Quantum computing device and quantum computer

Abstract

There is described a quantum computing device (1) comprising:-a permanent magnet device (2); and-a space (5) within the permanent magnet arrangement (2) for at least two captured quantum particles (6), the at least two captured quantum particles (6) being arranged along a first axis (7), in which-the permanent magnet arrangement (2) comprises 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 each other,-the space (5) of the at least two captured quantum particles (6) being arranged along the first axis (7). Thereby establishing a magnetic field having an intensity that varies along the first axis (7). The invention further relates to a quantum computer (8) comprising the quantum computing device (1).

Description

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

[0002] For many quantum computing processes using quantum computing devices, these devices can be configured to capture trapped quantum particles. The trapped quantum particles must be controlled and manipulated to perform calculations. For charged trapped quantum particles, interactions such as Coulomb repulsion produce coupling of adjacent trapped quantum particles and achieve entanglement. Therefore, in order to perform quantum computing processes using trapped quantum particles, the trapped quantum particles must be individually controllable and addressable relative to each other.

[0003] It is desirable to individually address multiple trapped quantum particles, such as qubit registers, with negligible crosstalk. However, crosstalk between adjacent trapped quantum particles is often a difficult-to-control error source in quantum computer processing and hinders meaningful application of quantum error correction protocols, thereby hindering scalability.

[0004] The object to be solved is therefore to specify a quantum computing device with improved controllability. Furthermore, a quantum computer comprising such a quantum computing device is specified.

[0005] This object is achieved 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, a quantum computing device comprises a permanent magnet device. The permanent magnet device has, for example, a first axis. The permanent magnet device has a main extension plane, wherein the first axis extends along the main extension plane.

[0007] The first axis is a virtual axis. For example, the first axis is an axis of symmetry in the main extension plane. That is, the first axis divides the permanent magnet arrangement into two halves along the main extension plane in a cross-sectional view, and the shapes of the two halves are substantially the same. "Substantially the same" exemplarily means that due to manufacturing tolerances of the permanent magnet arrangement, 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 comprises a space for at least two trapped quantum particles within a permanent magnet device, wherein the at least two trapped quantum particles are arranged along a first axis. Exemplarily, the space has a main extension direction extending along the first axis.

[0009] For example, a permanent magnet device surrounds the space. The space is defined as an area or volume surrounded by a permanent magnet device, where quantum particles are trapped during operation of the quantum computing device. Exemplarily, during operation of the quantum computing device, the trapped quantum particles are arranged linearly adjacent to each other along the first axis. In particular, during operation of the quantum computing device, more than two, for example at least 8, at least 20, or at least 100 and / or at most 1000 trapped quantum particles are arranged along the first axis.

[0010] Trapped quantum particles are represented, for example, by energy levels in atoms or molecules, spins of electrons and / or nuclei, charges, fluxes or phases in superconductors, or topological quantum numbers of anyons in topologically protected systems.

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

[0012] Exemplarily, each trapped quantum particle is trapped by a predetermined trap potential. The trap potential can be static or dynamic. For trapped quantum particles represented by energy levels in atoms or molecules, ions are trapped by electromagnetic fields. Exemplarily, ions are trapped by dynamic electric fields, particularly radio frequency fields. For trapped quantum particles represented by the spin of electrons, electrons are trapped in a potential well within a semiconductor system. For example, a 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 comprises a plurality of segments, i.e. at least four segments. For example, the permanent magnet device comprises at least four segments, in particular at least 8 segments, at least 16 segments or at least 32 segments. Each segment comprises a permanent magnetic material. In particular, each segment comprises the same permanent magnetic material. Exemplarily, the permanent magnetic material comprises a ferromagnetic material.

[0014] Each segment is, for example, formed in one piece. Alternatively, each segment is formed from at least two sub-segments, wherein at least two sub-segments have the same material and / or magnetization properties.

[0015] In a preferred embodiment, the first axis extends linearly from one of the segments to another of the segments, the other segment being positioned opposite one of the segments relative to the centre of the permanent magnet arrangement.

[0016] Exemplarily, the permanent magnet arrangement is a Halbach arrangement.

[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 corresponding permanent magnetic material. In other words, the corresponding permanent magnetic material exhibits a dipole moment. The vector field, in particular the dipole moment of the permanent magnetic material, defines the corresponding magnetization direction. The dipole moment mainly points in the magnetization direction.

[0018] Each magnetization direction is defined relative to the first axis. That is, 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 at least four segments are different from each other, thereby establishing a magnetic field with different strengths for different positions on the first axis. Exemplarily, the strength of the magnetic field varies along the first axis and for different positions on the first axis. The strength is, for example, symmetric along the first axis relative to the center of the permanent magnet device. That is, for example, there are two points on the first axis with the same strength.

[0020] For example, all magnetization directions of the segments are different from each other. That is, each magnetization direction has a different angle relative to the first axis. In other words, all angles formed 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 is predetermined in such a way that a magnetic multipolar field is generated. In particular, a magnetic quadrupole field is generated, wherein, in the center of the permanent magnet arrangement, the intensity of the magnetic field vanishes, for example, approximately 0 T. Due to the magnetic multipolar field, in particular the quadrupole field, the permanent magnet arrangement has a magnetic field intensity along the first axis which depends on the arrangement of the segments and the respective magnetic directions.

[0022] For such a permanent magnet arrangement, the strength of the magnetic field varies continuously along the first axis (ie for different positions on the first axis). Therefore, the strength of the magnetic field at different positions on the first axis is a representation of the magnetic field gradient along the first axis.

[0023] The magnetic field is represented by the magnetic flux density. In addition, the absolute value of the magnetic flux density corresponds to the strength of the magnetic field at a predetermined position on the first axis.

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

[0025] For example, for different positions on the first axis, at least some of the vectors of the magnetic field point to the same radial direction and / or the same axial direction of 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 intensity of the magnetic field is symmetrical along the first axis relative to the center of the permanent magnet device. Exemplarily, the first axis is divided into two halves by the center of the permanent magnet device. That is, for each point in one half of the first axis, there is another point with the same magnetic field intensity in the other half of the first axis. The intensity of the magnetic field has a negative slope for one half axis and a positive slope for the other half axis. Relative to the magnetic field intensity starting from the center along the first axis, the magnetic field gradient increases along the first axis, for example, approximately linearly. That is, the magnetic field gradient is approximately constant starting from the center along the first axis.

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

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

[0029] In particular, one idea is to use a permanent magnet device in combination with the space where the trapped quantum particles are located during the operation of the quantum computing device. The different magnetic field strengths of the permanent magnet device, i.e., the magnetic field gradient, make the equilibrium position of the trapped quantum particles state-dependent. In addition, due to the magnetic field gradient, the resonant frequency is unique for each trapped quantum particle.

[0030] That is, due to the different magnetic field strengths, i.e., magnetic field gradients, of the permanent magnet device, the trapped quantum particles can be individually addressed in frequency space, so that an improved multi-qubit gate can be advantageously implemented, and the coupling of adjacent trapped quantum particles can be controlled. In addition, by adjusting the coupling, highly entangled cluster states for quantum computing can be advantageously generated.

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

[0032] Exemplarily, if a magnetic field is applied to a two-level quantum system, the degeneracy of the second energy level is increased so that at least two, in particular at least three, sub-energy levels are generated. This results in two (in particular three) possible transitions from each of the two (in particular three) sub-energy levels to the first energy level.

[0033] If the trapped quantum particle is represented by an n-level quantum system, where n is a natural number equal to or greater than 2, each n-level quantum system includes n energy levels. For example, when a magnetic field is applied, at least some of the n energy levels correspond to sub-energy levels. In such an n-level quantum system, multiple transitions can be achieved.

[0034] In addition, the intensity of the energy level splitting and the sub-energy level splitting depends on the applied magnetic field. For the trapped quantum particles, the intensity of the magnetic field is different for different positions, and therefore, for these trapped quantum particles, the splitting is also different. Therefore, the frequency difference of the specific transition between adjacent trapped quantum particles is also achieved. Due to the frequency difference, different resonant frequencies for adjacent trapped quantum particles are also generated.

[0035] The total energy of each trapped quantum particle is predetermined by the trap potential and the energy that characterizes the corresponding transition.

[0036] If a trap potential, such as a harmonic trap potential, is superimposed with the energy levels and sub-energy levels of the corresponding trapped quantum particle, the equilibrium position depends on the state of the corresponding trapped quantum particle. If a trapped quantum particle in the ground state is excited to one of the excited states, for example, according to one of the possible transitions, the equilibrium position of the trapped quantum particle changes. Due to the change in the equilibrium position, an effective spin-spin coupling of the trapped quantum particle with the adjacent trapped quantum particle is achieved via the Coulomb interaction. Therefore, the equilibrium position depends on the state of each trapped quantum particle and the strength of the magnetic field, that is, the magnetic field gradient.

[0037] That is, the coupling of at least two trapped quantum particles depends on the strength of the magnetic field, i.e., the magnetic field gradient. Since the coupling is proportional to the square of the magnetic field gradient, the magnetic field gradient must be large enough to produce sufficient coupling for fast calculations, which can be achieved using the permanent magnet device described in this article. In other words, the magnetic field gradient must be large enough to produce a large coupling compared to the decoherence rate. Such a relatively large gradient improves addressing, as well as provides lower crosstalk and stronger coupling of trapped quantum particles. Therefore, faster quantum operations can be achieved and fewer error correction operations are required.

[0038] Advantageously, with the permanent magnet arrangement of the quantum computing device described herein, the magnetic gradient is extremely high while having a limited available solid angle and distance relative to space for the trapped quantum particles. Thus, such a quantum computing device can be implemented in a variety of systems.

[0039] In summary, a permanent magnet device is used to obtain a large magnetic field gradient experienced by a charged trapped quantum particle to produce a largely different magnetic field experienced by each trapped quantum particle. In a quantum information environment, this enables improved addressing in frequency space, and therefore enables individual single-qubit rotations with low crosstalk, and introduces coupling between charged trapped quantum particles to enable interaction, thereby realizing a multi-qubit gate. This can also be used in conjunction with a radio frequency (RF) field for qubit control, for which addressing by focused radiation is not an option due to the long wavelength, but the RF field may be more advantageous in terms of miniaturization and integration. To this end, a large or steep magnetic field gradient is required to enable better addressing and faster quantum gates with higher fidelity, and a permanent magnet device, especially a Halbach device, is able to achieve a large magnetic field gradient, even when the distance between the segments of the permanent magnet device and the quantum particles is limited by technical 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 contour of the ring or polygon has a virtual nature. Exemplarily, in a cross-sectional view along the main extension plane, each segment is arranged at a point, wherein the point is located on the contour of the ring or polygon. These points are spaced apart from each other so that these parts do not overlap each other in the main extension plane. For example, each point represents the center of the corresponding segment.

[0042] In the case where the segments are arranged on a ring, the shape of the ring is a circle or an ellipse. In the case where the segments are arranged on the outline of a polygon, the shape of the outline of the polygon may be a quadrilateral, a rectangle, a hexagon or an octagon.

[0043] For example, directly adjacent segments arranged on the contour of the ring or polygon are in direct and immediate contact with each other and / or have a distance of at most 50 mm, in particular at most 1 mm, from each other. Due to such a relatively small distance, the magnetic field is advantageously similar to 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 the outline of the ring or polygon. The central region is surrounded by the outline of the ring or polygon and is arranged in the center of the permanent magnet arrangement.

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

[0046] According to at least one embodiment of the quantum computing device, the distances between directly adjacent segments are equal to each other. For example, the segments arranged on the contour of a ring or polygon are arranged equidistant from each other. Due to production tolerances, there may be deviations 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 quadrilateral shape in cross section. Segments having a quadrilateral shape in cross section along the main extension plane are particularly easy to produce and are therefore particularly cost-effective.

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

[0049] Exemplarily, all sides are formed as straight. Advantageously, the edges of directly adjacent segments can be advantageously arranged close to each other. That is, the edges of directly adjacent segments facing each other can advantageously directly contact each other or at least relatively close together 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 to the space as possible. Advantageously, in the case of segments with a trapezoidal shape, the edges of each segment facing the space can be relatively close to the space over the entire length of these edges compared to quadrilateral segments.

[0051] Alternatively, the two opposite edges facing the space are formed to be curved. In particular, the normal beams of the two opposite edges point in the direction away from the space. Advantageously, the distances of the edges of the segments facing the space to the space are approximately the same compared to segments with straight edges. As a result, the magnetic multipole field can be particularly smooth, thereby generating 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 by a cuboid, 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 arranged at the opposite regions point in opposite directions. The segments are arranged at the opposite regions relative to the central region. The magnetization directions of the segments arranged at the opposite regions are opposite to each other.

[0054] In particular, a first axis is defined with respect to two segments arranged opposite one another, wherein the magnetization directions of the respective two segments are parallel to the first axis.

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

[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 strength of the magnetic field during operation of the quantum computing device. Because the trapped quantum particles are arranged along a first axis and because the magnetic field has different strengths along the first axis, there is a frequency difference of the same transition between adjacent trapped quantum particles. That is, the resonant frequency of a particular transition for each of the trapped quantum particles depends on the position of each of the trapped quantum particles 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 in space and time along the first axis.

[0058] The plurality of trapped quantum particles may be part of a quantum crystal, in particular 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 at least 5 μm and at most 500 μm apart from each other, in particular at least 50 μm and at most 100 μm apart.

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

[0060] If the trapped quantum particle is represented by a two-level quantum system with three sub-levels, then two of the three possible transitions are each the so-called σ ± transition, in which the magnetic quantum number of the corresponding sub-energy level to the first energy level does change. ± The transition is excited by left- or right-circularly polarized electromagnetic waves with polarization perpendicular to the local magnetic field.

[0061] The 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, approximately 40 MHz.

[0062] In accordance with at least one embodiment of the quantum computing device, the frequency difference of magnetic quantum number-invariant transitions between directly adjacent trapped quantum particles 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 a so-called π transition, in which the magnetic quantum number of the corresponding sub-level to the first energy level does not change. Such a π transition is excited by a linearly polarized electromagnetic wave with polarization parallel to the local magnetic field.

[0064] The frequency difference of the π transitions between directly 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 arranged in opposite areas and facing each other have a minimum distance of at least 0.001 cm and at most 100 cm relative to each other. 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, relative means, for example, relative to the center of gravity of the permanent magnet device and / or relative to the center of the magnetic field, i.e., the center of the quadrupole field.

[0066] For example, the minimum distance divided by 2 is defined as the inner radius of the permanent magnet arrangement.

[0067] According to at least one embodiment of the quantum computing device, each segment has a range along the corresponding minimum distance of at least 0.001 cm and at most 100 cm. In particular, the range is 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 2 and the range along the corresponding minimum distance is defined as the outer radius of the permanent magnet device.

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

[0070] With such a remanence and with such an inner radius and outer radius, a variation in the strength of the magnetic field in the central region of at least 0.5 T / m and at most 500 T / m can be achieved.

[0071] If the segments are arranged in the form of a ring, the magnetic flux density corresponding to the magnetic field Has the following form:

[0072]

[0073] Among them, B R is the remanence of the segment, R i is the inner radius, R o is the outer radius, and x and y are the coordinates within the permanent magnet arrangement.

[0074] According to at least one embodiment of the quantum computing device, the permanent magnet arrangement comprises NdFeB (neodymium iron boron). In particular, the permanent magnet arrangement comprises NdFeB N52. Exemplarily, each segment comprises NdFeB, in particular NdFeB N52, or consists of NdFeB, in particular NdFeB N52.

[0075] 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 may comprise several additional permanent magnet devices. The additional permanent magnet devices may have the same properties as the permanent magnet devices described above herein. Furthermore, the additional permanent magnet devices may have the same size as the permanent magnet devices described above herein. Alternatively, the additional permanent magnet devices may have different sizes than the permanent magnet devices described above herein.

[0076] In accordance with at least one embodiment of the quantum computing device, the permanent magnet arrangement and the additional permanent magnet arrangement are rotated relative to each other.

[0077] For example, the additional permanent magnet arrangement is arranged in a rotational form, in particular in an out-of-plane rotational form, relative to the permanent magnet arrangement, so that the corresponding main extension planes form an angle. That is, the additional main extension plane of the additional permanent magnet arrangement is rotated out-of-plane with respect to the main extension plane of the permanent magnet arrangement. Exemplarily, the angle can be between 0° and 180°, in particular can be 60°, 120° and / or 90°.

[0078] For example, the additional permanent magnet arrangement is rotated 90° relative to the permanent magnet arrangement so that the corresponding main extension planes enclose an angle of 90°. Exemplarily, the first axis and the additional first axis corresponding to the additional permanent magnet arrangement are positioned perpendicular to each other. Thus, the trapped quantum particles can advantageously be arranged in a cross-shaped manner.

[0079] In accordance with at least one embodiment of the quantum computing device, the permanent magnet arrangement and the additional permanent magnet arrangement are parallel to each other.

[0080] Exemplarily, the first axis and the additional first axis are positioned parallel to each other.

[0081] Alternatively, the additional permanent magnet arrangement is arranged in a rotational form, in particular in-plane rotational form, relative to the permanent magnet arrangement. 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 formed by the corresponding first axis, i.e. the first axis and the additional first axis. Exemplarily, the angle can be between 0° and 90°.

[0082] For example, the additional permanent magnet arrangement is rotated 90° in a plane relative to the permanent magnet arrangement so that the corresponding first axes enclose an angle of 90°. In this embodiment, the first axis and the additional first axis are positioned perpendicular to each other.

[0083] Such an arrangement comprising the permanent magnet arrangement and the additional permanent magnet arrangement exemplarily each forms a three-dimensional confined space in terms of magnetic field, for example a three-dimensional gradient space.

[0084] By adding more than one additional permanent magnet arrangement, more than one additional first axis is provided, so that also complex arrangements of trapped quantum particles can be envisaged.

[0085] In addition, a quantum computer is described, wherein the quantum computer comprises a quantum computing device as described above in this document. That is, the features about the quantum computer also apply to the quantum computing device, and vice versa.

[0086] The quantum computer is configured to perform quantum computing processing by using a quantum computing device. The trapped quantum particles of the quantum computing device can be particularly well controlled and manipulated using the permanent magnet device described above in this article to perform predetermined quantum computing.

[0087] Hereinafter, a quantum computing device will be described in more detail with reference to exemplary embodiments and associated drawings.

[0088] Figure 1 and Figure 2 Each shows a cross-sectional view of a quantum computing device according to an exemplary embodiment.

[0089] Figure 3 and Figure 4 Each shows an exemplary graph of the magnetic field strength of a permanent magnet device of a quantum computing device according to an exemplary embodiment.

[0090] Figure 5 A quantum computer according to an exemplary embodiment is shown.

[0091] Figure 6 , Figure 7 and Figure 8 Each shows a quantum computing device according to an exemplary embodiment.

[0092] In the drawings, identical, similar or elements having the same effect are given the same reference numerals. The drawings and the proportions of the elements shown in the drawings should not be considered to be drawn to true scale. On the contrary, individual elements may be shown enlarged for better representation and / or for better comprehensibility.

[0093] according to Figure 1 The quantum computing device 1 of the exemplary embodiment of 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 during operation of the quantum computing device, trapped quantum particles 6 are trapped in the space 5. The segments 3 surround the space 5 in the form of a ring. The center of each segment 3 is arranged at a point of the ring.

[0094] The permanent magnet device 2 has Figure 1 The main extension plane extending along the x-axis and y-axis shown in . Each segment 3 has a cross-sectional form of an annular sector or a circular ring sector, wherein all segments 3 share the same common inner ring and the same common outer ring. The width of each segment 3 tapers toward the space 5. That is, the relative edge of each segment 3 facing the space 5 is curved. The normal beam of the curved edge points in the direction away from the space 5. That is, the radius of the curved edge is defined relative to the central area of ​​the permanent magnet device 2.

[0095] The curved edges of the segments 3 arranged in opposite regions with respect to the central region and facing each other have a minimum distance of about 10 cm with respect to each other. The minimum distance divided by 2 defines the inner radius R of the permanent magnet arrangement 2 i .

[0096] Furthermore, each segment 3 has an extent along the corresponding minimum distance of approximately 20 cm. The minimum distance divided by 2 and the extent along the corresponding minimum distance define the outer radius R of the permanent magnet arrangement 2. o .

[0097] For example, directly adjacent segments 3 are spaced apart from each other. The edges of directly adjacent segments 3 facing each other have a distance of about 1 mm relative to each other.

[0098] In this exemplary embodiment, each segment 3 has a symmetry line that bisects the opposite edge facing the space 5. The symmetry lines are identical for segments 3 arranged opposite one another. One of the symmetry lines represents a first axis 7 of the permanent magnet arrangement 2, wherein the first axis 7 exemplarily extends in the main extension plane.

[0099] In addition, each segment 3 has a Figure 1The magnetization directions 4 of the arrows in the segments 3 in FIG. 4 are in opposite directions. The magnetization directions 4 of the segments 3 arranged in opposite regions relative to the center of the permanent magnet arrangement 2 point in opposite directions. A first axis 7 of the permanent magnet arrangement 2 is defined relative to two segments 3 arranged opposite to each other, wherein the magnetization directions 4 of the respective two segments 3 are parallel to the first axis 7.

[0100] Each magnetization direction 4 forms an angle with the first axis 7. All these angles are formed differently. For example, the angles of directly adjacent segments 3 differ from each other by 67.5°.

[0101] exist Figure 1 and Figure 2 In the exemplary embodiment of FIG. 1 , the first axis 7 points in the direction of the x-axis.

[0102] Furthermore, the angle of the segment 3 having the magnetization direction 4 parallel to the first axis 7 and pointing in the same direction as the first axis 7 is 0°. The angle of the opposite segment 3 having the magnetization direction 4 parallel to the first axis 7 and pointing in the opposite direction as the first axis 7 is 180°.

[0103] Going clockwise along the loop from a segment 3 having a magnetization direction 4 parallel to the first axis 7 and pointing in the same direction as the first axis 7 back to this segment 3 , the magnetization direction 4 also rotates clockwise.

[0104] With such segments 3, the permanent magnet arrangement 2 is configured to generate a quadrupole field and thus have different strengths 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 linearly arranged adjacent to each other along the first axis 7.

[0105] The strength of the magnetic field acting on the trapped quantum particles 6 is different for each trapped quantum particle 6 arranged on the first axis 7 .

[0106] Exemplarily, the trapped quantum particles 6 are trapped ions. That is, each trapped ion has n energy levels, wherein two of the n energy levels form a qubit. In this case, each trapped ion is represented by a two-level quantum system comprising a first electronic energy level and a second electronic energy level, wherein the two energy levels correspond to corresponding atomic eigenstates of the corresponding trapped ion.

[0107] In order to capture ions, an electromagnetic harmonic trap potential is used to confine the ions to be captured in the axial direction along the first axis. In addition, the harmonic trap potential is superimposed with the magnetic quadrupole potential to confine the ions to be captured in the radial direction along the first axis. These capture potentials are superimposed with the electron energy levels and the corresponding electron sub-energy levels, which appear due to different magnetic field strengths (i.e., magnetic gradient fields). There is a transition between the electron sub-energy levels corresponding to the excited states of the trapped ions and the first electron energy level corresponding to the ground state of the trapped ions. Due to the different magnetic field strengths, i.e., magnetic field gradients, there are frequency differences in specific transitions between adjacent trapped ions. Therefore, each trapped ion in the trapped ions can be excited with a different resonant frequency. Advantageously, with such different resonant frequencies, each trapped ion is distinguishable and therefore addressable.

[0108] The total energy of the system is predetermined by the harmonic trap potential and the internal energy. The internal energy depends on the state of the trapped ion, for example in the ground state or in an excited state. If the trapped ion is excited in one of the excited states at a specific resonance frequency, the equilibrium position of the trapped ion changes due to the superposition of the corresponding electronic sublevels and the harmonic trap potential.

[0109] As a result, the trapped ions start to oscillate and thus influence neighboring trapped ions via Coulomb interactions, so that efficient spin-spin coupling is obtained.

[0110] 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 trap potential. In addition, the relaxation time, in particular the spin relaxation time T 2 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 in a given time.

[0111] For example, according to this exemplary embodiment, the inner radius R i is about 5cm, and the outer radius R o About 25cm. The remanence B of each segment in segment 3 R is, for example, 1 T. Therefore, the magnetic field, in particular the corresponding magnetic flux density It can be calculated by the following formula:

[0112]

[0113] The origin of the coordinates x and y is located in the center of the permanent magnet arrangement 2 .

[0114] Furthermore, the distance d between directly adjacent trapped ions is about 3 μm. Therefore, the magnetic flux density can be calculated for each position of the trapped ion. Therefore, differences in specific transitions between adjacent trapped ions can also be determined.

[0115] and Figure 1 Compared to the exemplary embodiment of Figure 2 The quantum computing device 1 of the exemplary embodiment comprises a permanent magnet arrangement 2 having segments 3, each segment 3 having the form of a square.

[0116] Each segment 3 has a square cross-sectional form. The magnetization direction 4 relative to the edge 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 Figure 1 angle.

[0117] exist Figure 3 and Figure 4 , the intensity of the magnetic field in T represented by the absolute value of the magnetic field |B| shown on the vertical axis depends on the position x or y in mm shown on the horizontal axis.

[0118] Figure 3 The horizontal axis of the graph shown in corresponds to Figure 1 and Figure 2 The x-axis. Figure 4 The horizontal axis of the graph shown in corresponds to Figure 1 and Figure 2 The position x or y equal to 0 corresponds to the y-axis according to Figure 1 and Figure 2 The center of the permanent magnet device 2.

[0119] The absolute value of the magnetic flux density |B| (i.e., the strength of the magnetic field) is symmetrical relative to the center of the permanent magnet arrangement 2. For negative position values ​​x and y, the absolute value of the magnetic flux density |B| (i.e., the strength of the magnetic field) has a negative slope, and for positive position values ​​x and y, the absolute value of the magnetic flux density |B| (i.e., the strength of the magnetic field) has a positive slope.

[0120] according to Figure 5 The quantum computer 8 of the exemplary embodiment includes a Figure 1 or Figure 2 A quantum computing device 1 according to one of the exemplary embodiments of the invention and a quantum computing device 9 located in a chamber 10. The quantum computing device 9 is connected to external components of the quantum computer 8 via the chamber 10 via a plurality of connections 11. For example, the connections 11 connect the quantum computing device 9 with control electronics 12 and a classical computer 13.

[0121] For example, the quantum computing device 9 is configured to capture, manipulate and measure trapped quantum particles in the space 5 during operation, each trapped quantum particle being a qubit. To this end, the quantum computing device 9 may include electrodes, light guides and / or internal electronic devices including electronic devices. The electronic devices may include circuit systems, integrated electronic devices and / or detectors, such as photon detectors and / or charge detectors, controllers. Exemplarily, internal electronic devices are provided for preprocessing. For example, these components enable the measurement of the corresponding states of the qubits and enable gate operations on the qubits. Therefore, the quantum computing device 9 is configured to capture trapped quantum particles and perform operations and measurements on the trapped quantum particles.

[0122] The quantum computing device 9 is installed in a chamber 10, wherein the chamber 10 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 arranged outside the chamber 10. In this case, the permanent magnet device 2 surrounds the chamber 10. Alternatively, the permanent magnet device 2 may also be arranged in an ultra-high vacuum chamber or an extremely high vacuum chamber or a cryostat.

[0123] Exemplarily, if the chamber 10 is a cryostat, the permanent magnet arrangement 2 is arranged inside the chamber 10 (not shown here). It is also conceivable that if the chamber 10 is a cryostat, the permanent magnet arrangement 2 can also be arranged outside the chamber 10 (not shown here).

[0124] The quantum computing device 9 is connected to an external electronic device 12 via a connection 11. The external electronic device 12 may be located at least partially inside the chamber 10 and partially outside the chamber 10. Furthermore, the external electronic device 12 is connected to a classical computer 13.

[0125] The external electronic device 12 exemplarily 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 direct current signal generator. In addition, the external electronic device 12 may include transistor-transistor logic TTL.

[0126] Additionally, the external electronic device 12 may also include at least one laser system configured to cool the ions to be trapped. Additionally, the laser system may be configured to excite a specific state of the trapped ions.

[0127] For example, the classical computer 13 is configured to provide and receive digital signals. The digital signals correspond to control signals for operating the qubits and measurement signals corresponding to the states of the qubits.

[0128] The external electronic device 12 is configured in particular to convert digital signals into analog signals and vice versa. Thus, the external electronic device 12 is configured to provide the converted analog signals for manipulating the qubits to the quantum computing device 9. Furthermore, the external electronic device 12 is configured to provide the measured analog signals from the quantum computing device 9 to the classical computer 13, or to process such signals to directly initiate some response signals generated by the control electronic device 12.

[0129] The classical computer 13 is exemplarily configured to be equipped with a specific algorithm, i.e., a predetermined quantum calculation to solve a specific problem. The classical computer 13 is then configured to convert the compiled code corresponding to the algorithm into commands for the quantum computing device 9. These commands are then forwarded to the quantum computing device 9 via the external control electronics 12. In addition, the classical computer 13 is configured to receive the measurement results of the specific algorithm.

[0130] For example, all components of quantum computer 8 , in particular all electronic components of quantum computer 8 , are synchronized, for example, via an atomic clock reference.

[0131] according to Figure 6 , Figure 7 and Figure 8 The quantum computing device 1 of the exemplary embodiment each includes a combination of Figure 1 The permanent magnet device 2 and the ion trap 100 are described in detail in the exemplary embodiment of FIG.

[0132] according to Figure 6 The ion trap 100 is a linear Paul trap for trapping ions along the first axis 7. The Paul trap is also called 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.

[0133] The linear Paul trap includes two radio frequency (RF) electrodes 20, two direct current (DC) electrodes 30 and two end cap electrodes 40. Exemplarily, the end cap electrodes may be formed of a soft magnetic material, thereby forming a yoke structure 60 to increase the magnetic field gradient along the first axis 7.

[0134] according to Figure 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 and an end cap electrode 40 and a separation cap electrode 41. All these electrodes are metal films and are arranged in a common electrode plane.

[0135] according to Figure 8 The ion trap 100 is a segmented Paul trap for trapping ions along a predefined line, in particular a first axis 7. The segmented Paul trap comprises at least two sections 47, wherein each section 47 is configured to accommodate an ion crystal comprising a plurality of trapped ions. Each section comprises Figure 6 The two rf electrodes 20 and the two dc electrodes 30 are similarly arranged. Furthermore, these parts are arranged between at least two end cap electrodes 40. All these electrodes are metal films and are arranged in two electrode planes parallel to each other and stacked on each other.

[0136] The invention is not limited to the description of the exemplary embodiments. Rather, the invention covers any novel feature and any combination of features, any combination of features particularly including any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the claims or exemplary embodiments.

[0137] Reference numerals list

[0138] 1 Quantum computing device

[0139] 2 Permanent magnet device

[0140] 3 segments

[0141] 4 Magnetization direction

[0142] 5. Space

[0143] 6 Trapped Quantum Particles

[0144] 7 First axis

[0145] 8 Quantum Computers

[0146] 9 Quantum computing devices

[0147] 10 Chamber

[0148] 11. Connect

[0149] 12 External Electronic Devices

[0150] 13 Classical Computers

[0151] 100 Ion Trap

[0152] 20 rf electrode

[0153] 30 dc electrode

[0154] 40 End cap electrode

[0155] 41 Separation cover electrode

[0156] 47 parts

[0157] 50 substrate

[0158] 60 Yoke structure

[0159] d Distance

[0160] R iinner radius

[0161] R o Outer radius.

Claims

1. A quantum computing device (1), include: - a permanent magnet arrangement (2), and - a space (5) within the permanent magnet arrangement (2) for at least two trapped quantum particles (6), the at least two trapped quantum particles (6) being arranged along a first axis (7), wherein: - the permanent magnet arrangement (2) comprises a plurality of segments (3), namely 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 creating magnetic fields of different strengths for different positions on the first axis (7).

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

3. The quantum computing device (1) according to claim 2, in, The space (5) is located in the central area of ​​the outline of the ring or the polygon.

4. A quantum computing device (1) according to one of claims 1 to 3, in, The distances between directly adjacent segments (3) are equal to each other.

5. A quantum computing device (1) according to one of claims 1 to 4, in, At least some of the segments (3) have a quadrilateral shape in cross-section.

6. A quantum computing device (1) according to one of claims 1 to 5, in, At least some of the segments (3) have a trapezoidal shape in cross-section.

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

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

9. A quantum computing device (1) according to one of claims 1 to 8, in, 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. The quantum computing device (1) according to one of claims 1 to 9, in, At least some of the trapped quantum particles (6) in the space (5) form qubits during operation of the quantum computing device (1).

11. A quantum computing device (1) according to one of claims 1 to 10, in, The frequency difference of a specific transition between the trapped quantum particles (6) depends on the magnetic field during operation of the quantum computing device (1).

12. The quantum computing device (1) according to one of claims 1 to 11, in, - the distance (d) between directly adjacent trapped quantum particles (6) is at least 0.1 μm and at most 30 μm, and - the frequency difference of the transition of the magnetic quantum number change between directly adjacent trapped quantum particles (6) is at least 10 kHz and at most 100 MHz, and / or The frequency difference of the transitions of the magnetic quantum number that are constant between directly adjacent trapped quantum particles (6) is at least 1 kHz and at most 10 MHz.

13. A quantum computing device (1) according to one of claims 1 to 12, in, - the edges of the segments (3) arranged in opposite areas and facing each other have a minimum distance relative to each other of at least 0.001 cm and at most 100 cm, - Each segment (3) has an extent of at least 0.001 cm and at most 100 cm along the corresponding minimum distance.

14. A quantum computing device (1) according to one of claims 1 to 13, in, The remanence of each of the segments (3) is at least 0.1T and at most 1.5T.

15. The quantum computing device (1) according to one of claims 1 to 14, in, The permanent magnet arrangement (2) comprises NdFeB.

16. Quantum computing device (1) according to one of claims 1 to 15, further comprising at least one additional permanent magnet arrangement (2).

17. The quantum computing device according to claim 16, in, - said permanent magnet arrangement and said additional permanent magnet arrangement are rotated relative to each other, or - said permanent magnet arrangement and said additional permanent magnet arrangement are parallel to each other.

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

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