[0044] According to at least one embodiment of the quantum computing device, the space is located in a central region of a ring or a polygonal contour, the central region being surrounded by the ring or polygonal contour and located at the center of the permanent magnet device.

[0045] Illustratively, the magnetic field gradient along the first axis is approximately linear along the first axis within the central region. Due to manufacturing tolerances of the segments, there may be deviations from linearity of up to 5%, for example, within the central region.

[0046] According to at least one embodiment of the quantum computing device, the distance between directly adjacent segments is equal to one another. Illustratively, segments arranged on the contour of a ring or polygon are spaced equidistant from one another. Due to manufacturing tolerances, there may be a deviation of up to 5% from the average distance.

[0047] According to at least one embodiment of the quantum computing device, at least some of the segments have a rectangular cross section, wherein segments having a rectangular cross section along their main extension plane are particularly easy to manufacture and thus particularly cost-saving.

[0048] According to at least one embodiment of the quantum computing device, a cross section of at least some of the segments has a trapezoidal shape, the trapezoid having four opposing sides.

[0049] By way of example, all edges are formed linearly. Advantageously, the edges of directly adjacent segments can be arranged close to one another, i.e., the edges of directly adjacent segments facing one another can be in direct contact with one another or can be relatively close to one another at least over the entire length of these edges.

[0050] Furthermore, in order to generate particularly high magnetic field gradients, the permanent magnet arrangement must be as close as possible to said space. Advantageously, by having trapezoidal segments, the edges of each segment facing said space can be relatively close to said space over the entire length of these edges compared to square segments.

[0051] Alternatively, the two opposing edges facing the space are curved. In particular, the normal flux of the two opposing edges points away from the space. Advantageously, the distance of the edges of the segments facing the space to the space is approximately the same as that of a segment with straight edges. Thus, the multipole magnetic field is particularly smooth and can produce a particularly smooth magnetic field gradient.

[0052] According to at least one embodiment of the quantum computing device, all segments have the same shape. For example, each segment is formed as a rectangular parallelepiped, a prism, or a truncated pyramid. In particular, all segments have the same dimensions, such as width, length, and height.

[0053] According to at least one embodiment of the quantum computing device, the magnetization directions of the segments disposed in the opposing regions are oriented in opposite directions. The segments are disposed in opposing regions with respect to the central region. The magnetization directions of the segments disposed in the opposing regions are opposite to each other.

[0054] In particular, a first axis is defined for two segments arranged opposite each other, and the magnetization directions of each of the two segments are parallel to the first axis.

[0055] According to at least one embodiment of the quantum computing device, at least some of the trapped quantum particles in space form an at least two-level quantum system during operation of the quantum computing device, and / or at least some of the trapped quantum particles in space form quantum bits (qubits for short) during operation of the quantum computing device.

[0056] According to at least one embodiment of the quantum computing device, the frequency difference of a particular transition between trapped quantum particles depends on the magnitude of a magnetic field during operation of the quantum computing device. Because the trapped quantum particles are positioned along a first axis and the magnetic field has different magnitudes along the first axis, there is a frequency difference of the same transition between neighboring trapped quantum particles. That is, the resonant frequency for a particular transition of each trapped quantum particle depends on the position of each trapped quantum particle on the first axis.

[0057] According to at least one embodiment of the quantum computing device, the distance between directly adjacent trapped quantum particles is at least 0.1 μm and at most 30 μm. For example, the distance between directly adjacent trapped quantum particles is 5 μm. For example, the distance between directly adjacent trapped quantum particles can vary spatially and temporally along the first axis.

[0058] The trapped quantum particles may be part of a quantum crystal, particularly a Coulomb crystal. If the trapped quantum particles are trapped ions, the quantum crystal is an ionic crystal. Exemplarily, the space within the permanent magnet device may be configured to accommodate at least two quantum crystals. The quantum crystals may be spaced apart from one another by at least 5 μm, at most 500 μm, particularly at least 50 μm, at most 100 μm.

[0059] According to at least one embodiment of the quantum computing device, the frequency difference between the magnetic quantum number changing transitions between directly adjacent trapped quantum particles is at least 10 kHz and at most 100 MHz. In particular, the frequency difference between the magnetic quantum number changing transitions between directly adjacent trapped quantum particles is at least 1 MHz and / or at most 50 MHz.

[0060] If the trapped quantum particle is represented by a two-level quantum system with three sublevels, two of the three possible transitions are respectively called σ ± The magnetic quantum number of each sublevel to the first level changes. ± The transition is excited by left- or right-handed circularly polarized electromagnetic waves with polarization perpendicular to the local magnetic field.

[0061] σ between directly adjacent trapped quantum particles ± The frequency difference of the transitions is, for example, at least 10 kHz, at least 1 MHz, or at least 10 MHz, about 40 MHz.

[0062] According to at least one embodiment of the quantum computing device, the frequency difference between transitions between immediately adjacent trapped quantum particles that do not change the magnetic quantum number is at least 1 kHz and at most 10 MHz.

[0063] If the trapped quantum particle is a two-level quantum system, one of the three possible transitions is the so-called π transition, in which the magnetic quantum number of each sublevel to the first level remains unchanged. Such a π transition can be excited by a linearly polarized electromagnetic wave with polarization parallel to the local magnetic field.

[0064] The frequency difference of the π transitions between immediately adjacent trapped quantum particles is, for example, about 0.25 MHz.

[0065] According to at least one embodiment of the quantum computing device, the edges of the segments located in opposing regions facing each other have a minimum distance from each other of at least 0.001 cm and at most 100 cm. In particular, the minimum distance is at least 0.01 cm or at least 1 cm and at most 25 cm or at most 50 cm. In this context, opposite means, for example, opposite with respect to the center of gravity of the permanent magnet device and / or with respect to the center of the magnetic field, i.e., the center of the quadrupole field.

[0066] For example, the minimum distance divided by two is defined as the inner radius of the permanent magnet device.

[0067] According to at least one embodiment of the quantum computing device, each segment has an extent along a corresponding minimum distance of at least 0.001 cm and at most 100 cm, particularly at least 0.01 cm or at least 1 cm and at most 25 cm or at most 50 cm.

[0068] For example, the minimum distance divided by two and the corresponding spread along the minimum distance is defined as the outer radius of the permanent magnet array.

[0069] According to at least one embodiment of the quantum computing device, the remanent magnetic flux density of each of the segments is at least 0.1 T and at most 1.5 T. In particular, the remanent magnetic flux density of each segment is at least 0.5 T and / or at most 1 T.

[0070] With such a residual magnetic flux density and such inner and outer radii, it is possible to achieve a change in the magnitude of the magnetic field in the central region by at least 0.5 T / m and up to 500 T / m.

[0071] When the segments are arranged in a ring, the magnetic flux density B corresponding to the magnetic field → (Vectors are written this way for convenience) has the following form:

number

[0072] According to at least one embodiment of the quantum computing device, the permanent magnet device includes NdFeB. In particular, the permanent magnet device includes NdFeB N52. Illustratively, each segment includes or consists of NdFeB, in particular NdFeB N52.

[0073] According to at least one embodiment, the quantum computing device further comprises at least one additional permanent magnet device. In particular, the quantum computing device can comprise several additional permanent magnet devices. The additional permanent magnet devices can have the same characteristics as the permanent magnet devices described hereinabove. Furthermore, the additional permanent magnet devices can have the same dimensions as the permanent magnet devices described hereinabove. Alternatively, the additional permanent magnet devices can have different dimensions than the permanent magnet devices described hereinabove.

[0074] According to at least one embodiment of the quantum computing device, the permanent magnet device and the additional permanent magnet device are rotated relative to each other.

[0075] For example, the additional permanent magnet devices are arranged in a rotated manner, in particular out-of-plane rotated manner, relative to the permanent magnet devices, such that an angle is enclosed by the respective main extension planes, i.e., the additional main extension planes of the additional permanent magnet devices are rotated out of the plane of the main extension planes of the permanent magnet devices. Exemplarily, the angle may be between 0° and 180°, in particular 60°, 120° and / or 90°.

[0076] For example, the additional permanent magnet devices are rotated by 90° relative to the permanent magnet device so that their respective main extension planes enclose an angle of 90°. Illustratively, the first axis and the additional first axis corresponding to the additional permanent magnet device are positioned perpendicular to each other. Thus, the trapped quantum particles can advantageously be arranged in a cross shape.

[0077] According to at least one embodiment of the quantum computing device, the permanent magnet device and the additional permanent magnet device are parallel to each other.

[0078] Illustratively, the first axis and the additional first axis are positioned parallel to each other.

[0079] Alternatively, the additional permanent magnet device is arranged in a rotated manner, in particular in-plane rotated, relative to the permanent magnet device. In this case, the main extension plane and the additional main extension plane are parallel to each other. For such an in-plane rotation, an angle is enclosed by the respective first axis, i.e., the first axis and the additional first axis. Exemplarily, the angle may be between 0° and 90°.

[0080] For example, the additional permanent magnet device is rotated 90° in-plane relative to the permanent magnet device, so that each first axis subtends an angle of 90°. In this embodiment, the first axis and the additional first axis are positioned perpendicular to each other.

[0081] Such an arrangement, including the permanent magnet arrangement and the additional permanent magnet arrangement, exemplarily forms a three-dimensional restricted space, for example a three-dimensional gradient space, respectively, for the magnetic field.

[0082] By adding two or more additional permanent magnet devices, two or more additional first axes are provided, thereby allowing for complex arrangements of trapped quantum particles.

[0083] Furthermore, quantum computers are designated herein as comprising the quantum computing devices described above, i.e., features relating to quantum computers are also applicable to quantum computing devices and vice versa.

[0084] A quantum computer is configured to perform quantum computing processes by using a quantum computing device, the trapped quantum particles of which can be particularly well controlled and manipulated using the permanent magnet devices described herein above to perform a given quantum computation.

[0085] The quantum computing device is described in more detail below with reference to exemplary embodiments and associated figures. [Brief explanation of the drawings]

[0086] [Figure 1] 1 illustrates a cross-sectional view of a quantum computing device in accordance with an example embodiment. [Figure 2] 1 illustrates a cross-sectional view of a quantum computing device in accordance with an example embodiment. [Figure 3] 1 shows an exemplary diagram of the magnetic field magnitude of a permanent magnet device of a quantum computing device in accordance with an example embodiment. [Figure 4] 1 shows an exemplary diagram of the magnetic field magnitude of a permanent magnet device of a quantum computing device in accordance with an example embodiment. [Figure 5] 1 illustrates a quantum computer in accordance with an example embodiment. [Figure 6] 1 illustrates a quantum computing device in accordance with an example embodiment. [Figure 7] 1 illustrates a quantum computing device in accordance with an example embodiment. [Figure 8] 1 illustrates a quantum computing device in accordance with an example embodiment.

[0087] Elements that are identical, similar, or have the same effect are given the same reference numerals in the figures. The figures and the proportions of the elements shown therein are not to be considered to be true to scale. Rather, individual elements may be shown exaggeratedly large for better visibility and / or better comprehensibility. DETAILED DESCRIPTION OF THE INVENTION

[0088] The quantum computing device 1 according to the exemplary embodiment of FIG. 1 includes a permanent magnet device 2. The permanent magnet device 2 includes 16 segments 3. The segments 3 surround a space 5 of the quantum computing device, and trapped quantum particles 6 are trapped during operation of the quantum computing device. The segments 3 surround the space 5 in the form of a ring. Each segment 3 is positioned such that its center is at a point on the ring.

[0089] The permanent magnet device 2 has a main extension plane extending along the x-axis and y-axis shown in FIG. 1. Each segment 3 has a cross-sectional shape of an annular sector or a circular ring-sector, and all segments 3 share the same common inner ring and the same common outer ring. The width of each segment 3 tapers towards the space 5, i.e., the opposite edges of each segment 3 facing the space 5 are curved. The normal bundle of the curved edges points away from the space 5, i.e., the radius of the curved edges is defined relative to the central region of the permanent magnet device 2.

[0090] The curved edges of the segments 3, which are located in areas opposite to the central area and face each other, have a minimum distance of about 10 cm from each other. This minimum distance divided by 2 is the inner radius R of the permanent magnet device 2. i This stipulates:

[0091] Furthermore, each segment 3 has an extension along the corresponding minimum distance of about 20 cm. The minimum distance divided by 2 and the extension along the corresponding minimum distance are determined by the outer radius R of the permanent magnet device 2. o This stipulates:

[0092] For example, directly adjacent segments 3 are spaced apart from one another: the opposing edges of directly adjacent segments 3 have a distance of about 1 mm from one another.

[0093] In this exemplary embodiment, each segment 3 has a line of symmetry bisecting opposite edges facing the space 5. The line of symmetry is the same for segments 3 arranged opposite each other. One of the lines of symmetry represents a first axis 7 of the permanent magnet arrangement 2, which exemplarily extends in the main extension plane.

[0094] Furthermore, each segment 3 has a magnetization direction 4, which is shown as an arrow within the segment 3 in Figure 1. The magnetization directions 4 of the segments 3 located in opposite regions relative to the center of the permanent magnet device 2 are oriented in opposite directions. A first axis 7 of the permanent magnet device 2 is defined for the two segments 3 located opposite each other, and the magnetization directions 4 of each of the two segments 3 are parallel to the first axis 7.

[0095] Each magnetization direction 4 makes an angle with the first axis 7. These angles are all formed differently, for example the angles of directly adjacent segments 3 differ from each other by 67.5°.

[0096] In the exemplary embodiment of Figures 1 and 2, the first axis 7 points in the direction of the x-axis.

[0097] Furthermore, the angle of the segment 3 that is parallel to the first axis 7 and has a magnetization direction 4 pointing in the same direction as the first axis 7 is 0°. The angle of the opposite segment 3 that is parallel to the first axis 7 and has a magnetization direction 4 pointing in the opposite direction to the first axis 7 is 180°.

[0098] When moving clockwise around the ring from a segment 3 having a magnetization direction 4 that is parallel to and points in the same direction as the first axis 7 back to this segment 3, the magnetization direction 4 also rotates clockwise.

[0099] Using such segments 3, the permanent magnet device 2 is configured to generate a quadrupole field, thus having a different magnitude along the first axis 7, i.e., a magnetic field gradient along the first axis 7. Furthermore, during operation of the quantum computing device 1, the trapped quantum particles 6 are arranged linearly one after the other along the first axis 7.

[0100] The magnitude of the magnetic field acting on the trapped quantum particles 6 differs for each trapped quantum particle 6 arranged on the first axis 7 .

[0101] Illustratively, the trapped quantum particles 6 are trapped ions. That is, each trapped ion has n energy levels, two of which form a qubit. In this case, each trapped ion is represented by a two-level quantum system including a first electronic energy level and a second electronic energy level, both levels corresponding to respective atomic eigenstates of each trapped ion.

[0102] To trap ions, electromagnetic harmonic trapping potentials are used to axially confine trapped ions along a first axis. The harmonic trapping potentials are further superimposed with a magnetic quadrupole potential to radially confine trapped ions along the first axis. These trapping potentials are superimposed with electronic energy levels and corresponding electronic energy sublevels, which appear due to different magnitudes of the magnetic field, i.e., gradient magnetic field. There are transitions between the electronic energy sublevels, each corresponding to an excited state of the trapped ion, and the first electronic energy level, corresponding to the ground state of the trapped ion. Due to the different magnitudes of the magnetic field, i.e., the magnetic field gradient, there is a frequency difference between certain transitions between neighboring trapped ions. Thus, each trapped ion can be excited at a different resonant frequency. Advantageously, each trapped ion is distinguishable and therefore addressable with such different resonant frequencies.

[0103] The total energy of the system is predetermined by the harmonic trapping potential and the internal energy. The internal energy depends on the state of the trapped ion, e.g., ground state or excited state. When a trapped ion is excited at a specific resonant frequency in one of the excited states, the equilibrium position of the trapped ion changes due to the superposition of the corresponding electronic energy sublevel with the harmonic trapping potential. As a result, the trapped ion begins to oscillate, thus influencing neighboring trapped ions via Coulomb interactions, resulting in an effective spin-spin coupling.

[0104] In particular, the coupling strength between two directly adjacent trapped ions depends on the square of the magnetic field gradient and the square of the axial frequency of the trapping potential. Furthermore, the relaxation time, especially the spin relaxation time T2, is inversely proportional to the decoherence rate. Therefore, to provide multi-qubit gates, the magnetic field gradient must be relatively high to provide a large number of gates within a given time period.

[0105] For example, the inner radius R according to this exemplary embodiment i is approximately 5 cm, and the outer radius R o The residual magnetic flux density B of each segment 3 is approximately 25 cm. R is, for example, 1 T. Thus, the magnetic field, and in particular the corresponding magnetic flux density B → teeth,

number

[0106] Furthermore, the distance d between directly adjacent trapped ions is approximately 3 μm. → can be calculated for each position of the trapped ion, so that the difference for a particular transition between nearby trapped ions can also be determined.

[0107] In contrast to the exemplary embodiment of FIG. 1, the quantum computing device 1 according to the exemplary embodiment of FIG. 2 comprises a permanent magnet device 2 having segments 3 each having a square shape.

[0108] Each segment 3 has a square cross-sectional shape. The magnetization direction 4 relative to the edges of the square is the same for each segment 3. Directly adjacent segments 3 are rotated relative to each other so that the magnetization direction 4 of each segment 3 corresponds to the angle according to FIG.

[0109] In Figures 3 and 4, the magnitude of the magnetic field, expressed by the absolute value of the magnetic field |B| in T, is shown on the vertical axis in dependence on the position x or y, respectively, in mm, which is shown on the horizontal axis.

[0110] The horizontal axis of the diagram shown in Figure 3 corresponds to the x-axis according to Figures 1 and 2. The horizontal axis of the diagram shown in Figure 4 corresponds to the y-axis according to Figures 1 and 2. The position x or y equal to 0 corresponds to the center of the permanent magnet device 2 according to Figures 1 and 2.

[0111] The absolute value of the magnetic flux density |B|, i.e., the magnitude of the magnetic field, is symmetrical with respect to the center of the permanent magnet device 2. For negative position values ​​x and y, the absolute value of the magnetic flux density |B|, i.e., the magnitude of the magnetic field, has a negative gradient, and for positive position values ​​x and y, it has a positive gradient.

[0112] Quantum computer 8 according to the exemplary embodiment of Figure 5 comprises a quantum computing arrangement 1 according to one of the exemplary embodiments of Figure 1 or Figure 2 and a quantum computing device 9 located in chamber 10. Quantum computing arrangement 9 is connected to components external to quantum computer 8 through chamber 10 by a number of connections 11. For example, connections 11 connect quantum computing device 9 with control electronics 12 and classical computer 13.

[0113] For example, quantum computing device 9 is configured to capture, manipulate, and measure trapped quantum particles, each of which is a quantum bit, within space 5 during operation. To this end, quantum computing device 9 may include internal electronics, including electrodes, light guides, and / or electronic devices. The electronic devices may include circuits, integrated electronics, and / or detectors, such as photon detectors and / or charge detectors, and controllers. Illustratively, the internal electronics are provided for preprocessing. For example, these components allow measurement of the state of each of the qubits and allow gate operations on the qubits. Thus, quantum computing device 9 is configured to capture trapped quantum particles and perform operations and measurements on the trapped quantum particles.

[0114] The quantum computing device 9 is mounted in a chamber 10, which may be an ultra-high vacuum chamber, an extremely high vacuum chamber, and / or a cryostat. If the chamber 10 is an ultra-high vacuum chamber or an extremely high vacuum chamber, the permanent magnet device 2 may be located outside the chamber 10. In this case, the permanent magnet device 2 surrounds the chamber 10. Alternatively, the permanent magnet device 2 may be located inside an ultra-high vacuum chamber or an extremely high vacuum chamber or a cryostat.

[0115] Illustratively, if the chamber 10 is a cryostat, the permanent magnet device 2 is disposed inside the chamber 10 (not shown here). It is also contemplated that if the chamber 10 is a cryostat, the permanent magnet device 2 may also be disposed outside the chamber 10 (not shown here).

[0116] Quantum computing device 9 is connected to external electronics 12 via connection 11. External electronics 12 can be located at least partially inside chamber 10 and partially outside chamber 10. Furthermore, external electronics 12 is connected to classical computer 13.

[0117] The external electronics 12 illustratively includes an analog-to-digital converter and a signal generator, such as a radio frequency generator, a microwave signal generator, a low frequency signal generator, and / or a DC signal generator. Additionally, the external electronics 12 may include a transistor-transistor logic circuit (TTL).

[0118] Additionally, the external electronics 12 can further comprise at least one laser system configured to cool the trapped ions. Furthermore, the laser system can be configured to excite specific states of the trapped ions.

[0119] Classical computer 13 is configured, for example, to provide and receive digital signals that correspond to control signals used for operations on qubits and measurement signals that correspond to the states of the qubits.

[0120] External electronics 12 is configured, among other things, to convert digital signals to analog signals and vice versa. Thus, external electronics 12 is configured to provide converted analog signals for manipulating qubits to quantum computing device 9. Furthermore, external electronics 12 is configured to provide measured analog signals from quantum computing device 9 to classical computer 13, or to process such signals to directly initiate any response signals generated by control electronics 12.

[0121] Classical computer 13 is illustratively configured to be provided with a particular algorithm, i.e., a predetermined quantum computation that solves a particular problem. Classical computer 13 is then configured to convert compiled code corresponding to the algorithm into commands for quantum computing device 9. The commands are then transferred to quantum computing device 9 via external control electronics 12. Additionally, classical computer 13 is configured to receive measured results of the particular algorithm.

[0122] For example, all elements of the quantum computer 8, in particular all electronic elements of the quantum computer 8, are synchronized, for example by an atomic clock reference.

[0123] The quantum computing devices 1 according to the exemplary embodiments of FIGS. 6, 7, and 8 each include the permanent magnet device 2 and ion trap 100 described in connection with the exemplary embodiment of FIG.

[0124] According to Figure 6, the ion trap 100 is a linear Paul trap for trapping ions along a first axis 7. A Paul trap is also known as a quadrupole ion trap or a radio frequency trap. It is a type of ion trap 100 that uses a dynamic electric field to trap ions.

[0125] The linear Paul trap comprises two radio frequency (rf) electrodes 20, two direct current (dc) electrodes 30, and two end cap electrodes 40. Illustratively, the end cap electrodes may be formed from a soft magnetic material forming a yoke structure 60 to enhance the magnetic field gradient along the first axis 7.

[0126] 7, the ion trap 100 is a planar Paul trap for trapping ions along a first axis 7. The planar Paul trap comprises two rf electrodes 20, a dc electrode 30, an end cap electrode 40, and a separation cap electrode 41. All of these electrodes are metal films and are arranged on a common electrode plane.

[0127] According to FIG. 8, the ion trap 100 is a segmented Paul trap for trapping ions along a predetermined line, specifically a first axis 7. The segmented Paul trap includes at least two sections 47, each configured to host an ion crystal containing a plurality of tapped ions. Each section includes two RF electrodes 20 and two DC electrodes 30 arranged similarly to those described in FIG. 6. These sections are further disposed between at least two end cap electrodes 40. These electrodes are all metal films, parallel to each other, and arranged with the two electrode faces stacked on top of each other.

[0128] The present invention is not limited to the exemplary embodiments described therein, but rather includes any novel feature and any combination of features, and in particular any combination of features set forth in the claims, even if the feature or combination itself is not explicitly set forth in the claims or exemplary embodiments. [Explanation of symbols]

[0129] 1 Quantum computing device 2. Permanent magnet device 3 segments 4 Magnetization direction 5 Space 6 Trapped quantum particles 7 First Axis 8. Quantum Computers 9. Quantum Computing Devices 10 Chambers 11 Connection 12 External electronic equipment 13 Classical Computers 100 Ion Trap 20 rf electrodes 30 dc electrodes 40 End cap electrode 41 Separation cap electrode 47 Section 50 boards 60 yoke structure d distance R i inner radius R o outer radius

Claims

1. a permanent magnet device (2); a space (5) within said permanent magnet device (2) for at least two trapped quantum particles (6) arranged along a first axis (7); A quantum computing device (1) having: The permanent magnet device (2) comprises a plurality of segments (3), i.e., at least four segments (3); Each segment (3) has a magnetization direction (4), the magnetization directions (4) of the at least four segments (3) are different from one another, thereby establishing magnetic fields with different magnitudes for different positions on the first axis (7); Quantum computing device (1).

2. the segment (3) surrounds the space (5) in the form of a ring, or The segment (3) surrounds the space (5) in the form of a polygonal contour, Quantum computing device (1) according to claim 1.

3. The quantum computing device (1) according to claim 2, wherein the space (5) is located in the central region of the ring or on the contour of the polygon.

4. Quantum computing device (1) according to any one of claims 1 to 3, wherein the distances between immediately adjacent segments (3) are equal to each other.

5. 5. The quantum computing device (1) according to any one of claims 1 to 4, wherein at least some of the segments (3) have a rectangular cross section.

6. 6. The quantum computing device (1) according to any one of claims 1 to 5, wherein the cross section of at least some of the segments (3) has a trapezoidal shape.

7. 7. A quantum computing device (1) according to any one of claims 1 to 6, wherein all segments (3) have the same shape.

8. 8. The quantum computing device (1) according to any one of claims 1 to 7, wherein the magnetization directions (4) of the segments (3) arranged in opposite regions are oriented in opposite directions.

9. 9. The quantum computing device (1) of claim 1, wherein at least some of the trapped quantum particles (6) in the space (5) form at least a two-level quantum system during operation of the quantum computing device (1).

10. 10. The quantum computing device (1) of claim 1, wherein at least some of the trapped quantum particles (6) in the space (5) form quantum bits during operation of the quantum computing device (1).

11. 11. The quantum computing device (1) of claim 1, wherein the frequency difference of a particular transition between the trapped quantum particles (6) depends on the magnetic field during operation of the quantum computing device (1).

12. the distance (d) between directly adjacent trapped quantum particles (6) is at least 0.1 μm and at most 30 μm; the frequency difference between the transitions of the magnetic quantum number changing between directly adjacent trapped quantum particles (6) is at least 10 kHz and at most 100 MHz; and / or the frequency difference between transitions between directly adjacent trapped quantum particles (6) without changing the magnetic quantum number is at least 1 kHz and at most 10 MHz; Quantum computing device (1) according to any one of claims 1 to 11.

13. the edges of the segments (3) located in opposite areas and facing each other have a minimum distance from each other of at least 0.001 cm and at most 100 cm; Each segment (3) has an extension along a corresponding minimum distance of at least 0.001 cm and at most 100 cm; Quantum computing device (1) according to any one of claims 1 to 12.

14. 14. The quantum computing device (1) of any one of claims 1 to 13, wherein the residual magnetic flux density of each of the segments (3) is at least 0.1 T and at most 1.5 T.

15. 15. The quantum computing device (1) of any one of claims 1 to 14, wherein the permanent magnet device (2) comprises NdFeB.

16. 16. The quantum computing device (1) of any one of claims 1 to 15, further comprising at least one additional permanent magnet device (2).

17. the permanent magnet device and the further permanent magnet device are rotated relative to each other, or the permanent magnet device and the further permanent magnet device are parallel to each other. Quantum computing device (1) according to claim 16.

18. 18. A quantum computer (8) comprising a quantum computing device (1) according to any one of claims 1 to 17, configured to perform quantum computations.

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